SlideShare a Scribd company logo
ASET International Oil & Gas Training Academy
Comp Ex Hazardous Areas Course
March 2010 Revision
6th
Edition, March 2010
Introduction
Ex Facility
March 2010
©
2
National Training and Certification of Personnel for Work on Electrical
Apparatus for Use in Potentially Hazardous Atmospheres
This package has been compiled with information gathered from current standards and the
authors will not be held responsible for any inaccuracies found therein.
Acknowledgements:
The production of this document would not have been possible without the much
appreciated assistance from the following authorities and, therefore, the authors of the
document wish to thank and gratefully acknowledge all those who provided material and
advice for the production of the package, particularly the following:
The British Standards Institute
James Scott Ltd, Aberdeen, Scotland
Weidmuller (Klippon Products) Ltd, Sheerness, Kent
Hawke Cable Glands Ltd, Ashton-under-Lyne, Lancashire
Hecagon Technology Ltd, Aylesbury, Buckinghamshire
Measurement Technology Ltd, Luton, Bedfordshire
Brook Hansen, Huddersfield, West Yorkshire
The Design and Presentation Team of Aberdeen College, including all staff at the Altens
Centre.
The BASEEFA Crown mark shown in this document is the property of the Health and Safety
Executive and should not be interpreted to convey certification. The marks have been
reproduced with the kind permission of the EECS (HSE).
Copyright of Document:
No part of this document may be reproduced, stored in a retrieval system or transmitted in
any form by any means. i.e. electronic, electrostatic, magnetic media, mechanical,
photocopying, recording or otherwise without the permission in writing of the appointed
representative of Aberdeen College.
Ex Facility
March 2010
©
3
Introduction
About the ‘Ex’ Facility
Ex training courses have been run in Aberdeen College since 1990 and have developed to
the level of sophistication we have today. In its present form the CompEx course has been
in operation since August 1994 and has been designed and constructed specifically for the
National Training of personnel who work with electrical installations and plant in hazardous
and/or potentially explosive environments. The facility includes both classroom and
simulated work areas, these being designed to give as realistic site conditions as is possible
to achieve.
The practical work candidates are required to carry out will take place in these simulated
areas and this is intended to make the candidates feel they are working under site
conditions.
Approximately half of the week will be spent in the classroom where the ‘job knowledge’
elements of the course will be delivered by means of presentations incorporating lectures,
demonstrations, and photographic slides of good and bad practice on apparatus. The
remaining time will be spent on Competence Validation Testing in the simulated
hazardous areas. The tests are nationally set for Ex training.
The Outcome
The objective of the training is to introduce the candidate to operating procedures and
techniques and to give candidates and their employer’s confidence that the candidates are
competent to work on electrical apparatus in hazardous or potentially explosive
environments. The competence laid down nationally by industry and through this will help
make your industry a safer one.
About the Programme
The need for training in these areas of work is self evident in that the safe operation of
electrical equipment in hazardous areas is paramount. It is extremely important for all
personnel who operate in these conditions to be competent in the correct techniques and
operational procedures. This can best be achieved by means of training by skilled staff in an
environment as close to the ‘real thing’ as possible. In addition to this, the job knowledge
developed through the course must be put into operation in the actual working situation so
that the levels of expertise are increased through experience.
The Design of the Programme
The program is dived into two halves, namely:
a. Job Knowledge
b. Competence Validation Testing (CVT)
The ‘job knowledge’ component takes place during the first half of the week and provides the
information and experience you need to tackle the CVT’S.
Ex Facility
March 2010
©
4
Selection, Installation, and Maintenance of Electrical Apparatus for use in Hazardous
Locations.
Units:
1) General principles
(a) Nature of flammable materials
(b) gas grouping
(c) basic principles of area classification
(d) temperature codes
(e) ingress protection
2) Standards, Certification and Marking
3) Flameproof Ex d
4) Increased Safety Ex e
5) Type ‘n’ protection
6) Pressurisation Ex p
7) Intrinsic Safety Ex i
8) Other methods of protection, Ex o, Ex q, Ex m & Ex s
9) Combined (Hybrid) methods of protection
10) Wiring Systems
11) Inspection & Maintenance to BS EN60079-17
12) Sources of ignition
13) Induction to Competence Validation Testing
14) Permit to Work System and Safe Isolation
Appendix 1 Data for flammable materials for use with electrical equipment, ref BS5345:
Part 1: General recommendations.
Appendix 2 Self assessment project and apparatus label reading.
Ex Facility
March 2010
©
5
Course outline
The training scheme
The training scheme is arranged to prepare candidates for the assessment programme
which comprises four discreet Competence Validation Tests (CVT’s) offered as
complimentary pairs. The four CVT’s are as follows:
EX01 Preparation & Installation of Ex d, Ex e, Ex n and Ex p Systems
EX02 Inspection & Maintenance of Ex d, Ex e, Ex n and Ex p Systems
EX03 Preparation & Installation of Ex i Systems
EX04 Inspection & Maintenance of Ex i Systems
Job knowledge
The classroom (job knowledge) part of the training scheme consists of 12 Units which apply
to the four CVT’s as illustrated below.
Unit 1: General principles Unit 2: Standards,
Certification and
Marking
Unit 3: Flameproof Ex d
EX01 & EX02 EX01 & EX02 EX01 & EX02
EX03 & EX04 EX03 & EX04
Unit 4: Increased Safety
Ex e
Unit 5: Type ‘n’
protection
Unit 6: Pressurisation
Ex p
EX01 & EX02 EX01 & EX02 EX01 & EX02
(Written Assessment)
Unit 7: Intrinsic Safety Ex i Unit 8: Other methods of
protection
Unit 9: Combined (Hybrid)
protection methods
EX03 & EX04 (Written Assessment) EX01 & EX02
Unit 10: Wiring Systems Unit 11: Inspection &
Maintenance to
BS EN60079-17
Unit 12: Sources of ignition
EX01 & EX02 EX01 & EX02 EX01 & EX02
EX03 & EX04 EX03 & EX04 EX03 & EX04
Unit 13: Induction to
Competence
Validation Testing
Unit 14: Permit to Work
and
Safe Isolation
EX01 & EX02 EX01 & EX02
EX03 & EX04 EX03 & EX04
Ex Facility
March 2010
©
6
The CVT’s are a series of practical tests which you will undertake within the simulated work areas
during the second half of the programme. On successful completion of these tests you will be
awarded a Certificate of Core Competence which will indicate the areas the awarding body, Joint
Training Ltd. (JTL), has deemed you are competent.
During the final half-day of the programme you are required to sit written assessments in the form of
multi-choice papers which are related to the practical CVT assessments.
The staff who are involved in monitoring the various assessments are present only as observers and
not to prompt or offer technical assistance. Their observations of your work is recorded on Nationally
written checklists which are processed outwith the Centre and your results cannot be determined until
this process is complete.
Manual Units and applicable CVT’s
Unit 1: General Principles EX01, EX02, EX03 & EX04
Unit 2 : Standards, Certification & Marking EX01, EX02, EX03 & EX04
Unit 3: Flameproof Ex d EX01 & EX02
Unit 4: Increased Safety Ex e EX01 & EX02
Unit 5: Type ‘n’ Protection EX01 & EX02
Unit 6: Pressurisation Ex p EX01 & EX02 (Written Assessment)
Unit 7: Intrinsic Safety E x i EX03 & EX04
Unit 8: Other methods of Protection (Written Assessment)
Unit 9: Combined (Hybrid) Protection Methods EX01 & EX02
Unit 10: Wiring Systems EX01, EX02, EX03 & EX04
Unit 11: Inspection & Maintenance to BS EN60079-17 EX01, EX02, EX03 & EX04
Unit 12: Sources of Ignition EX01, EX02. EX03 & Ex04
Unit 13: Induction to Competence Validation Testing EX01, EX02. EX03 & Ex04
Unit 14: Permit to Work EX01, EX02. EX03 & Ex04
Course programme
The following course programme is for illustration purposes only, particularly for the CVT
assessments, and can change according to candidate numbers attending the course. A
programme for the CVT assessments will be compiled during the week.
Ex Facility
November 2008
7
Programme: Electrical Apparatus in Potentially Hazardous Areas
5 – Day Programme
y
a
d
i
r
F
y
a
d
s
r
u
h
T
y
a
d
s
e
n
d
e
W
y
a
d
s
e
u
T
y
a
d
n
o
M
r
e
t
n
e
s
e
r
P
8:30
12:30
Course
registration and
induction
Unit 1: General
Principles
Unit 10: Wiring
systems &
Demonstration of
compound filled
gland and
diaphragm seal
gland assembly
Unit 2: Standards:
certification &
marking
Unit 4: Increased
Safety Ex e
Unit 5: Type ‘n’
Protection
Unit 6:
Pressurisation Ex p
Unit 7: Intrinsic Safety E x i EX01 CVT
Inspection &
Maintenance
of d, e & n
apparatus
Candidates
7-12
EX02 CVT
Preparation
&
Installation
of d, e & n
apparatus
Candidates
1-6
EX03 CVT
Inspection &
Maintenance
of d, e & n
apparatus
Candidates
7-12
EX04 CVT
Preparation
&
Installation
of d, e & n
apparatus
Candidates
1-6
k
a
e
r
B
k
a
e
r
B
k
a
e
r
B
k
a
e
r
B
k
a
e
r
B
13:00
17:00
Unit 3: Flameproof
Ex d
Unit 10: Practical
exercise:
Assembly of
compound filled
and diaphragm
seal type glands.
Unit 8: Other
methods of
protection
Unit 9: Combined
(Hybrid) methods of
protection
Unit 11: Inspection &
Maintenance
Unit 13: Introduction
to CVT’s
Unit 14: Work permit
EX01 CVT
Preparation
&
Installation
of d, e & n
apparatus
Candidates
1-6
EX02 CVT
Inspection &
Maintenance
of d, e & n
apparatus
Candidates 7-
12
EX03 CVT
Preparation
&
Installation
of d, e & n
apparatus
Candidates
1-6
EX04 CVT
Inspection &
Maintenance
of d, e & n
apparatus
Candidates
7-12
Job Knowledge
assessment
EX01, EX02, EX03 & EX04
Multi-choice examination
Unit 1:
General Principles
March 2010 ©
2
Objectives:
On completion of this unit, ‘General Principles’, you should know:
a. The nature of flammable materials with regard to ‘explosive limits’ (LEL/UEL),
‘flashpoint’, ‘ignition’ temperature’, the effect of ‘oxygen enrichment’ and ‘relative
density’.
b. The basic principles of area classification.
c. The Grouping of gases according to ‘minimum ignition energy’ (MIE) and ‘maximum
experimental safe gap’ (MESG).
d. Appropriate T-ratings for apparatus relative to the ignition temperature of a given
flammable material.
e. The levels of ‘ingress protection’.
March 2010 ©
3
General Principles
Nature of Flammable Materials
Fire Triangle
The fire triangle represents the three elements which must be present before combustion
can take place. Each point of the triangle represents one of the essential elements which
are:
1. Fuel: This can be in the form of a gas, vapour, mist or dust
2. Oxygen: Plentiful supply since there is approximately 21% by volume in
air.
3. Source of Ignition: This can be an arc, spark, naked flame or hot surface.
Combustion will take place if all three elements, in one form or another, are present, the
gas/air mixture is within certain limits and the source of ignition has sufficient energy. The
removal of one element is sufficient to prevent combustion, as is the isolation or separation
of the source of ignition from the gas/air mixture. These are two techniques used in
explosion protected equipment. Other protection techniques allow the three elements to co-
exist and either ensures that the energy of the source of ignition is maintained below specific
values, or allows an explosion to take place and contains it within a robust enclosure. These
techniques are addressed in the various sections of this manual.
Gas or vapour
Oxygen
( 21% in air )
Source of
ignition
March 2010 ©
4
Flammable (Explosive) Limits
Combustion will only occur if the flammable mixture comprising fuel, in the form of a gas or
vapour, and air are within certain limits. These limits are the ‘lower explosive limit’ (LEL),
and the ‘upper explosive limit’ (UEL), and between these limits is known as the
flammable range.
An every day example of this is the carburettor of a petrol engine, which must be tuned to a
particular point between these limits in order that the engine may function efficiently.
Lower Explosive Limit: When the percentage of gas, by volume, is below this limit the
mixture is too weak to burn, i.e. insufficient fuel and/or too
much air.
Upper Explosive Limit: When the percentage of gas, by volume, is above this limit the
mixture is too rich to burn, i.e. insufficient air and/or too much
fuel.
The flammable limits of some materials are given below.
Material LEL
% by Volume
UEL
% by Volume
Propane 1.7 10.9
Methane 4.4 17
Ethylene 2.3 36
Hydrogen 4 77
Acetylene 2.3 100
Diethyl Ether 1.7 36
Kerosene 0.7 5
Carbon Disulphide 0.6 60
March 2010 ©
5
Flammable (Explosive) Limits (continued)
Different gases or vapours have different flammable limits and the greater the difference
between the LEL and the UEL, known as the flammable range, the more dangerous the
material. An explosive (flammable) atmosphere, therefore, only exists between these limits.
Operational safety with flammable mixtures above the UEL is possible, but is not a practical
proposition. It is more practical to operate below the LEL.
Sources of Ignition
Sources of ignition are many and varied and include:
a. Electrical arc/sparks
b. Frictional sparks
c. Hot surfaces
d. Welding activities
e. Cigarettes
f. Static discharges
g. Batteries
h. Exhausts of combustion engines
i. Thermite action
j. Sodium exposed to water
k. Pyrophoric reaction
l. Chemical reactions
m. Lightning strikes
The source of ignition as far as this text is concerned is primarily electrical equipment.
March 2010 ©
6
Flashpoint
By definition flashpoint is: ‘the lowest temperature at which sufficient vapour is given off a
liquid, to form a flammable mixture with air that can be ignited by an arc, spark or naked
flame’. Typical values are given below.
Material Flashpoint
°C
Propane -104
Ethylene -120*
Hydrogen -256*
Acetylene -82*
Diethyl Ether -45
Kerosene 38
Carbon Disulphide -95*
* Values obtained form a source other than PD IEC60079-20
The flashpoint of a material gives an indication of how readily that material will ignite in
normal ambient temperatures. Reference to the tables of flammable materials from PD
IEC60079-20 (see Appendix 1) reveals that different materials have different flashpoints,
which vary from well below to well above 0°C.
Materials with high flashpoints should not be overlooked as a potential hazard since
exposure to hot surfaces can allow a flammable mixture to form locally. Furthermore, if a
flammable material is discharged under pressure from a jet, its flashpoint may be reduced.
Amount of vapour released dependent
on temperature
March 2010 ©
7
Flashpoint (continued)
Kerosene: Flashpoint 38°C
At 38°C
“Ignition”
At 37°C
Insufficient vapour
given off
At 0°C
Negligible vapour
given off
March 2010 ©
8
Ignition Temperature
Ignition temperature is defined as: ‘the minimum temperature at which a flammable
material will spontaneously ignite’.
Ignition temperature, formerly known as auto-ignition temperature, is an important
parameter since many industrial processes generate heat. Careful selection of electrical
equipment will ensure that the surface temperature produced by the equipment, indicated by
the T-rating, will not exceed the ignition temperature of the flammable atmosphere which
may be present around the equipment. Typical values of ignition temperature are:
Material Ignition Temperature
°C
Propane 470
Methane 537
Ethylene 425
Hydrogen 560
Acetylene 305
Diethyl Ether 160
Kerosene 210
Carbon Disulphide 95
March 2010 ©
9
Oxygen Enrichment
The normal oxygen content in the atmosphere is around 20.95%, and if a given location has
a value which exceeds this it is deemed to be oxygen enriched. Typical examples of where
oxygen enrichment may occur are gas manufacturing plants, hospital operating theatres,
and where oxy-acetylene equipment is used.
Oxygen enrichment has three distinct disadvantages. First of all, it can lower the ignition
temperature of flammable materials as shown in the table below.
Air Increased Oxygen
Material
Ignition Temperature
°C
Ignition Temperature
°C
Hydrogen sulphide 260 220
Acetylene 305 296
Ethane 512 506
Secondly, oxygen enrichment significantly raises the upper explosive limit (UEL) of the
majority of gases and vapours, thereby widening their flammable range. This is illustrated in
the following table.
Air Increased Oxygen
Material
LEL
%
UEL
%
LEL
%
UEL
%
Methane 5 15 5.2 79
Propane 2.2 9.5 2.3 55
Hydrogen 4 75 4.7 94
Thirdly, oxygen enrichment of a flammable atmosphere can allow it to be ignited with much
lower values of electrical energy.
Explosion protected equipment will have been tested in normal atmospheric conditions and,
therefore, the safety of such equipment in an oxygen enriched atmosphere cannot be
assured because of the modified nature of the flammable mixture.
* All values obtained from a source other than PD IEC60079-20
* All values obtained from a source other than PD IEC60079-20
March 2010 ©
10
Density
If a flammable material is released, it is important to know whether the material will rise or
fall in the atmosphere. The different flammable materials are compared with air and
allocated a number to denote their relative density with air. Since air is the reference, its
relative density is 1 so that for a material twice as heavy as air, its relative density will be
2. Therefore, materials with a relative density less than unity will rise in the atmosphere,
and those greater than unity will fall in the atmosphere.
Materials which rise in the atmosphere can collect in roof spaces, and those which fall, such
as butane or propane, can drift along at ground level and possibly into a non-hazardous
location, or may collect in locations lower than ground level without ever dispersing. Such
locations should be well ventilated in order to avoid ignition due to a stray spark or a
discarded cigarette.
Knowledge of where a flammable material will collect ensures that gas detectors when fitted
will be located at the correct level and ventilation is directed accordingly.
<1
>1
Material
Relative vapour
density
Air 1
Propane 1.56
Methane 0.55
Ethylene 0.97
Hydrogen 0.07
Acetylene 0.9
Diethyl Ether 2.55
Kerosene 4.5*
Carbon
Disulphide
2.64
* Value obtained from a source
other than PD IEC60079-20
March 2010 ©
11
Area Classification
An hazardous area is defined as:
‘An area in which an explosive gas atmosphere is present, or may be expected to be
present, in quantities such as to require special precautions for the construction, installation
and use of apparatus.’
A non-hazardous area is defined as:
‘An area in which an explosive gas atmosphere is not expected to be present in quantities
such as to require special precautions for the construction, installation and use of apparatus.’
Zones
Zoning is a means of representing the frequency of the occurrence and duration of an
explosive gas atmosphere based on the identification and consideration of each and every
source of release in the given areas of an installation. Zoning will have a bearing on, and
simplify the selection of, the type of explosion protected equipment which may be used.
Hazardous areas are, therefore, divided into three Zones which represent this risk in terms
of the probability, frequency and duration of a release.
The three Zones, as defined in BS EN60079-10-1: Electrical apparatus for explosive gas
atmospheres, Part 10. Classification of hazardous areas, are as follows:
Zone 0 - An area in which an explosive gas atmosphere is present continuously
or for long periods or frequently.
Zone 1 - An area in which an explosive gas atmosphere is likely to occur in
normal operation occasionally.
Zone 2 - An area in which an explosive gas atmosphere is not likely to occur in
normal operation but, if it does occur, will persist for a short period
only.
Although not specified in IEC 60079-10-1, but quoted in API RP 505**, the duration of a gas
release, or a number of gas releases, on an annual basis (one year comprises circa 8760
hours), for the different Zones is as follows.
Zone 2 - 0 – 10 hours
Zone 1 - 10 – 1000 hours
Zone 0 - over 1000 hours
** The above document, API RP 505, is published by the American Petroleum Institute and
entitled “Recommended Practice for Classification of Locations for Electrical Installations
at Petroleum Facilities Classified as Class I, Zone 0, Zone 1, and Zone 2.
March 2010 ©
12
Area Classification (continued)
Zone representation for ‘Area Classification Diagrams’
In accordance with BS EN60079-10, the illustrations below are the preferred method for
representing the various zones in an hazardous area.
March 2010 ©
13
Area Classification (continued)
Fixed Roof Storage Tank
Distances: ‘a’ 3m from vent opening
‘b’ 3m above the roof
‘c’ 3m horizontally from the side of the tank
b
c
a
Zone 2
Zone 1
Zone 0
Sump:
Zone 1
March 2010 ©
14
Area Classification (continued)
Sources of Release
Welded pipe joint:
( Non-hazardous )
Flanged joint:
( Zone 2)
Pump gland:
( Zone 2 or Zone 1
depending on the
quality of the seal )
Space above liquid
in a closed tank:
( Zone 0)
March 2010 ©
15
Gas / Apparatus Grouping
In the IEC system, the group allocation for surface and underground (mining) industries are
separate. Group I is reserved for the mining industry, and Group II which is subdivided into
IIC, IIB and IIA for surface industries. The representative gases for the sub-groups are
shown in the table below.
Two methods have been used to ‘group’ these flammable materials according to the degree
of risk they represent when ignited. One method involved determining the minimum ignition
energy which would ignite the representative gases. The values obtained are relevant to
Intrinsically Safe apparatus. In the table below it can be seen that for Group II, hydrogen
and acetylene are the most easily ignited and propane the least easily ignited.
The other method involved tests using, for example, a special flameproof enclosure in the
form of an 8 litre sphere which was situated inside a gas-tight enclosure. Both halves of the
sphere had 25mm flanges and a mechanism enabled the gap dimension between the
flanges to be varied. During tests, the area inside and outside the sphere were occupied with
a gas in its most explosive concentration in air and, by means of a spark-plug the gas inside
the sphere was ignited. The maximum dimension between the flanges, which prevented
ignition of the gas/air mixture, is known as the ‘maximum experimental safe gap’ (MESG),
and the values for the representative gases are shown in the table below. The more
dangerous a gas, the tighter the gap at the flanges has to be. It is important to note that the
MESG values are not used for the design of Flameproof apparatus, only the maximum
working gaps.
The table also shows that these flammable materials fall into the same order for both tests,
i.e. in a relative context, hydrogen and acetylene present the most risk and propane the least
risk in terms of ‘minimum ignition energy’ and ‘MESG’.
Gas Group Representative
Gas
MESG
(mm)
Maximum
Working
Gap
(mm)
Minimum
Ignition
Energy
(μJ)
I
Methane
(Firedamp)
1.14 0.5 260
IIA Propane 0.91 0.4 160
IIB Ethylene 0.65 0.2 95
Hydrogen 0.28
IIC
Acetylene 0.37
0.1 20
Note: Apparatus other than flameproof or intrinsic safety, which has no sub-division letter
(A, B or C) after the group II mark, may be used in all hazards.
Apparatus marked IIxxxxx: xxxxx represents the chemical formula or name of a
flammable material, and apparatus marked in this way may
only be used in that hazard.
March 2010 ©
16
Gas / Apparatus Grouping (continued)
The sub-group marking is one of the important considerations during the selection process
of explosion protected apparatus. For example, apparatus marked IIA can only be used in
IIA hazards such as propane, it cannot be used in IIB or IIC hazards. Apparatus marked IIB
can be used in IIB and IIA hazards but not IIC hazards. Apparatus marked IIC can be used
in all hazards.
Apparatus for determination of M.E.S.G
March 2010 ©
17
Gas / Apparatus Grouping (continued)
Comparison of BS 229 and IEC
BS 229 is an old British Standard, which has now been withdrawn, but electrical apparatus
was still manufactured to this standard up until several years ago. Apparatus manufactured
to BS 229 has sub-group markings which are different to those of the IEC system and the
comparison is shown in the table below. The introduction of the ATEX Directives after 30
June 2003 has caused manufacturers to discontinue the production of apparatus to this
standard, but apparatus already in use will be unaffected.
BS 229 Representative Gas IEC
1 Methane I
2 Propane IIA
3a Ethylene
3b Coal Gas
IIB
4 Hydrogen & Acetylene IIC
March 2010 ©
18
Temperature Classification
Approved electrical equipment must be selected with due regard to the ignition temperature
of the flammable gas or vapour which may be present in the hazardous location. Apparatus
will usually be marked with one of the temperature classes shown in the table below. The
temperature class indicates the maximum temperature the surfaces of an enclosure, which
are exposed to a flammable gas, must not exceed during normal or specified fault
conditions.
Temperature Classes
T - Class
Maximum Surface
Temperature
T1 450°C
T2 300°C
T3 200°C
T4 135°C
T5 100°C
T6 85°C
In the table below, it will be observed that for each material, the T-rating temperature is
below the ignition temperature of the flammable material. Moreover, the T-rating
temperatures are based on a maximum ambient rating of 40°C as far as the UK is
concerned. For example, apparatus classified T5, based on a 40°C ambient rating, will have
a maximum permitted temperature rise of 60°C. In order to avoid infringement of the
apparatus certification, the ambient rating must be compatible with environmental ambient
temperatures, and the temperature rise not exceeded. This is demonstrated on page 20.
A further consideration is apparatus for use in hotter climates, typically found in Middle and
Far Eastern countries, which will usually require ambient ratings greater than 40°C.
Apparatus for use in colder (arctic) climates will require a much lower limit to the ambient
temperature range which may be as low as -50°C.
Material
Ignition
Temperature
T-Rating
Methane 537°C T1 (450°C)
Ethylene 425°C T2 (300°C)
Cyclohexane 259°C T3 (200°C)
Diethyl Ether 160°C T4 (135°C)
T5 (100°C)
Carbon Disulphide 95°C T6 (85°C)
March 2010 ©
19
Temperature Classification (continued)
-2
-2
March 2010 ©
20
Ingress Protection
Enclosures of electrical equipment are classified according to their ability to resist the
ingress of solid objects and water by means of a system of numbers known as the
‘International Protection (IP) Code’. This code, which is not always marked on apparatus,
consists of the letters IP followed by two numbers, e.g. IP56.
The first number, in the range 0-6, indicates the degree of protection against solid objects,
and the higher the number the smaller the solid object that is prevented from entering the
enclosure. Zero (0) indicates no protection and 6 indicate the apparatus is dust-tight.
The second number, ranging from 0-8, identifies the level of protection against water
entering the enclosure, i.e. 0 indicates than no protection is afforded, and 8 that the
apparatus can withstand continuous immersion in water at a specified pressure.
An abridged version of the full table is shown below.
Solid Objects Water
First
Numeral
Level of Protection
Second
Numeral
Level of Protection
0 No protection 0 No protection
1
Protection against objects
greater than 50 mm
1
Protection against drops of water
falling vertically
2
Protection against objects
greater than 12 mm
2
Protection against drops of water
when tilted up to 15°
3
Protection against objects
greater than 2.5 mm
3
Protection against sprayed water
up to 60°
4
Protection against objects
greater than 1.0 mm
4
Protection against splashed water
from any direction
5 Dust-protected 5
Protection against jets of water
from any direction
6 Dust-tight 6
Protection against heavy seas
- deck watertight
7
Protection against immersion in
water 1m in depth and for a
specified time
8
Protection against indefinite
immersion in water at a specified
depth
Unit 2:
Standards, Certification and
Marking
March 2010 ©
2
Objectives:
On completion of this unit, ‘Standards, Certification and Marking’, you should know:
a. Current British, European and International Standards and also relevant older British
Standards and Codes of Practice.
b. The certification process for explosion protected apparatus.
c. The methods of marking explosion protected apparatus.
d. The basic requirements of the ATEX Directives.
e. The correlation between the ATEX categories and Equipment Protection Levels
(EPL’s)
March 2010 ©
3
Standards, Certification and Marking
Introduction
There are many industries involved in the process of hazardous materials, and these include
chemical plants, oil refineries, gas terminals and offshore installations. These industries rely
heavily on electrical energy to power, for example, lighting, heating and rotating electrical
machines.
The safe use of electrical energy in the hazardous locations of these industries can only be
achieved if tried and tested methods of explosion protection are implemented and to this
end, the organisations involved in the writing of standards, testing and certification of
equipment have a very important role to play.
Since the early 1920’s, many standards have evolved as a result of careful research, often
prompted by incidents such as the Senghennydd colliery disaster in 1913 in which 439
miners lost their lives. The cause at that time was not fully understood but after investigation,
was thought to have been due to an electrical spark igniting methane (firedamp) present in
the atmosphere. Other disasters include Abbeystead Water Pumping Station in which 16
people lost their lives, once again due to the electrical ignition of methane gas, Flixborough
where an explosion killed 28 people due to ignition of a massive release of cyclohexane, and
more recently Piper Alpha in the North Sea in which 167 men lost their lives.
Construction of equipment to relevant standards coupled with testing by an independent
certification body will ensure that the equipment is suitable for its intended purpose.
Explosion protected equipment may be constructed in accordance with relevant standards,
but the integrity of such equipment will only be preserved if it is selected, installed and
maintained in accordance with the manufacturers recommendations. Guidance in this
respect has been provided for many years by the UK Code of Practice BS 5345, but this
document has been superseded by a new series of five separate standards based on the
IEC 60079 series of International standards. These five documents apply to explosion
protected equipment/systems in all countries in the EU and cover, (1) selection and
installation of equipment, (2) classification of hazardous areas, (3) inspection and
maintenance, (4) repair of explosion protected equipment, and (5) data for flammable gases
provided by an IEC document (See lower table on page 13). The BS EN60079 standards
are identical to the IEC60079 standards. Although BS 5345 has been withdrawn, it
nevertheless remains a source of information for older installations, but applies to the UK
only with regard to the EU.
In the United Kingdom, manufacturing and testing standards are published by an
organisation known as the British Standards Institute (BSI). With regard to the European
Community, the organisation which publishes harmonised standards for its member nations
is the European Committee for Electrotechnical Standardisation (CENELEC) and, with
global harmonisation of standards the ultimate aim, the International Electrotechnical
Commission (IEC) publishes standards for this purpose.
Historically, equipment designs are evaluated and prototypes tested by independent
organisations, one of which was formerly known as ‘British Approvals Service for
Electrical Equipment in Flammable Atmospheres (BASEEFA), but was later known as
‘Electrical Equipment Certification Service (EECS)’. The acronym BASEEFA, which has
been closely associated with explosion protected equipment for many years, was retained by
EECS for certification marking purposes. EECS, which was part of the Health and Safety
Executive (HSE), also published standards for special applications. EECS, however, closed
March 2010 ©
4
for business in September 2002, but encouraged by several major customers, former staff
established an independent organisation known as Baseefa (2001) Ltd, and became simply
Baseefa Ltd. two-years later. Having traded since March 2002, Baseefa Ltd. became an EU
Notified Body (NB) in June 2002 and was allocated the NB Number 1180.
With the introduction of the ATEX Directives, which become mandatory after 30 June 2003,
a procedure for the evaluation of equipment for compliance with the ATEX directives was
implemented. This procedure involves a series of modules, listed on page 5, covering the
design, quality control and production phases for equipment, which are audited by a Notified
Body. A Notified Body is an independent organisation that has been assessed and
accredited by a national body (United Kingdom Accreditation Service, UKAS, in the UK) as
having the expertise to operate as a Notified Body in accordance with the directives with
regard to conformity assessment of products. A Notified Body has been notified to the
European Commission by its member state
Notified Bodies have their own unique NB number, which will be marked on the certification
labels of ATEX compliant apparatus. Other Notified Bodies in the UK include SIRA
Certification Service, NB Number 0518, and ITS Testing and Certification Ltd., NB
Number 0359 and many others throughout the EU. Notified bodies may require the services
of other organisations for testing product prototypes.
ATEX Directives
On the 12 June 1989 a Framework Directive 89/391/EEC was adopted by the European
Commission the objective being to establish a basis for improving the safety of employees in
the workplace. Supplementary directives namely, 94/9/EC, introduced under Article 100a of
the Treaty of Rome and now known as ATEX 95, and 99/92/EC, now ATEX 137, address
equipment use and safety in hazardous areas. ATEX 95 is the product directive and ATEX
137 is the workplace directive. Both these directives, unlike previous directives, establish a
New Approach in that they are mandatory by law rather than advisory. ATEX 95, the
product directive, mandatory from 01 July 2003, requires all new equipment, which
includes not only electrical equipment but also mechanical (non-electrical) equipment, e.g.
pumps, gearboxes etc, and protective systems for use in potentially explosive atmospheres,
placed on the market of the European Community for the first time to be manufactured in
compliance with the directive. Equipment from out-with the EU, whether new or second
hand, imported into the European Community and placed on the market for the first time
must also be in compliance with the directive.
ATEX 95 applies to the design requirements of equipment and hence concerns mainly the
manufacturer and supplier but availability of spare parts and items held in stock would be of
concern to equipment users. Therefore, in order to comply with ATEX 95, products must
satisfy the Essential Health & Safety Requirements (EHSR’s) specified in the annexes of
the Directives, with regard to the inherent risks associated with the product for the protection
of the public. This is usually achieved by compliance with relevant harmonised standards,
and although it is possible to achieve compliance by means other than the harmonised
standards, difficulty would arise installing, inspecting and repairing such equipment to the BS
EN60079 standards 14, 17 & 19. Subject to a successful Conformity Assessment, the
product can display the CE mark which indicates compliance with the ATEX Directive.
ATEX 137, the user directive, became fully mandatory from 01 July 2006 and places
responsibilities on employers to provide a safe working environment for employees.
March 2010 ©
5
CE Conformity Assessment Modules
The Conformity Assessment involves a series of Basic Modules which are listed in the table
below and their application in the subsequent simplified flow chart.
A Internal control of production Covers internal design and production control. Does not
require the involvement of a notified body.
B EC type-examination Covers the design phase, the EC type-examination being
issued by a notified body. Has to be followed by a module
for assessment during the production phase.
C Conformity to type Covers the production phase after module B. This module
confirms conformity of the product with that described in
the EC examination certificate as issued during module B.
D Production quality assurance Covers the production phase following module B.
Production quality assurance is based on the standard EN
ISO 9002 and the involvement of a notified body who has
responsibility for the approval and control of the quality
system regarding production, end product inspection and
testing implemented by the manufacturer.
E Product quality assurance Covers the production phase following module B.
Production quality assurance is based on the standard EN
ISO 9003 and the involvement of a notified body who has
responsibility for the approval and control of the quality
system regarding end product inspection and testing
implemented by the manufacturer.
F Product verification Covers the production phase following module B. The EC
type examination carried out by the notified body, to
ensure conformity to type in module B, is followed by the
issue of a certificate of conformity.
G Unit verification Covers the design and production phases. A certificate of
conformity is issued after examination of every product by
the notified body.
H Full quality assurance Covers the design and production phases. Quality
assurance is based on the standard EN ISO 9003 and the
involvement of a notified body who has responsibility for
the approval and control of the quality system for design,
manufacture, final product inspection and testing
implemented by the manufacturer.
March 2010 ©
6
CE Conformity Assessment Modules (continued)
The illustration below shows how the modules listed on the previous page may be
implemented to obtain the CE marking for apparatus.
ATEX 95
The ATEX Directive 94/9/EC ( ATEX 95 ) was adopted by the EC to enable free trade of
products between member states through alignment of technical and legal requirements and
concerns the design of explosion protected equipment. The directive applies not only to
electrical equipment but also to mechanical equipment and protective systems used in the
presence of potentially explosive atmospheres containing gases/vapours or combustible
dusts.
Equipment is defined as any item which is inherently ignition capable or is potentially ignition
capable and requiring the inclusion of special design and installation techniques to prevent
ignition of any surrounding flammable atmosphere which may be present. The ‘equipment’
may also be interfaces located in the non-hazardous area which are part of an explosion
protection system. Protective systems include quenching systems, flame arrestors, fast-
acting shut-off valves and pressure relief panels installed to limit damage due to an
explosion or prevent the spread of explosions.
Design phase Production phase
Module A
Module C
Module D
Module E
Module F
Module G
Module B
Manufacturer
Module H
March 2010 ©
7
ATEX 137
The ATEX Directive 99/92/EC ( ATEX 137 ), commonly known as the ‘use’ directive, is
implemented in the UK via the Dangerous Substances and Explosives Atmosphere
Regulations 2002 (DSEARs). Employers are obliged to implement the following minimum
requirements in the workplace with regard to DSEARs.
a. Carry out a risk assessment where dangerous substances are or may be present.
b. Eliminate or reduce risk as far as is reasonably practicable.
c. Classify locations in the workplace where explosive atmospheres may be present
into hazardous or non-hazardous areas.
d. Have in place procedures/facilities to deal with accidents, incidents and emergencies
involving dangerous substances in the workplace.
e. Provide appropriate information and training of employees for their safety regarding
precautions to be taken when dangerous substances are present in the workplace,
written instruction for tasks undertaken by employees and operation of a permit-to-
work system.
f. Clearly identify the contents of containers and pipes.
g. Co-ordinate operations where two or more employees share a workplace in which a
dangerous substance may be present.
h. Posting of warning signs for locations where explosive atmospheres may occur.
i. Selection of equipment in accordance with ATEX 95 and establishment of a
maintenance programme.
Marking of Hazardous Areas
Article 7 in the Directive ATEX 137 states:
‘Where necessary, places where explosive atmospheres may occur in such
quantities as to endanger the health and safety of workers shall be marked
with signs at their points of entry in accordance with Annex III.’
Annex III of the directive specifies the exact requirements for the sign but generally it is
required to be triangular with a yellow background, black border and marked ‘Ex’.
Ex
March 2010 ©
8
European Notified Bodies
The illustration below shows some of the Notified Bodies along with their unique Notified
Body (NB) number. There are around sixty Notified bodies in the EU at the time of writing.
Finland: VTT Industrial Systems (0537)
Sweden: SP-Swedish National Testing (402)
Norway: NEMKO AS (0470)
DNV AS (0575)
Denmark: UL Int DEMKO A/S (0539)
UK: Baseefa (1180)
SIRA (0518)
BSI Product Services (0086)
ITS Testing & Cert. Ltd (0359)
Lloyd’s Reg Ver Ltd (0038)
Netherlands: KEMA (0344)
Belgium: ISSeP (0539)
France: LCIE (0081)
INERIS (0080)
Spain: LOM (0163)
Italy: CESI (0722)
Germany: PTB (0102)
March 2010 ©
9
Comparison of IEC, European (CENELEC) and British Standards
Prior to the closer ties between the UK and Europe, electrical equipment, such as flameproof
or increased safety etc., was manufactured in accordance with the British Standard BS 4683
(see table in page 11). Equipment built and certified to this standard was entitled to display
the mark Ex on its label, which indicated that the apparatus was explosion protected. This
term should not be confused with term explosion-proof as they are entirely different. In
addition to the ‘Ex’ mark, the label was also marked with a ‘crown’ symbol, which is the
distinctive mark for the UK test house BASEEFA, later to become known as EECS. Other
examples of marks are shown on page 14 of this Unit.
Because of the differences in standards, e.g. equipment manufactured in the UK could not
be used in the other European countries and vice-versa, and hence, equipment made to BS
4683 could only be used in the UK, or in other countries outside Europe. Co-operation
between the standards writing bodies in the UK and Europe resulted in the development of
‘Harmonised’ standards, also known as ‘Euronorms’, for which the English version was
published as BS 5501 and comprised nine separate parts as shown in the third column of
the table on page 10. The Euronorm equivalents, written in French or German, are shown on
the first column. Column four shows the second generation of the UK version of the
harmonised standards which replaced BS5501.
However, with the trend towards global harmonisation of standards continuing to make
progress, a new series of standards have been gradually introduced having numbers based
on the International Standard numbers (second column), i.e. BS EN60079, as shown in
column five of the following table.
March 2010 ©
10
Comparison of IEC, European (CENELEC) and British Standards
CENELEC
Euronorm
(EN) Number
International
Standards
British Standard
(BS) Number
Revised Standard
(BS EN) Number
Latest Revised
Standard
(BS EN) Number
Type of Protection
EN 50 014 IEC 60079-0 BS 5501: Pt. 1 BS EN50 014 BS EN60079-0 General Requirements
EN 50 015 IEC 60079-6 BS 5501: Pt. 2 BS EN50 015 BS EN60079-6 Oil Immersion ‘o’
EN 50 016 IEC 60079-2 BS 5501: Pt. 3 BS EN50 016 BS EN60079-2 Pressurised Apparatus ‘p’
EN 50 017 IEC 60079-5 BS 5501: Pt. 4 BS EN50 017 BS EN60079-5 Power Filling ‘q’
EN 50 018 IEC 60079-1 BS 5501: Pt. 5 BS EN50 018 BS EN60079-1 Flameproof Enclosure ‘d’
EN 50 019 IEC 60079-7 BS 5501: Pt. 6 BS EN50 019 BS EN60079-7 Increased Safety ’e’
EN 50 020 IEC 60079-11 BS 5501: Pt. 7 BS EN50 020 BS EN60079-11 Intrinsic Safety ‘i’
EN 50 028 IEC 60079-18 BS 5501: Pt. 8 BS EN50 028 BS EN60079-18 Encapsulation ‘m’
EN 50 039 IEC 60079-25 BS 5501: Pt. 9 BS EN50 039 BS EN60079-25 Intrinsic Safety Systems ‘i’
EN 50 021 IEC 60079-15 BS EN50 021 BS EN60079-15 Type of Protection ‘n’
IEC 60079-26 BS EN60079-26
Equipment with Equipment Protection
Level Ga
IEC 60079-27 BS EN60079-27
Fieldbus intrinsically safe concept
(FISCO)
IEC 60079-29-2 BS EN60079-29-2
Gas detector selection, installation,
use and maintenance
IEC 60079-30-1 BS EN60079-30-1
Electrical resistance trace heating –
General & testing requirements
IEC 60079-30-2 BS EN60079-30-2
Electrical resistance trace heating –
Application guide
March 2010
11
Other (older) British Standards
The standards listed below are those which preceded the harmonised European standards
listed in the previous table. These standards, with the exception of BS 889, were not entirely
obsolete, and older designs of equipment were still manufactured to these standards and
available on the market prior to 30 June 2003, the date after which implementation of the
ATEX Directives became mandatory. Apparatus manufactured to these standards, where
still in use, must be maintained in accordance with these standards. It is, therefore, important
that reference to the correct standard is made before maintenance is carried out on such
apparatus.
BS 229 Flameproof enclosure of electrical apparatus
BS 889 Flameproof electric fittings
BS 1259
Intrinsically safe electric apparatus and circuits for use in
explosive atmospheres
BS 4683: Part 1 Classification of maximum surface temperature
BS 4683: Part 2 The construction and testing of flameproof enclosures of
electrical apparatus
BS 4683: Part 3 Type of protection ‘N’
BS 4683: Part 4 Type of protection ‘e’
BS 6941 Type of Protection ‘N’
BS 5000: Part 15 Machines with type of protections ‘e’
BS 5000: Part 16 Type ‘N’ electric motors
March 2010 ©
12
Standards for Selection, Installation, Inspection and Maintenance
As previously stated, the UK Code of Practice BS 5345, which had for many years provided
recommendations for the selection, installation and maintenance of explosion protected
equipment for use in potentially explosive atmospheres (other than mining applications or
explosives processing and manufacture), listed in the upper table below, was superseded by
the standards listed in the lower table. BS 5345, however, may be referred to for
installations installed in accordance with its requirements. The table below illustrates the
component parts of BS 5345.
UK Code of Practice Type of Protection
BS 5345: Part 1 General Recommendations
BS 5345: Part 2 Classification of Hazardous Areas
BS 5345: Part 3 ‘d’ Flameproof enclosure
BS 5345: Part 4 ‘i’ Intrinsically safe apparatus and systems
BS 5345: Part 5
‘p’ Pressurisation, continuous dilution and
pressurised rooms
BS 5345: Part 6 ‘e’ Increased safety
BS 5345: Part 7 ‘N’ (Non - incendive)
BS 5345: Part 8 ‘s’ Special protection
BS 5345: Part 9
‘o’ Oil immersion
‘q’ Powder filling
The standards which supersede the Code of Practice BS 5345 are illustrated in the table
below. Furthermore, the BS EN standards are identical to the IEC standards shown within
brackets in the table below apart from a few informative annexes.
BS EN / IEC Nos.
Electrical Apparatus for Explosive Gas
Atmospheres:
BS EN60079-10: 2009
(IEC 60079-10-1: 2008)
Part 10: Classification of hazardous areas
BS EN60079-14: 2008
(IEC 60079-14: 2007)
Part 14: Electrical installations in hazardous
areas (other than mines)
BS EN60079-17: 2007
(IEC 60079-17: 2007)
Part 17: Inspection and maintenance of
electrical installations in hazardous
areas (other than mines)
BS EN60079-19: 2007
(IEC 60079-19: 2006)
Part 19: Repair and overhaul for apparatus used
in explosive atmospheres (other than
mines or explosives)
BS EN60079-20-1: 2010
(IEC 60079-20-1: 2010)
Material characteristics for gas and vapour
classification – Test methods and data
March 2010 ©
13
Certification body symbols
1) Equipment marked with this symbol may
only be used for underground (mining)
applications in the UK.
2)
Equipment marked with this symbol has
been constructed to the old British Standard
BS229
3) Symbol formerly used by EECS
(BASEEFA) to identify equipment for
surface industry use only.
4)
Equipment marked with this symbol, the
European Ex mark, indicates that the
equipment has been constructed and tested
in accordance with the CENELEC/
EURONORM standards. This mark only
will be used on ATEX compliant equipment.
5)
Symbol formerly used by the German
notified body PTB
6)
The most commonly used symbol of the
American certification authority
Underwriters Laboratories (UL)
7)
The mark used by the Canadian Standards
Association
MEx
March 2010 ©
14
Equipment Marking
Prior to the introduction of the ATEX Directives on 1 July 2003, equipment for use in
hazardous areas were marked as illustrated below. Equipment complying with the ATEX
Directives, however, will still be marked in this way but will have additional markings to
indicate that the apparatus conforms with the ATEX Directives. The ATEX markings are
shown on page 18. Equipment approved/certified as providing a method of protection for
use in hazardous locations is required to display the following markings.
a. The symbols Ex, and
b. The type of protection used, e.g. ‘d’, ‘e’, ‘N’, and
c. The gas group, e.g. IIA, IIB or IIC, and
d. The T-rating, e.g. T1, T2 etc.
e. The ambient rating, e.g. -200
C to +400
C (normal range for UK but may not be marked
on equipment.)
Note: For higher ambient ratings the marking may be either Tamb +500
C, or
-200
C < Tamb < +500
C
Examples:
(i) Ex d IIB T3
(ii) EEx d IIC T4
(iii) EEx e II T6
In example (i), equipment marked thus (Ex), as far as Europe was concerned, could only be
used in the UK because it had been constructed to the British Standard BS 4683, which was
not a harmonised European standard. Equipment constructed to this standard, however,
was used in other countries out-with the European Community. Such equipment would also
be marked with the EECS certification authority symbol (fig 3) on the previous page.
Equipment certified in accordance with the IEC Ex scheme will be marked Ex. See page 20
onwards for details of this scheme.
For equipment marked EEx as in example ii. and iii., the additional letter ‘E’ indicates that the
equipment has been constructed to a harmonised European standard. Such equipment
would be marked with the EECS certification authority symbol (fig 3) as well as the European
Community mark (fig 4). Sample labels are shown below, and it should be noted that the
construction standard to which the equipment has been manufactured to, i.e. BS 4683: Part
2, BS 5501: Parts 1 & 5 and EN50 014 & EN50 018 are also given on the labels. For BS
4683 equipment, the IEC equivalent standard, i.e. IEC 79-1 in example (a) below, is usually
included.
(a) (b)
March 2010 ©
15
Equipment marking (continued)
The certification labels attached to explosion protected equipment will display markings to
enable their correct selection for use in hazardous areas. For example, equipment
manufactured to the old UK standard BS4683 and the subsequent CENELEC EN500 series
of harmonised standards will be marked Ex and EEx respectively. However, with the
CENELEC and IEC standards becoming technically identical, i.e. the EN60079 standards
are identical to the IEC60079 standards, the marking has reverted to Ex.
The illustration below shows the marking on equipment constructed to the harmonised
standard BS EN50018.
Equipment manufactured to the latest standards, the BS EN60079 series, will be marked as
follows along with the ATEX markings shown on page 17. The main differences are the
removal of the letter ‘E’ compared to the illustration above and the introduction of the EPL
‘Gb’. EPL’s are explained on pages 18 to 21.
Ex d IIC T6 Gb
March 2010 ©
16
Certification Numbers
The certification number illustrated below was used by BASEEFA prior to the introduction of
the ATEX directives, but the numbers used by other certification authorities will be different.
Components typically displaying a suffix ‘U’ include Ex e terminals, Ex d stoppers for
flamepoof enclosures, and small volume plastic flameproof switches which have exposed
terminals.
ATEX compliant equipment will have standardised certification numbers which will include
the abbreviation of the notified body’s name followed by the year of certification, the acronym
ATEX, the serial number and either of the suffix’s ‘X’ or ‘U’ where applicable, as shown
below.
BAS 08 ATEX 1234 X
March 2010 ©
17
Marking of ATEX Compliant Equipment
The ATEX Directive 94/9/EC, now known as ATEX 95, specifies the new approach for the
certification of explosion protected equipment. An introduction to the ATEX approach has
been considered in pages 4-7 but its wider issues are beyond the scope of this Unit. What is
relevant, however, is the influence the directive will have on the marking of explosion
protected equipment. This will be the most obvious difference to those involved in the
selection, installation and maintenance of explosion protected apparatus.
The marking required by ATEX 95 is illustrated below, which is additional to the marking
requirements already discussed. Also, the hexagonal symbol below will replace the
individual symbols used by the different certification bodies, and the CE mark indicates
compliance with the ATEX Directive.
The Equipment Categories are defined overleaf
0000
CE Mark
Notified body
ID number
EU Explosive
Atmosphere
Symbol
March 2010 ©
18
Category (Cat) Definitions
The ATEX Categories were introduced to ‘break’ the traditional link between the protection
types and zones, i.e. the selection of equipment suitable for the zone. This approach
enables, for example, Cat 3 equipment, typically Ex n, to be used in zone 1 if a risk
assessment revealed that the consequences of ignition of a flammable atmosphere was low.
The Categories below, however, show the traditional link with the zones. Conversely, if the
consequences of ignition were greater then a better Category of protection may be required.
Group II Cat 1: Very high level of protection
Equipment with this category of protection may be used where an
explosive atmosphere is present continuously or for long periods, i.e.
Zone 0 or Zone 20.
Cat 2: High level of protection
Equipment with this category of protection may be used where an
explosive atmosphere is likely to occur in normal operation, i.e. Zone
1 or Zone 21.
Cat 3: Normal level of protection
Equipment with this category of protection may be used where an
explosive atmosphere is unlikely to occur or be short duration, i.e.
Zone 2 or Zone 22.
Group I Cat M1: Very high level of protection
Equipment can be operated in the presence of an explosive
atmosphere.
Cat M2: High level of protection
Equipment to be de-energised in the presence of an explosive
atmosphere.
Note: Zones 20, 21 and 22 are the corresponding zones for combustible dusts.
Equipment protection levels (EPL’s)
The introduction of Equipment Protection Levels (EPL’s), which are used internationally,
enables a risk assessment approach to be implemented for the selection of explosion
protected equipment in hazardous areas. This provides an alternative to the traditional
method of selecting equipment to suit the zone, which does not take into consideration the
consequences of an explosion. The table below shows the zones where both ATEX
Categories and EPL’s may be used from a traditional selection approach. Selection of
equipment according to the EPL will in future be according to the EPL’s specified for the
zones in area classification diagrams so that where the consequences of an explosion are
likely to be greater, a higher EPL will be specified. Alternatively, if the consequences of an
explosion are lower, a lesser EPL may be specified.
Zone ATEX Categories EPL’s
0 1 Ga
1 2 Gb
2 3 Gc
March 2010 ©
19
Equipment protection levels (EPL’s)
Equipment Protection Levels (EPL’s) are available for both gases and vapours and also
combustible dusts as illustrated in the table below. Equipment marked ‘G’ is for use in
flammable gases and vapours, and for use in combustible dusts when marked ‘D’.
Zone
Equipment protection levels
( EPL’s )
0 Ga
1 Ga or Gb
2 Ga, Gb or Gc
20 Da
21 Da or Db
22 Da, Db or Dc
EPL Definitions
Group II gases
Ga Equipment for explosive gas atmospheres, having a ‘very high’ level of protection,
which is not a source of ignition in normal operation, expected faults, or when subject
to rare faults.
Gb Equipment for explosive gas atmospheres, having a ‘high’ level of protection, which
is not a source of ignition in normal operation, or when subject to faults that may be
expected, though not necessarily on a regular basis.
Gc Equipment for explosive gas atmospheres, having an ‘enhanced’ level of protection,
which is not a source of ignition in normal operation and which may have some
additional protection to ensure that it remains inactive as an ignition source in the
case of regular expected occurrences, for example, failure of a lamp.
Group III Dusts
Da Equipment for combustible dust atmospheres, having a ‘very high’ level of protection,
which is not a source of ignition in normal operation, or when subject to rare faults.
Db Equipment for combustible dust atmospheres, having a ‘high’ level of protection,
which is not a source of ignition in normal operation, or when subject to faults that
may be expected, though not necessarily on a regular basis.
Dc Equipment for combustible dust atmospheres, having an ‘enhanced’ level of
protection, which is not a source of ignition in normal operation and which may have
some additional protection to ensure that it remains inactive as an ignition source in
the case of regular expected occurrences.
March 2010 ©
20
EPL’s assigned to protection types (gases)
EPL Ga
EPL Protection type Marking
Intrinsic Safety Ex ia
Ga
Encapsulation Ex ma
EPL Gb
EPL Protection type Marking
Flameproof Ex d
Increased Safety Ex e
Intrinsic Safety Ex ib
Encapsulation
Ex m
Exmb
Oil immersion Ex o
Pressurisation
Ex p, Ex px,
Ex py
Powder filled Ex q
Gb
Fieldbus Intrinsic Safety Concept
(FISCO)
**
** No designated marking code at the time of writing
EPL Gc
EPL Protection type Marking
Intrinsic Safety Ex ic
Encapsulation Ex mc
Non-sparking Ex n, Ex nA
Restricted breathing Ex nR
Energy limitation Ex nL
Sparking equipment Ex nC
Pressurisation Ex pz
Gc
Fieldbus non-incendive Concept
(FNICO)
**
** No designated marking code at the time of writing
March 2010 ©
21
EPL’s for combustible dusts
EPL Protection type Marking
Intrinsic Safety Ex iD
Encapsulation Ex mD
Da, Db, or Dc
Protection by enclosure tD
Db or Dc Pressurisation pD
Equipment marking
Since there is now technical alignment of the CENELEC and IEC standards, equipment
manufactured in Europe will no longer be marked EEx, and instead will be marked Ex.
Where equipment is certified under the IECEx scheme the IECEx Conformity Mark as
illustrated below will be displayed on the equipment. For the foreseeable future, however,
acceptance in the EU will require the equipment to comply with ATEX and display the
marking illustrated on page 18.
Area for code indicating
the Licensee Number
and the Certification
Body
March 2010 ©
22
Example of an EC – Type Examination Certificate
March 2010 ©
23
March 2010 ©
24
March 2010 ©
25
Baseefa Wallchart
UNIT 3
FLAMEPROOF
EEx d / Ex d
March 2010 ©
2
OBJECTIVES
On completion of this unit, ‘flameproof EEx d / Ex d apparatus, you should
know:
a. The principle of operation and causes of pressure piling.
b. The general constructional requirements including types of joints.
c. The installation requirements with regard to thread engagement of cable entries and
stopping devices, circuit protection, obstruction of flamepaths and additional
weatherproofing methods in accordance with BS EN60079-14.
d. The inspection requirements with regard to BS EN60079-17.
March 2010 ©
3
Flameproof EEx d / Ex d
Flameproof is one of the original methods of explosion protection developed for use in the
mining industry. It has a wide range of applications, typically junction boxes, lighting fittings,
electric motors etc.
The letter ‘d’, which symbolises this type of protection, is from the German word ‘druckfeste’
(kapselung), which roughly translated means ‘pressure tight’ (enclosure).
Flameproof apparatus, when properly installed in the intended location, enables components
such as switches, contractors and relays etc. to be safely used in hazardous areas.
Flameproof is the only one of the nine different methods of explosion protection in which an
explosion is permitted. This explosion, however, must be contained by the robustly
constructed flameproof enclosure so that ignition of the surrounding flammable atmosphere
cannot occur.
March 2010 ©
4
Standards
BS EN60079-1: 2007 Flameproof enclosures ‘d’
BS EN50 018: 2000 Flameproof enclosures ‘d’
BS 5501: Part 5: 1977 Flameproof enclosures ‘d’
BS 4683: Part 2: 1971
The construction and testing of flameproof enclosures of electrical
apparatus (Ex d)
BS 229: 1957 Flameproof enclosures of electrical apparatus
IEC 60079-1: 2007
Electrical Apparatus for explosive gas atmospheres –
Part 1: Flameproof enclosures ‘d’
BS EN60079-14: 2008
Electrical Apparatus for explosive gas atmospheres: Part 14
Electrical installations in hazardous areas (other than mines)
BS EN60079-17: 2007
Electrical Apparatus for explosive gas atmospheres: Part 17
Inspection and Maintenance of electrical installations in hazardous
areas (other than mines)
BS 5345: Part 3: 1979
(Withdrawn)
Code of Practice for the Selection, Installation and Maintenance of
flameproof apparatus
Definition
The construction standard BS EN60079-1 defines flameproof as:
‘An enclosure in which the parts which can ignite an explosive atmosphere are
placed and which can withstand the pressure developed during an internal explosion
of an explosive mixture, and which prevents the transmission of the explosion to the
explosive atmosphere surrounding the enclosure’
EPL: Gb
Zone of Use: 1 & 2
Ambient Conditions
Flameproof enclosures are normally designed for use in ambient temperatures in the range
- 20°C to +40°C unless otherwise marked.
March 2010 ©
5
Principle of Operation
Flameproof enclosures are not gas tight and a gas or vapour will enter the enclosure where,
for example, joints or cable entries exist. Since these enclosures are designed to contain
components which are an ignition source, ignition of the gas or vapour may occur, and the
resulting explosion pressure can reach a peak value of around 150 p.s.i.
The enclosure must, therefore, be strong enough to contain this explosion pressure, and the
gaps at the joints and threads of cable entries must be long and narrow to cool the
flames/hot gases before they reach and cause ignition of a flammable atmosphere which
may exist out with the enclosure.
Typical materials used for the construction of flameproof apparatus include cast iron,
aluminium alloys, and where corrosion resistance is required, gun metal bronze, phosphor
bronze and stainless steel may be used. Plastic materials are also used but the free internal
volume must not exceed 10cm3
. The latest standard specifies that for flanged joints ‘THERE
SHALL BE NO INTENTIONAL GAP AT THE JOINTS’ and infers the same for other joint
types. The average roughness Ra of the flamepath surfaces must not exceed 6.3μm.
Flammable MIxture
Arcs, Sparks
Hot Surfaces
Contactors, Relays
etc
Gap
March 2010 ©
6
Gap Dimensions
It is not necessary for a gap to exist at the flamepaths of a flameproof enclosure. The latest
standard BS EN60079-1 states there shall be no intentional gap between the surfaces of
enclosures with flanged joints.
This said, however, a gap will be necessary at the cylindrical joints of rotating machines, i.e.
where the rotor shaft exits the end-shield and also where push-button spindles pass through
flameproof enclosures to operate the internal switches.
Flameproof enclosures with spigot or screwed joints, however, require some clearance to
enable covers to be removed relatively easily for installation and maintenance purposes.
These clearance/gap dimensions, and also those for rotating machines and push-button
stations, must be within the dimensions specified in the tables for gap dimensions in the
construction standard for flameproof equipment, e.g. BS EN60079-1.
Factors which influence the dimension of the gap are:
a. The width of the joint
b. The gas group
c. The internal volume of the enclosure
d. The type of joint
March 2010 ©
7
Flamepath Joints
The diagrams below illustrate examples of three joint types specified in the British standard
BS EN60079-1 for use in flameproof apparatus. In a flanged joint, the machined surface on
the cover makes face-to-face contact with the corresponding surface on the base to give a
gap dimension normally less than that specified in the tables of gap dimensions in the
standard when the cover is properly bolted down. This type of joint will be used at the covers
of, for example, junction boxes.
Spigot joints will be used at junction box covers and motor enshields.
Threaded joints are used for cover joints, cable gland and conduit entries. An adequate
flamepath length is normally achieved with a thread engagement of five full threads.
In contrast to BS EN50019, the most recent standard, BS EN60079-1 permits the use of
flanged joints when a IIC gas such as acetylene is the hazard only if the gap is ≤ 0.04mm,
has a length L ≥ 9.5mm and the free internal volume does not exceed 500 cm3
.
a) Flanged joint
b) Spigot joint
c) Screwed joint
Interior
Interior
Interior
March 2010 ©
8
Flamepath Joints Types (Rotating Machines)
(d) cylindrical (shaft gland) joint
(d) labyrinth joint for shafts
March 2010 ©
9
Flamepath Joints (other examples)
Flamepaths other than those at cover joints are also necessary where, for example, an
actuator spindle passes through the wall of an enclosure, or where a cable gland or conduit
enters an enclosure. Examples are shown below.
Push-button spindle
Cable (gland) entry
March 2010 ©
10
Entry by Cable Gland or Conduit
The thread engagement requirements for cable and conduit entries are specified in the
standard BS EN60079-1 and apply to the three sub-groups IIA, IIB and IIC.
Only threaded entries are permitted for all cable glands or conduits entering flameproof
enclosures – clearance entries are not permitted.
Volume
≤ 100 cm3
> 100 cm3
Thread
Engagement
Axial
Length
Thread
Engagement
Axial
Length
> 5 Full Threads > 5mm > 5 Full Threads > 8 mm
As already stated the above requirements for thread engagement are specified in the latest
standard BS EN60079-1: 2007, but the previous standard BS EN50018: 2000 required at
least 6 full threads engagement in order to make sure that 5 full threads were actually
engaged.
Note: Flameproof equipment manufactured to the old British standard BS229 may have
different non-metric thread forms at cable gland entries. This difficulty can be
overcome by the use of certified Ex d adaptors which have compatible thread forms
to suit both the entry in the enclosure and the cable gland.
March 2010 ©
11
Unused Cable or Conduit Entries
It is important that unused cable/conduit entries in flameproof enclosures are closed using
appropriate stoppers, as specified in the standards, or those supplied by the manufacturer.
These must be ‘component certified’ metal stoppers – plastic stoppers are unacceptable –
which are fully engaged by 5 full threads. The construction standard specifies suitable types,
examples of which are illustrated below.
Stoppers of the type illustrated by example ‘C’ in the above diagram are available with
certification markings on either the plain side or the same side as the hexagon recess.
Ideally, stoppers of this type should be fitted with the plain side facing the exterior to make
unauthorised removal more difficult, but may be fitted with the hexagon recess facing the
exterior. Whichever way round they are fitted the certification markings must be visible for
ease of identification during ‘Visual’ inspection programmes. Also the thread engagement
requirements must be met. Stoppers of this type are tightened using an Allen Key.
Split pin
A
B
C
D
Interior
Screwdriver slot
Special fastener
Hexagon recess
Hexagon head
Shearable neck
Exterior
March 2010
12
Flamepath Gap Dimensions – BS EN60079-1, Table 1
Maximum gap
mm
For a volume
cm3
V ≤ 100
For a volume
cm3
100 < V ≤ 500
For a volume
cm3
500 < v ≤ 2 000
For a volume
cm3
V > 2 000
Type of Joint
Minimum
width of joint
L
mm
I IIA IIB I IIA IIB I IIA IIB I IIA IIB
6 0.30 0.30 0.20 - - - - - - - - -
9.5 0.35 0.30 0.20 0.35 0.30 0.20 - - - - - -
12.5 0.40 0.30 0.20 0.40 0.30 0.20 0.40 0.30 0.20 0.40 0.20 0.15
Flanged, cylindrical or
spigot joints
25 0.50 0.40 0.20 0.50 0.40 0.20 0.50 0.40 0.20 0.50 0.40 0.20
6 0.30 0.30 0.20 - - - - - - - - -
9.5 0.35 0.30 0.20 0.35 0.30 0.20 - - - - - -
12.5 0.40 0.35 0.25 0.40 0.30 0.20 0.40 0.30 0.20 0.40 0.20 -
25 0.50 0.40 0.30 0.50 0.40 0.25 0.50 0.490 0.25 0.50 0.40 0.20
Sleeve
bearings
40 0.60 0.50 0.40 0.60 0.50 0.30 0.60 0.50 0.30 0.60 0.50 0.25
6 0.45 0.45 0.30 - - - - - - - - -
9.5 0.50 0.45 0.35 0.50 0.40 0.25 - - - - - -
12.5 0.60 0.50 0.40 0.60 0.45 0.30 0.60 0.45 0.30 0.60 0.30 0.20
25 0.75 0.60 0.45 0.75 0.60 0.40 0.75 0.60 0.40 0.75 0.60 0.30
Cylindrical
joints for
shaft
glands of
rotating
electrical
machines
with:
Rolling-
element
bearings
40 0.80 0.75 0.60 0.80 0.75 0.45 0.80 0.75 0.45 0.80 0.75 0.40
NOTE: Constructional values rounded according to ISO 31-0 should be taken when determining the maximum gap.
March 2010 ©
13
Flamepath Gap Dimensions – BS EN60079-1, Table 2
Maximum gap
mm
Type of Joint
Minimum
width of joint
L
mm
For a volume
cm3
V ≤ 100
For a volume
cm3
100 < V ≤ 500
For a volume
cm3
500 < v ≤ 2 000
For a volume
cm3
V > 2 000
5 0.10 - - -
9.5 0.10 0.10 - -
15.8 0.10 0.10 0.4 -
Flanged joints
25 0.10 0.10 0.4 0.4
12.5 0.15 0.15 0.15 -
25 0.18b
0.18b
0.18b
0.18b
40 0.20c
0.20c
0.20c
0.20c
Spigot
joints
(Figure 2a)
c ≤ 6mm
d ≤ 0.5L
L = c + d
f ≤ 1mm
6 0.10 - - -
9.5 0.10 0.10 - -
12.5 0.15 0.15 0.15 -
25 0.l5 0.15 0.15 0.15
Cylindrical joints
Spigot joints
(Figure 2b)
40 0.20 0.20 0.20 0.20
6 0.15 - - -
9.5 0.15 0.15 - -
12.5 0.25 0.25 0.25 -
25 0.25 0.25 0.25 0.25
Cylindrical joints for
shaft glands of rotating
electrical machines with
rolling element bearings
40 0.30 0.30 0.30 0.30
a
Flanged joints are permitted for explosive mixtures of acetylene and air only in accordance with 5.2.7
b
Maximum gap of cylindrical part increased to 0.20 mm if f < 0.5 mm
c
Maximum gap of cylindrical part increased to 0.25 mm if f < 0.5 mm
NOTE: The constructional values rounded according to ISO 21 –D should be taken when determining the maximum
gap
March 2010 ©
14
Pressure Piling
If a flammable mixture us compressed prior to ignition, the resulting explosion will be
considerably higher than if the same mixture was ignited at normal atmospheric pressure.
Pressure piling can materialise as a result of sub-division of the interior of a flameproof
enclosure, which prevents the natural development of an explosion.
An explosion at one side of an obstacle pre-compresses the flammable mixture at the other
side, resulting in a secondary explosion that can reach an explosion pressure around three
times that of the first or normal explosion pressure.
Manufacturers, guided by relevant construction standards, must ensure that, in any cross-
section within an enclosure, there is adequate free space (typically 20 – 25% of the total
cross-section) around any potential obstruction, which may be a large component or a
number of components. This will ensure that pressure piling is kept under control.
March 2010 ©
15
Pressure Piling in Flameproof Motors
In rotating electrical machines, sections with appreciable free volume normally exist at each
end within the main frame of the machine. These sections are linked by the airgap between
the stator and rotor cores. In the illustration of a flameproof machine in the diagram above,
an explosion in section ‘1’ must be prevented from migrating to, and causing ignition of the
flammable mixture in section ‘2’ which will have been pressurised by the initial explosion.
The airgap, therefore, also acts as a flamepath.
Section 1 Section 2
March 2010 ©
16
Obstruction of Flamepaths
The UK Code of Practise BS 5345 Part 3 recommended that obstruction of flameproof
enclosures, particularly those with flanged joints, should be avoided. This recommendation is
also given in BS EN60079-14: Electrical installation in hazardous areas (other then mines).
A solid obstruction such as a wall, steelwork, conduit, brackets, weather guards or other
electrical apparatus etc., in close proximity to the opening at the joint can, in the event of an
internal explosion, reduce the efficiency of the flamepath to the extent that ignition of the
external gas or vapour could occur.
The minimum distance between the flamepath opening and an obstruction, as specified in
BS EN60079-14 (and BS 5345: Part 3) are:
Group Distance
IIA 10 mm
IIB 30 mm
IIC 40 mm
March 2010 ©
17
Ingress Protection Methods
The diagrams below illustrate the location of gaskets or rubber ‘O’ rings for ensuring a high
level of ingress protection. The gaskets etc. must be an integral part of the original design,
i.e. they cannot be added at a later date to an enclosure manufactured without gaskets.
Typical examples for outdoor use are illustrated below.
March 2010 ©
18
Weatherproofing / protection of flamepaths
Flameproof equipment must have a level of ingress protection to suit the environmental
conditions of the location in which the equipment is installed and hence equipment should
have, as part of their certified design, seals or gaskets to prevent the ingress of water and/or
dust. Flamepaths must also be protected in accordance with manufacturer’s instructions
and the requirements of BS EN60079-14 which will involve additional measures as detailed
below. This is particularly important where environmental conditions are extreme.
Protection of flamepaths
The following measures are not permissible:
a) painting of flamepath surfaces - enclosures may be painted after assembly;
b) fitting of unauthorised seals/gaskets – replacement seals/gaskets may only be
fitted where the originals, which are part of the certified design, are degraded or
damaged.
Permitted measures:
c) application of non-setting grease or anti-corrosive agents having no evaporating
solvents;
d) non-hardening grease-bearing (Denso) tape – see application/limitations of use
below.
Note: The use of non-setting grease on the machined surfaces of flamepaths has
two advantages since, in addition to providing an additional level of ingress
protection; it also inhibits the formation of rust on these surfaces.
Silicone based greases require careful consideration in order to avoid
possible damage to the elements of gas detectors.
For Flameproof equipment, the limitations for the use of non-hardening tape as specified in
BS EN60079-14 are as follows:
a. Non-hardening tape maybe applied around the flamepaths of apparatus with flanged
joints allocated to group IIA applying one layer only with a short overlap.
b. For group IIB apparatus, one layer with a short overlap may be applied around the
flamepaths of apparatus with flanged joints, but only if the gap is less than 0.1mm
regardless of the joint width.
Note: The Code of Practise BS 5345: Part 3 (withdrawn but a relevant source of
information for older installations) recommended that expert advice be sought
when considering the use of non-hardening tape on group IIB or IIC
equipment installed in locations containing group IIB gases or vapours.
c. Non-hardening tape must not be used on equipment marked IIC (or IIB + H2)
installed in locations containing group IIC gases or vapours.
March 2010 ©
19
Direct / Indirect Entry
The selection of cable glands for flameproof apparatus is influenced by several factors, one
of which is the method of entry into the apparatus. There are two entry methods, namely
direct and indirect, examples of which are shown below.
Direct entry comprises a single flameproof chamber within which components such as
switches, relays or contactors may be installed. Flameproof apparatus with indirect entry
has two separate chambers, one of which contains only terminals for connection of the
conductors of incoming cables or conduit. Connection to the arcing components in the
second compartment is made via these flameproof terminals which pass through the
flameproof interface between the two compartments.
Direct entry Indirect entry
EEx d
Enclosure
EEx d
Enclosure
Flamepaths
Bushings
EEx d cable
glands
March 2010 ©
20
Electrical Protection
Flameproof enclosures are tested for their ability to withstand internal gas explosions only;
they are not capable of withstanding the energy which may be released as a result of an
internal short-circuit. In order to avoid invalidation of the certification, it is important that
properly rated/calibrated electrical protection, e.g. fuses and/or circuit breakers, are utilised.
Cover bolt (fastener) requirements
Should the requirement arise where it is necessary to replace the cover bolts etc of a
flameproof enclosure, only steel bolts having the correct length, type of thread, type of head
and tensile strength should be used.
Regarding cover bolt tightness the torque values specified by the manufacturer should be
observed. In the absence of manufacturer’s torque values the minimum requirement is
spanner tight, however, care must be exercised to avoid under-tightening as this can allow
an increase in the flamepath gap. Also, over-tightening of the bolts can result in them
stretching and hence reducing their strength with the consequence that an internal explosion
may not be contained within the enclosure.
It is important that all cover bolts are in place and correctly tightened prior to energising a
flameproof enclosure.
March 2010 ©
21
Modification of Flameproof Enclosures
Flameproof enclosures are normally supplied complete with all internal components fitted
and certified as a single entity by a recognised test authority. The testing procedure will take
into consideration the free internal volume after all the components have been fitted, the
temperature rise (determined by the maximum power dissipation), creepage and
clearance distances, and the rise in pressure as a result of an internal explosion using a
gas/air mixture in its most explosive proportions.
The certification, therefore, “seals” the design of the apparatus so that any unauthorised
modifications will effectively invalidate the approval/certification. Modifications will
modify the original test results recorded by the test/certification authority and, consequently,
the following points should be observed.
a. Replacement components should always be exactly the same as the original
specified components in order to avoid infringement of the certification. For example,
a component larger or smaller than the original will affect the internal geometry of the
enclosure. Pressure piling is a possibility if a larger component is fitted, and
increased volume will result if a smaller component is fitted.
Note: Illustrations are for demonstration only and must not be carried out
Original
arrangement
Replacement of ‘A’
with a larger item
Replacement of ‘A’
with a smaller item
March 2010 ©
22
b. Adding components is also forbidden because of the possibility of increased
explosion pressure as a result of pressure piling.
Addition of component ‘C’
c. The removal of components should also be avoided since an increase in the free
internal volume will result. The original test results, prior to certification, would be
compromised as a result of a modification such as this.
Removal of component ‘B’
March 2010 ©
23
Note: Illustrations are for demonstration only and must not be carried out
d. Drilling and tapping of cable gland/conduit entries should only be carried out
by the manufacturer of the enclosure, or his approved agent. The threads of the
entries are required to be compatible with those of cable glands or conduit in terms of
type of thread, thread pitch and clearance tolerance since flamepaths exist at these
points.
Correct alignment of the threaded entry is also important since the flamepath
length at one side will be reduced if the cable gland or conduit is not fitted
perpendicular to the face of the enclosure.
The strength of a flameproof enclosure may be impaired if the number and size
of entries exceeds that permitted in the original design certified by the test authority.
Compliance with the original design is paramount with regard to number, size and
location of entries to ensure the enclosure will contain an internal explosion.
e. Gaskets can only be replaced; they must not be added retrospectively if not included
as part of the original design.
The use of unauthorised sealants should also be avoided when it is required to
maintain or improve the IP rating.
March 2010 ©
24
BS EN 60079-17 Table 1: Inspection Schedule for Ex’d’, Ex’e’, and Ex ‘n’
Installations (D = Detailed, C = Close, V = Visual)
Check that: Ex’d’ Ex’e’ Ex’n’
Grade of Inspection
D C V D C V D C V
A APPARATUS
1 Apparatus is appropriate to area classification * * * * * * * * *
2 Apparatus group is correct * * * * * *
3 Apparatus temperature class is correct * * * * * *
4 Apparatus circuit identification is correct * * *
5 Apparatus circuit identification is available * * * * * * * * *
6 Enclosure, glass parts and glass-to-metal sealing gaskets
and/or compounds are satisfactory
* * * * * * * * *
7 There are no unauthorised modifications * * *
8 There are no visible unauthorised modifications * * * * * *
9 Bolts, cable entry devices (direct and indirect) and blanking
elements are of the correct type and are complete and tight
- Physical check
- Visual check
* *
*
* *
*
* *
*
10 Flange faces are clean and undamaged and gaskets, if any,
are satisfactory
*
11 Flange gap dimensions are within maximal permitted values * *
12 Lamp rating, type and position are correct * * *
13 Electrical connections are tight * *
14 Condition of enclosure gaskets is satisfactory * *
15 Enclosed-break and hermetically sealed devices are undamaged *
16 Restricted breathing enclosure is satisfactory *
17 Motor fans have sufficient clearance to enclosure and/or covers * * *
18 Breathing and draining devices are satisfactory * * * * * *
B INSTALLATION
1 Type of cable is appropriate * * *
2 There is no obvious damage to cables * * * * * * * * *
3 Sealing of trunking, ducts, pipes and/or conduits is satisfactory * * * * * * * * *
4 Stopping boxes and cable boxes are correctly filled *
5 Integrity of conduit system and interface with mixed system is
maintained
* * *
6 Earthing connections, including any supplementary earthing
bonding connections are satisfactory (e.g. connections are tight
and conductors are of sufficient cross section)
- Physical check
- Visual check
*
* *
*
* *
*
* *
7 Fault loop impedance (TN system) or earthing resistance
(IT systems is satisfactory)
* * *
8 Insulation resistance is satisfactory * * *
9 Automatic electrical protective devices operate within permitted
limits
* * *
10 Automatic electrical protective devices are set correctly (auto reset
not possible)
* * *
11 Special conditions of use (if applicable) are complied with * * *
12 Cables not in use are correctly terminated * * *
13 Obstructions adjacent to flameproof flanged joints are in
accordance with IEC 60079-14
* * *
14 Variable voltage/frequency installation in accordance with
documentation
* * * * * *
C ENVIRONMENT
1 Apparatus is adequately protected against corrosion, weather,
vibration and other adverse factors
* * * * * * * * *
2 No undue accumulation of dust and dirt * * * * * * * * *
3 Electrical insulation is clean and dry * *
March 2010 ©
25
Note 1
Apparatus using a combination of both ‘d’ and ‘e’ types of protection will require reference to
both columns during inspection.
Note 2
The use of electrical test equipment, in accordance with items B7 and B8, should only be
undertaken after appropriate steps are taken to ensure the surrounding area is free of a
flammable gas or vapour
Unit 4:
Increased Safety
EEx e / Ex e
March 2010 ©
2
Objectives:
On completion of this unit, ‘Increased Safety EEx e / Ex e Apparatus’, you
should know:
a. The principle of operation.
b. The principle design features.
c. The methods for estimating terminal content of enclosures.
d. The installation requirements according to BS EN 60079-14.
e. The inspection requirements according to BS EN 60079-17.
March 2010 ©
3
Increased Safety EEx e / Ex e
The explosion protection concept Increased Safety was invented in Germany where it has
been widely used for many years. It is has become popular in the UK mainly because it has
a number of advantages for certain applications over the traditional flameproof method of
explosion protection. America has traditionally relied on the use of explosion-proof
enclosures in hazardous locations, and the prospect of using an Increased Safety enclosure,
which is not designed to withstand an internal explosion, as an alternative, has probably
been viewed with a little trepidation.
This method of protection has a good safety record and comparable with the other methods
of protection. The letter ‘e’ which symbolises this method of protection is taken from the
German phrase ‘Erhohte Sicherheit’, which roughly translated means ‘increased security’.
Typical applications are induction motors, lighting fittings and junction boxes.
Standards
BS EN60079-7: 2007
Electrical apparatus for explosive gas atmospheres.
Increased Safety ‘e’
BS EN50 019: 2000 Increased Safety enclosure ‘e’
BS 5501: Part 6: 1977 Increased Safety enclosure ‘e’
BS 4683: Part 4: 1973 Type of protection ‘e’
IEC 60079-7: 2001-11
Construction and Test of Electrical Apparatus, Type of
Protection “e”
BS EN60079-14: 2008
Electrical apparatus for explosive gas atmospheres: Part 14
Electrical installations in hazardous areas (other than
mines)
BS EN60079-17: 2007
Electrical apparatus for explosive gas atmospheres: Part 17
Inspection and maintenance of electrical installations in
hazardous areas (other than mines)
BS 5345: Part 6: 1978
(Withdrawn)
Code of Practice for the Selection, Installation and
Maintenance of Increased Safety apparatus.
March 2010 ©
4
Definition
‘A protection method in which increased measures are taken to prevent the possibility of
excessive HEAT, ARCS or SPARKS occurring on internal or external parts of the apparatus
in normal operation’.
EPL: Gb
Zones of use: 1 & 2
Ambient Temperatures
Increased Safety enclosures are normally designed for use in ambient temperatures in the
range -20 °C to +40 °C unless otherwise marked.
Increased Safety light fittings
Increased safety light fittings usually have other methods of protection, e.g powder filled Ex q
protected capacitors and flameproof protected lampholders, and hence the marking on the
certification label will be Ex edq. The following, however, note is important.
Note: Lamps for Ex e, luminaries, which have mono-pin, bi-pin or screw connections where
the caps are made from non-conductive material with a conductive coating, are not
permitted unless tested with the equipment.
March 2010 ©
5
Principle
The safe operation of Increased Safety apparatus is dependent on the prevention of any
source of ignition, i.e. excessive surface temperatures, arcs or sparks, which might
otherwise be produced by internal or external parts of the apparatus. Special design features
are, therefore, incorporated in the apparatus by the manufacturer and are as follows.
1. Mechanically strong enclosure resistant to impact - tested to 4 or 7 joules impact
energy depending on application.
2. Ingress protection against solid objects and water - at least IP 54.
3. Terminals manufactured from high quality insulation material.
4. Specified creepage and clearances incorporated in the design of terminals.
5. Terminal locking devices to ensure conductors remain secure in service.
6. Certified de-rating of terminals.
7. Terminal population of enclosure limited by circuit design.
8. Close excess current circuit protection.
Increased Safety Terminals
The terminals installed in an Increased Safety enclosure must be ‘component certified’
terminals. They will be manufactured from good quality materials such as Melamine,
Polyamide and, for special applications, Ceramic. These materials, which have good thermal
stability, have been subjected to a ‘Comparative Tracking Index (CTI)’ test to determine their
resistance to tracking.
The following definitions are relevant:
Clearance distance: The shortest distance through air between two conductors.
Creepage distance: The shortest distance between two conductors along the
surface of an insulator.
Tracking: The leakage current which passes across the
contaminated surface of an insulator between live
terminals, or live terminals and earth.
Comparative Tracking Index: The numerical value of maximum voltage, in volts at which
an insulation material withstands e.g., 100 drops of
electrolyte (usually ammonium chloride solution in distilled
water) without tracking.
March 2010 ©
6
Increased Safety Terminals
Test Criteria - Comparative Tracking Index (CTI)
The Comparative Tracking Index (CTI) test criteria are given in the table below. Four grades
of materials ‘a’, ‘b’, ‘c’ and ‘d’ are considered, the highest quality material being ‘a’ which is
subjected to the greatest number of drops of electrolyte falling between the test electrodes,
and the highest voltage applied across the electrodes from the variable voltage source. Each
material must withstand the specified number of drops of the electrolyte at the specified
voltage for it to be acceptable.
Thus, the combination of high quality materials and good design, which incorporates
specified creepage and clearance distances, ensures that Increased Safety terminals have a
greater resistance to tracking to prevent arcing or sparking.
Grade of Material C.T.I. Test Voltage Number of Drops
a - 600 > 100
b 500 500 > 50
c 380 380 > 50
d 175 175 > 50
The International Standard IEC 60112 groups insulating materials according to their tracking
resistance as illustrated in the following table.
Material group Comparative tracking index ( CTI )
I 600 < CTI
II 400 < CTI < 600
IIIa 175 < CTI < 400
Creepage and Clearance Distances
March 2010 ©
7
Increased Safety Terminals
Creepage and Clearance Distances
Terminals
Partition
Screw heads
Clearance
29 75
Creepage
path
30 6
Clearance & creepage
path 26.4mm
Clearance and creepage paths
to extend to adjacent clamping
screw
Clearance and
creepage paths
14.0mm
Creepage path runs
between locating rivet and
assembly rail 27.8 mm
Clearance path extends
from end of bolt to
assembly rail 20.5mm
March 2010 ©
8
Increased Safety Terminals
Creepage Distances Relative to Voltage and Grade of Insulation
The following table from BS EN60079-7 shows the creepage distances relative to the grade
of material and applied voltage.
Minimum creepage distance
(mm)
Material group
Voltage (see note 1)
U r.m.s a.c. or d.c.
(V)
I II IIIa
Minimum clearance
(mm)
10 ( see note 3 ) 1.6 1.6 1.6 1.6
12.5 1.6 1.6 1.6 1.6
16 1.6 1.6 1.6 1.6
20 1.6 1.6 1.6 1.6
25 1.7 1.7 1.7 1.7
32 1.8 1.8 1.8 1.8
40 1.9 2.4 3.0 1.9
50 2.1 2.6 3.4 2.1
63 2.1 2.6 3.4 2.1
80 2.2 2.8 3.6 2.2
100 2.4 3.0 3.8 2.4
125 2.5 3.2 4.0 2.5
160 3.2 4.0 5 3.2
200 4.0 5.0 6.3 4.0
250 5.0 6.3 8.0 5.0
320 6.3 8.0 10.0 6.0
400 8.0 10.0 12.5 6.0
500 10.0 12.5 16.0 8.0
630 12.0 16.0 20.0 10.0
800 16.0 20.0 25.0 12.0
1000 20.0 25.0 32.0 14.0
1250 22.0 26.0 32.0 18.0
1600 23.0 27.0 32.0 20.0
2000 25.0 28.0 32.0 23.0
2500 32.0 36.0 40.0 29.0
3200 40.0 45.0 50.0 36.0
4000 50.0 56.0 63.0 44.0
5000 63.0 71.0 80.0 50.0
6300 80.0 90.0 100.0 60
8000 100.0 110.0 125.0 80.0
10000 125.0 140.0 160.0 100.0
Note 1: Voltages shown are derived from IEC 60664-1. The working voltage may exceed
the voltages given in the table by 10%. This is based on the rationalisation of
supply voltages given in table 3b of IEC 60664-1
Note 2: The creepage distance and clearance values shown are based on a maximum
supply voltage tolerance of +10%.
Note 3: At 10 V and below, the value of CTI is not relevant and materials not meeting the
requirement for material group IIIa may be acceptable.
March 2010 ©
9
Increased Safety Terminal Types and Ratings
The terminals are de-rated so that the maximum current for Increased Safety applications is
nearly half that for standard industrial applications as illustrated in the following table for
enclosures manufactured to BS 5501 Part 6. This de-rating, along with other considerations,
ensures that internal and external surface temperatures are kept within prescribed limits.
The table below also shows the maximum conductor size for each terminal type.
Terminal
Type
Conductor
Size
Increased Safety
Maximum Current
(amps)
Industrial Maximum
Current
(amps)
SAK 2.5 2.5 15 27
SAK 4 4 21 36
SAK 6 6 26 47
SAK 10 10 37 65
SAK 16 16 47 87
SAK 35 35 75 145
SAK 70 70 114 220
Increased Safety Terminals
Terminal Locking Device
It is essential that conductors are securely connected in the terminals to prevent sparks
occurring as a result of loose connections. The illustration below shows how this is achieved.
March 2010 ©
10
Estimation of Terminal Population
The number of terminals which can be installed in a given size of enclosure is limited.
Several methods have been developed by manufacturers for this purpose. These are:
Enclosure Factor: A method used in apparatus manufactured to BS 4683 Part 4
in which the terminal content is assessed by dividing the
‘enclosure factor’ by the certified current rating of a given
terminal.
Load Limit: Similar to ‘enclosure factor’ but used only on apparatus
manufactured to BS 5501 Part 6.
Kelvin Rating: Normally used for high current applications and apparatus
manufactured to BS 4683 Part 4 and BS 5501 Part 6. In this
method, enclosures and terminals are assigned a temperature
rating. Enclosures will normally be limited to a temperature rise
of 40K for a T6 temperature rating, but the temperature for the
terminals will be dependent on their type, rated current, size of
associated conductor, and the size of enclosure in which they
are installed. This involves the use of tables which are
provided by the manufacturer. Once the terminal ‘K’ rating has
been established, it is divided into the ‘K’ rating for the
enclosure to give the number of terminals of one type which
may be installed.
Max Dissipated Power: This is a method which will replace the current ‘load limit’
method and applies to apparatus manufactured to BS 5501
Part 6 and BS EN50019. In this method, enclosures are
assigned a ‘watts dissipation’ rating, but the rating of the
terminals is determined by use of a unique table (provided by
the manufacturer) for the enclosure. This table provides the
‘watts dissipation’ of the terminal through consideration of
conductor size and load current. The terminal content is
determined by dividing the ‘watts dissipation’ value for the
terminal into that for the enclosure.
Another method used by manufacturers is to specify the maximum current per pole and
also the maximum current per mm2
.
Examples of labels with the above information are shown overleaf.
March 2010 ©
11
Examples of labels
(a) Enclosure factor (b) Load limit
(c) Enclosure factor (d) Maximum dissipated power
(e) Maximum current per pole and per sq. mm
Klippon
TYPE TB11EX S/No. 9364
EEx e II T6
BASEEFA CERT. No. EX84B1333X
BS5501 Pt.6 (EN50 019)
LOAD LIMIT 600A
Klippon
ENCLOSURE TYPE TB11
BS 4683 Pt.4 Ex e II T6
BASEEFA No. Ex 77152/B
MAX. CIRCUIT VOLTAGE 726
ENCLOSURE FACTOR 416
SERIAL NUMBER 1334
Klippon
TYPE TB12 S/No.867594
EEx e II T6
BASEEFA CERT. No. Ex84B3290X
BS5501 Pt.6 (EN50 019)
LOAD LIMIT 40K
Klippon
TYPE STB2 EEx II T6 S/No. T499
BASEEFA CERT. No. 86B 2138X
BS5501 Pt.6 (EN50 019)
MAX. DISSIPATED POWER 7 WATTS
HAWKE CABLE GLANDS Ltd.
BS5501: Pt.6: 1977
(EN50 019) EEx e II T6
BASEEFA No. Ex 8142BX
TYPE REF PL639 SERIAL No. 9960/89
PHASE-TO-PHASE 726
MAX VOLTS
PHASE-TO-EARTH
MAX.CURRENT DENSITY
AMPS PER SQ. MM 4
MAX AMPS PER POLE 10
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS
CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS

More Related Content

Similar to CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS

UET30812 Certificate III in ESI – Distribution Cable Jointing. Australian Qua...
UET30812 Certificate III in ESI – Distribution Cable Jointing. Australian Qua...UET30812 Certificate III in ESI – Distribution Cable Jointing. Australian Qua...
UET30812 Certificate III in ESI – Distribution Cable Jointing. Australian Qua...
Thorne & Derrick International
 
Certificate of degree
Certificate of degreeCertificate of degree
Certificate of degree
Diego Bettega
 
Competency of Staff new 4.
Competency of Staff new 4.Competency of Staff new 4.
Competency of Staff new 4.
Mel Wilmans
 
HNS L2 Curriculum.pdf
HNS L2 Curriculum.pdfHNS L2 Curriculum.pdf
HNS L2 Curriculum.pdf
teshomeneguse
 
Colin Bird. Doosan Babcock. 29th January
Colin Bird. Doosan Babcock. 29th JanuaryColin Bird. Doosan Babcock. 29th January
Colin Bird. Doosan Babcock. 29th January
UKTI2014
 
Phase 2 Core Power and Control RoA.3
Phase 2 Core Power and Control RoA.3Phase 2 Core Power and Control RoA.3
Phase 2 Core Power and Control RoA.3
Paul Patten
 
NIIT Presentation 2
NIIT Presentation 2NIIT Presentation 2
NIIT Presentation 2
NIIT Bahrain
 
Safety engineering and the environment (scqf level 5) dr2 d34
Safety engineering and the environment (scqf level 5) dr2 d34Safety engineering and the environment (scqf level 5) dr2 d34
Safety engineering and the environment (scqf level 5) dr2 d34
Ibrahim Khleifat
 
Mohammad Mustafa ( 01001645727) (Autosaved)
Mohammad Mustafa ( 01001645727) (Autosaved)Mohammad Mustafa ( 01001645727) (Autosaved)
Mohammad Mustafa ( 01001645727) (Autosaved)
mohammed mostafa
 
Mohammad Mustafa ( 01001645727) (Autosaved)
Mohammad Mustafa ( 01001645727) (Autosaved)Mohammad Mustafa ( 01001645727) (Autosaved)
Mohammad Mustafa ( 01001645727) (Autosaved)
mohammed mostafa
 
ME-MTT3871 - event
ME-MTT3871 - eventME-MTT3871 - event
ME-MTT3871 - event
Seng Jin Hung (Gale)
 
Ocs training calendar 2022
Ocs training calendar 2022Ocs training calendar 2022
Ocs training calendar 2022
Muanisa Waras
 
Bhagyesh's NIULAB
Bhagyesh's NIULABBhagyesh's NIULAB
Bhagyesh's NIULAB
Bhagyesh Haldankar
 
CURRICULUM_VITAE_BC_Botes dated 8 October 2014 for Maintenance Specialist E I
CURRICULUM_VITAE_BC_Botes dated 8 October 2014 for Maintenance Specialist E  ICURRICULUM_VITAE_BC_Botes dated 8 October 2014 for Maintenance Specialist E  I
CURRICULUM_VITAE_BC_Botes dated 8 October 2014 for Maintenance Specialist E I
Bernardus Cornelius Botes
 
NG3S903 - Electronic Systems - Louise Pennell - Assignment 2 - ESD
NG3S903 - Electronic Systems - Louise Pennell - Assignment 2 - ESDNG3S903 - Electronic Systems - Louise Pennell - Assignment 2 - ESD
NG3S903 - Electronic Systems - Louise Pennell - Assignment 2 - ESD
Chris Francis
 
Bzee presentation VET-Wind Norway
Bzee presentation VET-Wind NorwayBzee presentation VET-Wind Norway
Bzee presentation VET-Wind Norway
Frank Emil Moen
 
dl_catalog_hrREV3
dl_catalog_hrREV3dl_catalog_hrREV3
dl_catalog_hrREV3
Wendi Attaway Morris
 
R011409288E
R011409288ER011409288E
R011409288E
Allen Hsu
 
IRJET - Virtual Lab: Keep Away Physically but Not Technically
IRJET - Virtual Lab: Keep Away Physically but Not TechnicallyIRJET - Virtual Lab: Keep Away Physically but Not Technically
IRJET - Virtual Lab: Keep Away Physically but Not Technically
IRJET Journal
 
Eng Ibrahim Omar
Eng Ibrahim OmarEng Ibrahim Omar
Eng Ibrahim Omar
ibrahim omar
 

Similar to CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS (20)

UET30812 Certificate III in ESI – Distribution Cable Jointing. Australian Qua...
UET30812 Certificate III in ESI – Distribution Cable Jointing. Australian Qua...UET30812 Certificate III in ESI – Distribution Cable Jointing. Australian Qua...
UET30812 Certificate III in ESI – Distribution Cable Jointing. Australian Qua...
 
Certificate of degree
Certificate of degreeCertificate of degree
Certificate of degree
 
Competency of Staff new 4.
Competency of Staff new 4.Competency of Staff new 4.
Competency of Staff new 4.
 
HNS L2 Curriculum.pdf
HNS L2 Curriculum.pdfHNS L2 Curriculum.pdf
HNS L2 Curriculum.pdf
 
Colin Bird. Doosan Babcock. 29th January
Colin Bird. Doosan Babcock. 29th JanuaryColin Bird. Doosan Babcock. 29th January
Colin Bird. Doosan Babcock. 29th January
 
Phase 2 Core Power and Control RoA.3
Phase 2 Core Power and Control RoA.3Phase 2 Core Power and Control RoA.3
Phase 2 Core Power and Control RoA.3
 
NIIT Presentation 2
NIIT Presentation 2NIIT Presentation 2
NIIT Presentation 2
 
Safety engineering and the environment (scqf level 5) dr2 d34
Safety engineering and the environment (scqf level 5) dr2 d34Safety engineering and the environment (scqf level 5) dr2 d34
Safety engineering and the environment (scqf level 5) dr2 d34
 
Mohammad Mustafa ( 01001645727) (Autosaved)
Mohammad Mustafa ( 01001645727) (Autosaved)Mohammad Mustafa ( 01001645727) (Autosaved)
Mohammad Mustafa ( 01001645727) (Autosaved)
 
Mohammad Mustafa ( 01001645727) (Autosaved)
Mohammad Mustafa ( 01001645727) (Autosaved)Mohammad Mustafa ( 01001645727) (Autosaved)
Mohammad Mustafa ( 01001645727) (Autosaved)
 
ME-MTT3871 - event
ME-MTT3871 - eventME-MTT3871 - event
ME-MTT3871 - event
 
Ocs training calendar 2022
Ocs training calendar 2022Ocs training calendar 2022
Ocs training calendar 2022
 
Bhagyesh's NIULAB
Bhagyesh's NIULABBhagyesh's NIULAB
Bhagyesh's NIULAB
 
CURRICULUM_VITAE_BC_Botes dated 8 October 2014 for Maintenance Specialist E I
CURRICULUM_VITAE_BC_Botes dated 8 October 2014 for Maintenance Specialist E  ICURRICULUM_VITAE_BC_Botes dated 8 October 2014 for Maintenance Specialist E  I
CURRICULUM_VITAE_BC_Botes dated 8 October 2014 for Maintenance Specialist E I
 
NG3S903 - Electronic Systems - Louise Pennell - Assignment 2 - ESD
NG3S903 - Electronic Systems - Louise Pennell - Assignment 2 - ESDNG3S903 - Electronic Systems - Louise Pennell - Assignment 2 - ESD
NG3S903 - Electronic Systems - Louise Pennell - Assignment 2 - ESD
 
Bzee presentation VET-Wind Norway
Bzee presentation VET-Wind NorwayBzee presentation VET-Wind Norway
Bzee presentation VET-Wind Norway
 
dl_catalog_hrREV3
dl_catalog_hrREV3dl_catalog_hrREV3
dl_catalog_hrREV3
 
R011409288E
R011409288ER011409288E
R011409288E
 
IRJET - Virtual Lab: Keep Away Physically but Not Technically
IRJET - Virtual Lab: Keep Away Physically but Not TechnicallyIRJET - Virtual Lab: Keep Away Physically but Not Technically
IRJET - Virtual Lab: Keep Away Physically but Not Technically
 
Eng Ibrahim Omar
Eng Ibrahim OmarEng Ibrahim Omar
Eng Ibrahim Omar
 

Recently uploaded

21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
PradeepKumarSK3
 
Quadcopter Dynamics, Stability and Control
Quadcopter Dynamics, Stability and ControlQuadcopter Dynamics, Stability and Control
Quadcopter Dynamics, Stability and Control
Blesson Easo Varghese
 
Metrology Book, Bachelors in Mechanical Engineering
Metrology Book, Bachelors in Mechanical EngineeringMetrology Book, Bachelors in Mechanical Engineering
Metrology Book, Bachelors in Mechanical Engineering
leakingvideo
 
ARITMETICO.pdf xxxxxxxxxxxxxxxxxxxxxxxx
ARITMETICO.pdf  xxxxxxxxxxxxxxxxxxxxxxxxARITMETICO.pdf  xxxxxxxxxxxxxxxxxxxxxxxx
ARITMETICO.pdf xxxxxxxxxxxxxxxxxxxxxxxx
alemaro1123
 
Business Development_ Identifying and Seizing Market Opportunities with Skyle...
Business Development_ Identifying and Seizing Market Opportunities with Skyle...Business Development_ Identifying and Seizing Market Opportunities with Skyle...
Business Development_ Identifying and Seizing Market Opportunities with Skyle...
Skyler Bloom
 
RECENT DEVELOPMENTS IN RING SPINNING.pptx
RECENT DEVELOPMENTS IN RING SPINNING.pptxRECENT DEVELOPMENTS IN RING SPINNING.pptx
RECENT DEVELOPMENTS IN RING SPINNING.pptx
peacesoul123
 
Stiffness Method for structure analysis - Truss
Stiffness Method  for structure analysis - TrussStiffness Method  for structure analysis - Truss
Stiffness Method for structure analysis - Truss
adninhaerul
 
Ludo system project report management .pdf
Ludo  system project report management .pdfLudo  system project report management .pdf
Ludo system project report management .pdf
Kamal Acharya
 
EAAP2023 : Durabilité et services écosystémiques de l'élevage ovin de montagne
EAAP2023 : Durabilité et services écosystémiques de l'élevage ovin de montagneEAAP2023 : Durabilité et services écosystémiques de l'élevage ovin de montagne
EAAP2023 : Durabilité et services écosystémiques de l'élevage ovin de montagne
idelewebmestre
 
Thermodynamics Digital Material basics subject
Thermodynamics Digital Material basics subjectThermodynamics Digital Material basics subject
Thermodynamics Digital Material basics subject
JigneshChhatbar1
 
The world of Technology Management MEM 814.pptx
The world of Technology Management MEM 814.pptxThe world of Technology Management MEM 814.pptx
The world of Technology Management MEM 814.pptx
engrasjadshahzad
 
lecture10-efficient-scoring.ppmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmt
lecture10-efficient-scoring.ppmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmtlecture10-efficient-scoring.ppmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmt
lecture10-efficient-scoring.ppmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmt
RAtna29
 
How to Formulate A Good Research Question
How to Formulate A  Good Research QuestionHow to Formulate A  Good Research Question
How to Formulate A Good Research Question
rkpv2002
 
Online airline reservation system project report.pdf
Online airline reservation system project report.pdfOnline airline reservation system project report.pdf
Online airline reservation system project report.pdf
Kamal Acharya
 
CGR-Unit-1 Basics of Computer Graphics.pdf
CGR-Unit-1 Basics of Computer Graphics.pdfCGR-Unit-1 Basics of Computer Graphics.pdf
CGR-Unit-1 Basics of Computer Graphics.pdf
Rugved Collection
 
OSHA LOTO training, LOTO, lock out tag out
OSHA LOTO training, LOTO, lock out tag outOSHA LOTO training, LOTO, lock out tag out
OSHA LOTO training, LOTO, lock out tag out
Ateeb19
 
Best Practices of Clothing Businesses in Talavera, Nueva Ecija, A Foundation ...
Best Practices of Clothing Businesses in Talavera, Nueva Ecija, A Foundation ...Best Practices of Clothing Businesses in Talavera, Nueva Ecija, A Foundation ...
Best Practices of Clothing Businesses in Talavera, Nueva Ecija, A Foundation ...
IJAEMSJORNAL
 
DBMS Commands DDL DML DCL ENTITY RELATIONSHIP.pptx
DBMS Commands  DDL DML DCL ENTITY RELATIONSHIP.pptxDBMS Commands  DDL DML DCL ENTITY RELATIONSHIP.pptx
DBMS Commands DDL DML DCL ENTITY RELATIONSHIP.pptx
Tulasi72
 
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in CityGirls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
sunnuchadda
 
Disaster Management and Mitigation presentation
Disaster Management and Mitigation presentationDisaster Management and Mitigation presentation
Disaster Management and Mitigation presentation
RajaRamannaTarigoppu
 

Recently uploaded (20)

21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
21EC63_Module1B.pptx VLSI design 21ec63 MOS TRANSISTOR THEORY
 
Quadcopter Dynamics, Stability and Control
Quadcopter Dynamics, Stability and ControlQuadcopter Dynamics, Stability and Control
Quadcopter Dynamics, Stability and Control
 
Metrology Book, Bachelors in Mechanical Engineering
Metrology Book, Bachelors in Mechanical EngineeringMetrology Book, Bachelors in Mechanical Engineering
Metrology Book, Bachelors in Mechanical Engineering
 
ARITMETICO.pdf xxxxxxxxxxxxxxxxxxxxxxxx
ARITMETICO.pdf  xxxxxxxxxxxxxxxxxxxxxxxxARITMETICO.pdf  xxxxxxxxxxxxxxxxxxxxxxxx
ARITMETICO.pdf xxxxxxxxxxxxxxxxxxxxxxxx
 
Business Development_ Identifying and Seizing Market Opportunities with Skyle...
Business Development_ Identifying and Seizing Market Opportunities with Skyle...Business Development_ Identifying and Seizing Market Opportunities with Skyle...
Business Development_ Identifying and Seizing Market Opportunities with Skyle...
 
RECENT DEVELOPMENTS IN RING SPINNING.pptx
RECENT DEVELOPMENTS IN RING SPINNING.pptxRECENT DEVELOPMENTS IN RING SPINNING.pptx
RECENT DEVELOPMENTS IN RING SPINNING.pptx
 
Stiffness Method for structure analysis - Truss
Stiffness Method  for structure analysis - TrussStiffness Method  for structure analysis - Truss
Stiffness Method for structure analysis - Truss
 
Ludo system project report management .pdf
Ludo  system project report management .pdfLudo  system project report management .pdf
Ludo system project report management .pdf
 
EAAP2023 : Durabilité et services écosystémiques de l'élevage ovin de montagne
EAAP2023 : Durabilité et services écosystémiques de l'élevage ovin de montagneEAAP2023 : Durabilité et services écosystémiques de l'élevage ovin de montagne
EAAP2023 : Durabilité et services écosystémiques de l'élevage ovin de montagne
 
Thermodynamics Digital Material basics subject
Thermodynamics Digital Material basics subjectThermodynamics Digital Material basics subject
Thermodynamics Digital Material basics subject
 
The world of Technology Management MEM 814.pptx
The world of Technology Management MEM 814.pptxThe world of Technology Management MEM 814.pptx
The world of Technology Management MEM 814.pptx
 
lecture10-efficient-scoring.ppmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmt
lecture10-efficient-scoring.ppmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmtlecture10-efficient-scoring.ppmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmt
lecture10-efficient-scoring.ppmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmt
 
How to Formulate A Good Research Question
How to Formulate A  Good Research QuestionHow to Formulate A  Good Research Question
How to Formulate A Good Research Question
 
Online airline reservation system project report.pdf
Online airline reservation system project report.pdfOnline airline reservation system project report.pdf
Online airline reservation system project report.pdf
 
CGR-Unit-1 Basics of Computer Graphics.pdf
CGR-Unit-1 Basics of Computer Graphics.pdfCGR-Unit-1 Basics of Computer Graphics.pdf
CGR-Unit-1 Basics of Computer Graphics.pdf
 
OSHA LOTO training, LOTO, lock out tag out
OSHA LOTO training, LOTO, lock out tag outOSHA LOTO training, LOTO, lock out tag out
OSHA LOTO training, LOTO, lock out tag out
 
Best Practices of Clothing Businesses in Talavera, Nueva Ecija, A Foundation ...
Best Practices of Clothing Businesses in Talavera, Nueva Ecija, A Foundation ...Best Practices of Clothing Businesses in Talavera, Nueva Ecija, A Foundation ...
Best Practices of Clothing Businesses in Talavera, Nueva Ecija, A Foundation ...
 
DBMS Commands DDL DML DCL ENTITY RELATIONSHIP.pptx
DBMS Commands  DDL DML DCL ENTITY RELATIONSHIP.pptxDBMS Commands  DDL DML DCL ENTITY RELATIONSHIP.pptx
DBMS Commands DDL DML DCL ENTITY RELATIONSHIP.pptx
 
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in CityGirls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
Girls Call Chennai 000XX00000 Provide Best And Top Girl Service And No1 in City
 
Disaster Management and Mitigation presentation
Disaster Management and Mitigation presentationDisaster Management and Mitigation presentation
Disaster Management and Mitigation presentation
 

CompEx~Manual~1210 (2).pdf COMPEX GAS AND VAPOURS

  • 1. ASET International Oil & Gas Training Academy Comp Ex Hazardous Areas Course March 2010 Revision
  • 3. Ex Facility March 2010 © 2 National Training and Certification of Personnel for Work on Electrical Apparatus for Use in Potentially Hazardous Atmospheres This package has been compiled with information gathered from current standards and the authors will not be held responsible for any inaccuracies found therein. Acknowledgements: The production of this document would not have been possible without the much appreciated assistance from the following authorities and, therefore, the authors of the document wish to thank and gratefully acknowledge all those who provided material and advice for the production of the package, particularly the following: The British Standards Institute James Scott Ltd, Aberdeen, Scotland Weidmuller (Klippon Products) Ltd, Sheerness, Kent Hawke Cable Glands Ltd, Ashton-under-Lyne, Lancashire Hecagon Technology Ltd, Aylesbury, Buckinghamshire Measurement Technology Ltd, Luton, Bedfordshire Brook Hansen, Huddersfield, West Yorkshire The Design and Presentation Team of Aberdeen College, including all staff at the Altens Centre. The BASEEFA Crown mark shown in this document is the property of the Health and Safety Executive and should not be interpreted to convey certification. The marks have been reproduced with the kind permission of the EECS (HSE). Copyright of Document: No part of this document may be reproduced, stored in a retrieval system or transmitted in any form by any means. i.e. electronic, electrostatic, magnetic media, mechanical, photocopying, recording or otherwise without the permission in writing of the appointed representative of Aberdeen College.
  • 4. Ex Facility March 2010 © 3 Introduction About the ‘Ex’ Facility Ex training courses have been run in Aberdeen College since 1990 and have developed to the level of sophistication we have today. In its present form the CompEx course has been in operation since August 1994 and has been designed and constructed specifically for the National Training of personnel who work with electrical installations and plant in hazardous and/or potentially explosive environments. The facility includes both classroom and simulated work areas, these being designed to give as realistic site conditions as is possible to achieve. The practical work candidates are required to carry out will take place in these simulated areas and this is intended to make the candidates feel they are working under site conditions. Approximately half of the week will be spent in the classroom where the ‘job knowledge’ elements of the course will be delivered by means of presentations incorporating lectures, demonstrations, and photographic slides of good and bad practice on apparatus. The remaining time will be spent on Competence Validation Testing in the simulated hazardous areas. The tests are nationally set for Ex training. The Outcome The objective of the training is to introduce the candidate to operating procedures and techniques and to give candidates and their employer’s confidence that the candidates are competent to work on electrical apparatus in hazardous or potentially explosive environments. The competence laid down nationally by industry and through this will help make your industry a safer one. About the Programme The need for training in these areas of work is self evident in that the safe operation of electrical equipment in hazardous areas is paramount. It is extremely important for all personnel who operate in these conditions to be competent in the correct techniques and operational procedures. This can best be achieved by means of training by skilled staff in an environment as close to the ‘real thing’ as possible. In addition to this, the job knowledge developed through the course must be put into operation in the actual working situation so that the levels of expertise are increased through experience. The Design of the Programme The program is dived into two halves, namely: a. Job Knowledge b. Competence Validation Testing (CVT) The ‘job knowledge’ component takes place during the first half of the week and provides the information and experience you need to tackle the CVT’S.
  • 5. Ex Facility March 2010 © 4 Selection, Installation, and Maintenance of Electrical Apparatus for use in Hazardous Locations. Units: 1) General principles (a) Nature of flammable materials (b) gas grouping (c) basic principles of area classification (d) temperature codes (e) ingress protection 2) Standards, Certification and Marking 3) Flameproof Ex d 4) Increased Safety Ex e 5) Type ‘n’ protection 6) Pressurisation Ex p 7) Intrinsic Safety Ex i 8) Other methods of protection, Ex o, Ex q, Ex m & Ex s 9) Combined (Hybrid) methods of protection 10) Wiring Systems 11) Inspection & Maintenance to BS EN60079-17 12) Sources of ignition 13) Induction to Competence Validation Testing 14) Permit to Work System and Safe Isolation Appendix 1 Data for flammable materials for use with electrical equipment, ref BS5345: Part 1: General recommendations. Appendix 2 Self assessment project and apparatus label reading.
  • 6. Ex Facility March 2010 © 5 Course outline The training scheme The training scheme is arranged to prepare candidates for the assessment programme which comprises four discreet Competence Validation Tests (CVT’s) offered as complimentary pairs. The four CVT’s are as follows: EX01 Preparation & Installation of Ex d, Ex e, Ex n and Ex p Systems EX02 Inspection & Maintenance of Ex d, Ex e, Ex n and Ex p Systems EX03 Preparation & Installation of Ex i Systems EX04 Inspection & Maintenance of Ex i Systems Job knowledge The classroom (job knowledge) part of the training scheme consists of 12 Units which apply to the four CVT’s as illustrated below. Unit 1: General principles Unit 2: Standards, Certification and Marking Unit 3: Flameproof Ex d EX01 & EX02 EX01 & EX02 EX01 & EX02 EX03 & EX04 EX03 & EX04 Unit 4: Increased Safety Ex e Unit 5: Type ‘n’ protection Unit 6: Pressurisation Ex p EX01 & EX02 EX01 & EX02 EX01 & EX02 (Written Assessment) Unit 7: Intrinsic Safety Ex i Unit 8: Other methods of protection Unit 9: Combined (Hybrid) protection methods EX03 & EX04 (Written Assessment) EX01 & EX02 Unit 10: Wiring Systems Unit 11: Inspection & Maintenance to BS EN60079-17 Unit 12: Sources of ignition EX01 & EX02 EX01 & EX02 EX01 & EX02 EX03 & EX04 EX03 & EX04 EX03 & EX04 Unit 13: Induction to Competence Validation Testing Unit 14: Permit to Work and Safe Isolation EX01 & EX02 EX01 & EX02 EX03 & EX04 EX03 & EX04
  • 7. Ex Facility March 2010 © 6 The CVT’s are a series of practical tests which you will undertake within the simulated work areas during the second half of the programme. On successful completion of these tests you will be awarded a Certificate of Core Competence which will indicate the areas the awarding body, Joint Training Ltd. (JTL), has deemed you are competent. During the final half-day of the programme you are required to sit written assessments in the form of multi-choice papers which are related to the practical CVT assessments. The staff who are involved in monitoring the various assessments are present only as observers and not to prompt or offer technical assistance. Their observations of your work is recorded on Nationally written checklists which are processed outwith the Centre and your results cannot be determined until this process is complete. Manual Units and applicable CVT’s Unit 1: General Principles EX01, EX02, EX03 & EX04 Unit 2 : Standards, Certification & Marking EX01, EX02, EX03 & EX04 Unit 3: Flameproof Ex d EX01 & EX02 Unit 4: Increased Safety Ex e EX01 & EX02 Unit 5: Type ‘n’ Protection EX01 & EX02 Unit 6: Pressurisation Ex p EX01 & EX02 (Written Assessment) Unit 7: Intrinsic Safety E x i EX03 & EX04 Unit 8: Other methods of Protection (Written Assessment) Unit 9: Combined (Hybrid) Protection Methods EX01 & EX02 Unit 10: Wiring Systems EX01, EX02, EX03 & EX04 Unit 11: Inspection & Maintenance to BS EN60079-17 EX01, EX02, EX03 & EX04 Unit 12: Sources of Ignition EX01, EX02. EX03 & Ex04 Unit 13: Induction to Competence Validation Testing EX01, EX02. EX03 & Ex04 Unit 14: Permit to Work EX01, EX02. EX03 & Ex04 Course programme The following course programme is for illustration purposes only, particularly for the CVT assessments, and can change according to candidate numbers attending the course. A programme for the CVT assessments will be compiled during the week.
  • 8. Ex Facility November 2008 7 Programme: Electrical Apparatus in Potentially Hazardous Areas 5 – Day Programme y a d i r F y a d s r u h T y a d s e n d e W y a d s e u T y a d n o M r e t n e s e r P 8:30 12:30 Course registration and induction Unit 1: General Principles Unit 10: Wiring systems & Demonstration of compound filled gland and diaphragm seal gland assembly Unit 2: Standards: certification & marking Unit 4: Increased Safety Ex e Unit 5: Type ‘n’ Protection Unit 6: Pressurisation Ex p Unit 7: Intrinsic Safety E x i EX01 CVT Inspection & Maintenance of d, e & n apparatus Candidates 7-12 EX02 CVT Preparation & Installation of d, e & n apparatus Candidates 1-6 EX03 CVT Inspection & Maintenance of d, e & n apparatus Candidates 7-12 EX04 CVT Preparation & Installation of d, e & n apparatus Candidates 1-6 k a e r B k a e r B k a e r B k a e r B k a e r B 13:00 17:00 Unit 3: Flameproof Ex d Unit 10: Practical exercise: Assembly of compound filled and diaphragm seal type glands. Unit 8: Other methods of protection Unit 9: Combined (Hybrid) methods of protection Unit 11: Inspection & Maintenance Unit 13: Introduction to CVT’s Unit 14: Work permit EX01 CVT Preparation & Installation of d, e & n apparatus Candidates 1-6 EX02 CVT Inspection & Maintenance of d, e & n apparatus Candidates 7- 12 EX03 CVT Preparation & Installation of d, e & n apparatus Candidates 1-6 EX04 CVT Inspection & Maintenance of d, e & n apparatus Candidates 7-12 Job Knowledge assessment EX01, EX02, EX03 & EX04 Multi-choice examination
  • 10. March 2010 © 2 Objectives: On completion of this unit, ‘General Principles’, you should know: a. The nature of flammable materials with regard to ‘explosive limits’ (LEL/UEL), ‘flashpoint’, ‘ignition’ temperature’, the effect of ‘oxygen enrichment’ and ‘relative density’. b. The basic principles of area classification. c. The Grouping of gases according to ‘minimum ignition energy’ (MIE) and ‘maximum experimental safe gap’ (MESG). d. Appropriate T-ratings for apparatus relative to the ignition temperature of a given flammable material. e. The levels of ‘ingress protection’.
  • 11. March 2010 © 3 General Principles Nature of Flammable Materials Fire Triangle The fire triangle represents the three elements which must be present before combustion can take place. Each point of the triangle represents one of the essential elements which are: 1. Fuel: This can be in the form of a gas, vapour, mist or dust 2. Oxygen: Plentiful supply since there is approximately 21% by volume in air. 3. Source of Ignition: This can be an arc, spark, naked flame or hot surface. Combustion will take place if all three elements, in one form or another, are present, the gas/air mixture is within certain limits and the source of ignition has sufficient energy. The removal of one element is sufficient to prevent combustion, as is the isolation or separation of the source of ignition from the gas/air mixture. These are two techniques used in explosion protected equipment. Other protection techniques allow the three elements to co- exist and either ensures that the energy of the source of ignition is maintained below specific values, or allows an explosion to take place and contains it within a robust enclosure. These techniques are addressed in the various sections of this manual. Gas or vapour Oxygen ( 21% in air ) Source of ignition
  • 12. March 2010 © 4 Flammable (Explosive) Limits Combustion will only occur if the flammable mixture comprising fuel, in the form of a gas or vapour, and air are within certain limits. These limits are the ‘lower explosive limit’ (LEL), and the ‘upper explosive limit’ (UEL), and between these limits is known as the flammable range. An every day example of this is the carburettor of a petrol engine, which must be tuned to a particular point between these limits in order that the engine may function efficiently. Lower Explosive Limit: When the percentage of gas, by volume, is below this limit the mixture is too weak to burn, i.e. insufficient fuel and/or too much air. Upper Explosive Limit: When the percentage of gas, by volume, is above this limit the mixture is too rich to burn, i.e. insufficient air and/or too much fuel. The flammable limits of some materials are given below. Material LEL % by Volume UEL % by Volume Propane 1.7 10.9 Methane 4.4 17 Ethylene 2.3 36 Hydrogen 4 77 Acetylene 2.3 100 Diethyl Ether 1.7 36 Kerosene 0.7 5 Carbon Disulphide 0.6 60
  • 13. March 2010 © 5 Flammable (Explosive) Limits (continued) Different gases or vapours have different flammable limits and the greater the difference between the LEL and the UEL, known as the flammable range, the more dangerous the material. An explosive (flammable) atmosphere, therefore, only exists between these limits. Operational safety with flammable mixtures above the UEL is possible, but is not a practical proposition. It is more practical to operate below the LEL. Sources of Ignition Sources of ignition are many and varied and include: a. Electrical arc/sparks b. Frictional sparks c. Hot surfaces d. Welding activities e. Cigarettes f. Static discharges g. Batteries h. Exhausts of combustion engines i. Thermite action j. Sodium exposed to water k. Pyrophoric reaction l. Chemical reactions m. Lightning strikes The source of ignition as far as this text is concerned is primarily electrical equipment.
  • 14. March 2010 © 6 Flashpoint By definition flashpoint is: ‘the lowest temperature at which sufficient vapour is given off a liquid, to form a flammable mixture with air that can be ignited by an arc, spark or naked flame’. Typical values are given below. Material Flashpoint °C Propane -104 Ethylene -120* Hydrogen -256* Acetylene -82* Diethyl Ether -45 Kerosene 38 Carbon Disulphide -95* * Values obtained form a source other than PD IEC60079-20 The flashpoint of a material gives an indication of how readily that material will ignite in normal ambient temperatures. Reference to the tables of flammable materials from PD IEC60079-20 (see Appendix 1) reveals that different materials have different flashpoints, which vary from well below to well above 0°C. Materials with high flashpoints should not be overlooked as a potential hazard since exposure to hot surfaces can allow a flammable mixture to form locally. Furthermore, if a flammable material is discharged under pressure from a jet, its flashpoint may be reduced. Amount of vapour released dependent on temperature
  • 15. March 2010 © 7 Flashpoint (continued) Kerosene: Flashpoint 38°C At 38°C “Ignition” At 37°C Insufficient vapour given off At 0°C Negligible vapour given off
  • 16. March 2010 © 8 Ignition Temperature Ignition temperature is defined as: ‘the minimum temperature at which a flammable material will spontaneously ignite’. Ignition temperature, formerly known as auto-ignition temperature, is an important parameter since many industrial processes generate heat. Careful selection of electrical equipment will ensure that the surface temperature produced by the equipment, indicated by the T-rating, will not exceed the ignition temperature of the flammable atmosphere which may be present around the equipment. Typical values of ignition temperature are: Material Ignition Temperature °C Propane 470 Methane 537 Ethylene 425 Hydrogen 560 Acetylene 305 Diethyl Ether 160 Kerosene 210 Carbon Disulphide 95
  • 17. March 2010 © 9 Oxygen Enrichment The normal oxygen content in the atmosphere is around 20.95%, and if a given location has a value which exceeds this it is deemed to be oxygen enriched. Typical examples of where oxygen enrichment may occur are gas manufacturing plants, hospital operating theatres, and where oxy-acetylene equipment is used. Oxygen enrichment has three distinct disadvantages. First of all, it can lower the ignition temperature of flammable materials as shown in the table below. Air Increased Oxygen Material Ignition Temperature °C Ignition Temperature °C Hydrogen sulphide 260 220 Acetylene 305 296 Ethane 512 506 Secondly, oxygen enrichment significantly raises the upper explosive limit (UEL) of the majority of gases and vapours, thereby widening their flammable range. This is illustrated in the following table. Air Increased Oxygen Material LEL % UEL % LEL % UEL % Methane 5 15 5.2 79 Propane 2.2 9.5 2.3 55 Hydrogen 4 75 4.7 94 Thirdly, oxygen enrichment of a flammable atmosphere can allow it to be ignited with much lower values of electrical energy. Explosion protected equipment will have been tested in normal atmospheric conditions and, therefore, the safety of such equipment in an oxygen enriched atmosphere cannot be assured because of the modified nature of the flammable mixture. * All values obtained from a source other than PD IEC60079-20 * All values obtained from a source other than PD IEC60079-20
  • 18. March 2010 © 10 Density If a flammable material is released, it is important to know whether the material will rise or fall in the atmosphere. The different flammable materials are compared with air and allocated a number to denote their relative density with air. Since air is the reference, its relative density is 1 so that for a material twice as heavy as air, its relative density will be 2. Therefore, materials with a relative density less than unity will rise in the atmosphere, and those greater than unity will fall in the atmosphere. Materials which rise in the atmosphere can collect in roof spaces, and those which fall, such as butane or propane, can drift along at ground level and possibly into a non-hazardous location, or may collect in locations lower than ground level without ever dispersing. Such locations should be well ventilated in order to avoid ignition due to a stray spark or a discarded cigarette. Knowledge of where a flammable material will collect ensures that gas detectors when fitted will be located at the correct level and ventilation is directed accordingly. <1 >1 Material Relative vapour density Air 1 Propane 1.56 Methane 0.55 Ethylene 0.97 Hydrogen 0.07 Acetylene 0.9 Diethyl Ether 2.55 Kerosene 4.5* Carbon Disulphide 2.64 * Value obtained from a source other than PD IEC60079-20
  • 19. March 2010 © 11 Area Classification An hazardous area is defined as: ‘An area in which an explosive gas atmosphere is present, or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of apparatus.’ A non-hazardous area is defined as: ‘An area in which an explosive gas atmosphere is not expected to be present in quantities such as to require special precautions for the construction, installation and use of apparatus.’ Zones Zoning is a means of representing the frequency of the occurrence and duration of an explosive gas atmosphere based on the identification and consideration of each and every source of release in the given areas of an installation. Zoning will have a bearing on, and simplify the selection of, the type of explosion protected equipment which may be used. Hazardous areas are, therefore, divided into three Zones which represent this risk in terms of the probability, frequency and duration of a release. The three Zones, as defined in BS EN60079-10-1: Electrical apparatus for explosive gas atmospheres, Part 10. Classification of hazardous areas, are as follows: Zone 0 - An area in which an explosive gas atmosphere is present continuously or for long periods or frequently. Zone 1 - An area in which an explosive gas atmosphere is likely to occur in normal operation occasionally. Zone 2 - An area in which an explosive gas atmosphere is not likely to occur in normal operation but, if it does occur, will persist for a short period only. Although not specified in IEC 60079-10-1, but quoted in API RP 505**, the duration of a gas release, or a number of gas releases, on an annual basis (one year comprises circa 8760 hours), for the different Zones is as follows. Zone 2 - 0 – 10 hours Zone 1 - 10 – 1000 hours Zone 0 - over 1000 hours ** The above document, API RP 505, is published by the American Petroleum Institute and entitled “Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Zone 0, Zone 1, and Zone 2.
  • 20. March 2010 © 12 Area Classification (continued) Zone representation for ‘Area Classification Diagrams’ In accordance with BS EN60079-10, the illustrations below are the preferred method for representing the various zones in an hazardous area.
  • 21. March 2010 © 13 Area Classification (continued) Fixed Roof Storage Tank Distances: ‘a’ 3m from vent opening ‘b’ 3m above the roof ‘c’ 3m horizontally from the side of the tank b c a Zone 2 Zone 1 Zone 0 Sump: Zone 1
  • 22. March 2010 © 14 Area Classification (continued) Sources of Release Welded pipe joint: ( Non-hazardous ) Flanged joint: ( Zone 2) Pump gland: ( Zone 2 or Zone 1 depending on the quality of the seal ) Space above liquid in a closed tank: ( Zone 0)
  • 23. March 2010 © 15 Gas / Apparatus Grouping In the IEC system, the group allocation for surface and underground (mining) industries are separate. Group I is reserved for the mining industry, and Group II which is subdivided into IIC, IIB and IIA for surface industries. The representative gases for the sub-groups are shown in the table below. Two methods have been used to ‘group’ these flammable materials according to the degree of risk they represent when ignited. One method involved determining the minimum ignition energy which would ignite the representative gases. The values obtained are relevant to Intrinsically Safe apparatus. In the table below it can be seen that for Group II, hydrogen and acetylene are the most easily ignited and propane the least easily ignited. The other method involved tests using, for example, a special flameproof enclosure in the form of an 8 litre sphere which was situated inside a gas-tight enclosure. Both halves of the sphere had 25mm flanges and a mechanism enabled the gap dimension between the flanges to be varied. During tests, the area inside and outside the sphere were occupied with a gas in its most explosive concentration in air and, by means of a spark-plug the gas inside the sphere was ignited. The maximum dimension between the flanges, which prevented ignition of the gas/air mixture, is known as the ‘maximum experimental safe gap’ (MESG), and the values for the representative gases are shown in the table below. The more dangerous a gas, the tighter the gap at the flanges has to be. It is important to note that the MESG values are not used for the design of Flameproof apparatus, only the maximum working gaps. The table also shows that these flammable materials fall into the same order for both tests, i.e. in a relative context, hydrogen and acetylene present the most risk and propane the least risk in terms of ‘minimum ignition energy’ and ‘MESG’. Gas Group Representative Gas MESG (mm) Maximum Working Gap (mm) Minimum Ignition Energy (μJ) I Methane (Firedamp) 1.14 0.5 260 IIA Propane 0.91 0.4 160 IIB Ethylene 0.65 0.2 95 Hydrogen 0.28 IIC Acetylene 0.37 0.1 20 Note: Apparatus other than flameproof or intrinsic safety, which has no sub-division letter (A, B or C) after the group II mark, may be used in all hazards. Apparatus marked IIxxxxx: xxxxx represents the chemical formula or name of a flammable material, and apparatus marked in this way may only be used in that hazard.
  • 24. March 2010 © 16 Gas / Apparatus Grouping (continued) The sub-group marking is one of the important considerations during the selection process of explosion protected apparatus. For example, apparatus marked IIA can only be used in IIA hazards such as propane, it cannot be used in IIB or IIC hazards. Apparatus marked IIB can be used in IIB and IIA hazards but not IIC hazards. Apparatus marked IIC can be used in all hazards. Apparatus for determination of M.E.S.G
  • 25. March 2010 © 17 Gas / Apparatus Grouping (continued) Comparison of BS 229 and IEC BS 229 is an old British Standard, which has now been withdrawn, but electrical apparatus was still manufactured to this standard up until several years ago. Apparatus manufactured to BS 229 has sub-group markings which are different to those of the IEC system and the comparison is shown in the table below. The introduction of the ATEX Directives after 30 June 2003 has caused manufacturers to discontinue the production of apparatus to this standard, but apparatus already in use will be unaffected. BS 229 Representative Gas IEC 1 Methane I 2 Propane IIA 3a Ethylene 3b Coal Gas IIB 4 Hydrogen & Acetylene IIC
  • 26. March 2010 © 18 Temperature Classification Approved electrical equipment must be selected with due regard to the ignition temperature of the flammable gas or vapour which may be present in the hazardous location. Apparatus will usually be marked with one of the temperature classes shown in the table below. The temperature class indicates the maximum temperature the surfaces of an enclosure, which are exposed to a flammable gas, must not exceed during normal or specified fault conditions. Temperature Classes T - Class Maximum Surface Temperature T1 450°C T2 300°C T3 200°C T4 135°C T5 100°C T6 85°C In the table below, it will be observed that for each material, the T-rating temperature is below the ignition temperature of the flammable material. Moreover, the T-rating temperatures are based on a maximum ambient rating of 40°C as far as the UK is concerned. For example, apparatus classified T5, based on a 40°C ambient rating, will have a maximum permitted temperature rise of 60°C. In order to avoid infringement of the apparatus certification, the ambient rating must be compatible with environmental ambient temperatures, and the temperature rise not exceeded. This is demonstrated on page 20. A further consideration is apparatus for use in hotter climates, typically found in Middle and Far Eastern countries, which will usually require ambient ratings greater than 40°C. Apparatus for use in colder (arctic) climates will require a much lower limit to the ambient temperature range which may be as low as -50°C. Material Ignition Temperature T-Rating Methane 537°C T1 (450°C) Ethylene 425°C T2 (300°C) Cyclohexane 259°C T3 (200°C) Diethyl Ether 160°C T4 (135°C) T5 (100°C) Carbon Disulphide 95°C T6 (85°C)
  • 27. March 2010 © 19 Temperature Classification (continued) -2 -2
  • 28. March 2010 © 20 Ingress Protection Enclosures of electrical equipment are classified according to their ability to resist the ingress of solid objects and water by means of a system of numbers known as the ‘International Protection (IP) Code’. This code, which is not always marked on apparatus, consists of the letters IP followed by two numbers, e.g. IP56. The first number, in the range 0-6, indicates the degree of protection against solid objects, and the higher the number the smaller the solid object that is prevented from entering the enclosure. Zero (0) indicates no protection and 6 indicate the apparatus is dust-tight. The second number, ranging from 0-8, identifies the level of protection against water entering the enclosure, i.e. 0 indicates than no protection is afforded, and 8 that the apparatus can withstand continuous immersion in water at a specified pressure. An abridged version of the full table is shown below. Solid Objects Water First Numeral Level of Protection Second Numeral Level of Protection 0 No protection 0 No protection 1 Protection against objects greater than 50 mm 1 Protection against drops of water falling vertically 2 Protection against objects greater than 12 mm 2 Protection against drops of water when tilted up to 15° 3 Protection against objects greater than 2.5 mm 3 Protection against sprayed water up to 60° 4 Protection against objects greater than 1.0 mm 4 Protection against splashed water from any direction 5 Dust-protected 5 Protection against jets of water from any direction 6 Dust-tight 6 Protection against heavy seas - deck watertight 7 Protection against immersion in water 1m in depth and for a specified time 8 Protection against indefinite immersion in water at a specified depth
  • 30. March 2010 © 2 Objectives: On completion of this unit, ‘Standards, Certification and Marking’, you should know: a. Current British, European and International Standards and also relevant older British Standards and Codes of Practice. b. The certification process for explosion protected apparatus. c. The methods of marking explosion protected apparatus. d. The basic requirements of the ATEX Directives. e. The correlation between the ATEX categories and Equipment Protection Levels (EPL’s)
  • 31. March 2010 © 3 Standards, Certification and Marking Introduction There are many industries involved in the process of hazardous materials, and these include chemical plants, oil refineries, gas terminals and offshore installations. These industries rely heavily on electrical energy to power, for example, lighting, heating and rotating electrical machines. The safe use of electrical energy in the hazardous locations of these industries can only be achieved if tried and tested methods of explosion protection are implemented and to this end, the organisations involved in the writing of standards, testing and certification of equipment have a very important role to play. Since the early 1920’s, many standards have evolved as a result of careful research, often prompted by incidents such as the Senghennydd colliery disaster in 1913 in which 439 miners lost their lives. The cause at that time was not fully understood but after investigation, was thought to have been due to an electrical spark igniting methane (firedamp) present in the atmosphere. Other disasters include Abbeystead Water Pumping Station in which 16 people lost their lives, once again due to the electrical ignition of methane gas, Flixborough where an explosion killed 28 people due to ignition of a massive release of cyclohexane, and more recently Piper Alpha in the North Sea in which 167 men lost their lives. Construction of equipment to relevant standards coupled with testing by an independent certification body will ensure that the equipment is suitable for its intended purpose. Explosion protected equipment may be constructed in accordance with relevant standards, but the integrity of such equipment will only be preserved if it is selected, installed and maintained in accordance with the manufacturers recommendations. Guidance in this respect has been provided for many years by the UK Code of Practice BS 5345, but this document has been superseded by a new series of five separate standards based on the IEC 60079 series of International standards. These five documents apply to explosion protected equipment/systems in all countries in the EU and cover, (1) selection and installation of equipment, (2) classification of hazardous areas, (3) inspection and maintenance, (4) repair of explosion protected equipment, and (5) data for flammable gases provided by an IEC document (See lower table on page 13). The BS EN60079 standards are identical to the IEC60079 standards. Although BS 5345 has been withdrawn, it nevertheless remains a source of information for older installations, but applies to the UK only with regard to the EU. In the United Kingdom, manufacturing and testing standards are published by an organisation known as the British Standards Institute (BSI). With regard to the European Community, the organisation which publishes harmonised standards for its member nations is the European Committee for Electrotechnical Standardisation (CENELEC) and, with global harmonisation of standards the ultimate aim, the International Electrotechnical Commission (IEC) publishes standards for this purpose. Historically, equipment designs are evaluated and prototypes tested by independent organisations, one of which was formerly known as ‘British Approvals Service for Electrical Equipment in Flammable Atmospheres (BASEEFA), but was later known as ‘Electrical Equipment Certification Service (EECS)’. The acronym BASEEFA, which has been closely associated with explosion protected equipment for many years, was retained by EECS for certification marking purposes. EECS, which was part of the Health and Safety Executive (HSE), also published standards for special applications. EECS, however, closed
  • 32. March 2010 © 4 for business in September 2002, but encouraged by several major customers, former staff established an independent organisation known as Baseefa (2001) Ltd, and became simply Baseefa Ltd. two-years later. Having traded since March 2002, Baseefa Ltd. became an EU Notified Body (NB) in June 2002 and was allocated the NB Number 1180. With the introduction of the ATEX Directives, which become mandatory after 30 June 2003, a procedure for the evaluation of equipment for compliance with the ATEX directives was implemented. This procedure involves a series of modules, listed on page 5, covering the design, quality control and production phases for equipment, which are audited by a Notified Body. A Notified Body is an independent organisation that has been assessed and accredited by a national body (United Kingdom Accreditation Service, UKAS, in the UK) as having the expertise to operate as a Notified Body in accordance with the directives with regard to conformity assessment of products. A Notified Body has been notified to the European Commission by its member state Notified Bodies have their own unique NB number, which will be marked on the certification labels of ATEX compliant apparatus. Other Notified Bodies in the UK include SIRA Certification Service, NB Number 0518, and ITS Testing and Certification Ltd., NB Number 0359 and many others throughout the EU. Notified bodies may require the services of other organisations for testing product prototypes. ATEX Directives On the 12 June 1989 a Framework Directive 89/391/EEC was adopted by the European Commission the objective being to establish a basis for improving the safety of employees in the workplace. Supplementary directives namely, 94/9/EC, introduced under Article 100a of the Treaty of Rome and now known as ATEX 95, and 99/92/EC, now ATEX 137, address equipment use and safety in hazardous areas. ATEX 95 is the product directive and ATEX 137 is the workplace directive. Both these directives, unlike previous directives, establish a New Approach in that they are mandatory by law rather than advisory. ATEX 95, the product directive, mandatory from 01 July 2003, requires all new equipment, which includes not only electrical equipment but also mechanical (non-electrical) equipment, e.g. pumps, gearboxes etc, and protective systems for use in potentially explosive atmospheres, placed on the market of the European Community for the first time to be manufactured in compliance with the directive. Equipment from out-with the EU, whether new or second hand, imported into the European Community and placed on the market for the first time must also be in compliance with the directive. ATEX 95 applies to the design requirements of equipment and hence concerns mainly the manufacturer and supplier but availability of spare parts and items held in stock would be of concern to equipment users. Therefore, in order to comply with ATEX 95, products must satisfy the Essential Health & Safety Requirements (EHSR’s) specified in the annexes of the Directives, with regard to the inherent risks associated with the product for the protection of the public. This is usually achieved by compliance with relevant harmonised standards, and although it is possible to achieve compliance by means other than the harmonised standards, difficulty would arise installing, inspecting and repairing such equipment to the BS EN60079 standards 14, 17 & 19. Subject to a successful Conformity Assessment, the product can display the CE mark which indicates compliance with the ATEX Directive. ATEX 137, the user directive, became fully mandatory from 01 July 2006 and places responsibilities on employers to provide a safe working environment for employees.
  • 33. March 2010 © 5 CE Conformity Assessment Modules The Conformity Assessment involves a series of Basic Modules which are listed in the table below and their application in the subsequent simplified flow chart. A Internal control of production Covers internal design and production control. Does not require the involvement of a notified body. B EC type-examination Covers the design phase, the EC type-examination being issued by a notified body. Has to be followed by a module for assessment during the production phase. C Conformity to type Covers the production phase after module B. This module confirms conformity of the product with that described in the EC examination certificate as issued during module B. D Production quality assurance Covers the production phase following module B. Production quality assurance is based on the standard EN ISO 9002 and the involvement of a notified body who has responsibility for the approval and control of the quality system regarding production, end product inspection and testing implemented by the manufacturer. E Product quality assurance Covers the production phase following module B. Production quality assurance is based on the standard EN ISO 9003 and the involvement of a notified body who has responsibility for the approval and control of the quality system regarding end product inspection and testing implemented by the manufacturer. F Product verification Covers the production phase following module B. The EC type examination carried out by the notified body, to ensure conformity to type in module B, is followed by the issue of a certificate of conformity. G Unit verification Covers the design and production phases. A certificate of conformity is issued after examination of every product by the notified body. H Full quality assurance Covers the design and production phases. Quality assurance is based on the standard EN ISO 9003 and the involvement of a notified body who has responsibility for the approval and control of the quality system for design, manufacture, final product inspection and testing implemented by the manufacturer.
  • 34. March 2010 © 6 CE Conformity Assessment Modules (continued) The illustration below shows how the modules listed on the previous page may be implemented to obtain the CE marking for apparatus. ATEX 95 The ATEX Directive 94/9/EC ( ATEX 95 ) was adopted by the EC to enable free trade of products between member states through alignment of technical and legal requirements and concerns the design of explosion protected equipment. The directive applies not only to electrical equipment but also to mechanical equipment and protective systems used in the presence of potentially explosive atmospheres containing gases/vapours or combustible dusts. Equipment is defined as any item which is inherently ignition capable or is potentially ignition capable and requiring the inclusion of special design and installation techniques to prevent ignition of any surrounding flammable atmosphere which may be present. The ‘equipment’ may also be interfaces located in the non-hazardous area which are part of an explosion protection system. Protective systems include quenching systems, flame arrestors, fast- acting shut-off valves and pressure relief panels installed to limit damage due to an explosion or prevent the spread of explosions. Design phase Production phase Module A Module C Module D Module E Module F Module G Module B Manufacturer Module H
  • 35. March 2010 © 7 ATEX 137 The ATEX Directive 99/92/EC ( ATEX 137 ), commonly known as the ‘use’ directive, is implemented in the UK via the Dangerous Substances and Explosives Atmosphere Regulations 2002 (DSEARs). Employers are obliged to implement the following minimum requirements in the workplace with regard to DSEARs. a. Carry out a risk assessment where dangerous substances are or may be present. b. Eliminate or reduce risk as far as is reasonably practicable. c. Classify locations in the workplace where explosive atmospheres may be present into hazardous or non-hazardous areas. d. Have in place procedures/facilities to deal with accidents, incidents and emergencies involving dangerous substances in the workplace. e. Provide appropriate information and training of employees for their safety regarding precautions to be taken when dangerous substances are present in the workplace, written instruction for tasks undertaken by employees and operation of a permit-to- work system. f. Clearly identify the contents of containers and pipes. g. Co-ordinate operations where two or more employees share a workplace in which a dangerous substance may be present. h. Posting of warning signs for locations where explosive atmospheres may occur. i. Selection of equipment in accordance with ATEX 95 and establishment of a maintenance programme. Marking of Hazardous Areas Article 7 in the Directive ATEX 137 states: ‘Where necessary, places where explosive atmospheres may occur in such quantities as to endanger the health and safety of workers shall be marked with signs at their points of entry in accordance with Annex III.’ Annex III of the directive specifies the exact requirements for the sign but generally it is required to be triangular with a yellow background, black border and marked ‘Ex’. Ex
  • 36. March 2010 © 8 European Notified Bodies The illustration below shows some of the Notified Bodies along with their unique Notified Body (NB) number. There are around sixty Notified bodies in the EU at the time of writing. Finland: VTT Industrial Systems (0537) Sweden: SP-Swedish National Testing (402) Norway: NEMKO AS (0470) DNV AS (0575) Denmark: UL Int DEMKO A/S (0539) UK: Baseefa (1180) SIRA (0518) BSI Product Services (0086) ITS Testing & Cert. Ltd (0359) Lloyd’s Reg Ver Ltd (0038) Netherlands: KEMA (0344) Belgium: ISSeP (0539) France: LCIE (0081) INERIS (0080) Spain: LOM (0163) Italy: CESI (0722) Germany: PTB (0102)
  • 37. March 2010 © 9 Comparison of IEC, European (CENELEC) and British Standards Prior to the closer ties between the UK and Europe, electrical equipment, such as flameproof or increased safety etc., was manufactured in accordance with the British Standard BS 4683 (see table in page 11). Equipment built and certified to this standard was entitled to display the mark Ex on its label, which indicated that the apparatus was explosion protected. This term should not be confused with term explosion-proof as they are entirely different. In addition to the ‘Ex’ mark, the label was also marked with a ‘crown’ symbol, which is the distinctive mark for the UK test house BASEEFA, later to become known as EECS. Other examples of marks are shown on page 14 of this Unit. Because of the differences in standards, e.g. equipment manufactured in the UK could not be used in the other European countries and vice-versa, and hence, equipment made to BS 4683 could only be used in the UK, or in other countries outside Europe. Co-operation between the standards writing bodies in the UK and Europe resulted in the development of ‘Harmonised’ standards, also known as ‘Euronorms’, for which the English version was published as BS 5501 and comprised nine separate parts as shown in the third column of the table on page 10. The Euronorm equivalents, written in French or German, are shown on the first column. Column four shows the second generation of the UK version of the harmonised standards which replaced BS5501. However, with the trend towards global harmonisation of standards continuing to make progress, a new series of standards have been gradually introduced having numbers based on the International Standard numbers (second column), i.e. BS EN60079, as shown in column five of the following table.
  • 38. March 2010 © 10 Comparison of IEC, European (CENELEC) and British Standards CENELEC Euronorm (EN) Number International Standards British Standard (BS) Number Revised Standard (BS EN) Number Latest Revised Standard (BS EN) Number Type of Protection EN 50 014 IEC 60079-0 BS 5501: Pt. 1 BS EN50 014 BS EN60079-0 General Requirements EN 50 015 IEC 60079-6 BS 5501: Pt. 2 BS EN50 015 BS EN60079-6 Oil Immersion ‘o’ EN 50 016 IEC 60079-2 BS 5501: Pt. 3 BS EN50 016 BS EN60079-2 Pressurised Apparatus ‘p’ EN 50 017 IEC 60079-5 BS 5501: Pt. 4 BS EN50 017 BS EN60079-5 Power Filling ‘q’ EN 50 018 IEC 60079-1 BS 5501: Pt. 5 BS EN50 018 BS EN60079-1 Flameproof Enclosure ‘d’ EN 50 019 IEC 60079-7 BS 5501: Pt. 6 BS EN50 019 BS EN60079-7 Increased Safety ’e’ EN 50 020 IEC 60079-11 BS 5501: Pt. 7 BS EN50 020 BS EN60079-11 Intrinsic Safety ‘i’ EN 50 028 IEC 60079-18 BS 5501: Pt. 8 BS EN50 028 BS EN60079-18 Encapsulation ‘m’ EN 50 039 IEC 60079-25 BS 5501: Pt. 9 BS EN50 039 BS EN60079-25 Intrinsic Safety Systems ‘i’ EN 50 021 IEC 60079-15 BS EN50 021 BS EN60079-15 Type of Protection ‘n’ IEC 60079-26 BS EN60079-26 Equipment with Equipment Protection Level Ga IEC 60079-27 BS EN60079-27 Fieldbus intrinsically safe concept (FISCO) IEC 60079-29-2 BS EN60079-29-2 Gas detector selection, installation, use and maintenance IEC 60079-30-1 BS EN60079-30-1 Electrical resistance trace heating – General & testing requirements IEC 60079-30-2 BS EN60079-30-2 Electrical resistance trace heating – Application guide
  • 39. March 2010 11 Other (older) British Standards The standards listed below are those which preceded the harmonised European standards listed in the previous table. These standards, with the exception of BS 889, were not entirely obsolete, and older designs of equipment were still manufactured to these standards and available on the market prior to 30 June 2003, the date after which implementation of the ATEX Directives became mandatory. Apparatus manufactured to these standards, where still in use, must be maintained in accordance with these standards. It is, therefore, important that reference to the correct standard is made before maintenance is carried out on such apparatus. BS 229 Flameproof enclosure of electrical apparatus BS 889 Flameproof electric fittings BS 1259 Intrinsically safe electric apparatus and circuits for use in explosive atmospheres BS 4683: Part 1 Classification of maximum surface temperature BS 4683: Part 2 The construction and testing of flameproof enclosures of electrical apparatus BS 4683: Part 3 Type of protection ‘N’ BS 4683: Part 4 Type of protection ‘e’ BS 6941 Type of Protection ‘N’ BS 5000: Part 15 Machines with type of protections ‘e’ BS 5000: Part 16 Type ‘N’ electric motors
  • 40. March 2010 © 12 Standards for Selection, Installation, Inspection and Maintenance As previously stated, the UK Code of Practice BS 5345, which had for many years provided recommendations for the selection, installation and maintenance of explosion protected equipment for use in potentially explosive atmospheres (other than mining applications or explosives processing and manufacture), listed in the upper table below, was superseded by the standards listed in the lower table. BS 5345, however, may be referred to for installations installed in accordance with its requirements. The table below illustrates the component parts of BS 5345. UK Code of Practice Type of Protection BS 5345: Part 1 General Recommendations BS 5345: Part 2 Classification of Hazardous Areas BS 5345: Part 3 ‘d’ Flameproof enclosure BS 5345: Part 4 ‘i’ Intrinsically safe apparatus and systems BS 5345: Part 5 ‘p’ Pressurisation, continuous dilution and pressurised rooms BS 5345: Part 6 ‘e’ Increased safety BS 5345: Part 7 ‘N’ (Non - incendive) BS 5345: Part 8 ‘s’ Special protection BS 5345: Part 9 ‘o’ Oil immersion ‘q’ Powder filling The standards which supersede the Code of Practice BS 5345 are illustrated in the table below. Furthermore, the BS EN standards are identical to the IEC standards shown within brackets in the table below apart from a few informative annexes. BS EN / IEC Nos. Electrical Apparatus for Explosive Gas Atmospheres: BS EN60079-10: 2009 (IEC 60079-10-1: 2008) Part 10: Classification of hazardous areas BS EN60079-14: 2008 (IEC 60079-14: 2007) Part 14: Electrical installations in hazardous areas (other than mines) BS EN60079-17: 2007 (IEC 60079-17: 2007) Part 17: Inspection and maintenance of electrical installations in hazardous areas (other than mines) BS EN60079-19: 2007 (IEC 60079-19: 2006) Part 19: Repair and overhaul for apparatus used in explosive atmospheres (other than mines or explosives) BS EN60079-20-1: 2010 (IEC 60079-20-1: 2010) Material characteristics for gas and vapour classification – Test methods and data
  • 41. March 2010 © 13 Certification body symbols 1) Equipment marked with this symbol may only be used for underground (mining) applications in the UK. 2) Equipment marked with this symbol has been constructed to the old British Standard BS229 3) Symbol formerly used by EECS (BASEEFA) to identify equipment for surface industry use only. 4) Equipment marked with this symbol, the European Ex mark, indicates that the equipment has been constructed and tested in accordance with the CENELEC/ EURONORM standards. This mark only will be used on ATEX compliant equipment. 5) Symbol formerly used by the German notified body PTB 6) The most commonly used symbol of the American certification authority Underwriters Laboratories (UL) 7) The mark used by the Canadian Standards Association MEx
  • 42. March 2010 © 14 Equipment Marking Prior to the introduction of the ATEX Directives on 1 July 2003, equipment for use in hazardous areas were marked as illustrated below. Equipment complying with the ATEX Directives, however, will still be marked in this way but will have additional markings to indicate that the apparatus conforms with the ATEX Directives. The ATEX markings are shown on page 18. Equipment approved/certified as providing a method of protection for use in hazardous locations is required to display the following markings. a. The symbols Ex, and b. The type of protection used, e.g. ‘d’, ‘e’, ‘N’, and c. The gas group, e.g. IIA, IIB or IIC, and d. The T-rating, e.g. T1, T2 etc. e. The ambient rating, e.g. -200 C to +400 C (normal range for UK but may not be marked on equipment.) Note: For higher ambient ratings the marking may be either Tamb +500 C, or -200 C < Tamb < +500 C Examples: (i) Ex d IIB T3 (ii) EEx d IIC T4 (iii) EEx e II T6 In example (i), equipment marked thus (Ex), as far as Europe was concerned, could only be used in the UK because it had been constructed to the British Standard BS 4683, which was not a harmonised European standard. Equipment constructed to this standard, however, was used in other countries out-with the European Community. Such equipment would also be marked with the EECS certification authority symbol (fig 3) on the previous page. Equipment certified in accordance with the IEC Ex scheme will be marked Ex. See page 20 onwards for details of this scheme. For equipment marked EEx as in example ii. and iii., the additional letter ‘E’ indicates that the equipment has been constructed to a harmonised European standard. Such equipment would be marked with the EECS certification authority symbol (fig 3) as well as the European Community mark (fig 4). Sample labels are shown below, and it should be noted that the construction standard to which the equipment has been manufactured to, i.e. BS 4683: Part 2, BS 5501: Parts 1 & 5 and EN50 014 & EN50 018 are also given on the labels. For BS 4683 equipment, the IEC equivalent standard, i.e. IEC 79-1 in example (a) below, is usually included. (a) (b)
  • 43. March 2010 © 15 Equipment marking (continued) The certification labels attached to explosion protected equipment will display markings to enable their correct selection for use in hazardous areas. For example, equipment manufactured to the old UK standard BS4683 and the subsequent CENELEC EN500 series of harmonised standards will be marked Ex and EEx respectively. However, with the CENELEC and IEC standards becoming technically identical, i.e. the EN60079 standards are identical to the IEC60079 standards, the marking has reverted to Ex. The illustration below shows the marking on equipment constructed to the harmonised standard BS EN50018. Equipment manufactured to the latest standards, the BS EN60079 series, will be marked as follows along with the ATEX markings shown on page 17. The main differences are the removal of the letter ‘E’ compared to the illustration above and the introduction of the EPL ‘Gb’. EPL’s are explained on pages 18 to 21. Ex d IIC T6 Gb
  • 44. March 2010 © 16 Certification Numbers The certification number illustrated below was used by BASEEFA prior to the introduction of the ATEX directives, but the numbers used by other certification authorities will be different. Components typically displaying a suffix ‘U’ include Ex e terminals, Ex d stoppers for flamepoof enclosures, and small volume plastic flameproof switches which have exposed terminals. ATEX compliant equipment will have standardised certification numbers which will include the abbreviation of the notified body’s name followed by the year of certification, the acronym ATEX, the serial number and either of the suffix’s ‘X’ or ‘U’ where applicable, as shown below. BAS 08 ATEX 1234 X
  • 45. March 2010 © 17 Marking of ATEX Compliant Equipment The ATEX Directive 94/9/EC, now known as ATEX 95, specifies the new approach for the certification of explosion protected equipment. An introduction to the ATEX approach has been considered in pages 4-7 but its wider issues are beyond the scope of this Unit. What is relevant, however, is the influence the directive will have on the marking of explosion protected equipment. This will be the most obvious difference to those involved in the selection, installation and maintenance of explosion protected apparatus. The marking required by ATEX 95 is illustrated below, which is additional to the marking requirements already discussed. Also, the hexagonal symbol below will replace the individual symbols used by the different certification bodies, and the CE mark indicates compliance with the ATEX Directive. The Equipment Categories are defined overleaf 0000 CE Mark Notified body ID number EU Explosive Atmosphere Symbol
  • 46. March 2010 © 18 Category (Cat) Definitions The ATEX Categories were introduced to ‘break’ the traditional link between the protection types and zones, i.e. the selection of equipment suitable for the zone. This approach enables, for example, Cat 3 equipment, typically Ex n, to be used in zone 1 if a risk assessment revealed that the consequences of ignition of a flammable atmosphere was low. The Categories below, however, show the traditional link with the zones. Conversely, if the consequences of ignition were greater then a better Category of protection may be required. Group II Cat 1: Very high level of protection Equipment with this category of protection may be used where an explosive atmosphere is present continuously or for long periods, i.e. Zone 0 or Zone 20. Cat 2: High level of protection Equipment with this category of protection may be used where an explosive atmosphere is likely to occur in normal operation, i.e. Zone 1 or Zone 21. Cat 3: Normal level of protection Equipment with this category of protection may be used where an explosive atmosphere is unlikely to occur or be short duration, i.e. Zone 2 or Zone 22. Group I Cat M1: Very high level of protection Equipment can be operated in the presence of an explosive atmosphere. Cat M2: High level of protection Equipment to be de-energised in the presence of an explosive atmosphere. Note: Zones 20, 21 and 22 are the corresponding zones for combustible dusts. Equipment protection levels (EPL’s) The introduction of Equipment Protection Levels (EPL’s), which are used internationally, enables a risk assessment approach to be implemented for the selection of explosion protected equipment in hazardous areas. This provides an alternative to the traditional method of selecting equipment to suit the zone, which does not take into consideration the consequences of an explosion. The table below shows the zones where both ATEX Categories and EPL’s may be used from a traditional selection approach. Selection of equipment according to the EPL will in future be according to the EPL’s specified for the zones in area classification diagrams so that where the consequences of an explosion are likely to be greater, a higher EPL will be specified. Alternatively, if the consequences of an explosion are lower, a lesser EPL may be specified. Zone ATEX Categories EPL’s 0 1 Ga 1 2 Gb 2 3 Gc
  • 47. March 2010 © 19 Equipment protection levels (EPL’s) Equipment Protection Levels (EPL’s) are available for both gases and vapours and also combustible dusts as illustrated in the table below. Equipment marked ‘G’ is for use in flammable gases and vapours, and for use in combustible dusts when marked ‘D’. Zone Equipment protection levels ( EPL’s ) 0 Ga 1 Ga or Gb 2 Ga, Gb or Gc 20 Da 21 Da or Db 22 Da, Db or Dc EPL Definitions Group II gases Ga Equipment for explosive gas atmospheres, having a ‘very high’ level of protection, which is not a source of ignition in normal operation, expected faults, or when subject to rare faults. Gb Equipment for explosive gas atmospheres, having a ‘high’ level of protection, which is not a source of ignition in normal operation, or when subject to faults that may be expected, though not necessarily on a regular basis. Gc Equipment for explosive gas atmospheres, having an ‘enhanced’ level of protection, which is not a source of ignition in normal operation and which may have some additional protection to ensure that it remains inactive as an ignition source in the case of regular expected occurrences, for example, failure of a lamp. Group III Dusts Da Equipment for combustible dust atmospheres, having a ‘very high’ level of protection, which is not a source of ignition in normal operation, or when subject to rare faults. Db Equipment for combustible dust atmospheres, having a ‘high’ level of protection, which is not a source of ignition in normal operation, or when subject to faults that may be expected, though not necessarily on a regular basis. Dc Equipment for combustible dust atmospheres, having an ‘enhanced’ level of protection, which is not a source of ignition in normal operation and which may have some additional protection to ensure that it remains inactive as an ignition source in the case of regular expected occurrences.
  • 48. March 2010 © 20 EPL’s assigned to protection types (gases) EPL Ga EPL Protection type Marking Intrinsic Safety Ex ia Ga Encapsulation Ex ma EPL Gb EPL Protection type Marking Flameproof Ex d Increased Safety Ex e Intrinsic Safety Ex ib Encapsulation Ex m Exmb Oil immersion Ex o Pressurisation Ex p, Ex px, Ex py Powder filled Ex q Gb Fieldbus Intrinsic Safety Concept (FISCO) ** ** No designated marking code at the time of writing EPL Gc EPL Protection type Marking Intrinsic Safety Ex ic Encapsulation Ex mc Non-sparking Ex n, Ex nA Restricted breathing Ex nR Energy limitation Ex nL Sparking equipment Ex nC Pressurisation Ex pz Gc Fieldbus non-incendive Concept (FNICO) ** ** No designated marking code at the time of writing
  • 49. March 2010 © 21 EPL’s for combustible dusts EPL Protection type Marking Intrinsic Safety Ex iD Encapsulation Ex mD Da, Db, or Dc Protection by enclosure tD Db or Dc Pressurisation pD Equipment marking Since there is now technical alignment of the CENELEC and IEC standards, equipment manufactured in Europe will no longer be marked EEx, and instead will be marked Ex. Where equipment is certified under the IECEx scheme the IECEx Conformity Mark as illustrated below will be displayed on the equipment. For the foreseeable future, however, acceptance in the EU will require the equipment to comply with ATEX and display the marking illustrated on page 18. Area for code indicating the Licensee Number and the Certification Body
  • 50. March 2010 © 22 Example of an EC – Type Examination Certificate
  • 55. March 2010 © 2 OBJECTIVES On completion of this unit, ‘flameproof EEx d / Ex d apparatus, you should know: a. The principle of operation and causes of pressure piling. b. The general constructional requirements including types of joints. c. The installation requirements with regard to thread engagement of cable entries and stopping devices, circuit protection, obstruction of flamepaths and additional weatherproofing methods in accordance with BS EN60079-14. d. The inspection requirements with regard to BS EN60079-17.
  • 56. March 2010 © 3 Flameproof EEx d / Ex d Flameproof is one of the original methods of explosion protection developed for use in the mining industry. It has a wide range of applications, typically junction boxes, lighting fittings, electric motors etc. The letter ‘d’, which symbolises this type of protection, is from the German word ‘druckfeste’ (kapselung), which roughly translated means ‘pressure tight’ (enclosure). Flameproof apparatus, when properly installed in the intended location, enables components such as switches, contractors and relays etc. to be safely used in hazardous areas. Flameproof is the only one of the nine different methods of explosion protection in which an explosion is permitted. This explosion, however, must be contained by the robustly constructed flameproof enclosure so that ignition of the surrounding flammable atmosphere cannot occur.
  • 57. March 2010 © 4 Standards BS EN60079-1: 2007 Flameproof enclosures ‘d’ BS EN50 018: 2000 Flameproof enclosures ‘d’ BS 5501: Part 5: 1977 Flameproof enclosures ‘d’ BS 4683: Part 2: 1971 The construction and testing of flameproof enclosures of electrical apparatus (Ex d) BS 229: 1957 Flameproof enclosures of electrical apparatus IEC 60079-1: 2007 Electrical Apparatus for explosive gas atmospheres – Part 1: Flameproof enclosures ‘d’ BS EN60079-14: 2008 Electrical Apparatus for explosive gas atmospheres: Part 14 Electrical installations in hazardous areas (other than mines) BS EN60079-17: 2007 Electrical Apparatus for explosive gas atmospheres: Part 17 Inspection and Maintenance of electrical installations in hazardous areas (other than mines) BS 5345: Part 3: 1979 (Withdrawn) Code of Practice for the Selection, Installation and Maintenance of flameproof apparatus Definition The construction standard BS EN60079-1 defines flameproof as: ‘An enclosure in which the parts which can ignite an explosive atmosphere are placed and which can withstand the pressure developed during an internal explosion of an explosive mixture, and which prevents the transmission of the explosion to the explosive atmosphere surrounding the enclosure’ EPL: Gb Zone of Use: 1 & 2 Ambient Conditions Flameproof enclosures are normally designed for use in ambient temperatures in the range - 20°C to +40°C unless otherwise marked.
  • 58. March 2010 © 5 Principle of Operation Flameproof enclosures are not gas tight and a gas or vapour will enter the enclosure where, for example, joints or cable entries exist. Since these enclosures are designed to contain components which are an ignition source, ignition of the gas or vapour may occur, and the resulting explosion pressure can reach a peak value of around 150 p.s.i. The enclosure must, therefore, be strong enough to contain this explosion pressure, and the gaps at the joints and threads of cable entries must be long and narrow to cool the flames/hot gases before they reach and cause ignition of a flammable atmosphere which may exist out with the enclosure. Typical materials used for the construction of flameproof apparatus include cast iron, aluminium alloys, and where corrosion resistance is required, gun metal bronze, phosphor bronze and stainless steel may be used. Plastic materials are also used but the free internal volume must not exceed 10cm3 . The latest standard specifies that for flanged joints ‘THERE SHALL BE NO INTENTIONAL GAP AT THE JOINTS’ and infers the same for other joint types. The average roughness Ra of the flamepath surfaces must not exceed 6.3μm. Flammable MIxture Arcs, Sparks Hot Surfaces Contactors, Relays etc Gap
  • 59. March 2010 © 6 Gap Dimensions It is not necessary for a gap to exist at the flamepaths of a flameproof enclosure. The latest standard BS EN60079-1 states there shall be no intentional gap between the surfaces of enclosures with flanged joints. This said, however, a gap will be necessary at the cylindrical joints of rotating machines, i.e. where the rotor shaft exits the end-shield and also where push-button spindles pass through flameproof enclosures to operate the internal switches. Flameproof enclosures with spigot or screwed joints, however, require some clearance to enable covers to be removed relatively easily for installation and maintenance purposes. These clearance/gap dimensions, and also those for rotating machines and push-button stations, must be within the dimensions specified in the tables for gap dimensions in the construction standard for flameproof equipment, e.g. BS EN60079-1. Factors which influence the dimension of the gap are: a. The width of the joint b. The gas group c. The internal volume of the enclosure d. The type of joint
  • 60. March 2010 © 7 Flamepath Joints The diagrams below illustrate examples of three joint types specified in the British standard BS EN60079-1 for use in flameproof apparatus. In a flanged joint, the machined surface on the cover makes face-to-face contact with the corresponding surface on the base to give a gap dimension normally less than that specified in the tables of gap dimensions in the standard when the cover is properly bolted down. This type of joint will be used at the covers of, for example, junction boxes. Spigot joints will be used at junction box covers and motor enshields. Threaded joints are used for cover joints, cable gland and conduit entries. An adequate flamepath length is normally achieved with a thread engagement of five full threads. In contrast to BS EN50019, the most recent standard, BS EN60079-1 permits the use of flanged joints when a IIC gas such as acetylene is the hazard only if the gap is ≤ 0.04mm, has a length L ≥ 9.5mm and the free internal volume does not exceed 500 cm3 . a) Flanged joint b) Spigot joint c) Screwed joint Interior Interior Interior
  • 61. March 2010 © 8 Flamepath Joints Types (Rotating Machines) (d) cylindrical (shaft gland) joint (d) labyrinth joint for shafts
  • 62. March 2010 © 9 Flamepath Joints (other examples) Flamepaths other than those at cover joints are also necessary where, for example, an actuator spindle passes through the wall of an enclosure, or where a cable gland or conduit enters an enclosure. Examples are shown below. Push-button spindle Cable (gland) entry
  • 63. March 2010 © 10 Entry by Cable Gland or Conduit The thread engagement requirements for cable and conduit entries are specified in the standard BS EN60079-1 and apply to the three sub-groups IIA, IIB and IIC. Only threaded entries are permitted for all cable glands or conduits entering flameproof enclosures – clearance entries are not permitted. Volume ≤ 100 cm3 > 100 cm3 Thread Engagement Axial Length Thread Engagement Axial Length > 5 Full Threads > 5mm > 5 Full Threads > 8 mm As already stated the above requirements for thread engagement are specified in the latest standard BS EN60079-1: 2007, but the previous standard BS EN50018: 2000 required at least 6 full threads engagement in order to make sure that 5 full threads were actually engaged. Note: Flameproof equipment manufactured to the old British standard BS229 may have different non-metric thread forms at cable gland entries. This difficulty can be overcome by the use of certified Ex d adaptors which have compatible thread forms to suit both the entry in the enclosure and the cable gland.
  • 64. March 2010 © 11 Unused Cable or Conduit Entries It is important that unused cable/conduit entries in flameproof enclosures are closed using appropriate stoppers, as specified in the standards, or those supplied by the manufacturer. These must be ‘component certified’ metal stoppers – plastic stoppers are unacceptable – which are fully engaged by 5 full threads. The construction standard specifies suitable types, examples of which are illustrated below. Stoppers of the type illustrated by example ‘C’ in the above diagram are available with certification markings on either the plain side or the same side as the hexagon recess. Ideally, stoppers of this type should be fitted with the plain side facing the exterior to make unauthorised removal more difficult, but may be fitted with the hexagon recess facing the exterior. Whichever way round they are fitted the certification markings must be visible for ease of identification during ‘Visual’ inspection programmes. Also the thread engagement requirements must be met. Stoppers of this type are tightened using an Allen Key. Split pin A B C D Interior Screwdriver slot Special fastener Hexagon recess Hexagon head Shearable neck Exterior
  • 65. March 2010 12 Flamepath Gap Dimensions – BS EN60079-1, Table 1 Maximum gap mm For a volume cm3 V ≤ 100 For a volume cm3 100 < V ≤ 500 For a volume cm3 500 < v ≤ 2 000 For a volume cm3 V > 2 000 Type of Joint Minimum width of joint L mm I IIA IIB I IIA IIB I IIA IIB I IIA IIB 6 0.30 0.30 0.20 - - - - - - - - - 9.5 0.35 0.30 0.20 0.35 0.30 0.20 - - - - - - 12.5 0.40 0.30 0.20 0.40 0.30 0.20 0.40 0.30 0.20 0.40 0.20 0.15 Flanged, cylindrical or spigot joints 25 0.50 0.40 0.20 0.50 0.40 0.20 0.50 0.40 0.20 0.50 0.40 0.20 6 0.30 0.30 0.20 - - - - - - - - - 9.5 0.35 0.30 0.20 0.35 0.30 0.20 - - - - - - 12.5 0.40 0.35 0.25 0.40 0.30 0.20 0.40 0.30 0.20 0.40 0.20 - 25 0.50 0.40 0.30 0.50 0.40 0.25 0.50 0.490 0.25 0.50 0.40 0.20 Sleeve bearings 40 0.60 0.50 0.40 0.60 0.50 0.30 0.60 0.50 0.30 0.60 0.50 0.25 6 0.45 0.45 0.30 - - - - - - - - - 9.5 0.50 0.45 0.35 0.50 0.40 0.25 - - - - - - 12.5 0.60 0.50 0.40 0.60 0.45 0.30 0.60 0.45 0.30 0.60 0.30 0.20 25 0.75 0.60 0.45 0.75 0.60 0.40 0.75 0.60 0.40 0.75 0.60 0.30 Cylindrical joints for shaft glands of rotating electrical machines with: Rolling- element bearings 40 0.80 0.75 0.60 0.80 0.75 0.45 0.80 0.75 0.45 0.80 0.75 0.40 NOTE: Constructional values rounded according to ISO 31-0 should be taken when determining the maximum gap.
  • 66. March 2010 © 13 Flamepath Gap Dimensions – BS EN60079-1, Table 2 Maximum gap mm Type of Joint Minimum width of joint L mm For a volume cm3 V ≤ 100 For a volume cm3 100 < V ≤ 500 For a volume cm3 500 < v ≤ 2 000 For a volume cm3 V > 2 000 5 0.10 - - - 9.5 0.10 0.10 - - 15.8 0.10 0.10 0.4 - Flanged joints 25 0.10 0.10 0.4 0.4 12.5 0.15 0.15 0.15 - 25 0.18b 0.18b 0.18b 0.18b 40 0.20c 0.20c 0.20c 0.20c Spigot joints (Figure 2a) c ≤ 6mm d ≤ 0.5L L = c + d f ≤ 1mm 6 0.10 - - - 9.5 0.10 0.10 - - 12.5 0.15 0.15 0.15 - 25 0.l5 0.15 0.15 0.15 Cylindrical joints Spigot joints (Figure 2b) 40 0.20 0.20 0.20 0.20 6 0.15 - - - 9.5 0.15 0.15 - - 12.5 0.25 0.25 0.25 - 25 0.25 0.25 0.25 0.25 Cylindrical joints for shaft glands of rotating electrical machines with rolling element bearings 40 0.30 0.30 0.30 0.30 a Flanged joints are permitted for explosive mixtures of acetylene and air only in accordance with 5.2.7 b Maximum gap of cylindrical part increased to 0.20 mm if f < 0.5 mm c Maximum gap of cylindrical part increased to 0.25 mm if f < 0.5 mm NOTE: The constructional values rounded according to ISO 21 –D should be taken when determining the maximum gap
  • 67. March 2010 © 14 Pressure Piling If a flammable mixture us compressed prior to ignition, the resulting explosion will be considerably higher than if the same mixture was ignited at normal atmospheric pressure. Pressure piling can materialise as a result of sub-division of the interior of a flameproof enclosure, which prevents the natural development of an explosion. An explosion at one side of an obstacle pre-compresses the flammable mixture at the other side, resulting in a secondary explosion that can reach an explosion pressure around three times that of the first or normal explosion pressure. Manufacturers, guided by relevant construction standards, must ensure that, in any cross- section within an enclosure, there is adequate free space (typically 20 – 25% of the total cross-section) around any potential obstruction, which may be a large component or a number of components. This will ensure that pressure piling is kept under control.
  • 68. March 2010 © 15 Pressure Piling in Flameproof Motors In rotating electrical machines, sections with appreciable free volume normally exist at each end within the main frame of the machine. These sections are linked by the airgap between the stator and rotor cores. In the illustration of a flameproof machine in the diagram above, an explosion in section ‘1’ must be prevented from migrating to, and causing ignition of the flammable mixture in section ‘2’ which will have been pressurised by the initial explosion. The airgap, therefore, also acts as a flamepath. Section 1 Section 2
  • 69. March 2010 © 16 Obstruction of Flamepaths The UK Code of Practise BS 5345 Part 3 recommended that obstruction of flameproof enclosures, particularly those with flanged joints, should be avoided. This recommendation is also given in BS EN60079-14: Electrical installation in hazardous areas (other then mines). A solid obstruction such as a wall, steelwork, conduit, brackets, weather guards or other electrical apparatus etc., in close proximity to the opening at the joint can, in the event of an internal explosion, reduce the efficiency of the flamepath to the extent that ignition of the external gas or vapour could occur. The minimum distance between the flamepath opening and an obstruction, as specified in BS EN60079-14 (and BS 5345: Part 3) are: Group Distance IIA 10 mm IIB 30 mm IIC 40 mm
  • 70. March 2010 © 17 Ingress Protection Methods The diagrams below illustrate the location of gaskets or rubber ‘O’ rings for ensuring a high level of ingress protection. The gaskets etc. must be an integral part of the original design, i.e. they cannot be added at a later date to an enclosure manufactured without gaskets. Typical examples for outdoor use are illustrated below.
  • 71. March 2010 © 18 Weatherproofing / protection of flamepaths Flameproof equipment must have a level of ingress protection to suit the environmental conditions of the location in which the equipment is installed and hence equipment should have, as part of their certified design, seals or gaskets to prevent the ingress of water and/or dust. Flamepaths must also be protected in accordance with manufacturer’s instructions and the requirements of BS EN60079-14 which will involve additional measures as detailed below. This is particularly important where environmental conditions are extreme. Protection of flamepaths The following measures are not permissible: a) painting of flamepath surfaces - enclosures may be painted after assembly; b) fitting of unauthorised seals/gaskets – replacement seals/gaskets may only be fitted where the originals, which are part of the certified design, are degraded or damaged. Permitted measures: c) application of non-setting grease or anti-corrosive agents having no evaporating solvents; d) non-hardening grease-bearing (Denso) tape – see application/limitations of use below. Note: The use of non-setting grease on the machined surfaces of flamepaths has two advantages since, in addition to providing an additional level of ingress protection; it also inhibits the formation of rust on these surfaces. Silicone based greases require careful consideration in order to avoid possible damage to the elements of gas detectors. For Flameproof equipment, the limitations for the use of non-hardening tape as specified in BS EN60079-14 are as follows: a. Non-hardening tape maybe applied around the flamepaths of apparatus with flanged joints allocated to group IIA applying one layer only with a short overlap. b. For group IIB apparatus, one layer with a short overlap may be applied around the flamepaths of apparatus with flanged joints, but only if the gap is less than 0.1mm regardless of the joint width. Note: The Code of Practise BS 5345: Part 3 (withdrawn but a relevant source of information for older installations) recommended that expert advice be sought when considering the use of non-hardening tape on group IIB or IIC equipment installed in locations containing group IIB gases or vapours. c. Non-hardening tape must not be used on equipment marked IIC (or IIB + H2) installed in locations containing group IIC gases or vapours.
  • 72. March 2010 © 19 Direct / Indirect Entry The selection of cable glands for flameproof apparatus is influenced by several factors, one of which is the method of entry into the apparatus. There are two entry methods, namely direct and indirect, examples of which are shown below. Direct entry comprises a single flameproof chamber within which components such as switches, relays or contactors may be installed. Flameproof apparatus with indirect entry has two separate chambers, one of which contains only terminals for connection of the conductors of incoming cables or conduit. Connection to the arcing components in the second compartment is made via these flameproof terminals which pass through the flameproof interface between the two compartments. Direct entry Indirect entry EEx d Enclosure EEx d Enclosure Flamepaths Bushings EEx d cable glands
  • 73. March 2010 © 20 Electrical Protection Flameproof enclosures are tested for their ability to withstand internal gas explosions only; they are not capable of withstanding the energy which may be released as a result of an internal short-circuit. In order to avoid invalidation of the certification, it is important that properly rated/calibrated electrical protection, e.g. fuses and/or circuit breakers, are utilised. Cover bolt (fastener) requirements Should the requirement arise where it is necessary to replace the cover bolts etc of a flameproof enclosure, only steel bolts having the correct length, type of thread, type of head and tensile strength should be used. Regarding cover bolt tightness the torque values specified by the manufacturer should be observed. In the absence of manufacturer’s torque values the minimum requirement is spanner tight, however, care must be exercised to avoid under-tightening as this can allow an increase in the flamepath gap. Also, over-tightening of the bolts can result in them stretching and hence reducing their strength with the consequence that an internal explosion may not be contained within the enclosure. It is important that all cover bolts are in place and correctly tightened prior to energising a flameproof enclosure.
  • 74. March 2010 © 21 Modification of Flameproof Enclosures Flameproof enclosures are normally supplied complete with all internal components fitted and certified as a single entity by a recognised test authority. The testing procedure will take into consideration the free internal volume after all the components have been fitted, the temperature rise (determined by the maximum power dissipation), creepage and clearance distances, and the rise in pressure as a result of an internal explosion using a gas/air mixture in its most explosive proportions. The certification, therefore, “seals” the design of the apparatus so that any unauthorised modifications will effectively invalidate the approval/certification. Modifications will modify the original test results recorded by the test/certification authority and, consequently, the following points should be observed. a. Replacement components should always be exactly the same as the original specified components in order to avoid infringement of the certification. For example, a component larger or smaller than the original will affect the internal geometry of the enclosure. Pressure piling is a possibility if a larger component is fitted, and increased volume will result if a smaller component is fitted. Note: Illustrations are for demonstration only and must not be carried out Original arrangement Replacement of ‘A’ with a larger item Replacement of ‘A’ with a smaller item
  • 75. March 2010 © 22 b. Adding components is also forbidden because of the possibility of increased explosion pressure as a result of pressure piling. Addition of component ‘C’ c. The removal of components should also be avoided since an increase in the free internal volume will result. The original test results, prior to certification, would be compromised as a result of a modification such as this. Removal of component ‘B’
  • 76. March 2010 © 23 Note: Illustrations are for demonstration only and must not be carried out d. Drilling and tapping of cable gland/conduit entries should only be carried out by the manufacturer of the enclosure, or his approved agent. The threads of the entries are required to be compatible with those of cable glands or conduit in terms of type of thread, thread pitch and clearance tolerance since flamepaths exist at these points. Correct alignment of the threaded entry is also important since the flamepath length at one side will be reduced if the cable gland or conduit is not fitted perpendicular to the face of the enclosure. The strength of a flameproof enclosure may be impaired if the number and size of entries exceeds that permitted in the original design certified by the test authority. Compliance with the original design is paramount with regard to number, size and location of entries to ensure the enclosure will contain an internal explosion. e. Gaskets can only be replaced; they must not be added retrospectively if not included as part of the original design. The use of unauthorised sealants should also be avoided when it is required to maintain or improve the IP rating.
  • 77. March 2010 © 24 BS EN 60079-17 Table 1: Inspection Schedule for Ex’d’, Ex’e’, and Ex ‘n’ Installations (D = Detailed, C = Close, V = Visual) Check that: Ex’d’ Ex’e’ Ex’n’ Grade of Inspection D C V D C V D C V A APPARATUS 1 Apparatus is appropriate to area classification * * * * * * * * * 2 Apparatus group is correct * * * * * * 3 Apparatus temperature class is correct * * * * * * 4 Apparatus circuit identification is correct * * * 5 Apparatus circuit identification is available * * * * * * * * * 6 Enclosure, glass parts and glass-to-metal sealing gaskets and/or compounds are satisfactory * * * * * * * * * 7 There are no unauthorised modifications * * * 8 There are no visible unauthorised modifications * * * * * * 9 Bolts, cable entry devices (direct and indirect) and blanking elements are of the correct type and are complete and tight - Physical check - Visual check * * * * * * * * * 10 Flange faces are clean and undamaged and gaskets, if any, are satisfactory * 11 Flange gap dimensions are within maximal permitted values * * 12 Lamp rating, type and position are correct * * * 13 Electrical connections are tight * * 14 Condition of enclosure gaskets is satisfactory * * 15 Enclosed-break and hermetically sealed devices are undamaged * 16 Restricted breathing enclosure is satisfactory * 17 Motor fans have sufficient clearance to enclosure and/or covers * * * 18 Breathing and draining devices are satisfactory * * * * * * B INSTALLATION 1 Type of cable is appropriate * * * 2 There is no obvious damage to cables * * * * * * * * * 3 Sealing of trunking, ducts, pipes and/or conduits is satisfactory * * * * * * * * * 4 Stopping boxes and cable boxes are correctly filled * 5 Integrity of conduit system and interface with mixed system is maintained * * * 6 Earthing connections, including any supplementary earthing bonding connections are satisfactory (e.g. connections are tight and conductors are of sufficient cross section) - Physical check - Visual check * * * * * * * * * 7 Fault loop impedance (TN system) or earthing resistance (IT systems is satisfactory) * * * 8 Insulation resistance is satisfactory * * * 9 Automatic electrical protective devices operate within permitted limits * * * 10 Automatic electrical protective devices are set correctly (auto reset not possible) * * * 11 Special conditions of use (if applicable) are complied with * * * 12 Cables not in use are correctly terminated * * * 13 Obstructions adjacent to flameproof flanged joints are in accordance with IEC 60079-14 * * * 14 Variable voltage/frequency installation in accordance with documentation * * * * * * C ENVIRONMENT 1 Apparatus is adequately protected against corrosion, weather, vibration and other adverse factors * * * * * * * * * 2 No undue accumulation of dust and dirt * * * * * * * * * 3 Electrical insulation is clean and dry * *
  • 78. March 2010 © 25 Note 1 Apparatus using a combination of both ‘d’ and ‘e’ types of protection will require reference to both columns during inspection. Note 2 The use of electrical test equipment, in accordance with items B7 and B8, should only be undertaken after appropriate steps are taken to ensure the surrounding area is free of a flammable gas or vapour
  • 80. March 2010 © 2 Objectives: On completion of this unit, ‘Increased Safety EEx e / Ex e Apparatus’, you should know: a. The principle of operation. b. The principle design features. c. The methods for estimating terminal content of enclosures. d. The installation requirements according to BS EN 60079-14. e. The inspection requirements according to BS EN 60079-17.
  • 81. March 2010 © 3 Increased Safety EEx e / Ex e The explosion protection concept Increased Safety was invented in Germany where it has been widely used for many years. It is has become popular in the UK mainly because it has a number of advantages for certain applications over the traditional flameproof method of explosion protection. America has traditionally relied on the use of explosion-proof enclosures in hazardous locations, and the prospect of using an Increased Safety enclosure, which is not designed to withstand an internal explosion, as an alternative, has probably been viewed with a little trepidation. This method of protection has a good safety record and comparable with the other methods of protection. The letter ‘e’ which symbolises this method of protection is taken from the German phrase ‘Erhohte Sicherheit’, which roughly translated means ‘increased security’. Typical applications are induction motors, lighting fittings and junction boxes. Standards BS EN60079-7: 2007 Electrical apparatus for explosive gas atmospheres. Increased Safety ‘e’ BS EN50 019: 2000 Increased Safety enclosure ‘e’ BS 5501: Part 6: 1977 Increased Safety enclosure ‘e’ BS 4683: Part 4: 1973 Type of protection ‘e’ IEC 60079-7: 2001-11 Construction and Test of Electrical Apparatus, Type of Protection “e” BS EN60079-14: 2008 Electrical apparatus for explosive gas atmospheres: Part 14 Electrical installations in hazardous areas (other than mines) BS EN60079-17: 2007 Electrical apparatus for explosive gas atmospheres: Part 17 Inspection and maintenance of electrical installations in hazardous areas (other than mines) BS 5345: Part 6: 1978 (Withdrawn) Code of Practice for the Selection, Installation and Maintenance of Increased Safety apparatus.
  • 82. March 2010 © 4 Definition ‘A protection method in which increased measures are taken to prevent the possibility of excessive HEAT, ARCS or SPARKS occurring on internal or external parts of the apparatus in normal operation’. EPL: Gb Zones of use: 1 & 2 Ambient Temperatures Increased Safety enclosures are normally designed for use in ambient temperatures in the range -20 °C to +40 °C unless otherwise marked. Increased Safety light fittings Increased safety light fittings usually have other methods of protection, e.g powder filled Ex q protected capacitors and flameproof protected lampholders, and hence the marking on the certification label will be Ex edq. The following, however, note is important. Note: Lamps for Ex e, luminaries, which have mono-pin, bi-pin or screw connections where the caps are made from non-conductive material with a conductive coating, are not permitted unless tested with the equipment.
  • 83. March 2010 © 5 Principle The safe operation of Increased Safety apparatus is dependent on the prevention of any source of ignition, i.e. excessive surface temperatures, arcs or sparks, which might otherwise be produced by internal or external parts of the apparatus. Special design features are, therefore, incorporated in the apparatus by the manufacturer and are as follows. 1. Mechanically strong enclosure resistant to impact - tested to 4 or 7 joules impact energy depending on application. 2. Ingress protection against solid objects and water - at least IP 54. 3. Terminals manufactured from high quality insulation material. 4. Specified creepage and clearances incorporated in the design of terminals. 5. Terminal locking devices to ensure conductors remain secure in service. 6. Certified de-rating of terminals. 7. Terminal population of enclosure limited by circuit design. 8. Close excess current circuit protection. Increased Safety Terminals The terminals installed in an Increased Safety enclosure must be ‘component certified’ terminals. They will be manufactured from good quality materials such as Melamine, Polyamide and, for special applications, Ceramic. These materials, which have good thermal stability, have been subjected to a ‘Comparative Tracking Index (CTI)’ test to determine their resistance to tracking. The following definitions are relevant: Clearance distance: The shortest distance through air between two conductors. Creepage distance: The shortest distance between two conductors along the surface of an insulator. Tracking: The leakage current which passes across the contaminated surface of an insulator between live terminals, or live terminals and earth. Comparative Tracking Index: The numerical value of maximum voltage, in volts at which an insulation material withstands e.g., 100 drops of electrolyte (usually ammonium chloride solution in distilled water) without tracking.
  • 84. March 2010 © 6 Increased Safety Terminals Test Criteria - Comparative Tracking Index (CTI) The Comparative Tracking Index (CTI) test criteria are given in the table below. Four grades of materials ‘a’, ‘b’, ‘c’ and ‘d’ are considered, the highest quality material being ‘a’ which is subjected to the greatest number of drops of electrolyte falling between the test electrodes, and the highest voltage applied across the electrodes from the variable voltage source. Each material must withstand the specified number of drops of the electrolyte at the specified voltage for it to be acceptable. Thus, the combination of high quality materials and good design, which incorporates specified creepage and clearance distances, ensures that Increased Safety terminals have a greater resistance to tracking to prevent arcing or sparking. Grade of Material C.T.I. Test Voltage Number of Drops a - 600 > 100 b 500 500 > 50 c 380 380 > 50 d 175 175 > 50 The International Standard IEC 60112 groups insulating materials according to their tracking resistance as illustrated in the following table. Material group Comparative tracking index ( CTI ) I 600 < CTI II 400 < CTI < 600 IIIa 175 < CTI < 400 Creepage and Clearance Distances
  • 85. March 2010 © 7 Increased Safety Terminals Creepage and Clearance Distances Terminals Partition Screw heads Clearance 29 75 Creepage path 30 6 Clearance & creepage path 26.4mm Clearance and creepage paths to extend to adjacent clamping screw Clearance and creepage paths 14.0mm Creepage path runs between locating rivet and assembly rail 27.8 mm Clearance path extends from end of bolt to assembly rail 20.5mm
  • 86. March 2010 © 8 Increased Safety Terminals Creepage Distances Relative to Voltage and Grade of Insulation The following table from BS EN60079-7 shows the creepage distances relative to the grade of material and applied voltage. Minimum creepage distance (mm) Material group Voltage (see note 1) U r.m.s a.c. or d.c. (V) I II IIIa Minimum clearance (mm) 10 ( see note 3 ) 1.6 1.6 1.6 1.6 12.5 1.6 1.6 1.6 1.6 16 1.6 1.6 1.6 1.6 20 1.6 1.6 1.6 1.6 25 1.7 1.7 1.7 1.7 32 1.8 1.8 1.8 1.8 40 1.9 2.4 3.0 1.9 50 2.1 2.6 3.4 2.1 63 2.1 2.6 3.4 2.1 80 2.2 2.8 3.6 2.2 100 2.4 3.0 3.8 2.4 125 2.5 3.2 4.0 2.5 160 3.2 4.0 5 3.2 200 4.0 5.0 6.3 4.0 250 5.0 6.3 8.0 5.0 320 6.3 8.0 10.0 6.0 400 8.0 10.0 12.5 6.0 500 10.0 12.5 16.0 8.0 630 12.0 16.0 20.0 10.0 800 16.0 20.0 25.0 12.0 1000 20.0 25.0 32.0 14.0 1250 22.0 26.0 32.0 18.0 1600 23.0 27.0 32.0 20.0 2000 25.0 28.0 32.0 23.0 2500 32.0 36.0 40.0 29.0 3200 40.0 45.0 50.0 36.0 4000 50.0 56.0 63.0 44.0 5000 63.0 71.0 80.0 50.0 6300 80.0 90.0 100.0 60 8000 100.0 110.0 125.0 80.0 10000 125.0 140.0 160.0 100.0 Note 1: Voltages shown are derived from IEC 60664-1. The working voltage may exceed the voltages given in the table by 10%. This is based on the rationalisation of supply voltages given in table 3b of IEC 60664-1 Note 2: The creepage distance and clearance values shown are based on a maximum supply voltage tolerance of +10%. Note 3: At 10 V and below, the value of CTI is not relevant and materials not meeting the requirement for material group IIIa may be acceptable.
  • 87. March 2010 © 9 Increased Safety Terminal Types and Ratings The terminals are de-rated so that the maximum current for Increased Safety applications is nearly half that for standard industrial applications as illustrated in the following table for enclosures manufactured to BS 5501 Part 6. This de-rating, along with other considerations, ensures that internal and external surface temperatures are kept within prescribed limits. The table below also shows the maximum conductor size for each terminal type. Terminal Type Conductor Size Increased Safety Maximum Current (amps) Industrial Maximum Current (amps) SAK 2.5 2.5 15 27 SAK 4 4 21 36 SAK 6 6 26 47 SAK 10 10 37 65 SAK 16 16 47 87 SAK 35 35 75 145 SAK 70 70 114 220 Increased Safety Terminals Terminal Locking Device It is essential that conductors are securely connected in the terminals to prevent sparks occurring as a result of loose connections. The illustration below shows how this is achieved.
  • 88. March 2010 © 10 Estimation of Terminal Population The number of terminals which can be installed in a given size of enclosure is limited. Several methods have been developed by manufacturers for this purpose. These are: Enclosure Factor: A method used in apparatus manufactured to BS 4683 Part 4 in which the terminal content is assessed by dividing the ‘enclosure factor’ by the certified current rating of a given terminal. Load Limit: Similar to ‘enclosure factor’ but used only on apparatus manufactured to BS 5501 Part 6. Kelvin Rating: Normally used for high current applications and apparatus manufactured to BS 4683 Part 4 and BS 5501 Part 6. In this method, enclosures and terminals are assigned a temperature rating. Enclosures will normally be limited to a temperature rise of 40K for a T6 temperature rating, but the temperature for the terminals will be dependent on their type, rated current, size of associated conductor, and the size of enclosure in which they are installed. This involves the use of tables which are provided by the manufacturer. Once the terminal ‘K’ rating has been established, it is divided into the ‘K’ rating for the enclosure to give the number of terminals of one type which may be installed. Max Dissipated Power: This is a method which will replace the current ‘load limit’ method and applies to apparatus manufactured to BS 5501 Part 6 and BS EN50019. In this method, enclosures are assigned a ‘watts dissipation’ rating, but the rating of the terminals is determined by use of a unique table (provided by the manufacturer) for the enclosure. This table provides the ‘watts dissipation’ of the terminal through consideration of conductor size and load current. The terminal content is determined by dividing the ‘watts dissipation’ value for the terminal into that for the enclosure. Another method used by manufacturers is to specify the maximum current per pole and also the maximum current per mm2 . Examples of labels with the above information are shown overleaf.
  • 89. March 2010 © 11 Examples of labels (a) Enclosure factor (b) Load limit (c) Enclosure factor (d) Maximum dissipated power (e) Maximum current per pole and per sq. mm Klippon TYPE TB11EX S/No. 9364 EEx e II T6 BASEEFA CERT. No. EX84B1333X BS5501 Pt.6 (EN50 019) LOAD LIMIT 600A Klippon ENCLOSURE TYPE TB11 BS 4683 Pt.4 Ex e II T6 BASEEFA No. Ex 77152/B MAX. CIRCUIT VOLTAGE 726 ENCLOSURE FACTOR 416 SERIAL NUMBER 1334 Klippon TYPE TB12 S/No.867594 EEx e II T6 BASEEFA CERT. No. Ex84B3290X BS5501 Pt.6 (EN50 019) LOAD LIMIT 40K Klippon TYPE STB2 EEx II T6 S/No. T499 BASEEFA CERT. No. 86B 2138X BS5501 Pt.6 (EN50 019) MAX. DISSIPATED POWER 7 WATTS HAWKE CABLE GLANDS Ltd. BS5501: Pt.6: 1977 (EN50 019) EEx e II T6 BASEEFA No. Ex 8142BX TYPE REF PL639 SERIAL No. 9960/89 PHASE-TO-PHASE 726 MAX VOLTS PHASE-TO-EARTH MAX.CURRENT DENSITY AMPS PER SQ. MM 4 MAX AMPS PER POLE 10