The brochure describes in detail biogas (methane) processing. Biogas is created from landfills, wastewater facilities etc. The instrumentation involved with Biogas plants is reviewed in detail along with key applications for instrumentation

1. Biogas Production – Safe and Sustainable
Measurement and control system concepts from a single source

3. The Biogas Boom
The EU directive is being
implemented differently in
individual member states.
The growing biogas market is
developing almost exponentially
within the countries in which
the EU directive is being
implemented using fixed price
regulations. These countries
include Germany, Austria and
the new Eastern European EU
member states. But even in
countries outside of Europe
comparable regulations exist,
including Japan and the
United States. Amidst the
positive news, it is important
to remember that Biogas plants
also hold potential dangers for
mankind and the environment.
When it comes to safety, a
clear trend is noticeable as
lawmakers assign responsibility
for plant safety to the plant
operators. The operator must
assess, evaluate and control
potential dangers using ap-
propriate safety measures.
It is clear that profitability
be taken into account
despite current subsidies to
ensure that the biogas industry
remains sustainable. All of this
calls for a higher degree of
plant control and intelligent
measurement and control
concepts that take into
account the different aspects of
• Plant safety
• Plant availability
• Keeping plants well balanced
This is providing solutions that
ensure optimum operation for
plant operators.
The current climate change
discussion and increasing
natural gas and fossil fuels
prices are clear signs that we
need to look for alternative
energy supply strategies. As a
result of the Kyoto protocol, the
European Union adopted
a directive to promote
renewable energy sources.
The aim is increasing the
percentage of electrical power
produced by renewables
in the EU’s gross electrical
power consumption from an
average of 13.9% in 1997 to
approximately 22% in 2010.
This is to be the basis for
doubling the percentage of
renewables in the overall gross
domestic energy consumption
in the EU (including thermo-
electric power and power
consumption) to 12% by 2010.
3
DE
DK
UKIE
ES
FR
BE
NL
EU (25)
LU
IT
CZ
AT
SI
SK
HU
GR
RO1
BG1
LT*
LV*
MT* CY*
EE
FI
SE
PT
PL
5346,7
94,2
1923,2
33,3
63,5
1,3
93,8
59,9
118,1
8,4
10,5
4,8
69,4
353,8
227,0
334,39,2
34,7
1696,0
83,3
8,9
119,0
Map: Primary energy production of biogas of the European Union in 2006
(in KTOE/thousand tonnes of oil equivalent)
Landfill gas *Not significant
Sewage sludge gas ¹ Bulgaria and Romania are not included in this survey
Other biogases (agricultural waste, etc.)
33,3 Red figures show total production Source: EurObserve’ER 2007

4. The World of Endress+Hauser
“People for Process Automation“
The Endress+Hauser Group
Endress+Hauser is one of the leading
international suppliers of measuring
equipment, services and solutions for
industrial process engineering. The
company was established in 1953 by
Georg H. Endress and Ludwig Hauser and
has operated under the sole ownership of
the Endress family since 1975. In 1995,
Klaus Endress took over management of
the Group from his father. In 2006, the
Group of 7,045 employees generated
€985.2 million in sales and €86.4 million
in earnings. The family corporation includes
75 companies in 38 countries, managed
and coordinated by a holding company in
Reinach, Switzerland. Expert employees
and partners guarantee global sales and
service.
When the company was first established
in 1953, Georg H. Endress laid down the
company’s core values, which are still
valid today: maintain a strict customer
orientation, a high degree of knowledge
and expertise in process measurement
technology, a constant willingness to
learn from our customers, and maintain
communication, quality and a culture of
innovation. These values played a key
role in making Endress+Hauser one of the
largest family companies today in the areas
of industrial measurement technology and
automation. Since its founding over 50
years ago, the company has developed from
being a niche supplier of capacitive level
measuring instruments to an international
supplier of solutions, distinguishing itself
internationally through a diverse product
range of measuring instruments for process
engineering.
Instruments
Endress+Hauser provides a wide range
of sensors, devices, systems and services
for measuring level, flow, pressure and
temperature as well as liquid analysis and
measurement registration. The company
also links field devices to process control
systems and supports its customers with
technological and logistical automation
solutions. The products are setting standards
in terms of quality and technology. In 2006,
Endress+Hauser spent 8.0% of its revenues
on research and development and applied
for patents for 179 new developments.
We know your industry’s requirements
Our customers are predominantly
from the chemical and petrochemical,
pharmaceutical, food and beverage, pulp
and paper, primaries, environmental,
energy, oil and gas and renewable fuels
industries. These diverse industries have
very different measurement technology
requirements. Thus, Endress+Hauser
formed a team of specialists over ten years
ago known as Industry Management,
which focuses on the needs of individual
industries. Our Industry Managers work
together with leading suppliers in the
individual industries. Today, they have the
appropriate knowledge and expertise to
help our customers operate a plant cost-
effectively.
4

5. 5
Expertise in Measurement Technology
Endress+Hauser as a service provider
Engineering office/plant planner
consulting for new installation and
converted facility planning
We provide our customers with our
knowledge and expertise as early as
during the planning phase of the process
or installation concept for new plants or
plant sections. We are able to provide you
with optimum, goal-oriented support as
a result of our several years of experience
in implementing measurement and
control projects. Our core expertise
includes PROFIBUS®
engineering and the
development of measurement technology
plans, including layout.
Plant operator consulting
Even for optimizing and renovating plants,
we provide on-site consultation for issues
relating to measurement technology
design, migration planning (replacement)
or improvement of existing measuring
systems. The foundation for this is the
Endress+Hauser “Installed Base Audit”
(IBA) maintenance plan. This service
includes assessing and evaluating the
installed base and a maintenance plan
based on this with recommendations for
reducing the number of instrument types
and stocking spare parts.
Installation
We have system partners available for
implementing planned installations who
handle the entire range of electrical systems
engineering and electrical installation
services.
Commissioning
More safety for the plant operator is
guaranteed through careful and professional
commissioning of measuring equipment.
This includes detailed inspection of
installation, calibration and programming
measuring equipment, and training
operating personnel.
Maintenance and calibration
Maintenance contracts are discussed
and agreed upon to ensure smooth
plant operation. A complete range of
maintenance support services is available to
the operator, from simple functional testing
to specific agreements. Maintenance of
externally manufactured products can also
be handled by arrangement.
Training and seminars
Endress+Hauser offers a large number of
training programs and seminars. In addition
to basic training on individual measuring
principles, general as well as individually
tailored training services are also available.
Comprehensive topics, such as the ATEX
directive and SIL (plant safety), fieldbus
technologies and data communication,
round off our seminar program.
A working measuring device does not guarantee that a measuring point is OK!
Any expert can agree to this statement, most likely because of a lesson learned
from their own experience. Choosing devices that are not ideally suited to the job
during the planning phase, mistakes made during installation and commission-
ing, and performing no maintenance or incorrect maintenance of equipment are
all major causes of unsatisfactory measurement results. Endress+Hauser provides
support at all phases in the measurement technology lifecycle, starting with plan-
ning and extending to installation and commissioning and finally to operation,
with a well-coordinated range of services.

6. 6
Universal – Complete – Simple
Measurement and control plans for the biogas industry
Making biogas production profitable
Despite government subsidies, a biogas plant can only operate
profitably under long running times. Currently, the average
availability of biogas plants is estimated to be 60 to 65% and is thus
below the percentage considered to be profitable, which is 80%.
The reason for this insufficient plant availability is frequently due
to lack of a measurement and control plan, which would allow for
early interventions when there are negative changes in the status
of fermentation. In this case, the issue is not only about operation
of a measuring device or its technical properties. For the planning
engineer, tasks regarding design and the correct selection of
measuring principles play a decisive role. For the general business
operator, who is responsible for coordinating different maintenance
groups, the issue is about optimizing commissioning times as well
as minimizing the cost of coordinating project events. Last but not
least, the operator must be able to operate the plant efficiently,
which means at a minimum cost. Here, aspects of training costs,
replacement part storage and commissioning are crucial when
assessing whether a measurement and control plan is to be valued
as universal, complete and simple.
Biogas plant instrumentation
Depending on the complexity and size of the plant, a more or less
comprehensive measuring installation is important for monitoring
and controlling central plant areas. Fermentation and biogas
processing/CHP are the focus, since they have considerable
influence over the plant’s entire efficiency.
Measuring equipment recommendations for biogas plants
Lquidmanure,silage)
Delivery
Pretreatment
Fermenter
Gasholder
FinalStorage
Biogasprocessing
Sludgetreatment
Thermalcycle
Exhaustairdecont.
Continuous level measurement, no contact with medium Radar
Ultrasonic
Continuous level measurement, contact with medium Pressure/hydrostatic
Level measurement as the level limit Capacitive
Vibration
Temperature measurement Pt 100
Pressure measurement Pressure
Differential pressure
Liquid flow measurement, volumetric Electromagnetic inductive
Biogas flow measurement, volumetric Dynamic pressure sensor/aperture
Biogas flow measurement, mass Thermal
Liquid analysis measurement technology Digital pH measurement
Measurement of solids
Measurement of acids

7. Measurement technology for reliable process control
Examples of typical measuring points at biogas plants
The biogas process can be monitored
and controlled by determining a few
critical parameters.
The most important parameters include
temperature, gas volume and pressure,
methane content and hydrogen sulfide. In
addition, the rate of flow of the substrate
and the solid matter content are important
variables for the holding time and volume
Level limit detection: Liquicap M
and Liquiphant
The preferred area of application for
capacitive level measurement is in smaller
tanks, where a level limit (min/max)
or even a continuous measurement is
required. Capacitance level is also the
easier option for detecting the level limit
in the fermenter. Integrated build-up
compensation allows for a high degree
of functionality, even when build-up is
heavy. Shielding against condensation also
provides a high degree of availability and
ensures plant safety for the operator. A
key advantage of the Liquiphant vibration
limit switch is its calibration-free operation.
Adaptation to different media is not
necessary. The level limit is safely detected
with hardly any influence from the physical
properties of the medium.
Level measurement based on the
Time-of-Flight principle (radar and
ultrasonic): Micropilot and Prosonic
Both radar and ultrasonic level
measurements are non-contact measuring
systems. The advantage is that the sensor
does not come into contact with the
medium, eliminating negative influences
and potential contamination. Both systems
measure the time difference between the
signal sent from the sensor and the signal
being received after reflection on the
surface of the material being measured.
Ultrasonic devices generate ultrasonic
waves, while radar devices produce and
use radar pulses to measure level. The
advantage of radar measurement is that
measurement is not affected when gas
composition, pressures and temperatures
are variable. A typical application for a radar
measuring device detecting foam in the
fermenter. The less expensive ultrasonic
method is used extensively in all types of
collection tanks and feeding systems.
7
Level limit in hygienization: Liquiphant M Level limit in fermenter: Liquicap M
load in the fermenter. For additional
process management, there are also
level measurements, in collecting tanks
(hygienization, suspension), in fermenters
(foam detection) and even in gathering
systems (screw conveyors, conveying
equipment). All of these parameters can be
continuously measured and evaluated using
electronic measurement technology.
1 2
3
1
3 Gas holder (post-fermenter) level measurement by
sensing the position of the pendulum (Prosonic M)
Measurement of level in batch using
Ultrasonic device (Prosonic M)
2 Continuous level measurement in fermenter using
Radar: Micropilot M

8. Electromagnetic induction flow
measurement of liquids: Proline
Promag 50W/55S
The electromagnetic induction flow
measurement principle has been frequently
tested and is widely used throughout
the process industry. Electromagnetic
devices have a high degree of accuracy
(0.5 to 0.2%), cause no loss in pressure
and are also suitable for solid suspensions,
which can occur in renewable primary
product plants. These flowmeters are
ideal for detecting substrate solutions and
for balancing. These highly sophisticated
transmitters also have integrated extensive
diagnostic capabilities and contribute to
increased process safety.
Renewable primary
products
Fermenter
Dry fermentation
Wet fermentation
Renewable primary
products
Liquid
manure Homogenization Hygienization
Liquid manure
Out
Measurement of entered volume: Proline Promag

9. Fermenter
Post-fermenter
tput
Output
Flow measurement for biogas:
Deltatop/Deltaset and Proline t-mass 65
Measuring the volume of biogas is
important for operation and poses a
challenge in terms of measurement
technology and planning. This challenge
is due to the nature of the process and the
characteristics of biogas that are linked
to this process: extremely variable biogas
production requires a high dynamic
measuring range. The variable composition
and moisture load of biogas as well as the
issue of minimized pressure losses are
aspects to be considered when selecting
the best measuring principle. It is critical to
work with a partner who is able to provide
different methods for measuring the volume
of biogas. Endress+Hauser has a variety of
physical measurement methods available.
The method usually used for measuring
the volume of biogas includes a dynamic
pressure sensor or aperture (pressure
differential), or the thermal measuring
principle can be used.
Biogas utilization
Measuring biogas mass: t-mass in inlet to CHP system

10. Temperature measurement: Omnigrad
In addition to the volume of organic
acids and the pH value, temperature
is the most important parameter for
the microbial breakdown process into
biogas and is usually measured in every
fermenter. Endress+Hauser has a wide
range of temperature sensors available.
Omnigrad resistance thermometers (PT100)
are usually used for biogas plants. This
thermometer has a measuring probe with
a protective well and a connecting head
that contains a transmitter. Since the
immersion length and process connections
are adjustable, the temperature sensors
can be easily tailored to the customer’s
requirements.
Pressure measurement: Cerabar and
Deltabar
Pressure measurement requirements can
vary depending on the insertion site and
measurement task. The range of pressure
sensors made by Endress+Hauser is
organized accordingly: from simple pressure
switches to high-precision pressure sensors.
The pressure measurement in biogas plants
is usually taken in the biogas line to check
the compression output, but it is also
used for hydrostatic level measurement in
collection tanks or fermenters. Even biogas
metering using a dynamic pressure sensor
or aperture utilizes a pressure differential
measurement that must be extremely
accurate due to the very low pressure
differences.
Measurement technology analysis for
biogas plants: Liquisys M-series for
measuring solids, acids and pH
In some biogas plants, there is a need to
measure the pH due to the significance of
the parameter for microbial breakdown.
However, the pH can provide only partial
information on the existing concentration
of organic acids due to the high buffering
capacity of the fermenter suspension.
Measuring solids in connection with the
suspension volume provides information on
the fermenter’s volume load and can help
make the process more efficient. Measuring
acids for biogas desulphurization is
recommended, where the hydrogen sulfide
is converted to sulfur by adding air.
8
Measuring temperature in fermenter: Omnigrad
Measuring pressure in biogas line: Cerabar
pH measurement (left) and solid matter measurement (right) with Liquisys transmitter, sensors and process fitting

11. 9
Universal – Complete – Simple
Measurement and control plan for the biogas industry
Endress+Hauser is investing in the research and development of new and innovative measuring
methods. Measurement is our core competence and we use our expertise each day to help our
customers. We work closely with our customers to understand their special challenges. We
use this information with our development specialists to invent new and better instrumentation
designed to meet or exceed our customer’s needs.
Level:
Micropilot – non-contact radar level meas-
urement is not affected by pressure and
temperature fluctuations. Ideally suited for
level detection in the fermenter; certified
for use in zones 0 and 1.
Level:
Prosonic M/S – non-contact level measure-
ment using ultrasonic technology features
envelope curve evaluation and integrated
temperature measurement for time-of-flight
correction to ensure a high degree of
operating safety. Ideal for measuring liquids
and silages; certified for Ex zones.
Level:
Multicap T – continuous level measuring,
especially for small tanks offers reliable
functionality due to active build-up com-
pensation as well as shielding against con-
densation build-up in the connecting pipe.
Temperature:
Omnigrad resistance thermometer – ideal
for liquid, solid and gaseous media provides
excellent price/performance ratio. Certified
for Ex zones.
Registration:
Memograph – videographic recorder with
adjustable sets of parameters guarantees
data secure from manipulation: TÜV tested,
remote alarm via Telealarm software.
Flow:
Proline Promag – high-precision, solid and
reliable electromagnetic inductive flow
measurement with abrasion-resistant hous-
ing, even for sludge that contains particu-
lates (15 to 20%).
Flow:
Proline t-mass – thermal flow metering for
biogas (behind dryer). High dynamic meas-
uring range and a high degree of accuracy
even at the lowest pressures.
Flow:
Deltatop/Deltaset – flow measurement
with restrictors or dynamic pressure sensor
measurement for gaseous media. Includes
pressure and temperature correction for
detecting Nm3
.
Analysis:
Liquisys M – a device for all important
analysis parameters, completed by a wide
range of fittings.

12. 10
From Sensor to Solution
Automation solutions from Endress+Hauser
Since the introduction of communication
technologies more than a decade ago, the
barriers between field instrumentation and
the system level began to disappear. The
instruments became more intelligent and an
integral part of the automation architecture.
Endress+Hauser recognized this trend
and has been actively involved in different
standardizing bodies and user organizations
since the beginnings of fieldbus technology.
We support technologies established in
the market and are actively engaged with
emerging integration technologies, like
FDT. We offer comprehensive engineering
services for the integration of field
instruments into all relevant control and
asset management systems in process
industry.
Process control and regulation through
ControlCare
ControlCare is an open, field-based process
control platform. It takes full advantage of
intelligent fieldbus devices, exploiting their
ability to provide extended information about
themselves, the process and the plant.
ControlCare uses standardized function
blocks that can be easily combined, confi-
gured and expanded. The open architecture,
based on modular components, provides the
freedom to choose components and suppliers
for the most cost-effective solution. Open
standards and protocols are used at all
levels – from measuring device to system –
for communication, data access, configura-
tion and diagnosis
• Device and process information is
available at every point in the system
• Plant information is available where and
when it is needed
• Simple system integration
• Easily scalable
SCADA integration for operation and
observation
ControlCare uses state-of-the-art technolo-
gies to ensure ease of SCADA integration.
• OPC client/server architecture makes
communication efficient: all process data
are brought together into a single data-
base.
• ControlCare P View offers all of the
functions of a current SCADA software
package for operation and observation. P
View communicates with the process by
way of OPC interfaces. The integrated
Web server creates the foundation for
distributed operation and observation,
visualization and monitoring.
• FieldCare, an FDT based tool, allows for
setup of a parallel or integrated plant-ori-
ented asset management system.
• XML-integrated process data in MS
Office™ and commercial applications

13. From Sensor to Solution
Endress+Hauser as a system integrator for the biogas industry
Process monitoring
For process monitoring and system
optimization, measuring devices are
integrated at points relevant to the
process. This includes input material flow
measurements (holding time and volume
load), temperature and pH measurements
in the fermenter, level measurements in
collection tanks and flow and pressure
measurements in the biogas line. The
entire system is automated via four
process controls from different suppliers
(hygienization, fermentation pipes,
CHP system and internal technology).
Endress+Hauser handled the overall
metrological plan for the system as well
as the linking of the four process controls
using the P View visualization system. In
addition to linking and data access from
the four controls, the P View visualization
system took over the following tasks:
• Visualization of the process
• Constant monitoring of critical
system views
• Alert via e-mail for threshold violations
• Remote access to visualization system
for servicing
One of the first projects using the
Endress+Hauser SCADA system was an
industrial biogas plant built in southern
Germany in 2002 for generating electricity
and heat from food waste. The plant
generated approximately 2,900 MWh of
electricity and 3,500 MHw of heat annually
from approximately 8,000 t of food waste.
The process
The substrate delivered in a sump is
pumped into four fermentation pipes after
one hour of hygienization at 70º C and then
fermented under mesophilic conditions.
The remaining biogenous material is
transferred via a post-fermenter to final
storage. The heavily loaded wastewater is
treated via a wastewater treatment plant.
The resulting biogas is delivered to the CHP
system after drying and desulphurization.
All of the resulting electricity is fed into
the network; the heat is used to heat the
fermenter, including hygienization.
pH measurement in the supply line to the fermenter:
Liquisys M transmitter
Fermentation
Visualization of the sump and hygienization Hygienization system
11

14. Plant or operating areas where combustible
materials are used in sufficient amounts in
conjunction with oxygen are designated
as hazardous areas. In these areas,
measures are required to eliminate the
possibility of ignition due to electrical or
mechanical operating material (devices,
tools, machines or vehicles). Mixtures of
biogas with oxygen can form explosive
atmospheres. Consequently, measures
must be taken for all biogas plants to avoid
or reduce explosion hazards.
Basic principles of explosion protection
An explosion is the sudden chemical
reaction of a combustible substance with
oxygen with the simultaneous release of
high energy. Combustible substances may
be present in the form of gases, vapors,
mists or dusts. Explosion can only occur,
when three factors come together at the
same time and in the same place:
1.Combustible substance
(in ignitable quantities)
2.Oxygen (e. g. in the air)
3.Ignition source (with sufficient
ignition energy)
An atmosphere is described as hazardous
or explosive if there is danger to human life
or property by an explosion. An explosive
atmosphere of even just a few liters can be
dangerous in an enclosed space.
Explosion Protection in Biogas Plants
Basic principles – Explosion protection in Europe and North America
The principle of integrated explosion
protection requires the following explosion
protection measures in a certain sequence.
1.Preventing the formation of an explosive
atmosphere
2.Avoidance of the ignition of an explosive
atmosphere
3.Mitigation of the effects of an explosion
to an acceptable extent
Regulations and Standards
Areas in which there is a risk of explosion
that may harm people or the environment
are subject to various rules and regulations
in most countries of the world. While these
rules were initially issued at the national
level, they have since been replaced
over the last years by regional European
Directives and Standards, and in the field
of standardization they have partially been
replaced by international regulations.
Marking examples of apparatus for hazardous areas
Comparison of different markings
NEC 500
CEC J18
IS, Class I, Division 1,
Groups A, B, C, D
T6
NEC 505
CEC 18
Class I, Zone 0, AEx
Ex
ia IIC T6
IEC Ex ia IIC T6
CENELEC (ATEX) II 1 G Ex ia IIC T6
12
The basic principles of explosion protection
are the same all over the world. However,
technologies have developed in North
America in the field of explosion protection
for electrical equipment and installations
which deviate considerably from those of
the IEC (International Electrotechnical
Commission). The differences from
IEC technologies are among others the
classification of hazardous locations,
the construction of apparatus and the
installation of electrical systems.
Classification of Hazardous Locations
For potentially explosive atmospheres the
term “hazardous (classified) locations” is
used in North America. Hazardous locations
are locations, where fire or explosion
hazards may exist due to flammable gases,
vapors or mists (Class I), combustible
dusts (Class II), or ignitable fibers (Class
III). Based on the likelihood or risk that
an ignitable concentration of a flammable
substance will be present, the hazardous
locations are traditionally subdivided into
Division 1 and Division 2.
The traditional North American
classification system divides Class I
flammable gases, vapors, mists and liquids
into Gas Groups A, B, C and D, and Class II
combustible dusts into Groups E, F and G.
Further the temperature codes classifying
the ignition temperatures of flammable
gases are subdivided into 14 levels (T1…T6).
Class Division
USA (NEC 500-5),
Canada (CEC J18-004)
Zone
USA (NEC 505-7),
Canada (CEC 18-006)
Class I
Gas,
vapours,
mists
1 (continuous or
occasional hazard)
0 (hazard continuous-
ly, for a long period,
frequently)
1 (hazard occasionally)
2 (hazard only
under abnormal
operating condi-
tions)
2 (hazard rarely and
for a short period)
Class II
Dusts
1
2
Class III
Fibres
1
2
The zone classification was introduced as a parallel sys-
tem to the division system for Class I in North America.
Explosion protection in North America (USA and Canada)

15. The Directive 94/9/EC (ATEX 95)
The EC Directive 94/9/EC was issued
in 1994 to further standardize explosion
protection and make corresponding
adjustments in line with a new directive
approach. It specifies the requirements
for explosion protected equipment
and protective systems by prescribing
essential health and safety requirements. It
guarantees free trade within the European
Community, as agreed in Article 95 of the
Treaty established between the European
Community member states. The term
ATEX is the abbreviation of the French
designation for explosive atmosphere
“ATmosphère EXplosible”.
The directive had to be implemented
into national law without any changes/
exceptions. The scope covers all electrical
and non-electrical equipment, and
protective systems for use in potentially
explosive atmospheres.
Equipment categories: The manufacturer
of equipment that includes their own
potential ignition sources, and therefore
can cause an explosion, have to ensure
that the equipment undergoes an ignition
hazard assessment procedure, and takes
measures according to the essential safety
requirements to exclude the risk of ignition.
In the directive, Group I apparatus (Surface
and Underground Mining Systems) are
divided into two categories and Group
II apparatus (other explosive areas) are
divided in three categories with various
levels of safety (see table).
Categories of Group II apparatus: Other Explosive Areas
Category 1 Category 2 Category 3
Very high degree of safety High degree of safety Normal degree of safety
Safe even when two faults
occur independently
Safe even when a
fault occurs
Safe during normal
operation
The Directive 1999/92/EC (ATEX 137)
The 1999/92/EC Directive states “Mini-
mum requirements for improving the health
and safety protection of worker potentially
at risk from explosive atmospheres” refers
to the operation of potentially explosive
installations, and is therefore intended for
the employer. This directive contains only
minimum requirements. When implment-
ing it into national law, the single states can
adopt further regulations.
According to the 1999/92/EC Directive, it is
the duty of the employer to verify where there
is a risk of explosion, classify the hazardous
areas into zones accordingly, and document
all measures taken to protect the personnel in
the explosion protection documents.
Anywhere in the world that a Biogas plant will be constructed or maintained,
Endress+Hauser can deliver the best instruments with right certificates.
Zones and allocation of equipment according to the category
Zone Duration of occurrence of
an explosive atmosphere
Equipment category
Gas,
vapors,
mists
0 continuously, for a long
period, frequently
1G
1 occasionally 2G OR 1G
2 rarely and for a short period 3G OR 2G OE 1G
Dusts 20 continuously, for a long
period, frequently
1D
21 occasionally 2D or 1D
22 rarely and for a short period 3D* or 2D or 1D (* non
conductive dusts only)
13
The table contains an overview of the zones for explosion protection
and allocation of equipment according to the category.
Explosion protection in Europe
Assessment of explosion risks
When assessing the risks of explosion,
the following factors are to be taken into
account:
• the likelihood that explosive atmospheres
will occur and their persistence
• the likelihood that ignition sources,
including electrostatic discharges, will be
present and become active and effective
• the installations, substances used, pro-
cesses, and their possible interactions
• the scale of the anticipated effects
Zone classification
The employer has to classify the areas
in which explosive atmospheres may be
present into zones, and to ensure that the
minimum organizational and technical
requirements of the Directive are observed.
Flammable gases are classified into the ex-
plosion groups IIA, IIB and IIC depending on
their ignition energy. Six temperature classes
(T1…T6) classify the ignition temperatures
of flammable gases. The explosion group and
temperature class of used apparatus has to be
equal or higher than the classification of the
ambient flammable gases.
Types of Protection
Only explosion protected equipment may
be used in areas in which an explosive at-
mosphere may still be expected despite the
implementation of prevention measures.
Example: Biogas explosion hazard
Methane is the flammable part of biogas. For its
Ignition temperature 537 °C Temperature class T1
Ignition energy 280 μJ Explosion group IIA/Gas Group D
100%
70%
50%
0%
0%
30%
50%
100%
Bio-Gas
Carbon dioxide CO2
no ignition it´s inert
Methane CH4
Tignition
= 537 °C T1
Eignition
= 280 μJ IIA
Bio-Gas
with
Oxygen
>11.6%
Danger explosion!

16. Instruments International
Endress+Hauser
Instruments International AG
Kaegenstrasse 2
4153 Reinach
Switzerland
Tel. +41 61 715 8100
Fax +41 61 715 2500
http://www.endress.com
info@ii.endress.com
01.07/MMC
SO 705B/11/en/09.07
71062957
INDD CS2
Additional information
• Brochure Competence in renewable fuels
Managing ethanol and biodiesel process measuremt
safely, reliably and profitably – from load-in to load-out
SO 050B/24/ae
• Poster Explosion Protection
Marking Overview
CP 001Z/11/en