Research On Comprehensive Detection & Evaluation Method Of External Corrosion For Buried Steel Pipeline

Pipeline is more and more widely used for its advantages such as low cost, safety and reliability for transporting oil and gas. However, because the steel pipeline was buried in the complex environment for a longtime, and according to the problems such as the increasing of service year of the pipeline, the natural aging of the equipment, and the third-party's damage and corrosion exists, it results in the invalidation of the pipeline's coating, and then leads to the corrosion of steel pipeline body itself, which could produces potential safety hazard. The safety of the pipeline transportation relates to the constructions of a stable country and harmonious society, the steady development of national economy, the economic efficiency of an enterprise as well as the security of people's life and property. So in order to ensure the pipeline runs safely, the research and analysis of the major factors that cause external corrosion of the buried steel pipeline and how to evaluate it effectively is urgently needed.Based on the study of large quantity of documents at home and abroad, through analysis of test parameter values of external corrosion, following on the basis of the principles of scientificity and feasibility, taking the relevant factor that affect the external corrosion of buried steel pipeline into account. It defines that the major factor of the comprehensive evaluation of the external corrosion of the pipeline includes the corrosion environment, the corrosion protection system and the corrosion of the pipe body, and then an assessment system of external corrosion of pipeline is established completely.In the external corrosion comprehensive assessment of the pipeline, many factors have uncertainty. In order to describe these uncertain factors exactly, the concept of fuzzy knowledge is introduced and the fuzzy multi-criteria modeling is applied to the comprehensive evaluation of the buried steel pipeline. The analytical hierarchy process (AHP) is determined to weights of affecting factors, and the method of membership grade function is used to establish single factor evaluation matrix, which each impact factor can be fuzzed. Finally the quantitative analysis method is applied to evaluate external corrosion status of pipeline by selecting proper fuzzy operator based on comprehensive considering weight of each affecting factor. Then based on this, an external corrosion fuzzy comprehensive assessment model is constructed and the comprehensive evaluation method of buried steel pipeline is proposed.Eventually, based on the mathematical model and applying Visual C# compiled language, a computer-aided system on external corrosion comprehensive assessment of buried steel pipeline is developed. The system has primarily some functions as follows: Firstly, it has the pipeline information management and search function, some basic information of pipeline can be searched in the system. Secondly, safe comprehensive assessment grade about external corrosion of pipeline can be calculated quickly, and the single factor graphic evaluation results can be obtained in the system.The application of the software can decrease the burden of technician in assessing inspection data and provides a convenient tool for relative people to access the related information of pipeline. Furthermore, the accuracy, applicability and reliability of the system have been verified by the engineering practice.