DIRECTED WATER DELUGE PROTECTION OF LIQUEFIED PETROLEUM GAS VESSELS

摘要

The adequate fire protection of Liquefied Petroleum Gas (LPG) storage vessels to guard against their catastrophic failure and possibly Boiling Liquid, Expanding Vapour Explosion (BLEVE) is recognised to be of key importance. One means of achieving this is by directed water deluge that, for LPG vessels of 50 tonnes or larger, should be a fixed system on the vessel. The deluge rate currently recommended for such systems is designed to provide adequate protection against hydrocarbon pool fires. However, it is now recognised that the incident scenario most likely to threaten the integrity of such vessels is impingement by a hydrocarbon fuel jet fire. HSE therefore decided to sponsor studies of the effectiveness of directed water systems in protecting against jet fires. This paper describes the work carried out by the Health and Safety Laboratory (HSL) in which a nominal 2 kg s~(-1) flashing liquid propane jet fire was impinged upon two tonne propane vessels protected by a range of water deluge systems. The results from the work show that a directed water deluge system designed to provide protection against a pool fire (using the minimum recommended rate of 9.8 dm~3 m~(-2) min~(-1)) provides inadequate protection against jet-fires. However, improved designs of water deluge systems proved more successful. A number of aspects concerning the design of directed water deluge systems were studied, including: type of nozzle and their arrangement, water flow rate and pressure, effect of blocked nozzles and delayed deluge initiation. Critical design parameters are proposed for directed water deluge systems.