Fire protection

Fire kills. During 1997 UK fire brigades attended over 36,000 fires in workplaces, these fires killed 30 people and injured over 2600. A high density storage system utilising pallet racking presents its own, unique fire protection challenge. The purpose of this column is to throw some light on this subject.

Risk assessment will highlight a number of hazards in a high rise racking system that may increase the risk to the workforce in the event of a fire. A racking system will have aisles which may be long and narrow or have dead ends. A racking block will also have large vertical openings through which fire, heat and smoke can spread.

These features in themselves do not constitute a fire hazard. For a fire to start it requires a source of ignition, fuel to feed it and oxygen. However, if a fire starts within a racked storage area and the storage system contains materials that are highly flammable, burn readily, give-off noxious fumes as they burn, are high value or in some other way special then some advanced form of fire protection will be required. The size and type of the storage system will also have a bearing on these considerations.

In these situations many racking systems are fitted with a sprinkler system. In-rack sprinklers are an accepted way of reducing the fire hazard within a storage system. They will not prevent a fire from starting, in fact they rely on the heat generated by the fire to trigger them, but they will help contain the fire to a specific area, and extinguish it. This in turn limits fire damage and will reduce the risk to life from fire.
Automatic sprinkler systems are used more than any other fixed fire protection system, with more than 40 million sprinklers being installed worldwide each year. In buildings protected by sprinklers 99% of fires are controlled by sprinklers alone, and 60% of fires are controlled by the spray from no more than 4 sprinklers.

Sprinkler systems need to be carefully designed and installed to the appropriate hazard category in accordance with an approved code of practice eg BS5306 pt2. This will ensure that the system will effectively limit and control the effects of the fire. A properly designed and maintained system will also suffer less failures and unwanted operations.

A sprinkler system comprises three major components: the grid of pipes and sprinkler heads, a set of valves to control the water flow, and the water supply. In operation the sprinkler head will open when it reaches a specific temperature. When used within a racking system they will spray water on an area immediately below them. The sprinkler heads are arranged so that if one or more operate there is sufficient flow of water to control the fire given the type and density of the products being stored.

At the point where the water enters the sprinkler system there is a valve. This is used to shut off the water for maintenance, and for safety reasons will be locked open. When a sprinkler opens and water flows these valves direct water to another pipe and this causes an alarm to activate. In this way the sprinkler system controls the fire and gives an alarm.
The most common type of sprinkler system will have its pipes always full of water. However, if the building is not heated and there is the chance of the water freezing during the winter then alternative systems have been developed. These generally have air under pressure in the pipes which keeps the water back until a sprinkler head operates.
Fitting a sprinkler system within a racking system is relatively easy. Support for the pipes is readily available from the rack structure, and our range of accessories includes most of the components necessary.
For more information on automatic sprinkler systems visit the British Automatic Sprinkler Association’s excellent website at www.basa.org.uk.

P3BOT.TIF Fire Protection