There are a number of different types of fires that may be experienced on an offshore platform or onshore plant including:
Cloud fire: transient fire resulting from the ignition of a cloud of gas or vapour and not subject to significant flame acceleration via the effects of confinement or turbulence. It can therefore only occur after a relatively slow release of hydrocarbon and in an open free space.
Fireball: the rapid, turbulent combustion of fuel as an expanding usually rising ball of flame. It is more intense than a cloud fire and can be close to an explosion.
BLEVE: Boiling Liquid Expanding Vapour Explosion which results from the sudden failure of a vessel containing a pressurised liquid at a temperature will above its normal (atmospheric) boiling point.
Pool fire: A turbulent diffusion fire burning above an upward facing horizontal pool of vaporising fuel under conditions where the fuel vapour or gas has zero or very low initial momentum. A boiling pool fire is very difficult to control; it may accompany a jet fire where liquid rains out of the jet.
Running fire: A fire from a burning liquid fuel which flows by gravity over surfaces.
Jet fire: A turbulent diffusion flame resulting from the combustion of a fuel continuously released with some significant momentum in a particular direction.
Blow-out: A form of jet fire resulting from a well blow-out.
A suggested approach to implementing the assessment and control of a situation dominated by a fire hazard is outlined in the Interim Guidance Notes and suggests that as far as practicable:
- Identify all potential fires of a size or duration which could threaten life, lead to escalation or cause unacceptable loss
- For the critical fire hazards, identify possible causes of release and concentrate all reasonably practical measures on prevention
- Seek to reduce remaining fire hazards to minimum levels by modifying the process design, the equipment layout, the style of operation and/or use of passive or active fire protection
- Consider mitigation by active fire protection
- If residual frequency of hazard is such that it cannot be ignored, the scale and intensity of the hazard should be quantified, including the maximum area exposed and the maximum duration
- Identify all plant and structures which could fail when subjected to the fire exposure, releasing further inventory and endangering emergency equipment or personnel
- Select, specify and apply protection to match the fire type and duration
- Finally, review the fire hazards and specify protection for critical production equipment and capital items where justified by engineering judgement, cost benefit analysis or where required by operational management.
Detailed guidance on fire hazard management, fire loading and fire response can be found in the following documents:
1) Interim Guidance Notes for the design and protection of topside structures against explosion and fire, SCI, 1992
2) Fire and Explosion Guidance, Oil and Gas UK, 2007
3) Lees’ Loss Prevention in the Process Industries, Mannan, S. (ed), 3rd edition, Elsevier Butterworth-Heinemann
4) The SFPE Handbook of Fire Protection Engineering, SFPE/NFPA, 3rd Edition
5) Fire system integrity assurance, OGP, 2000