PWHT of a vessel in repair case 1

[Yasir Irshad]

A Section VIII, Div. 1 vessel was originally PWHT for code related reasons only. However, the vessel is not stamped. An R Certificate Holder while modifying the internals, welds a 10 mm thick demister support ring internally with the shell of 50 mm thickness by fillet welding. The weld throat thickness is 7 mm. The material of construction is SA516-70. Does this fillet welding of 10 mm thick support ring has to undergo PWHT? If yes, then which clause of Sec VIII or NBIC mandates it?

Note: Service of this vessel doesn't require PWHT.
Please clarify

 

[oknow]

No help for your question as there are too many variables. Going forward

http://videos.asme.org/detail/video...lared?autoStart=true&sort_by=PLAYS_TOTAL:DESC

 

[Yasir Irshad]

@Oknow, what other information/variable you require to come to a conclusion??

 

[weldstan]

Review API 510 and Method 1 in NBIC. What was your preheat temp? What was your welding filler metal? Lastly review your Jurisdiction requirements.

 

[Yasir Irshad]

@weldstan My question is why should I look for alternate welding methods of PWHT or why I go for preheat? Why PWHT or its alternative methods are required?
UW 40 or UCS56 not fulfilled for this throat thickness.

 

[weldstan]

ASME VIII would still require preheat of 200 F min for initial construction. The reason for preheating is to reduce the potential for hydrogen assisted cracking and will also reduce the hardness in the HAZ. If preheating was not done and you want to accept the repair as is, why ask the question?

Since the repair was done by an R stamp holder, ask the contractor if he welded in accordance with Method 1 or some other procedure. Ask to see its WPS for the repair and the Examination used to confirm repair integrity.

 

[david339933]

Based on info given, this weld would not need PWHT on initial construction....it should not require PWHT on repair.

 

[Yasir Irshad]

@David The vessel was PWHTed during initial construction because the shell thickness was 50 mm. Now we are attaching supporting plates of thickness less than 10 mm only.

 

[weldstan]

Weld thickness is the governing criteria for PWHT for P no.1 materials per ASME VIII. It could well have been that the support rings were welded to the shell after PWHT. If no preheat was done during repair welding, I would advise wet fluorescent magnetic particle testing with direct current be done to the repair 72 hours after completion to assure freedom from delayed cracking.

 

[david339933]

Yasir, exactly.....the governing thickness of butt welds is the thickness of the weld (50mm)....which would require PWHT. The governing thickness of the fillet weld attaching the support plate is 7mm (throat thickness). This is below the thickness PWHT is required.
There is no need to PWHT after welding support plate.

 

[Yasir Irshad]

Thanks David for clarifying, But then why AI is insisting on doing PWHT of this fillet weld? When I asked for justification, he is saying that since full vessel was originally pwhted (due to butt weld thickness of 50 mm), this new repair fillet weld would have to undergo pwht. Is there any code reference for this requirement?

 

[SnTMan]

Wouldn't be the first (or last) AI doesn't know what he's doing...

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[weldstan]

Why do you have an AI involved for a repair to a non stamped vessel? An R-Stamp is not required. The R-Stamp holder doing the repair need not employ a an AI to sign off on the repair. And echoing SnTMan, I have more than once had to disabuse an AI of his notions, even going to his AIA superiors when necessary.