Fire And Gas Devices And System

Fire & Gas System
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In this post I would like to introduce completely new and specialized topic of Fire and Gas Devices and System.

Codes And Standards generally referred in various country

  • IEC 61508 (Functional Safety of Electrical / electronics / programmable electronics
  • IEC 60409 Guides for the inclusion of Reliability Clauses into Specification of Component of Electronic Equipment
  • IEC 60529 Degrees of Protection of Enclosure
  • IS 2189 Code of practice for Installation of automatic fire alarm system using heat sensitive type fire detectors
  • IS 5780 Intrinsically Safe electrical apparatus and circuits
  • IS 5469 Code of practice for the use of semi-conductor junction devices
  • BS 5839 Part 1 Code of Practice for installation of Fire alarm system for Buildings
  • BS 5839 Part 2 Code of Practice for installation of Manual Call Points
  • BS 3116 Part 4- Automatic Fire Alram System in Buildings: Control and Indicating Equipment.
  • BS EN 60079 Code of Practice for the selection,installation and maintenance of electrical apparatus
  • BS EN 54 HEat Detector,Flame & Ionisation Type Detector.
  • BS 5445 Components of Automatic Fire Detection System
  • BS 5446 Point Type Smoke Detector
  • NFPA 72 Code of practice for automatic fire alarm system
  • ISA S12.15 Performance requirement for Hydrogen Sulphided detection instruments
  • ISA S12.13 Performance Requiremnt for Combustibke gas detector

Shell DEP 32.30.20.11 GEN Fire, Gas and Smoke Detection Systems

Fire & Gas devices are broadly divided as follows

  • Detectors
  • Call Points
  • Beacons
  • Hooters/Bells
  • Signs( Exit Sign, Assembly Area)

Safety and Emergency Devices/Equipment are the most important part of any plant. Specially in OIl & Gas and Chemical Industry.

Type of Detectors / Selection of Detectors

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Notes:

  1. Line Of Sight IR detector technology provides greater coverage than point detector for detection (of flammable and toxic) and thus suggested to be used wherever practicable for detecting gas accumulation or gas cloud migration in open facilities. If necessary additional points detectors can be considerd.

  2. IR3 flame detectors can be protected from tropical environmental conditions (rains, humidity, solar radiations) by the following means:

Orientation of the detectors towards the ground floor to limit their exposition to the rains: they shall be oriented at an angle of pitch between 5 and 40 degrees below horizontal, so as to promote natural drainage of any condensed water or rain and to reduce accumulation of dust or debris;

Protection of the detectors by a rain covers or weather protection;

Heating of the sensor’s optic to facilitate the evaporation of the condensation.

  1. IR3 and UV/IR flame detectors must have a cone of vision of at least 90° in horizontal and 90° in vertical.

  2. Particular attention shall be taken during installation of supports of Line Of Sight detectors to limit the loss of signal between the transmitter and the receptor.

  3. It is suggested that in air ducts to have air speeds above 5 m/s, windshields to be provided.

  4. Where air intakes are greater than 1. 5 x 1.5m, Line Of Sight gas detectors are preferred.

  5. Use of High Sensitivity Smoke Detector is for Field Auxiliary Rooms, CTRs, UPS, TER (administrative buildings).

  6. Due to relatively high sensitivity, IR optical oil mist detectors can be used to alert operators to a potential incident rather than as a sole means of initiation shutdown or other control actions. If not properly installed and maintained, they will be less reliable and could give high unwanted alarm rates. They shall be considered for Emergency Diesel Generator and other enclosed equipment able to generate oil mists. Particular attention regarding the environmental conditions as the sensor is not suitable for ambient temperatures above 75°C.

  7. Use of UV/IR flame detectors is required for hydrogen fire detection.

  8. Acoustic gas leak detectors may be used in process units handling gas at high pressure (above 10 barg) where other detectors are not suitable. Voting with other technologies (point and/or LOS) could be performed for alarming purposes.

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