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Prevention and Control of Fires

Background

Preventative measures are the most effective means of minimising the probability of equipment failure and its associated risk. Protection systems are not substitutes for well-designed and well-maintained detection, warning and shutdown systems. However, they can protect the structure and process equipment, limit damage to these facilities and prevent escalation of fire.

Design features can be provided, such as shielding which can reduce the likelihood of vessel failure. The choice between active and passive systems (or their combination) is influenced by the protection philosophy, the fire type and duration, the equipment or structure requiring protection, water availability and the time required for evacuation. In all cases, the specification must be matched to the fire type and exposure. The various types of protection system are considered in more detail below.

Strategy objectives

Current knowledge of prevention and control measures

There are two categories of prevention and control of fires; passive protection and active control and protection.

Passive fire protection (PFP) is defined, in the recently issued ISO standard (ISO, 1999), as 'a coating, cladding or free-standing system which, in the event of a fire, will provide thermal protection to restrict the rate at which heat is transmitted to the object or area being protected'. These materials are used to:

  1. Prevent escalation of the fire due to progressive releases of inventory, by separating the different fire risk areas, and hence protect personnel until safe evacuation can take place,
  2. Protect essential safety items and critical components such as separators, risers and topside emergency shutdown valves,
  3. Minimise damage by protecting the critical structural members, particularly those which support the temporary refuge, escape routes and critical equipment.

Spray applied epoxy intumescent and subliming coatings are most frequently used now, although cementitious materials were extensively used in the past.

Active 'protection' consists of several systems that may require human intervention to initiate. These include ESD and blowdown mechanisms, water deluge and foam systems, monitors, inerting systems, fire extinguishers etc. The installation and activation of these systems is well understood, although the physics of water droplet size and mists, on explosions hazards may require further work. The primary form of active fire protection for hydrocarbon processing areas is fixed deluge. Such systems may be provided to:

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Areas of uncertainty

There is an HSE cross-divisional need (preliminary steps are being taken) to develop guidance on the use and operational requirements for passive fire protection materials. At present, there is a lack of consistency in the requirements for protection of pressure vessels. This is reinforced by the recommendation in the HSE report on the Associated Octel incident that 'HSE, in conjunction with the industry, should consider what guidance, if any, should be published on the provision of passive fire protection on vessels.' This should include;

Industry practice in prevention and control of fire hazards

PFP is generally applied using ISO 13702, where the following functional requirements are given:

Active prevention systems are also based on the FES, but with significant input from QRA studies. Active systems are considerably more expensive to install and maintain and hence further justification is required.

QRA studies usually take some degree of credit for operation of active fire protection systems. These systems are usually designated as Safety Critical Elements (SCE's), pursuant to the requirements of the DCR Regulations and have associated performance standards, in accordance with the requirements of PFEER.

Strategic development issues

Passive fire protection

Active fire protection

Updated 2012-12-13