How many times can a weld be repaired without impairing its quality?

[Shashank Vagal]

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

[Muthu Samy]

Dear Vagal,
The repair can be attended for two times only and cut and re weld if repair found again.

 

Muthusamy@balu

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[Tarantula Ghosh]

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

Tarantula

[sankar bombay]

Dear friend,
As this condiction we want to check the material hardness... as
per code 2 times we can cut out the joint , after that if u check the
Hadness on material at heat affected zone , the micro structure will
be have changes due to heat
My friend Ghost i have accepted ur command max we allowed only twice
, thice is risck of u


regards
sankar.k

On 6/8/12, Tarantula Ghosh <ghosh.t...@gmail.com> wrote:
> 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 <jenie...@gmail.com> wrote:
>
>> Dear Vagal,
>> The repair can be attended for two times only and cut and re weld if
>> repair found again.
>>
>> [image: Visit Us @ www.MumbaiHangOut.Org]

>> *Muthusamy*@*balu* <Muthusamy@balu>

shankar

[K.Babu]

Gents,

 

Though the 2 times allowed  in normal is an generic specification and concerned project specs.

 

In my opinion you want to do repair  "n" number of times, the base materials & Consumbles shall be verified for the same by simulation tests.

 

For example, as per API 6A, it specifies separate qualification is required for the repair, doest restrict the number of times .

 

If you want to do three times repair, base materials & welding consumables shall be simulated for the three times to ensure it retaining mechanical properties after three cycle of PWHT time and temperature if undergoes PWHT

Thanks & regards,

K.Babu

Singapore

 

[pgoswami]

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:-

1. carefully cut the weld with controlled flame, with minimum possible kerfs width.
2. grind at least 1/8"  off from the gas cut surface  and  beveled to sound base metal.
3. perform LPI on the WEP.
4. Fit-up and weld as per the original weld procedure followed.
5. PWHT as required.
6. The combined PWHT cycle (original weld +repair) shall not exceed the PWHT cycle of  original base  simulation coupon results.
7. In addition it must not exceed the PWHT (T&T) followed while qualifying the PQR.
8. Usually all 9% Nickel steel has to procured with the simulation heat treatment results.
9. 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.

 

Pradip Goswami,P.Eng.IWE

Welding & Metallurgical Specialist

Ontario, Canada.

Email-p...@sympatico.ca,

pgos...@quickclic.net

 

---

From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of Tarantula Ghosh
Sent: Thursday, June 07, 2012 11:38 PM
To: material...@googlegroups.com
Subject: Re: [MW:14493] How many times can a weld be repaired without impairing its quality?

[Biswajit Mukherjee]

Sashank,

The TWI article that you quoted below is still there. Fearing a copyright issue I did not attach a scanned copy of it. But just google it....

There's a somewhat similar q&a in the link below:

http://www.ndt.net/forum/thread.php?admin=&forenID=1&msgID=38203&rootID=38032

Regards,

BM

From:        "pgoswami" <pgos...@quickclic.net>
To:        <material...@googlegroups.com>
Cc:        <nach...@yahoo.com>
Date:        12-06-2012 08:20
Subject:        RE: [MW:14518] How many times can a weld be repaired without impairing its quality?
Sent by:        material...@googlegroups.com

---

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:-

1.        carefully cut the weld with controlled flame, with minimum possible kerfs width.
2.        grind at least 1/8"  off from the gas cut surface  and  beveled to sound base metal.
3.        perform LPI on the WEP.
4.        Fit-up and weld as per the original weld procedure followed.
5.        PWHT as required.
6.        The combined PWHT cycle (original weld +repair) shall not exceed the PWHT cycle of  original base  simulation coupon results.
7.        In addition it must not exceed the PWHT (T&T) followed while qualifying the PQR.
8.        Usually all 9% Nickel steel has to procured with the simulation heat treatment results.
9.        Total PWHT-T&T following original weld and repair should not exceed  results of the simulation test coupon.

[attachment "20.jpg" deleted by Biswajit Mukherjee/LNTENC]

[Shashank Vagal]

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 <pgos...@quickclic.net> wrote:

From: pgoswami <pgos...@quickclic.net> Subject: RE: [MW:14518] How many times can a weld be repaired without impairing its quality? To: material...@googlegroups.com Cc: nach...@yahoo.com

[Shashank Vagal]

Hi Biswajeet, Thanks, sir. I could get at it a little later. I had a mistake in the URL. But still, it does not exactly help me as to what we do now. The plates are in their places, can not be removed nor replaced (no extra plates available), nor can we afford too much repairing for we may damage the plate. Physically and otherwise, I mean. Perhaps build up of the repaired edges could be the solution...? With which electrode? How can we justify all that extra heat input? Thanks all of you for your time and efforts, Shashank Vagal --- On Tue, 12/6/12, Biswajit Mukherjee <BMukh...@lntenc.com> wrote:

[Elshan Feyzullayev]

Hi Shashank,


Only the way you repair you must refer to PQR that you have qualified for this repair. I would think the amount of repair depends on the amount of the repair PQR's. All extra heat inputs and other bad effects on materials caused by multiple repairs can be eliminated by PWHT as per the qualified PQR's.

regards
Elshan.  

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Date: Tue, 12 Jun 2012 16:45:00 +0800
From: nach...@yahoo.com
Subject: RE: [MW:14524] How many times can a weld be repaired without impairing its quality?