Prevention of Flare Overload During Emergency Depressurization
Large oil and gas processing installations are commonly equipped with the ability to quickly depressure hydrocarbon inventories to minimise risks in abnormal situations. For the largest installations, it can be case that the flare capacity is insufficient to accommodate the full plant depressurising load at a single time. These plants depressure section by section, to remain within the constraints of the flare capacity. However, despite the fact that simultaneous depressurising of multiple sections may potentially overload the flare system, there is often no physical interlock system to prevent coincident operation of multiple sections; instead administrative systems are used, with a reliance on operator action. It is a concern that during emergency response situations, the potential exists for a flare system to be overloaded. Through the use of dynamic simulation of the flare network and depressurising system this paper demonstrates, via a case study of a large LNG plant, how an emergency depressurising interlock system was designed and implemented, to safeguard the flare system against overload.