Fatigue analysis and testing of SX-22 couplers

Abstract

General Electrics Oil and Gas delivers couplers for subsea applications. In orderto validate the fatigue properties on one of there products, the SX-22 coupler, afatigue assessment was desired.The seal in the coupler system is subjected to non proportional multiaxial loading,which makes traditional fatigue approaches invalid. A stress based critical planeapproach was used in order to predict the life time and location of failure in theseals being subjected to pressure cycles after being compressed at connection.Three dierent critical plane models were examined, and the results from thesefatigue calculations gave similar results.To validate the results, a physical test based on the fatigue calculations was alsoperformed. Two dierent test setups were tried, whereof one did not handle theoperation and failed. The physical test results proved to correlate well with thecritical plane fatigue assessment regarding both lifetime and where on the seal thecrack formed.