The Index System Establishment And Evaluation Of Oil Tank Bottom Corrosion Risk

Large vertical storage tank is an important storage equipment in the oil station, leakage is the main form of tank failure, the floor plate corrosion perforation is the most common cause of tank leakage. Tank floor corrosion state is a main factor of tank safe operation, its severity is the leading indicator which guides tank maintenance decision-making, so storage tank floor corrosion state detection is main method to ensure the safe operation of the storage tank to the next cycle. In view of the floor special operating environment, international mainly carry out the acoustic emission on-line detection of the floor corrosion, based on the operating life and spill occurring. However, this technique can not only detect the floor corrosion leakage incident, also easy to cause excessive detection. In order to optimize tank floor corrosion of acoustic emission testing strategy, reduce the incidence of corrosion leakage accident, avoid unnecessary testing. This paper establishes an tank floor corrosion risk evaluation method based on risk indicators, realized the efficiency of the acoustic emission on-line detection for the storage tank floor corrosion inspection.This article does not consider the forms of roof, first introduced the tank bottom material, structure, size,installation, welding, installation and other physical processes, including accessories connected and the structure of the tank bottom base. Then researched corrosion mechanism of inner and outer side of the tank floor, and summarized the types and mechanism of corrosion. Combining the analysis of floor corrosion leakage accident, studding in detail from the inner corrosion and outer corrosion, floor manufacturing and construction three aspects. Inside corrosion can be divided into electrochemical corrosion, SRB corrosion, crevice corrosion and corrosion caused by coating defects. External corrosion can be divided into the soil erosion, oxygen concentration corrosion, stray current corrosion, and galvanic corrosion caused by the different characteristics of metals. It built the corrosion risk index system and the index score standard. The reference of the pressure equipment risk assessment method, this paper established the oil tank floor corrosion risk assessment process, through the analysis of judgment matrix, determined the index weight, established the calculation method of floor corrosion risk probability and consequences; combined with practice, discussed the calculation formula for floor corrosion risk assessment values; according to the level of risk, determined the next phase of the bottom plate corrosion test plan. Application instance, compared with acoustic emission detection and open-can examination results, is shown that the conclusion is the same, to verify the corrosion risk evaluation model is basically reliable.Through the above work, this paper summed up the floor corrosion mechanism, built the corrosion risk index system, which covered floor design, construction and running environment, etc; set up the floor corrosion process of risk assessment and evaluation calculation model, optimized the floor corrosion acoustic emission detection strategy.The original data involved in this paper is from the China Petroleum Pipeline Technology&Research Center, the object of the example application is from the oil station of Chan-gqing branch located on the northwest region.This is the beneficial exploration that tank floor corrosion assessment technology applicate in the formulation of acoustic emission detection decisions; after analyzing the floor structure, corrosion mechanism, corrosion factor, got the conclusion related to the floor corrosion risk assessment, this has promoting effect on the development of the floor risk analysis technology and the practical guidance to the acoustic emission floor corrosion detection technology cycle.