Specifying valves for oil pipelines
15 Jan 2000
Long pipelines are often used to transport large quantities of hydrocarbons under high pressure. In the case of a typical offshore platform in the North Sea, for example, the amount of gas present in a 150 km pipeline at 100bar is 637,000kg.
This represents an enormous source of energy release which, in the event of full bore pipeline rupture (FBR), poses the risk of fire exposure to personnel and also undermines platform integrity. The Piper Alpha tragedy clearly demonstrated the catastrophic nature of this type of accident.
Under Haroun Mahgerefteh, UCL researchers have developed a mathematical model based on the method of characteristics for the study of the dynamic response of ball valves and check valves (the two main types of valves which are employed in emergency shutdown) following FBR of a long pipeline.
It is a statutory requirement that all pipelines larger than 40mm diameter conveying flammable gases or liquids must be equipped with emergency shutdown valves.
A variety of scenarios, including valve proximity to rupture plane and delay in valve closure, are considered. Accompanying pressure oscillations and surges are also accounted for. The results are employed to recommend guidelines regarding the appropriate choice of emergency shut-down valve, depending on type of failure.
