A Comparative Study of the Non-destructive Testing Methods on Gas Pipelines in a Steel Manufacturing Plant

• Main Authors: Chu , Li Chih, 朱立志
• Other Authors: Chia ,Tau Pau
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/4k4e7v

碩士 === 弘光科技大學 === 環境工程研究所 === 103 === Pipeline is a very important part in chemical process, since Kaohsiung gas explosion occurred which caused heavy casualties and property losses due to neglected pipeline management. Chemical pipeline management become imperative. The purpose of this study is to compare the applicability of four non-destructive testing methods applied on steel plant gas pipelines. Besides, ultrasonic testing method was used to measure the pipeline thickness in order to evaluate the remaining life and the schedule of replacing a new pipeline. In this study, two welding traces were completed on 2-inch oxygen and natural gas supply pipelines, one is a qualified weld, the other is a defective weld. Three non-destructive testing used for analysis include liquid penetrant testing, magnetic particle testing and radiographic testing. The advantages and disadvantages of each testing were discussed in five perspectives include internal functions, pipeline materials, object shape, real-time observation and the harmfulness of the testing methods. Ultrasonic testing method was used to evaluate the remaining life of the pipelines. The main results of this study is 1) internal functions: radiographic testing, ultrasonic testing can be used to detect the internal part of the pipelines; whether liquid penetrant testing, magnetic particle testing cannot be. 2) pipeline material: liquid penetrant testing, radiographic testing and ultrasonic testing can be used for most materials; whether magnetic particle testing cannot be. 3) object shape: liquid penetrant testing can be used for more complex shapes;radiographic testing, ultrasonic testing and magnetic particle testing can only detect relatively simple shapes. 4) real-time observation: liquid penetrant testing, magnetic particle testing, ultrasonic testing can show the testing results immediately; whether radiographic testing cannot. 5) hazards of testing method: liquid penetrant testing, magnetic particle testing and radiographic testing are hazardous themselves; ultrasonic testing is not hazardous. 6) the remaining life of the oxygen pipeline was estimated to be 7.3 years; natural gas pipeline was 8.3 years. 7) From the analysis of ultrasonic testing, it is found that the wearing rate of the pipeline elbow is more serious, therefore thinner thickness was measured relative to the other sampling tests. It is recommended that radiographic testing should be used for highly hazardous pipelines in the steel plant. In the case of flange welding, as the film cannot be placed evenly, penetrant testing should be used instead of radiographic testing. For the welding trace on the oxygen and the natural gas supply pipelines, it is recommended to adopt 100 percent proportional sampling test. Regarding life estimation of the pipeline, as the remaining life and the next testing time of both pipelines are close, and the pipeline position is adjacent to each other. It is recommended to test both pipelines in the meantime. Special attention should be paid for the abrasion in the elbow of pipelines to prevent pipeline leak. Keywords: Non-destructive testing, Liquid penetrant testing, Magnetic particle testing, Radiographic testing, Ultrasonic testing