Again-Induction Bends 1

[Andy49]

If the yield test(y psi)of the induction bend is lower than the mother pipe(Y psi ), My understanding from ASME B16.49-2007 is that the paragraph 8.1 allows the following procedure.
1 Take the wall thickness of the pipe to which the bend connects (.x inch)
2 Divide the tested yield of the bend to the specified yield of the mother pipe (Y/y), which is a number greater than 1
3 Multiply the pipe (to which the bend connects) thickness (.x)with value obtained in 2
4. The bend thickness has to be equal or greater than the value obtained in 3.(Extrado thickness? even if not specifically stated in B16.49)
I just wanted to know if I was understanding the paragraph correctly. Thanks.

 

[LittleInch]

Certainly looks right to me and yes, it is the minimum thickness on the extrados.

Beware that the start thickness of the pipe needs to be thicker than your minimum to acocunt for bend thinning (about 8% for a 5D bend). There is an issue in how you then weld this thicker lower yield bend in. What you can't do is machine off the inner side of the bend, but you may need a transition piece of thicker mother pipe or limit the change of ID to a few mm.

Alternatively you can order special pipe with the same ID of the mother pipe and hence have a larger OD, which makes it much easier to transition the weld and also eases any issues of getting pigs stuck in your narrower bend.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Andy49]

Thanks. That really helped. A follow up question, the same paragraph 8.1 further states that "For bends from welded pipe of NPS 8 (DN 200) or larger, a transverse weld tensile in the final heat-treat condition shall be conducted to determine the ultimate tensile strength. See para. 11.1.1
for number, location, and orientation of test samples required."
1 Is this an additional test to the tests already required?

 

[LittleInch]

I think so yes. Below 8" and even higher, seamless is generally preferred for induction bends.

Tests should ALWAYS include hardness tests after heat treatment as increased hardeness is a real issue for induction bends if they get the cooling wrong.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way