Weld caracks in a pressure vessel are mostly belonging delayed cold cracking and the distribution is very broad. In the process of the pressure vessel manufacturing and field compound by special attention, but because of its “delay”, under the action of restraint stress, often in a year inspection, there can still be found in large quantities. Here it is not investigating local stress concentration, or heat treatment is not timely, uniform and other reasons, only for such extremely subtle, and may not be entirely exposed to the workpiece surface crack detection method will be discussed.

Such surface breaking cracks generally with a magnifying glass or a microscope can be visually observed. Its presence not only reduces the weld strength, but also stress concentration will lead to a new, when the workpiece is by the load, resulting in some of the crack will rapidly spread, causing component damage. Therefore, in some cases, it is more dangerous than other types of macroscopic crack. On the pressure vessel inspection, how to more effectively detect microcracks, improve the detection rate of micro-cracks, which is placed in a container inspector exploration and wounded in front of a very real problem, and how to accurately locate and quantify defects in order to establish rehabilitation program is crucial.

CRACK DETECTION TYPE

The rapid development of modern industry, there is a variety of detection technology, which has his own strengths and weaknesses. So how to choose the most effective crack detection technology, a variety of detection methods should first be compared to find out the best in a suitable environment detection technology. It can be roughly divided into: visual inspection (VT), magnetic particle testing method (MT), penetrant testing method (PT), ultrasonic testing (UT), radiographic inspection method (RT).

In order to improve the detection rate of micro-cracks, with a single method for detecting the presence inevitably many limitations and omissions likely to cause undetected. Through practice, we believe that great harm to the medium and high pressure vessel welds microcracks testing should be comprehensive use of various detection methods. Vessel Inspectors conducting inspection commission should analyze specific issues, comprehensive use of various detection methods, and indicate the detected key positions; exploration wounded should also deal with specific issues, rational scientific application of various detection methods, definite purpose