Flaw detection ratio and weld coefficient of butt welds of cryogenic pressure vessels
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How to determine the flaw detection ratio of butt welds of cryogenic pressure vessels? What is the weld coefficient?
The weld coefficient of butt welds of low-temperature pressure vessels should still be based on GB150. The flaw detection ratio should be determined according to the specific equipment, but the local flaw detection ratio is 50%.
Low-temperature pressure vessels (except those with a volume less than 5 cubic meters) belong to the third category of pressure vessels. According to Article 85 of the "Capacity Regulations", the butt joints must undergo all radiographic or ultrasonic testing. According to 150 C4.6.1 a) The design temperature of the vessel is lower than -40 degrees. The butt joints should undergo 100% radiographic or ultrasonic testing. The welding joint coefficient is 1. If local flaw detection is performed, the flaw detection ratio is 50%.
GB150 stipulates: 1. The butt joints (A, B) of the container that meet one of the following conditions should be subject to 100% radiographic or ultrasonic testing. The design temperature of the container is lower than -40°C or higher than or equal to -40°C, but the rest of the joint thickness is greater than 25mm and is subject to local non-destructive testing.
It should be noted that when the flaw detection ratio of butt welds of cryogenic pressure vessels is 50%, the qualification level is Level 2, not Level 3.
Add something to the 4th floor: Comply with GB150 10.8.2.1 and 10.8.2.2 Class A and B joints must also undergo 100% radiographic or ultrasonic testing.