NFPA 850-2020 Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations. 5.4.6.5 Cable Trays. Cable tray fres should be handled like any fre involving energized electrical equipment. It might not be practical or desirable to de-energize the cables involved in the fre. Water is the most effective extinguishing agent for cable insulation fres but should be applied with an electrically safe nozzle. Some cables [polyvinyl chloride (PVC), neoprene, or Hypalon] can produce dense smoke in a very short time. In addition, PVC liberates hydrogen chloride (HCl) gas. Self- contained breathing apparatus should be used by personnel attempting to extinguish cable tray fres. 5.4.6.6 Hydrogen System. Hydrogen has a relatively large fammability range (4 to 75 percent by volume) in air. The explosive range (for defagrations and detonations) is narrower than the fammability range, but hydrogen explosions can occur inside turbine halls in the event of accidental release and delayed ignition. Under most conditions, it is safer to allow a hydrogen fre to burn in a controlled manner until such time as the gas source can be shut off. Extinguishing the fre while gas is still escaping could allow an explosive mixture to be generated. The Fire Protection Design Basis Document should include provisions so that hydrogen supplies can be shut off from a readily accessible location outside the fre area if called for in an emergency situation. 5.4.6.7* Fuel Storage and Handling. 5.4.6.7.1 Once the location and extent of a fre in a solid-fuel storage pile have been determined, the fuel should be dug out and the heated fuel removed. Because moisture accelerates oxidation, water used for fre-fghting can aggravate the situa‐ tion if the seat of the fre is not reached. Water additives should be considered, to break the water tension and improve pene‐ tration.NFPA 850 pdf download.
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