Buckling failure mechanism of liner pipe in bimetal mechanical clad pipe under complex loading

Abstract

Bimetal mechanical clad pipe is one of the main measures for anti-corrosion control adopted in oil and gas fields. The liner pipe failure is a key problem that restricting the clad pipe applications. In this paper, a calculation model of clad pipe is established, and the buckling failure of liner pipe under complex loading was investigated. Effects of forming process, working pressure, external environmental loading and structural parameters on the failure mode of liner pipe were studied. The results show that increasing the residual contact pressure in the forming process is helpful to improve the buckling resistance of the liner pipe. The residual stress between liner and outer pipes can make the clad pipes bear a larger bending loads and have a larger critical curvature. Buckling mode “8” of the liner pipe occurs under complex loading. A larger working pressure can reduce the buckling degree and fold amplitude of the liner pipe. The liner pipe is more resistant to buckling in shallow water than in deep water. With the increasing of the wall thickness for liner and outer pipes, buckling resistance of the liner pipe becomes stronger. Finally, prediction formulas for critical curvature and the maximum normalized bending moment of the clad pipe are presented. The research results can provide a theoretical basis for the design, manufacture, and safety evaluation of clad pipe.