Is a single-sided weld with a backing equivalent to a fully penetrated butt joint obtained through double-sided welding?
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This post was last edited by megaherz_IGGE on 2021-1-4 at 17:04. Dear experts, as shown in Figure 1 \"Solutions and Examples for Problem 150\", a joint with a gasket and full penetration is considered equivalent to a double-sided welded joint with full penetration; therefore, according to Figure 2, it falls under case a) of the 150 joint coefficient, and the joint coefficient is set to 1 when full non-destructive testing is performed； However, b) states that when all joints with gaskets are subjected to non-destructive testing, the joint coefficient should be 0.9. Is there a contradiction here? For joints with gaskets that have been proven to be fully welded through, should the joint coefficient be 1 or 0.9 when all such joints are tested using non-destructive methods?
It is a fully penetrated weld joint; weld joints with gussets suffer from stress concentration due to the gussets, which is why there are coefficients of 0.9 and 0.8. Also, be aware that this type of connector is not suitable for many applications.
May I ask, in clause b), the phrase \"gaskets in close contact with the base metal along the entire length of the weld\" refers to permanent gaskets, such as steel gaskets, right?； For gaskets that are removed after welding, such as ceramic gaskets or copper gaskets, they should not be included in case b); rather, they should be considered as \"single-sided welding equivalent to double-sided welding\", with a coefficient of 1.0, right?
The last edit to this post was made by ftxswb on 2021-1-6 at 07:54. The gussets that are in close contact with the base metal along the entire length of the weld seam, as mentioned in GB150, are permanent gussets that cannot be removed after welding; as for gussets that can be removed after welding, the coefficient for welded joints with single-sided welding and double-sided formation can also be set at 1.0.
In accordance with the ASME 8-1 construction rules, the shims can be removed after welding; as long as double-sided welding is achieved, a joint factor of 1.0 can be used for all inspected joints. The national standards do not specify anything regarding this; if removing the temporary gasket results in a double-sided welding effect and there is process evaluation to support it, then using a value of 1.0 is also acceptable.
Generally, single-sided welding with TIG welding as the root pass is considered equivalent to full penetration in double-sided welding, while single-sided welding with a backing plate is still regarded as single-sided welding with full penetration and not as the former.
That’s impossible. As you can see, the weld coefficient for 100% RT welding with backing plates is only 0.9; in other words, the strength of such welds is only 0.9 times that of the base material. In contrast, the weld coefficient for 100% RT welding without backing plates can reach 1.0, meaning its strength is equivalent to that of the base material.
That’s impossible. As you can see, the weld coefficient for 100% RT welding with backing plates is only 0.9; in other words, the strength of such welds is only 0.9 times that of the base material. In contrast, the weld coefficient for 100% RT welding without backing plates can reach 1.0, meaning its strength is equivalent to that of the base material.
A single-sided welded structure with gussets does not necessarily equate to a fully penetrated butt joint welded on both sides
What impact does this coefficient have on welding quality? If I don’t understand, I’d like to ask for help