Fire and Gas Detection System Requirements for the Oil and Gas Industry. Offshore Platforms are also applicable for onshore plants/terminals. Safeguarding and Protective System to ensure oil and gas facilities are safe to operate.

1. Fire and Gas Detection System
(Offshore Facilities)
(Part 3 : Technical Features, Locating Detectors and Cables)
Chun Chet Gan (Ir.)
MSc Operations Management
[Manchester School Management]
University of Manchester Institute of Science and Technology (UMIST),
United Kingdom.
BEng (Hons) Mechanical Engineering
[Simon Building]
University of Manchester, United Kingdom

2. Technical Features Fire and Gas System (FGS)
• Fire and Gas System FGS is a system comprising one or more initiators, a logic
solver, and one of more final elements, whose purpose is to detect, mitigate and
return to normal hazardous situations involving gas leak or fire and loss of product
containment.
• The initiators includes smoke detectors, temperature/heat detectors, fire/flame
detectors, manual call points, etc.
• The logic solver are programmable logic controllers to perform the required
function such as a shutdown, activate alarms, etc.
• The final elements are solenoid valves, which are connected to the shutdown
system activated from the fire and gas panel via a shutdown panel.
• These connections, input or output signals, are hardwired armoured cables.
• These forms an integral part of the fire and gas system.
• Some industrial standards pertaining to this are as follows:-
- NFPA 72 Code of Practice
- API RP 14C – recommended practices

3. Features - Gas Detectors
• Principle of detection – Infrared, electrochemical, catalytic, etc.
• Signal Protocol : 4-20 mA, HART or without, Foundation Fieldbus, Modbus.
• SIL requirements – Required with SIL 2 certification by a third party firm?
• One man calibration – Gas detectors are require to be calibrated at recommended
intervals. This is done usually by a maintenance personnel. Thus, gas detectors are
required to be calibrated at man height. The detectors usually are supplied with
remote port to connect a hand held unit. Consider a connection port at man level.
• Line-of-Sight Gas Detectors (hydrocarbon) – the option for wiring connection,
whether direct from the control system to individual detectors (transmitter or
receiver unit) or power looped to the transmitter unit from the receiver unit has to
be carefully thought off. A reflector plate, called the transceiver unit, is also
available.
• Sunshades – To protect the gas detectors from direct sunlight (heat/UV).
• Other considerations : Cable entry size, mounting size, number of wires, calibration
tools (alignment tool), etc.
• Standard requirements : IEC, EN, BS.
• IP rating and Hazardous Area Classification.
• With self diagnostics feature monitored by the FGS, and historical report shown on
the display.

4. Features - Flame Detectors
• Principle of detection – Infrared, ultra violet, combination of infrared and ultra
violet.
• Signal Protocol : 4-20 mA, HART or without, Modbus.
• SIL requirements – Required with SIL 2 certification by a third party firm?
• Sunshades – To protect the flame detectors from direct sunlight (heat/UV).
• Other considerations : Cable entry size, mounting size, number of wires, calibration
tools, etc.
• Standard requirements : IEC, EN, BS, NFPA.
• IP rating and Hazardous Area Classification.
• With self diagnostics feature monitored by the FGS, and historical report shown on
the display.

5. Features – Manual Call Points
• Principle of detection – Manual
• Colour Code : Red, Blue, Yellow.
• Sunshades – To protect the call points from direct sunlight (heat).
• Parallel or serial resistors (End-of-line and In-line devices)
• Other considerations : Cable entry size, mounting size, number of terminals (looped
or individual), keyswitches (to bypass), etc.
• Standard requirements : IEC, EN, BS
• IP rating and Hazardous Area Classification.

6. Features – Smoke/Heat Detectors
• Principle of detection - Optical
• Removal pole (smoke or heat) : To remove detector from the base.
• Other considerations : Cable entry size, mounting size, number of terminals (looped
or individual), calibration tools, etc.
• Standard requirements : IEC, EN, BS.
• IP rating.

7. Features – Control Panel / Addressable Panel
• Control/FGS Panel – Human machine interface, alarms, graphic screen.
• Ergonomically design (shape).
• Graphic layouts, console pushbuttons positioning.
• Size and space dimensions.
• Flip buttons, button colours.
• Addressable Panel – LED screen, room descrip, alarms, indicators.
• Ergonomically design (shape).
• Size and space dimensions.

8. Features – Fusible Plugs Panel
• The use of pneumatic loops containing melting material with pressure transmitter
installed in each loop.
• The signal from the pressure transmitters is wired to the FGS logic solver to
monitor and initiate executive actions such as a shutdown.
• Troubleshooting feature is also available on to pneumatic panel (charge or
depressurized indicators).
• Other features:
- Charge knob, pressure indicators, manual or automatic drain.
• Panel are solid frame material to ensure firm vertical standing, with base plate to
secure on the support structure.

9. Locating Gas Detectors
• Gas Detectors are located near to the leakage source. The areas that contain
hydrocarbon liquid or gas require protection. These areas that are identified by
Safety will require gas detectors.
• Due to voting requirement, at least 2 detectors will be placed in a designated areas.
• If there are too many point detectors, consider combining with one line-of-sight gas
detector.
• Line-of-sight are perimeter (line) detection, whereas points are area detection.
• The height is important, whether it is 1.2 metres or 3 metres above the grating. The
height is due to the weight of the measured gas. If it is heavier than air, locate the
detectors 1.2 metres above the grating. Otherwise, locate the detectors 3 meters
above the grating.
• You will need to locate these detectors on the layout drawings. But most of the
time, safety engineers will locate these detectors.
• Consider a third party mapping consultant if required. This is possible only after
locating the detectors.
• Do consider hidden equipment that requires protection. Please note that emergency
diesel engine, compressors requires gas detectors to inhibit start when gas leak is
detected in that area.
• Equip HVAC air intake with three(3) gas detectors to shut the gas tight dampers
when there is a dispersion of a gas leak near that area.

10. Locating Flame Detectors
• Flame detectors are located almost in the same areas as gas detectors.
• Locate flame detectors adjacent to each other. A third detector, located opposite the
first two detectors, will detect fire in the shadow area.
• The height of the detectors is important to consider all possible views to protect the
area. Ensure that these areas are detectable.
• Similarly, you will need to locate these detectors on the layout drawings. But most
of the time safety engineers will locate these detectors.
• A third party mapping consultant is possible after this exercise at a cost.
• Inside the outdoor enclosures, locate at least two(2) flame detectors. Sometimes
rooms like emergency diesel generator are installed with two(2) flame detectors.

11. Locating Fusible Plugs
• Fusible Plugs are located based on Safety Engineer’s Hazardous Equipment Table.
This table identifies the equipment that are hazard on the platform.
• Locate fusible plugs at the hazard equipment.
• Designer will ensure that the detail loops are done properly and acceptable to client.
However, engineers will locate these plugs on the equipment with reference to API
RP 14C (for recommended practice).
• Locate at least two plugs above or near the equipment to protect the area.
• Check the temperature setpoint offered by fusible plugs suppliers.

12. Locating Manual Call Points
• Locate manual call points at door exits. The red call points will sound the alarm
when it is activated manually by a person that spotted a fire.
• At outdoor areas, call points are located along the escape routes.
• So, a person escaping a fire, after noticing this, will activate the call points.
• Suppose the call point is hidden or there is no clear sign, a person will not notice it.
Thus, is must be visible to the inhabitants on the platform.

13. Estimation of the Number of Smoke or Heat
Detectors
• The number of smoke or heat detectors in a room depends on the size of the room.
• Normally, one smoke or heat is placed inside a room. With the requirement to avoid
a spurious trip, two detectors will meet this requirement.
• This two detectors are connected to two(2) separate loops. It is then voted in the
control panel or the addressable panel.
• By referring to BS5839-Part 1, the details are stated in this standard.
• Another standard that writes on smoke or heat detectors is in NFPA 72.

14. Cable Type & Number of Wire
• Whether cable screen is required depends on the signals. If the signal is 4-20 mA
then screen is required to ensure that the condition of the superimposed signal is
protected.
• Otherwise, digital signals do not require screen because it is only a 24VDC current.
• Cable to detectors are individual from the field junction box to the detector.
• Cable from marshalling cabinet to the field junction box will be multi-cable.
• Cables located in the field are armoured to avoid discontinuity in signal when the
cable is physically damaged. This is a mechanical mean of protecting the wire.
• Fire resistance cable are required because when there is a fire on the platform, the
outer sheath will not catch fire.
• Number of wire to the detector is based on individual device vendor. As a general
guide, gas and flame detectors are 3 wire, manual call points are 2 wire, smoke and
heat are 2 wire, solenoid valves (deluge valves) are 2 wire, pressure
switches/transmitters (fusible plug panel) are 2 wire.
• Some flame detectors are 4 wire. The wire between receiver and transmitter unit for
line-of-sight gas detectors can be 4 wire.

15. Part 3 : Technical Features, Locating Detectors
& Cables
• End of Lesson 3
• Questions

16. OWN NOTES
• Part 3 : Technical Features, Locating Detectors & Cables
• Technical Features of Fire and Gas System
• Features - Gas Detectors
• Features - Flame Detectors
• Features – Manual Call Points.
• Features – Smoke/Heat Detectors
• Features – Control Panel / Addressable Panel
• Features – Fusible Plugs Panel
• Locating Gas Detectors
• Locating Flame Detectors
• Locating Fusible Plugs
• Locating Manual Call Points
• Estimation of the Number of Smoke or Heat Detectors
• Cable Type & Number of Wire