关键词: 输油管道, 缺陷修复, 焊接结构, 应力集中, 屈服极限, 爆破压力, 疲劳载荷, 实验评价

Abstract: The welding-repaired pipelines are identified as two types of a single hole drilled on pipeline and several holes drilled in short span. A set of the full scale burst and fatigue experiments for the two kinds of repaired pipelines were conducted. The strain distributions were measured, and the stress concentration and yield limit load and burst pressure were analyzed. The results showed that the yield limit pressure of the repaired pipelines were lowered. The lowest yield limit pressure of repaired pipelines was 85% of that of the perfect pipelines, while their burst pressure was up 96%. The burst of pipeline was a ductile fracture resulted from the maximal shear stress. On the pipelines with a single hole, the burst occurred far from the welding sites, while on the pipelines with several holes drilled in short span, the burst occurred between the two adjacent tube caps welded on the drilled holes. Multi-cap repair is disadvantageous to the normal loading capability. Welding repairing process could result in the stress concentration. The maximum concentration coefficient of the hoop stress was 1.65, and the maximum axial stress was 2.25. The yield limit pressure, burst pressure and location of the repaired pipelines subjected to 5000 cyclic loading tests in high stress level were same as those of the repaired pipeline that did not experience cyclic loading, which indicated that the repaired pipelines have good anti-fatigue capability. The fullsize experiments demonstrated the loading capacity of the repaired pipelines.

Key words: petroleum pipeline, defect repairing, welding structure, stress concentration, yield limit, burst pressure, fatigue load, experiment assessment