Effective Use of Expansion Joints in Gas Transmission Systems
There are a multitude of problems that can occur when expansion joints are not used properly, or at all, in gas transmission compressor stations. These problems occur at two major locations in the pump station: the inlet and outlet of the reciprocating engine or gas turbine used to rotate a pump and the piping networks that transmit low and high pressure air between equipment at the station. Most designs incorporate some types of expansion joints, but quite often they are not used properly or are missing where needed. This paper is written to alleviate the headaches and shed light on the mysteries of system failure because of poor use of expansion joints. We will show several examples of ideal systems and work backwards into a real-life piping system to show how proper use of guides and anchors will reduce the amount of expansion joints needed. We will also explain how to select the correct materials for themetal bellows to combat corrosion while still performing well during cycling at high temperatures. We will discuss the use of internal flow liners in the expansion joint to stop flow-induced vibration. There will be a section showing how multi-ply bellows are used to greatly increase the cycle life of expansion joints that must isolate vibration of the pump or engine. The concept of pressure thrust on high pressure systems will be described and design techniques to control the pressure thrust through proper anchoring or the use of pressure balanced expansion joins will be explained. Specific site examples using pressure balanced joints will be used for this. Finally, a redundant ply option for high-pressure critical-service expansion joints will be introduced to increase the reliability of the joints and act as a warning system for future bellows failure.