Fatigue life and crack propagation analysis of ram blowout preventer casing
In order to study the effects of pit and crack defects on the safety of the ram blowout preventer(BOP)shell in practical use,ABAQUS simulation and experiment were carried out to analyze the stress variation of BOP shell under working pressure(70 MPa)and hydrostatic testing pressure(105 MPa).The influence of pit defects on the service life of ram BOP was studied,and the fatigue crack propagation characteristics of BOP shell were analyzed.It is found that,when the diameter of the shell is ϕ170 mm,the maxi-mum stress reaches 520 MPa.This maximum stress is located on the edge surface of the pit,while the stress in other areas is much less than the yield strength of the material.When there is a corrosion pit(diameter<40 mm)at the high stress position of the shell chamber and the diameter,the maximum stress amplitude is 520 MPa and 344 MPa,respectively.The fatigue cracks of ram BOP gradually appear symmetric semi-elliptic cracks with the continuous expansion.An in-depth analysis of the corrosion pits in the chamber and high-stress areas of the borehole of the BOP casing indicates that the impact of these corrosion pits on the safe operation of the BOP is relatively minor.Additionally,the study has elucidated the relationship between the size of BOP defects and the fre-quency of use,substantiating the rationality of not using a uniform service life as the criterion for BOP decommissioning.
万方数据
维普
