Re: Welding Steel Pipe with Backing Rings

>Is the weld considered a full penetration weld if backing rings (P-1
>material)are used?

Why do you ask? The answer may depend on what the problem is. 'Full penetration' ('Complete joint penetration' is the preferred term) connotes a butt weld where the deposited weld metal completely fills the groove and is fully fused over the entire groove depth. Complete joint penetration can be achieved with a backing ring, but it can't be verified. So the answer is 'maybe,' since you haven't mentioned that the conditions for complete joint penetration are met.

The permissible load for the joint depends on whether you leave the backing ring in place after welding. For ASME Code Div 1 welds, there's a stress reduction of 10% if the backing strip is not removed--the permissible joint efficiency is reduced. In that case, the effect is that the weld penetration is effectively 90%. So if the backing strip remains in place your answer is 'no.'

>Is the penetration only determined by radiographic examination?
Absolutely not. It's determined by design and verified by inspection.

Did this come up in the course of an argument with an inspector or a customer? Not meaning to slander anyone, but if I were to guess, someone noted that a backing strip remained in place and called you on it, then suggested radiography to verify the weld penetration so the inspector or customer would buy off the weld. If I'm right, you'll probably need to remove the backing strip to insure complete fusion.

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw@skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)