Development And Application Of In-service Natural Gas Pipeline Defect Safety Assessment System

Gas pipeline transportation is the only way to transport large amount of natural gas on land, natural gas pipelines have been getting longer and longer. Security is an important part of the pipelines, The assessment of defects and software development are key factor of pipelines safety. This paper reviews the development of fracture mechanics and the evaluation methods of pressure vessels containing defects both domestic and abroad. According to the gas pipelines’actual operating conditions of the Southwest Oil and Gas Field Company, and based on the "fit for purpose" principle and mechanical performance test and CTOD calculation, the method of safety assessment for natural gas pipeline defects is formed based on the GB/T 19624-2004 standard. On this basis, this paper provides an effective method for safety assessment of natural gas pipeline, and the complex security assessment problem is transformed into a preliminary safety assessment based on the simple data of magnetic leakage detection, then made the safety assessment of the three natural gas pipelines, the evaluation period is greatly shortened, and compared the results with Safety institute of environmental protection and technical supervision’s. The main study process and production are as follows:(1) Tracking and retrieval valuation system defect of pipeline both in China and abroad and the latest progress in the relevant areas of related literature research, comparison, summarized the relevant literature research results.(2) This paper analyzes the defect assessment method of pressure vessels in China and abroad, based on the GB/T 19624-2004 standard for safety assessment of pressure vessels with defects.(3) The mechanical properties of X70 steel, L415 steel,16Mn steel and other three kinds of pipeline steel were carried out, and the CTOD value was calculated.(4) According to the results of CTOD test and magnetic leakage detection, the safety assessment of all the defects of the 3 natural gas pipelines was carried out by using the new software, and the finite element software ANSYS was used to analyze the defects of the system. At the same time, the results were analyzed with the foreign software, which proved the safety assessment method and the reliability of the software.(5) This paper makes use of the finite element software ANSYS to analyze the influence on the bearing capacity of the pits, the wrong side, the edge of the hole in the welding of natural gas pipeline, and the effect of the high volume defect on the bearing capacity.(6) The assessment system of natural gas pipeline defects is developed based on the safety assessment method and VB program.(7) Make the assessments of North ring, Ping qu, Fu na pipelines for corrosion, bearing capacity of the pits, the wrong side, the edge of the hole and etc. Make the forecast of pipeline corrosion and repair plan.