Research on the failure mechanism of non-metallic oil pipeline flange

Abstract

Abstract Fiberglass flanges are gradually being applied in oil field mixed transportation pipelines due to their advantages such as corrosion resistance and easy forming. However, at the same time, the anisotropy and local discontinuity are present in glass fiber components. Starting from the discovery of cracking, leakage, and other issues in the fiberglass flange of a certain oilfield sewage export pipeline, a combination of experimental research and numerical analysis is used to study the on-site fiberglass flange joint. Considering the internal pressure, bending moment, bolt load, and other loads in actual operating conditions, mechanical performance tests are conducted on the flange substrate, and the mechanical properties and damage conditions are obtained. A finite element model including pipeline gasket flange is constructed, and the flange damage under preloading, operation, external bending moment, and other operating conditions is analyzed based on the nonlinear Hashin failure criterion and the Tserpes sudden stiffness degradation model. It is found that bolt holes are more prone to large-scale failure damage due to stress concentration. As the external bending moment increases, it will simultaneously reduce the gasket compressive stress and cause flange surface failure and damage. According to research, it is recommended that the pre-tightening force of bolts during pipeline operation should not exceed 400000 N, and the bending moment generated by factors such as wind load and soil load should not exceed 200 N·m.