Excavation Inspection and Integrity Evaluation of Girth Weld in Oil and Gas Pipeline

Abstract

Since the occurrence of the “6.10” accident in China-Myanmar gas pipeline, the quality problems of pipeline girth welds are gradually exposed, and pipeline companies are carrying out therefore the hidden danger investigation and maintenance of the oil and gas pipeline on a large scale by pipeline companies. The main problems in the current pipeline girth weld investigation are analyzed, such as too many excavation points, poor applicability of non-destructive testing methods, imperfect defect integrity evaluation process, lack of repair principles and unified repair methods. Considering the main risk factors of girth weld failure, the priority excavation point selection principle of girth weld is established. The classification of girth weld defects is refined and the quantitative nondestructive testing method is established combining radiographic testing, ultrasonic testing, surface crack detection and macroscopic examination. The evaluation of construction acceptance and conformity verification, together with fitness-for-service are carried out. Based on the integrity evaluation results, defect harmfulness, pipeline high consequence area, special weld and other attributes, a reasonable maintenance criterion is established to avoid missed inspection or excessive maintenance of hazardous defects. In conclusion, the research results are helpful to reduce the failure probability of girth weld and ensure the safe operation of pipeline.