Research On Assessment Of Long Distance Pipeline Based On The Magnetic Flux Leakage Testing Data

In China, oil and natural gas are very important for the economic development. And they are the necessity of people. Most of the oil and gas are stored in the area, which is very remote and there is few people in there. The longdistance pipeline is the carrier of oil and gas, so the safe and effective operation is safeguard to national normal production and life. Pipeline indetector(PIG)had been developed, and all kinds of flow can be deteceted. When the detector finds flaw in the pipelines, what can be done is digging and replacing it. However, some small flaw can not influence the operationo of the carrying of oil and gas. And if the measures should be adopted, lots of time and money will be wasted. It is very important to evaluate the residual intensity of pipeline which is damaged, and it is based on the data coming from the PIG.The task is research on two standards about residual intensity, which are widely used in the world. The standards Manual for Deremining the Remaining Strength of Corroded Pinelines (ASME B31G) (2009) and API579-1/ASME FFS-1 2007 Fitness-For- Service (API579), are pulished by the American Society of Mechnical Engineers and the American Petroleum Institute, separately. The reliability of the standards is higher than others. A study of acceptable application of the standards and evalution procedure has been made, and analyze about evaluate result has been made too.There is comparison about ASME B31G and API579 based on the study. Assessment of pitting corrosion of API579 evaluation standard is used to evaluate the practical continuous pitting corrosion. Finite element simulation is used to evaluate the continuous pitting corrosion calculated, and the result of simulation can make guidance of evalution by assessment.Standard photographs of pitting corrosion are compared and classified based on the fractal geometry of nature, and MATLAB is useed to achieve the function of it. The assessment of leve 0 and level 1of B31G is to achieve by MATLAB.When all of the researches had been done, some cases are found which are as follows: the range of acceptable application of ASME B31G is less than that of API579; evaluated results of B31G are also conservative, but it is easier to perform. However API579 is complex, conservativer and priciser than other standards; in the example, result of calculation of practical continuous pitting corrosion is conservative after comparison with that of finite element simulation; the meseasure, based on the fractal, to classifiy the standard photographs of pitting corrosion has been proved that is high-speed and effective, and it is helpful to engineering of pitting evaluation. With the MATLAB, engineering of assessment of level 0 and level 1 of B31G is high-speed, so ASME B31G can be used widely.