Study On Residual Life Evaluation (Bulk Type) For Oil/Gas Corroded Pipeline

The evaluation of residual strength and life of oil and gas pipelines is the important component in their integrality assessment. The evaluation of residual strength assesses the pipe actual load ability, and the evaluation of residual life forecasts the running time of the pipelines in the future and provides scientific basis for planning the examination period. The later is a little more difficult than the former for that in the evaluation process there are many uncertainties, including circumstance, mechanics and material factors, which can not gain exact values, and especially the developing law of flaw is ascertained very difficult.First, this paper discusses the present main assessment approaches of residual strength and residual life include the ASME/ANSI B31G (1991) , API 579 (2000) and the recommended approach of eroded pipeline evaluation made by CNOOC (SY/T10048-2003) . Then in chapter 3, the multilevel assessment system of residual strength of corrosion pipeline is introduced on the base of API579 and double shearing yield strength principles.Because the complexity of pipeline corrosion, it is very difficult to gain factors that affect corrosion. In addition, the size of buried pipe, mechanics data of structures and materials are random and disperse, so method of statistics analysis can be used to deal with these data and reflect the developing principle of objective things. As long as enough sample data is collected, probability method is suitable. Therefore, statistics analysis of relative parameter of eroded pipeline is introduced in chapter 4. The methods of forecasting the future corrosion rate are proposed in chapter 5, which mainly focuses on electrochemistry and provides basis for the evaluation of residual life. The assessment approaches of residual life of oil and gas pipe grounded on wall thickness, residual strength, practical use in engineering project and reliability are discussed in chapter 6.On the basis of the evaluation of residual strength of oil and gas pipe, the software of the evaluation of residual life of oil and gas pipe has been written with Visual C++ 6.0 programming language.