Student Declaration on Submission I confirm that all the work in this coursework is my own. Student Signature. Date. 03-03-17 General Feedback by Tutor Fair work, tasks 1 & 2 are fine, update tasks 3 & 4 You can optionally correct the merit tasks 5-7. See feedback comments attached Please return within 10 working days and remember to attach your corrections to the bottom of this document, and don’t change any of the original work 11/3/17 Sampled by IV: Sign Date: 03-03-2017 Assessment grading instructions: Tasks 1 to 4 are required for PASS (P) grade and must be attempted Tasks 5 to 7 are required for MERIT (M) grade Tasks 8 is required for DISTINCTION (D) grade. Work for Merit/Dist grades should also be supported by fully referenced evidence Tasks for Assessment 2 (2 of 2) All answers must be your own worK Note: Copy and paste these cover and task sheets to the front of your written work as you must sign (electronic signature) and date these in order to have your assessment marked and graded Task 1 [P1] The Maintenance Manager has asked you to review the planned maintenance (PM) procedure for 2 pieces of equipment in the factory. The 1st piece of equipment is a 50m conveyor used to transport product in a cleanroom between process steps. The conveyor also contains a number of elevators protected by guarding. The 2nd piece of equipment is a mixing tank agitator driven by an induction motor controlled by an inverter. The tank is made of stainless steel and contains acidic chemicals when in use. As part of the review you will need, for each apparatus, to explain and identify the hazards that exist when a planned maintenance (PM) is being carried out. These are risks posed to anyone in the area, not just the Technicians carrying out the PM. In particular focus on electrical hazards Task 2 [P2] From the information in task 1 you must also specifically list the control measures required to eliminate or manage the risks to the Maintenance Technicians and others. In particular give a detailed range of control measures to prevent/reduce the risk of electric hazards Task 3 [P3] A quality and safety audit is to be carried out on all the maintenance procedures in the factory. The Maintenance manager has asked you with reference to at least 4 pieces of safety legislation, regulations or standards,and how these might apply to the PM activities described in task 1 Task 4 [P9] From the audit you have been asked to draw a start/stop/retain relay control circuit that could be used for the safe and emergency operation of a 3-phase drilling machine and lathe in the workshop that must include 2 emergency stop positions.Also explain how the circuit would operate and what types of commercial relays/contactors could you select. Task 5 [M1] The production manager also wants your help in deciding the best type of motor system for controlling the speed of a new automatic conveyor line. He has asked y.

1. Student Declaration on Submission
I confirm that all the work in this coursework is my own.
Student Signature.
Date.
03-03-17
General Feedback by Tutor
Fair work, tasks 1 & 2 are fine, update tasks 3 & 4 You can
optionally correct the merit tasks 5-7. See feedback comments
attached
Please return within 10 working days and remember to attach
your corrections to the bottom of this document, and don’t
change any of the original work
11/3/17
Sampled by IV: Sign
Date:
03-03-2017

2. Assessment grading instructions:
Tasks 1 to 4 are required for PASS (P) grade and must be
attempted
Tasks 5 to 7 are required for MERIT (M) grade
Tasks 8 is required for DISTINCTION (D) grade.
Work for Merit/Dist grades should also be supported by fully
referenced evidence
Tasks for Assessment 2 (2 of 2)
All answers must be your own worK
Note: Copy and paste these cover and task sheets to the front of
your written work as you must sign (electronic signature) and
date these in order to have your assessment marked and graded
Task 1 [P1]
The Maintenance Manager has asked you to review the planned
maintenance (PM) procedure for 2 pieces of equipment in the
factory. The 1st piece of equipment is a 50m conveyor used to
transport product in a cleanroom between process steps. The
conveyor also contains a number of elevators protected by
guarding. The 2nd piece of equipment is a mixing tank agitator
driven by an induction motor controlled by an inverter. The tank
is made of stainless steel and contains acidic chemicals when in
use.
As part of the review you will need, for each apparatus, to
explain and identify the hazards that exist when a planned
maintenance (PM) is being carried out. These are risks posed to
anyone in the area, not just the Technicians carrying out the
PM. In particular focus on electrical hazards
Task 2 [P2]

3. From the information in task 1 you must also specifically list
the control measures required to eliminate or manage the risks
to the Maintenance Technicians and others. In particular give a
detailed range of control measures to prevent/reduce the risk of
electric hazards
Task 3 [P3]
A quality and safety audit is to be carried out on all the
maintenance procedures in the factory. The Maintenance
manager has asked you with reference to at least 4 pieces of
safety legislation, regulations or standards,and how these might
apply to the PM activities described in task 1
Task 4
[P9]
From the audit you have been asked to draw a start/stop/retain
relay control circuit that could be used for the safe and
emergency operation of a 3-phase drilling machine and lathe in
the workshop that must include 2 emergency stop positions.Also
explain how the circuit would operate and what types of
commercial relays/contactors could you select.
Task 5
[M1]
The production manager also wants your help in deciding the
best type of motor system for controlling the speed of a new
automatic conveyor line. He has asked you to explain with the
aid of diagrams and research evidence, the operational features
system for an AC drive system with variable speed control.

4. Task 6
[M2]
As an alternative to the AC system in task 5, you have also been
asked to produce a circuit design that can control the speed and
direction of the conveyor using a DC motor drive system. With
reference to circuit layout drawings and research sources,
explain how it operates.
Task 7 [M3]
A new robot cell has been installed to operate along with the
conveyor system above. You have been asked to:
a) Describe with the aid of diagrams, the operation of a safety
relay system used on a robot cell. (400 words)
b) Explain how this system addresses the hazards and control
measures by also referencing relevant legislation, regulations or
standards. (400 words)
Task 8 [D2]
To ensure that the conveyor system is safe and complies with
legislation, compare the construction and operation of two
different types of stop/start/retain relay control circuits for
suitable for either the AC or DC system in task 5 or 6.
For example you may compare an electro-magnetic relay system
with an electronic logic system. Include appropriate drawings,
parts, truth tables and their advantages/disadvantages in your
explanation.

5. Task 1 [P1]
The Maintenance Manager has asked you to review the planned
maintenance (PM) procedure for 2 pieces of equipment in the
factory. The 1st piece of equipment is a 50m conveyor used to
transport product in a cleanroom between process steps. The
conveyor also contains a number of elevators protected by
guarding. The 2nd piece of equipment is a mixing tank agitator
driven by an induction motor controlled by an inverter. The tank
is made of stainless steel and contains acidic chemicals when in
use.
As part of the review you will need, for each apparatus, to
explain and identify the hazards that exist when a planned
maintenance (PM) is being carried out. These are risks posed to
anyone in the area, not just the Technicians carrying out the
PM. In particular focus on electrical hazards
Conveyor Comment by Geoff Tweed: 1 format could be better,
but ok
a) The common hazard is doing maintenance to a conveyor
connected to power, air or hydraulic that has not been locked
out, such as cut off valves not being closed, circuit breakers not
being pulled/gagged and power not being isolated or given time

6. to dissipate. As a result during working, a technician may
accidentally close the guards or activate a sensor. The program
running this conveyor may then start the conveyor. As a result
of this, it could cause injuries to not only the maintenance crew
but to people around the machinery.. If parts of the machinery
have been taken off for maintenance an electrical hazard could
potentially occur if cable looms or wiring becomes caught up in
the workings of the conveyer leading to not only injuries to
personnel but expensive and time consuming damage to the
equipment.
b) Maintenance operations without all covers and guards open.
This is a dangerous and poor maintenance practice because the
guards and covers are there to protect the technician and
personnel. If for example the conveyer is controlled by IR
sensor sytem the technician could inadvertently block the beam
which could then lead to the conveyer program commencing
resulting in injury.
c) Loading a stopped conveyor. This is to eliminate overheating
during starting. Overheating may lead to break down of
insulation of the machinery wiring. This will cause a short
circuit of power which may lead to a fire or electrical hazard.
d) Explosive Hazards. On a conveyer system this can occur this
can occur due to poor ventilation which does not remove or
filter the duct particles of the product being transported.
Respiratory damage will also effect those working in an
environment with poor ventilation.
e) Poorly laid out or insufficient emergency stops or cut off
switches.
f) Nip points. which can easily draw in clothing, tools, loose
hair, fingers or limbs, depending on the size, speed and power
of the conveyor.
g) Static electricity damage to components- Many caused by
mishandling and poorly stored equipment.
h) Faulty electrical equipment/ excessive extension leads.
Tank agitator

7. i) Never interchange the signals at the inverter. This is because
the inverter may respond differently and drive the agitator in
undesired way. This may cause even spillage of its acidic
contents that may cause harm to personnel around.
j) Never alter the terminals of the motor. This will make it run
in an opposite direction, if done without informing operators
spillage of dangerous load.
k) Never allow motor terminals to come into contact with the
acidic substance or water. As the two can conduct electricity.
This may result to a short circuit resulting in a fire hazard.
Task 2 [P2]
From the information in task 1 you must also specifically list
the control measures required to eliminate or manage the risks
to the Maintenance Technicians and others. In particular give a
detailed range of control measures to prevent/reduce the risk of
electric hazards
· Most importantly value of education, training, safe systems of
work, power lock-offs and effective supervision should not be
underestimated. Comment by Geoff Tweed: 2 ok, but should
have better linked to hazards in T1
· Positioning and selection of types of guards-It is highly likely
that fixed guards (ie those requiring the use of tools for their
removal) or movable guards will be chosen, depending upon the
frequency with which access is required. For long conveyors, it
is often not practical to interlock every movable guard due to
the large numbers involved. In such situations, isolation
procedures, safe working practices and rope-operated
emergency stop controls have an important role to play.
· Maintenance pionts installed-such as fitting remote grease
points so that the conveyor can be lubricated without having to
remove guards, and belt alignment mechanisms that can be
operated from outside the guards. Guarding should also be

8. designed, so far as possible, such that routine cleaning and
clearing of spillages can take place without disturbing the
guarding - such as by incorporating rodding access points.
· Appropriate signs/ warning notices- during PM operations
appropriate signs should be displayed informing personnel not
to apply power or enter the work area.
· Adequate air filtration/ ventilation- This will prevent build up
of potentially explosive duct i.e coal particles.
· Physical circuit breaker and power switch gags on a shadow
board- this will prevent the system being left live and accidental
application of power. By using the shadow board to keep them
on it is an easy visual indication if they have not all been put in
place.
· Strict tool control system- again a shadow board system will
ensure that all tools are accounted for after maintenance has
been carried out. This will prevent tools being left in the
machinery potentially causing a short circuit.
· Tagging in system for personnel- During maintenance
technicians are to tag into the work area and tag out on
completion. Power is not to be applied nor is the machinery to
be in any other way operated whist personnel are tagged in.
This prevents potential hazards to technicians in the area.
· Dual control powering system- For example two buttons far
enough apart having to be pressed within 5 seconds of each
other for power to be applied. This removes the danger of
accidentally applying power and provides a second person to
ensure it is safe to apply power.
· Ant static wrist bands, rubber mats and correct storage for
components- This will reduce the risk of static electrical
damage.
· Pat testing for all electrical items- This will reduce the risk of
faulty electrical items entering or being used in the work area.
Task 3 [P3]

9. A quality and safety audit is to be carried out on all the
maintenance procedures in the factory. The Maintenance
manager has asked you with reference to at least 4 pieces of
safety legislation, regulations or standards,and how these might
apply to the PM activities described in task 1
It is important to ensure that a conveyor complies with the
relevant standard and code of practice but the question of CE
marking is a more difficult area. While there are some situations
where a conveyor will be supplied as a standalone machine -
and will therefore need to be CE marked - there are others
where the conveyor needs a certificate of Conformity so that it
can be incorporated within a larger machine that is then CE
marked as a whole. If in doubt, seek advice from suppliers,
consultants, or contact the HSE. Comment by Geoff Tweed:
3 need to see 4 pieces of legislation clearly linked to 4
hazards/control measures for the conveyor/tank - update
The goal is to ensure that the machinery is safe, so users should
undertake a risk assessment and install the necessary safeguards
to reduce the risks to an acceptable level.
Risk assessments should be carried out by qualified staff this
will usually be the health and safety executive.
In line with general good practice, the objective should be to
design-out hazards, rather than safeguarding them but, in
reality, this is unlikely to be feasible where conveyors are
already operating or have been purchased as off-the-shelf or
configured-to-order units.
Since 1998, users of conveyors have been legally obliged to
perform a PUWER assessment - which often reveals that
existing safeguards are inadequate and that additional measures
are needed. In addition, companies purchasing off-the-shelf,
configured-to-order or custom-built conveyors frequently have
to design and fit extra guarding. Elsewhere, companies are in a

10. slightly better position if they build new conveyors in-house
and are able to take safeguarding into account at the design
early stage.
The PUWER 98 Regulations (Provision and User of Work
Equipment Regulations, 1998) have already been mentioned, but
there are several other regulations, standards and codes of
practice that need to be considered. Three such examples are BS
EN 620: 2002, 'Continuous handling equipment and systems -
Safety and EMC requirements for fixed belt conveyors for bulk
materials', BS 4531: 1986, ' Specification for portable and
mobile troughed belt conveyors', and BS 7300: 1990, ' Code of
practice for safeguarding of the hazard points on troughed belt
conveyors.
Task 4
[P9]
From the audit you have been asked to draw a start/stop/retain
relay control circuit that could be used for the safe and
emergency operation of a 3-phase drilling machine and lathe in
the workshop that must include 2 emergency stop positions.Also
explain how the circuit would operate and what types of
commercial relays/contactors could you select.
Safety is a major concern in a good many motor-driven
applications. This is true in industrial applications where
motion starts when power is applied and especially true when
power is restored after an outage. In such cases, unwanted or
unexpected motion is a risk to life or limb. The most simple
solution to this problem is the simple, time-proven Run /Stop
Relay Circuit. Comment by Geoff Tweed: 4 good start, but
commercial relay system for the 3-ph machines is missing - add

11. With this control circuit, motion cannot commence (or restart)
without the operator’s specific pushbutton command.
The control circuit draws 9V from the dc supply. It is first
passed through fuse then first emergency switch. Then a stop
switch is placed in series with the first emergency switch. Then
there is the second emergency switch., activating either will
open the circuit and de-energise the relay . Then there is a start
push button. Its single action powers the coil of the relay.
Therefore, the contact will shift down. Its output is looped back
to provide a holding mechanism. Then the output is fed to the
bulb but which in this case represents three phase relay or
contactor coil. A Dc relay or electromagnetic relay would be
suitable for this application.
Task 5
[M1]
The production manager also wants your help in deciding the
best type of motor system for controlling the speed of a new
automatic conveyor line. He has asked you to explain with the
aid of diagrams and research evidence, the operational features
system for an AC drive system with variable speed control.
A three phase induction motor is best suited for this operation.
This is because it is self-starting and it uses frequency of the
supply to determine its speed. There should be in inverter
circuit. Power inversion should be controlled by controlling the
gate triggering so that frequency can be controlled.
The circuit above shows a single phase inverter. The
potentiometer used to vary frequency of the output waveform by
adjusting how the capacitor charges and discharges. This circuit
can be cascaded to generate a three phase inverter. Comment by
Geoff Tweed: 4a Not sure this is right as it appears to an
amplifier, and there is no ac input
In a drive above. First the supply voltages are converted to dc

12. voltages. Through the dc link, the inverter circuit receives dc
power. With the help of a stored program, it is inverted into a
desired variable frequency to be used by the motor Comment by
Geoff Tweed: Incomplete explanation of VSD and needs
supporting references
Task 6
[M2]
As an alternative to the AC system in task 5, you have also been
asked to produce a circuit design that can control the speed and
direction of the conveyor using a DC motor drive system. With
reference to circuit layout drawings and research sources,
explain how it operates.
This circuit will contain an emergency switch, start latching
button, potentiometer, double pole double throw switch and a
motor. They will be arranged as shown below. Comment by
Geoff Tweed: 6 Ok for very small motors, but I would like to
see a system using transistors and thyristors for direction and
speed control with supporting references
Power from the battery is passed through and emergency switch.
It is then connected in series with the start button. An action of
this two will either turn the motor on or off. A potentiometer is
connected in series. This will be used to vary the speed of the
dc motor by varying the supply voltage. Then a double pole
double throw switch is connected in series to the circuit and
lastly, the motor. DPDT is used to change the direction of motor
rotation. And it is connected as above. When its selection
switch is in a certain position, it rotates as show by an arrow
above. When the position is changed, it will rotate as shown
below.

13. Task 7 [M3]
A new robot cell has been installed to operate along with the
conveyor system above. You have been asked to:
a) Describe with the aid of diagrams, the operation of a safety
relay system used on a robot cell. (400 words)
A safety relay has an electromagnetic coil. The coil is only
energized when powered. Once powered, it will act like a
normal magnet and attract anything metallic near it. Hence, it
will attract the contacts of the relay to close the circuit. When
any guards or emergency or stop button is pressed, its supply
power is cut, this will de-energize the electromagnetic coil.
Hence, it loses its magnetic effect, releasing the contacts. This
results to instant opening of the contacts of the relay
Comment by Geoff Tweed: 7a this does not answer the task
about a robot cell safety relay, please research and update
Comment by Geoff Tweed:
The circuit above show for an open control switch. This control
switch can be a stop switch, emergency switch and even a
sensor. When sensors are used for this purpose. They are
usually photo sensors. This sensors are placed around the
conveyor system entry point. They are manipulated to represent
a normally closed contacts. In this case, if a maintainer or other
personnel was to pass between the transmitter and the receiver
or the reflector plates, light is blocked and the beam is broken.
This will make the cause an open circuit and isolate flow of the
electrical power through the circuit. Since the relay will not
receive power, it will isolate the conveyor system from the
mains power and therefore stopping it. The emergency switches,
stop switches and other safety switches are also normally closed
and do function the same as explained above. This is shown by
the relay in the circuit above

14. When the control switches are closed, the relay shifts position
as shown above to close/complete the circuit.
During the construction of this, it is good to use a holding
circuit. This will enable restarting the conveyor belt once it has
been interrupted when in operation and reduce risk of accident.
If left the conveyor restarts itself once the emergency switch or
stop push button is released or when the safety guard or doors
are closed. But once a holding circuit is incorporated, it will
require an operator to safely restart it once it is safe and the
problem have been cleared. Hence, this is used to minimize any
accident associated with the conveyors. To incorporate a
holding circuit, the above circuit will be modified so as to
appear as the one shown in the diagram below.
When the start push button is pressed, the relay will be
powered. This will make the coil in the relay an electromagnet
and pull the contacts in a way that the contacts will become
closed. This will appear as shown in the diagram below.
When the stop push button is pressed, the coil of the relay will
be de-energized and release the contacts. Its diagram will
appear as the previous diagram.
b) Explain how this system addresses the hazards and control
measures by also referencing relevant legislation, regulations or
standards. (400 words)
According to Electrical control gear, this methods is used to
interface all safety signals to a control panel of a system. It can
be noticed that any action of any safety switch for example
emergency switch or gourd door switch will affect the supply
power to the coil. This will in turn isolate the machine from
power and make the machine safe for any intended operation.
This will make entry of restricted machine environment safety
and doing maintenance safe. This is achieved by either using a

15. PLC program or putting physically this safety switches in series
to one another so as to interrupt the flow of an electrical signal
in the control circuit. This power interrupt is then used to
isolate the conveyor power supply from the motor that runs the
conveyors. Relays and holding circuit become handy when
working in this circuits. Relays are used to interface the control
signal with the high voltage supply that powers the conveyors.
This is just done by just powering its coil in a controlled
manner so as to effect the closing of the contacts or opening of
the contacts. The holding circuit is incorporated in order to
eliminate the automatic switching on of the conveyor once the
problem that caused the breakdown has been cleared. This will
require an operator to manually restart it when he or she has
analysed that the situation is safe to restart it. Comment by
Geoff Tweed: Needs 4 pieces of legislation that relates to robot
cells - update Comment by Geoff Tweed: Ref?
Positioning of the safety control gears is an important
concideration. The safety switches and all other control
switches are placed in a very accessible manner and in a way
they can be easily be noticed by anyone. This ranges from the
way they are manufactured to the way that they have been
installed. . For example, colouring red colour to emergency
switch and stop switches while the start push button is coloured
green as a standard.
. In terms of positioning, they should be positioned at the
entrances to the confiscated areas of the machines. This is used
to ensure that the machine is isolated from the power supply in
any manner of entry in this confiscated area of the machine
either by switching it off or by opening the safety door of the
machine.
Again in this case it is relevent to quote legislation from puwer.
The regulations require that machinery provided for use at work
is:
Suitable for its intended use
Safe for use – including keeping it maintained in a safe
condition with regular inspections to ensure it is installed

16. correctly and that its level of safety doesn’t subsequently
decline
Used only by people who have received adequate training,
instruction and information
Accompanied by suitable health and safety measures, such as
protective controls and devices
Used in accordance with specific requirements – mobile work
equipment and power presses.
Regulation 18 deals with taking realistic and practical
allowances into account when choosing or specifying control
systems, and not increasing risk when the control system is
operating, either directly or indirectly, by impeding the
operation of other safety measures; not increasing risk if a
control system fails or loses its power supply.
This regulation states that every employer shall ensure, so far as
is reasonably practicable, that all control systems of work
equipment are safe, and are chosen making due allowance for
the failures, faults and constraints to be expected in the planned
circumstances of use.
Failure of any part of the control system or its power supply
should lead to a ‘fail-safe’ condition. Fail-safe can be more
correctly and realistically called ‘minimised failure to danger’
where the minimisation can actually be quantified as a
“probability of dangerous failure per hour”, or PFH. This should
not impede the operation of the ‘stop’ or ‘emergency stop’
controls. The greater the risk, the more resistant the control
system should be to the effects of failure. Bringing a machine to
a safe halt may achieve the objective. Halting a chemical
process, however, could create further hazards. Care should be
taken to fully assess the consequences of such events and
provide further protection, for example standby power plant or
diverting chemicals to a place of safety. It should always be
possible to recover to a safe condition.
[D2]

17. References
Www.wikipedia.org
Electronics for dummies-Dickon Ross BTEC Level 3
National Engineering Student Book- Ernie Cooke
http://www.hse.gov.uk/work-equipment-
machinery/puwer.htm
Revision 2 U18A2