Post weld heat treatment with AWS D1.1

[78500902]

Hello, I have the following question.

We have welded a trunnion to a pipe with a full penetration single side weld. This weld, because of the thickness of the trunnion (65mm), has required PWHT as specification requires PWHT for thickness over 40mm. After being treated, a modification of the dwg requires a fillet weld with a leg of 45mm. As per specification this fillet weld would require PWHT.

I would like to know if the requirement of PWHT can be avoided, as they have already qualified a CJP WPS without PWHT, that would cover up to 40mm (over 40mm would require PWHT), and this would cover all fillet welds.

 

[DekDee]

78500902,
You are governed by the specification - this overrules the code.

"As per specification this fillet weld would require PWHT. "

If that is the requirement then there is no way to avoid other than by a Concession Request to the Client / Owner
Regards,
BB

 

[weldstan]

Please clarify if "specification" is the Contract Engineering Specification or the Code governing construction. And if it is the Code, state which Code is applicable. Generally the Code governing the pipe (assuming pipe is pressurized and not part of a structure) applies to the trunnion attachment to the pipe. For example, if the governing Code of construction is B31.3 and the material is carbon steel, the fillet weld thickness governing PWHT is the throat thickness - not the leg length.

 

[DekDee]

Weldstan,
"Post weld heat treatment with AWS D1.1" is the title of the post

Cheers,
DD

 

[gtaw]

If AWS D1.1 is the governing document, PWHT is not a code requirement. PWHT, if required, must be stipulated by the Engineer. It is also the Engineer's responsibility to specify the temperature, the hold time, etc. under the auspices of AWS D1.1. It may be prequalified if there is documented evidence that the PWHT provides the required results. Typically, the manufacturer has test data for the base metal and the electrode manufacturer can provide information about the properties of the weld subjected to PWHT and the parameters of the PWHT used.

Best regards - Al

 

[Duwe6]

ASME Sect VIII Division-1 gives excellent guidance for PWHT. You might think about proposing that you conduct the PWHT i.a.w. Sect VIII instead of D1.1. As gtaw states, there is no PWHT under D1.1.

If the 'engineer' for your client persists in demanding D1.1, the essential elements are; width/size of heating band, temperature ramp-up rate [degrees/hour], holding [soak] temperature, soak duration, maximum variation of temperature across the PWHT'd area, ramp-down rate, temperature where the PWHT can be stopped and the weldment allowed to cool naturally. Bet you a farthing that that person cannot spec these items.

 

[weldstan]

DekDee,
It has been my experience in this forum that many of our questioners are confused. Knowing that D1.1 does not require PWHT but B31.3 does and the questioner is from the Petroleum industry, would it not be possible that the trunnion attached to a pipe is governed by B31.3 - not D1.1? Or the requirement was specified in the Contract Engineering Specifications as you also indicated.

It is also noted that 78500902 has not responded to any of the replies made to date.

 

[78500902]

Sorry for the late response.

This is governed by the specification that requires PWHT. As mentioned by gtaw and weldstan AWS D1.1 refers to the specification as itself doesn't contemplate PWHT. I have read the complete specification and it is based in LR rules for offshore structures. The good news is that these rules contemplate PWHT as not mandatory, but recommended, therefore I have submitted a clarification/deviation to the client to accept the complete weld (CJP+fillet) without PWHT with the background of qualified WPS without PWHT. I think this should be enough for them to accept the "deviation".

thank you!

 

[weldstan]

Fatigue and brittle fractures are common concerns with offshore structures. Changing from a full penetration weld to a fillet weld greatly diminishes the fatigue life. Engineering should decide whether stress relief should be eliminated.