Safe and Economical Design and Operation of Liquefied Natural Gas (LNG) Pipelines: From the Perspective of Hydraulic Transients

Abstract

Hydraulic transient events can result in excessive pressures leading to catastrophic pipe and/or equipment failures, and possibly injuries or even fatalities, if water hammer phenomena are not accounted for in the design and operation of the Liquefied Natural Gas (LNG) and/or LNG byproduct conveying pipelines. Additionally, leaking of hazardous liquid due to water hammer damage can contaminate the environment and threaten the health of wild life and human beings. With the steady increase of LNG trading worldwide, a large number of LNG loading and unloading pipelines have been built in the past decades. Using lower piping class and schedule is a common cost-saving choice. However, it puts the pipeline systems in greater danger as various hydraulic transient events occur within the increasingly complicated pipelines during loading or unloading to or from the dedicated LNG carriers (ships). In this study, transient pressures and dynamic loads associated with pump trips, valve closures, column separation, and column rejoining initiated by the potentially troublesome operating conditions are simulated numerically. Recommended pressure and loading mitigation measures include slowing down of valve closure, increasing pump polar moment of inertia, placement of surge relief vessels, avoiding check valve slamming, and establishing safe system operation procedures.