(146c) Inherently Safe Design for Vertical Knock-out Drums and Vapor/Liquid Separators

IN GAS PROCESSING AND LNG PRODUCTION, LARGE DIAMETER VERTICAL COMPRESSOR SUCTION DRUMS AND VAPOR/LIQUID SEPARATORS ARE COMMON. THE LIQUID LEVEL IN THESE VESSELS ARE CONTROLLED ABOVE THE BOTTOM TANGENT LINE, RESULTING IN STORAGE OF LARGE AMOUNT OF FLAMMABLE LIQUID INVENTORY BELOW HIGH LIQUID LEVEL, WHICH OFTEN IS IN EXCESS OF  THRESHOLD VOLUME FOR POOL FIRE. TO MITIGATE AGAINST HAZARD OF FIRE, SUCH SYSTEMS HAVE TO BE DESIGNED FOR FIRE-DEPRESSURING AND EQUIPMENT AND PIPING AROUND THE VESSEL HAVE TO BE FIRE PROOFED.  INCLUSION OF A SMALL DIAMETER BOOT AT THE BOTTOM OF THE VESSEL WILL ENABLE SHIFTING OF LEVEL CONTROL FROM THE MAIN VESSEL TO THE BOOT.  WITH HIGH LIQUID LEVEL SET IN THE BOOT, THE LIQUID INVENTORY WILL BE WELL BELOW THE THRESHOLD VOLUME FOR POOL FIRE, MAKING THE SYSTEM INHERENTLY SAFE BY ELIMINATING FIRE HAZARD AND AVOIDING NECESSITY FOR FIRE MITIGATION.