Weld repair after PWHT 3

[IPE435]

Good day all
A Vendor of ours has built an ASME 8 Div.1 pressure vessel for a refrigeration package. The vessel will be used in ammonia service and is fabricated of SA516 Gr 70 material 12.7mm thick. Due to fabrication errors the vessel has been PWHT 3 x and now there are no cycles left. The fabricator then damaged the reinforcing weld of the nozzle to shell weld and it now needs to be repaired again. Any ideas on how we can do this repair with out PWHT?

IS ammonia regarded as lethal service?

 

[rustbuster]

Assuming the damaged weld is on the OD of the vessel and the PWHT is required for service vs. code requirements I would discuss with your AI and have the repairs done without PWHT.

If the repair area is internal, a local stress relief might be acceptable.

Amonia is considered lethal service.

Good Luck

 

[metengr]

IS ammonia regarded as lethal service?

For most US Jurisdictions, no it is not lethal service. Vessels for anhydrous ammonia storage built to ASME Section VIII, Div 1 are U stamped and are not fabricated to provisions U-2 and UW-2(a).

 

[alimohd20009]

you could used some welding techniques for deleting PWHT like temper bead tech.
you gould find tham in API 510 and ASME sec 8 div 2

 

[jovizhu]

I don't do ASME 8 stuffs but maybe you can try to discuss with your AI and customer and see whether they can accept following disposition.

Repair it without PWHT;
Note this repair on the Data Report;
The site erector to do the local PWHT for the nozzle butt welds and the repaired welds together.

Of course, the maunfacurer should be back charged.

 

[deco0404]

I agree with alimohd2009, temper-bead is a good proven substitute. I am not entirely familiar with vessel standards, but we use this technique on main steam pipework in Power generating plant.

Declan

 

[bernoullies123]

wow, are you apply to identify the fabricator??? I procure lots of vessels and I wouldn't want to go anywhere near this mop!

 

[5BELLELI]

IS IT MANDATORY TO REPEAT A PWHT AFTER A REPAIR OF A WELD ?

 

[786392]

I am not a code conversant genius in any degree.

But reasonable engineering knowledge and judgement

makes us to decide such things with respect to their magnitude,dimensions and

possible process safety risks associated with respect to "CONTAINMENT" I believe.

Hope this conceptually shows way forward.

Best Regards
Qalander(Chem)

 

[integridadmecanica]

Dear,

The best option to repair without PWHT is using temper bead technique. The vessel it was put on service? if yes API 510 code apply to your vessel.The PWHT is mandatory after repair if PWHT it was required by code rules. Unless the service type require PWHT

Regards

Fernando

 

[stanweld]

I believe that vessels constructed of carbon steel in anhydrous amonia service are governed by OSHA in the USA and PWHT is mandated.

Apparently the WPS used in vessel construction is subject to impact testing. It is advised that you impact test qualify the procedure originally used with additional PWHT.

 

[metengr]

Stanweld is correct, anhydrous ammonia storage vessels are regulated by OSHA 29CFR 1910.111. Some Jurisdictions in the US have adidtional specific rules and exemptions.

 

[Guest102023]

I agree with Stanweld; requalification with additional PWHT time may be the path of least resistance.

Recommend of course you never go to that vendor again, although your purchasing agent probably got a big bonus for 'saving' a ton of money. You may be forced to mud wrestle him to prevent a repeat FUBAR in future.

[The worst-quality, hillbilly* heat exchanger shop in my area (they handle high alloy bundles on a gravel shop floor) keeps on getting work from local refineries based purely on price.]

*No offence to actual mountain people intended.

 

[t1t2t3]

Yes, depending the size of the repair you can apply:

1.- Temper Bead (Half bead)
2.- Weld the repair with IXCONE 182 (Ni Cr 3) or
3.- Repair and new PWHT.

 

[SJKWS]

Temper-bead welding is a proven repair method which requires no PWHT.

WTIA Australia has this great tech note.

http://www.wtia.com.au/pdf/TGN-PE-02 Temper Bead Welding.pdf

 

[metengr]

For anhydrous ammonia, I would not recommed temper bead weld repair. First off, one has to consider the service duty for this repair method and with the risk of SCC from tensile residual stresses after a temper bead weld repair it would not be wise.

Considering the mandate for PWHT, most Jurisdictions would not permit temper bead for these types of vessels.

 

[Duwe6]

Agree with metengr [again]: The requirement for PWHT is due to "Service", not Code. There is no data that I know of to support using Temper-Bead in lieu of PWHT for Ammonia service. PWHT it.

As stanweld said, the PWHT requirement is also incorporated into OSHA, along with 'no threaded Sch40 joints', no back-welding of threaded Sch40, no cast iron fittings, etc. Being part of OSHA,they are all now LEGAL requirements for anywhere in the USA. No choice on PWHT, just do it.

 

[Guest102023]

I also agree with metengr. Temper bead is not universally applicable.