| Pipeline transportation, especially oil and gas pipeline transportation, has played a very important role for a country's economic development. Therefore, figuratively, pipelines are often referred as the blood vessels of a country. Different from other modes of transportation, pipeline transportation can still work normally with external interference such as bad weather, but once the accident occurred, it would often result in very significant economic losses and extremely harsh casualties. That is why pipeline safety inspection and maintenance is always a top priority for the pipeline transportationPipelines require regular testing and maintenance. Early in the pipeline construction, weld inspection is an essential process. For a long time, the X-ray film method plays the most important role for pipe welds detection in China. With the high development of computer technology, digital technology is tightly integrated with X-ray non-destructive testing. Compared with the film method, digital detection is efficient, convenient, environmentally friendly and even cost saving. At present, research on digital oil and gas pipeline weld inspection system is not indepth in China, and relevant standards are not very mature. Domestic enterprises usually imported expensive foreign equipment, and the cost is considerable. Therefore, research on the digital real-time X-ray detection system has important significance.For the reason above, a video-capture-card composed of CMOS image sensors is designed, which can be used in a non-destructive testing (NDT) real time system with X-ray. In X-ray camera panel, we select the appropriate CMOS image sensor and a scintillating screen to convert X-ray to visible light, and then, we change the visible light into simulating electric-signal. ARM and CPLD-based video-capture-card is also designed according to the characteristics of the CMOS sensor, which is an embedded system. The hardware that involves in the design includes LPC2378 microcontroller, which is produced using ARM7 core by the NXP Company, and the EPM7256AE type CPLD from Altera Company. The software that involves in the design operates on the microcontroller. In order to realize the design objective, the realization uses the open-source operating systemμC/OS-Ⅱas the operating system on the microcontroller software, and a light weight protocol stack, LwIP, is also used as the network protocol module to communicate with the computer. The video-capture-card executes the conversion of analog signals from the camera panel and the digital data is transferred to a remote computer with the TCP/IP protocol, which ensures an operator's safety without any protection in a lead house. The computer can change the data into image timely with our image software. The image's quality formed by our system is up to the standard B-Class NDT film. The video-capture-card can also control the movement of our crawling machine, which can cope with the shooting process and the crawling process collaboratively. This makes the process of pipeline-girth-weld-inspection flexible. Our experiments in industry show that this reliable system can easily work in harsh environments. |
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