FRACTURE ANALYSIS OF 73.0 mm EU J55 TUBING JOINT

The macro-fracture and micro-fracture of broken tubing joint were analyzed,the material properties of fracture tubing joint and the new tubing joint were compared by testing. It was found that tubing elevator face borne was worn severely,and its bore diameter was larger than that specified in standard,and the shoulder dimension of tubing joint coupling that bears the weight of the tubing string was smaller than that specified in standard by measuring dimension of broken tubing joint and the tubing elevator. The load borne on tubing joint was discussed based on the test result of fracture morphology analysis,material property and dimension measurement. According to test and analysis result,it is concluded that the tubing joint broke process as the follows: one side of the coupling face borne load slipped into the bore of the elevator,then cracked and deformed because tubing joint is inclined and stroke with down circularity arc edge of the elevator bore,and finally broke due to impact load and deflexion tension load.