Influence of Make-up Torque on the Fatigue Performance of Gas Storage

Gas storage well is a kind of high pressure gas storage facilities subjected to alternating pressure load.The sectional casing is connected by thread and collar,and the stress of thread structure is influenced by the make-up torque under this kind of connecting,then involving in the fatigue life of gas storage well.A finite element model of thread connection of casing and collar of gas storage was established,then the calculation method and the influence of fatigue performance of the make-up torque in the gas storage well were analyzed.Results shows that the make-up torque cannot be simply ignored due to its great impact on internal stress distribution of gas storage well.Under the action of the pre-tightening force,the overall stress level inside the gas storage well tube is higher than the external coupling;However,the maximum stress occurs in the coupling.For the structure of thread and collar,the first tooth root of whole tooth of casing and the tooth root of thread tooth of attaching location of casing and collar is liable to fatigue failure.The make-up torque who has a less influence of fatigue property of gas storage doesn′t change the stress amplitude at the point of stress concentration of casing and collar.