Research And Development On Non-destructive Testing System Of High Temperature Tube

In recent years, with the rapid development of petroleum and chemical industry, the high temperature furnace tube using in hydrogen and ethylene cracker equipment has been widely used. High temperature furnace tube is usually served in very abominable environment which is suffering from different kinds of conditions containing high temperature, high pressure, oxidative flaking, wall carburization and thermal fatigue, etc. The main damage form of high temperature furnace tube is the creeping rupture, not only the new furnace tube needs rigorous testing in factory, the tube in battle also needs to conduct the regular testing to prevent it bursting accidents, the main means of NDT detecting the creeping damage of tube in the Battle is the ultrasonic testing in current. In the late eighties of last century, The Materials Science and Engineering in Dalian University of Technology has developed the ultrasonic testing system working for creeping damage of high temperature furnace tube firstly in China, which has the intellectual property rights, it has made a great contribution for safe operation of domestic furnace tubes serving in the major domestic petrochemical enterprises. With the rapid development of NDT techniques in recent years, the traditional detection system needs an urgent replacement as it is very old and far behind.The paper has made a series of basal experiments to determine the stability, reliability and detective accuracy of the new ultrasonic of the ultrasonic testing system. First the experiments confirm the reliability of the testing system, and then test the attenuation regularity of the transmitted wave affected by the state of material organization, the distance of ultrasonic sound and the number of cracks using the cast of HK40high temperature tube which has prefabricated different artificial defects, finally it explores the resolution capability of the ultrasonic testing equipment for the scale of the cracks by changing the position of the ultrasound beam continuously which passes the surface of the crack.For the different extent creeping inflation of the type HP heat-resistant steel tube before it has a certain number of creep cracking, which is caused by high temperature strength and ductility, thinning pipe (compared with the traditional type HK furnace tube), the paper creates a new detective function in NDT system that can execute creeping inflation testing. According to the burning form of the furnace, the distribution and arrangement of the tube in the furnace, stress state and temperature of the wall, as well as the large case analysis of in-service creep cracking, the paper has designed a testing equipment for creeping inflation of high temperature tube, which works by continuously measuring the changes of the diameter between two unexposed surface. The new creeping inflation testing device is not only conducive to fast installation and efficient detection, it also perfectly matches with the existing mechanical device which can crawl on the tube.Adopting analog signals, the traditional ultrasonic non-destructive testing system has a lower accuracy (centimeter-level) detecting the position automatically or locating the defect. The new system can locate the position of detection or crack at millimeter accuracy by using the digital signal technology, the pulse radio transmission, the combination of encoders and comptroller.Instead of the traditional combinatorial type containing the detector and the recorder, the new system combines the all-digital ultrasonic card with the portable computer, it not only reduces the number and weight of the testing equipment significantly, also facilitates the processing and storage of the detective signal. Relying on the existing mechanical device which can crawl on the furnace tube, the new system mixes the ultrasonic non-destructive testing system of creep cracking, continuously detective testing system of creeping inflation and locating system together organically.Using the new NDT testing system of high temperature furnace tube, we have done some experiments online at the beginning of the year in the Dalian West Pacific Petrochemical Co., Ltd. and the China Petroleum Dalian Petrochemical Company, etc, the results show that the new system is working properly and reliably under the indicators meets the design requirements essentially.