Weld repair after PWHT
Weld repair after PWHT
(OP)
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?
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?





RE: Weld repair after PWHT
If the repair area is internal, a local stress relief might be acceptable.
Amonia is considered lethal service.
Good Luck
RE: Weld repair after PWHT
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).
RE: Weld repair after PWHT
you gould find tham in API 510 and ASME sec 8 div 2
RE: Weld repair after PWHT
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.
RE: Weld repair after PWHT
Declan
RE: Weld repair after PWHT
RE: Weld repair after PWHT
RE: Weld repair after PWHT
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)
RE: Weld repair after PWHT
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
RE: Weld repair after PWHT
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.
RE: Weld repair after PWHT
RE: Weld repair after PWHT
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.
RE: Weld repair after PWHT
1.- Temper Bead (Half bead)
2.- Weld the repair with IXCONE 182 (Ni Cr 3) or
3.- Repair and new PWHT.
RE: Weld repair after PWHT
WTIA Australia has this great tech note.
http:/
RE: Weld repair after PWHT
Considering the mandate for PWHT, most Jurisdictions would not permit temper bead for these types of vessels.
RE: Weld repair after PWHT
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.
RE: Weld repair after PWHT