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Sprinkler Save London Underground Station
August 1 @ 12:00 am - August 31 @ 11:59 pm
Summary
- London Fire Brigade (LFB) reported a sub-surface fire involving an electrical motor in a London Underground escalator plant room.
- After conducting a dynamic risk assessment, the incident commander determined that the escalator water suppression system (EWSS) had been activated within one of the station escalator chambers.
- Firefighters wearing breathing apparatus entered the area and confirmed that the fire had been controlled and contained due to the activation of the EWSS.
- The remaining fire was extinguished by firefighters using appropriate firefighting media. No injuries occurred.
- The investigation found that the fire resulted from a heated motor brake drum igniting accumulated debris.
- The station was reopened shortly after the incident was resolved.
Escalator Water Suppression System
A bespoke¹ fire suppression system, specifically engineered for the London Underground, designed to safeguard escalators within sub-surface stations from fire. This solution provides full coverage along the entire incline, including upper and lower tread areas, machinery, dust trays, and the open spaces surrounding the sides of the escalators.
Each system comprises of range pipes divided into fire zones, (dry pipe system) terminating in open sprinkler heads, the heads are directed into the escalator machinery to suppress the risk.
Each zone is controlled by a multiple Jet Control valve, which incorporates glass bulb type mechanical detection device and an electrically operated detonator fuse. Distribution pipes connect the system to a suitable water supply usually ²town’s main system.
In the system standby condition, water is stopped from entering the range pipework by the multiple jet control valves. (MJC)
An MJC will only allow water to flow, into the zone that it controls, when it is either; triggered by an independent automatic fire detection system or subjected to sufficient heat to operate the mechanical detection glass bulb.
The fire detection system is managed by a dedicated fire panel monitoring a linear heat cable positioned in the escalator truss work. Should a fire affect a fire zone an adjacent zone of the EWSS will operate. The hydraulic calculations were based on supplying two zones simultaneously.
Kings Cross Underground Escalator Fire
37 years ago, a fire at Kings Cross underground station claimed the lives of 31 people which also started in an escalator. It is reported that a lit match fell through a gap on a wooden escalator and set fire to the grease and litter beneath the steps.
A subsequent investigation revealed a lethal combination of flashover, a rapid air-borne fire spread due to intense heat, and the trench effect, a newly identified phenomenon on steep surfaces, as the reasons behind the disaster.
Following a public enquiry by Sir Desmond Fennell published in December 1988, 157 recommendations were made which included banning smoking to all station areas, replacing of wooden escalators.
Major stations underwent comprehensive fire safety upgrades, including the gradual replacement of ³275 wooden escalators with metal ones, installation of heat detectors and escalator water suppression systems beneath escalators, accompanied by enhancements in radio communication and staff emergency training for the London Underground.
Conclusion
This incident provides further evidence on the benefits of fitting automatic water suppression systems in London underground sub stations, providing a further layer of safety from fire for passengers, staff and firefighters as part of a package of fire safety measures through early detection and suppression minimising disruption from fire.
- ¹There is no British or European Standard which deals directly with EWSS
- ²EWSS are required to be a secure supply conforming to the requirements of BS5306 and BSEN12845 for duplicate or superior single water supplies
- ³Uk Parliament, London underground: Escalator maintenance debate July 1989
Sources/further reading
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