| Hi Pradip,
Thanks for a very useful info as usual, appreciate your contribution to this blog.
Data requested:
Equipment:LNG Storage Tank ( MDMT -1460C / PQR Impact done at -1960 C)
Material SA553 Type 1,
Vertical welds Incoloy, SMAW, Electrode ENiCrFe-9 (Kobelco)
Horizontal welds Hastelloy SAW Filler ERNiMo-8 / PF-N4 (Kobelco)
Case: In PAMI it was detected that a wrong electrode was used for one vertical weld and this weld was ground out and re-welded with ENiCrFe-9. In this weld, transverse cracks were seen in RT. Well, in essence, this in itself is R2. After the crack was repaired, an additional defect was introduced (LoF) in the repaired portion of the weld. Hence, the query.
Regards,
Shashank Vagal
--- On Tue, 12/6/12, pgoswami <pgoswami@quickclic.net> wrote:
From: pgoswami <pgoswami@quickclic.net>
Subject: RE: [MW:14518] How many times can a weld be repaired without impairing its quality?
To: materials-welding@googlegroups.com
Cc: nach_sam@yahoo.com
Date: Tuesday, 12 June, 2012, 8:21 AM
Hi Sashank, The issue is with 9% Nickel steel. This steel has very specific design and application requirements, typically for Cryogenic services, minus 160 Deg C or below. I would think as a bare minimum the following should be followed for any repair:-Cutting out the existing weld and reusing the same plate--This may be done, however the following shall be followed:- -
carefully cut the weld with controlled flame, with minimum possible kerfs width. -
grind at least 1/8" off from the gas cut surface and beveled to sound base metal. -
perform LPI on the WEP. -
Fit-up and weld as per the original weld procedure followed. -
PWHT as required. -
The combined PWHT cycle (original weld +repair) shall not exceed the PWHT cycle of original base simulation coupon results. -
In addition it must not exceed the PWHT (T&T) followed while qualifying the PQR. -
Usually all 9% Nickel steel has to procured with the simulation heat treatment results. -
Total PWHT-T&T following original weld and repair should not exceed results of the simulation test coupon. It's not clear from the query what was the welding consumable used. But Inconel -112(E-NiCrMo-3) or Kobelco's product (e.e hastelloy C-276) would be the recommendations. Hope this would clarify the query. Thanks. Dear friends, What we must do to take care of this issue is this: When running a PQR, also run additional repair PQRs. Repair once, twice, thrice..... with WPS conditions and subject welded coupons to mechanical tests (impact mainly) and see at what level you have to stop. Two times repair is just an arbitrary statement, not supported anywhere but what I suggest is from the point of view of a good engineering practice and more reliable.I hope I am not reinventing the wheel ! Comments, please. Thankfully, TG On Thu, Jun 7, 2012 at 10:04 AM, Muthu Samy <jenieragav@gmail.com> wrote: Dear Vagal,
The repair can be attended for two times only and cut and re weld if repair found again.
Muthusamy@balu On 6 June 2012 07:33, Shashank Vagal <nach_sam@yahoo.com> wrote: Gents,
A very sensitive issue for most of us, I am sure from time to time, particularly when we are working at site with limited inventories at a given time: How many times can a weld be repaired without impairing its quality? We are facing a cut out of plate butt weld (9% Ni) with no additional plates if required to replace the welded ones if they are condemned.
There was an article some time ago addressing this issue ( http://www.twi.co.uk/services/technical-information/faqs/material-faqs/faq-how-many-times-can-a-weld-be-re-weldwed), but unfortunately it seems to have been taken off from TWI site. Please advise. Best regards, Shashank Vagal
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