Regarding the head weld coefficient
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How should the weld coefficient for small-diameter end caps formed by pressing an entire steel plate be determined? I previously designed a type of container with a diameter of 600; for the longitudinal welds of the cylinder, I used a weld coefficient of 0.85. Since the end caps were not joined together, I applied a weld coefficient of 1.0 when calculating those end caps. However, the reviewers said that 0.85 should be used. On page 58 of the training manual for pressure vessel design engineers, it also states that 1.0 should be used. I’m a bit confused – could everyone share how they determine these values in their designs? ?
Our company has always used 0.85 for the cylinder and 1 for the head. I think a value of 1 can be used for the head if it isn’t welded together; however, 0.85 should still be used if welding is involved
In the 2003 national examination questions for the certification of Class A pressure vessels, there was a question similar to this one, and the answer was 0.85.
It should be consistent with the weld coefficient of the cylinder; in the case of welded assemblies, 100% non-destructive testing is required according to GB150 standards, yet the acceptance level is determined based on the non-destructive testing requirements for the cylinder itself.
The head is not joined; when calculating the head, a weld coefficient of 1.0 is used
If there are no seams, use 1.0
If it is formed from a single plate, it is of course possible to use a welding joint coefficient of 1.0. However, there are two issues here: first, what size limit applies for end caps that can be formed from a single plate, and second, how can the designer ensure that smaller end caps are indeed formed from a single plate? So personally, I think using 0.85 is more reliable.
This post was last edited by prt0683 on 2010-10-10 at 20:59. For end caps that are formed as a single piece, the weld coefficient should still be set to 1, since there are no welds. In the case of end caps that are assembled from separate parts, the weld coefficient should be determined based on the inspection ratio and the required quality standard; it can be treated in the same way as the weld coefficients for the cylinder walls
1.0 should be taken. Since the end caps are not joined, there is no weakening due to welds; therefore, the value of 0.85 is not applicable. The use of 0.85 is a precautionary measure, as is traditional in China
According to the new code requirements, the weld coefficient depends on the type of weld joint and the proportion of non-destructive testing; in other words, the degree to which the weld weakens the base material must be taken into account. For unspliced heads, should the weakening effect of the head-to-tube welds on the head be considered?
ASME specifies that for seamless heads, if the weld joint between the head and the cylinder is subject to 100% non-destructive testing, the welding joint factor for the head is set at 1.0; if only partial non-destructive testing is carried out, then the factor is 0.85. It seems the regulations in GB are quite vague