基于X射线衍射的在役全尺寸管道应力测试方法

Stress testing of in-service full-scale pipeline based on X-Ray

为验证X射线衍射法对于野外在役管道应力测试的适用性,首先重复测试铁粉、钢块、钢条和钢管的残余应力,分别验证X射线应力测试的可重复性。然后通过对比测试圆周域内9点的应力,分析测试点位置对应力测试结果的影响。再通过对比3个月前后的应力测试结果,观察测试时间间隔对应力测试的影响。最后分别采用等强度梁、静压全尺寸管道、悬臂弯曲的全尺寸管道开展加载试验,验证X射线应力测试的精度范围。试验结果表明,X射线重复性测试的最大差值为15.6 MPa。微小位置偏差对应力测试的影响范围在±30 MPa以内。3个月前后应力测试的最大差异值为30.7 MPa。等强度梁试验中,随着载荷增加,应力增量的理论计算值和X射线测试值的斜率几乎相同,应力增量最大偏差仅7.1 MPa。全尺寸管道静压试验中,X射线应力测试值与应变片环向应力测试值的最大差值为9.4 MPa。全尺寸管道弯曲试验中,X射线应力测试值与应变片轴向应力测试值的最大差值为17.9 MPa。以上试验结果表明,X射线衍射法应力测试的可重复性、可再现性和精度均可以满足在役油气管道应力测试的要求。

In order to verify the applicability of X-ray diffraction method for stress testing of field pipelines in service,the residual stresses of iron powder,steel block,steel bar and steel pipe are tested repeatedly to verify the repeatability of X-ray stress testing respectively.Then,by comparing the stress of nine points in the test circle,the influence of the location of the test points on the stress test results is analyzed.Then by comparing the stress test results before and after three months,to observe the impact of the test time interval on the stress test.Finally,loading tests were carried out with equal strength beams,static pressure full-size pipes and cantilever bending full-size pipes to verify the accuracy range of X-ray stress testing.The test results show that the maximum difference of X-ray repeatability test is 15.6 MPa.The influence range of small position deviation on stress test is within±30 MPa.The maximum difference value of stress test before and after three months is 30.7 MPa.In the equal strength beam test,with the increase of load,the slopes of stress increment of the theoretical calculated value and the X-ray test value are almost the same,and the maximum deviation of stress increment is 7.1 MPa.In the static pressure test of full-scale pipeline,the maximum difference between the X-ray stress test value and the circumferential stress test value of strain gauge is 9.4 MPa.In the full-scale pipe bending test,the maximum difference between the X-ray stress test value and the axial stress test value of the strain gauge is 17.9 MPa.The above test results show that the repeatability,reproducibility and accuracy of X-ray diffraction stress test can meet the requirements of in-service oil and gas pipeline stress test.