Loss Prevention 2016 (DECHEMA)
Loss of containment due to mechanical seal failure, flange connection leak or small bore connection failure associated with pumps is recognised as a significant hazard. To minimise the inventory that could leak, Emergency Isolation Valves (EIVs) are provided at the suction of pumps or at the bottom of the vessel connecting to the pump suction. In addition, double mechanical seals, EIVs at pump discharge, fire and gas detection system and fire suppression systems are provided. These measures are commonly adopted for pumps handling LPG or liquids at above auto-ignition temperature, but less common for flammable liquids operating at elevated temperatures.
Flammable liquids operating at elevated temperature like kerosene and diesel for example, on release can produce significant flash vapours. Flash calculation for diesel and kerosene at their bubble point yields more than 15% and 30% flash vapours respectively presenting a significant fire and explosion hazard.
Also, with plant capacities getting bigger, hazardous liquid volume in piping is increasing – multiple pumps taking suction from a common header; booster pumps operating in series; pumps taking suction from chimney tray of a column are some examples. The requirement of EIVs and other mitigation measures such as double mechanical seal, fire and gas detection system and fire suppression systems for pumps is reviewed in the context of these factors – piping inventory, nature of liquid and the risk of leakage followed by a fire or explosion. The current industry standards and guidelines do not address these aspects in detail.
The objective of this review is to not only enhance safety but also availability of the rest of the plant in case of failure leading to fire in any one equipment.
The full paper has been published in Chemical Engineering Transactions, Vol 48 2016, which can be accessed online at www.aidic.it/cet/16/48/112.pdf