LNG Loading Lines High Surge Analysis

Abstract

Proper design of LNG loading lines and verification of emergency shutdown (ESD) interlock systems are critical in ensuring overall safety of the LNG facility. During an emergency, ESD interlock is activated with ESD valves closure initiated simultaneously with all loading pumps trip and the kickback valves open. During the ESD valves closure, the pipeline can be exposed to a risk of high surge pressures exerted onto the wall. A pressure surge or liquid hammering phenomenon in piping systems can be caused by a fluid in motion forced to stop or change direction suddenly (rapid momentum change) and also due to cavitation effect. Cavitation is caused by the formation and instantaneous collapse of vapour bubbles. The collapsing bubbles exert severe localized impact forces that can result in pressure surges. This paper discusses the methodology used to evaluate any potential occurrence of surge and the peak pressure associated with it, using several case studies for analysis. This paper also shares best practice identified from the study to facilitate with safe operations at an LNG loading facility.