Welding joint coefficient of the head
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This post was last edited by zjq1962 on 2021-12-1 08:45. The overall requirement of the equipment is partial inspection. After the head is formed, 100% RT inspection is performed, and the level II is qualified. When calculating the thickness of the head, should the welding joint coefficient be 1.0 or 0.85?
This post was last edited by zjq1962 on 2021-12-1 09:02. This is a passage from the engineer training tutorial. This means that the main body is a local inspection, and the qualification index for the head inspection is Level III. At this time, the joint coefficient is 0.85.
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This is what we are doing now. When splicing the head, press 100% RT-Ⅱ and take 1.0 to reduce the gap caused by the amount of thinning.
There is no problem with this, after all, the head thickness calculation formula only involves the joint coefficient of the tailor weld. The extra thickness can also be used for hole reinforcement.
Heads are generally purchased finished products. According to GB/T25198, if there are any seams, they must be 100% inspected. RT is Level II qualified. Of course, the weld coefficient is 1. The expert in that explanation is obviously not from the manufacturer. His assembly welding and other assembly welding inspections based on the head are all carried out in the manufacturing factory. It may be reasonable for extra-large heads that are made in splits and assembled by the manufacturer. The flaw detection may be a local inspection like the equipment. But it is obviously not suitable for the purchased tailor-welded heads. The head manufacturing factory has already done it and has a supervisory inspection certificate. There is no need to lower it and it is uneconomical.
According to GB150, the head seams must be 100% inspected after forming, and there is no partial inspection.
If designed in accordance with GB/T 150-2011, the welding joint coefficient is 0.85. I completely agree with you. This is the real correct answer. If the design is in accordance with ASME Ⅷ-1, and the girth weld between the head and the cylinder meets the requirements of UW-51 a(5)b for local inspection, the joint coefficient of the head joint is 1.0 ；
Your understanding is wrong. Regardless of whether the container is 100% inspected or partially inspected, the head welds need to be 100% inspected. The qualification level of the head is based on the container, and the welding joint coefficient should also be implemented according to the container. It cannot be said that there are two welding joint coefficients on the same drawing, 1.0 for the head and 0.85 for the cylinder. This violates the standard requirements and is never allowed.