Re: Re: [MW:29183] Backing gas as per API RP 582

Dear All,

What Mr. Muneedb explained is the scenario I had faced.  My questions may be confused everybody. In my case purging is not at all practical as the line is very long and diameter wise also it is 12 to 24 inch. 

I had done a mock up sample on a 3 mm thick pipe + 3 mm thick pad plate with different options by our best welder who can do fastest welding and noted the heat input. 

Option 1) GTAW with single pass with and without purging.

            2) GTAW with 2 passes with and without purging.

            3) SMAW with single pass with and without purging.

            4) SMAW with 2 passes with and without purging.

All options done with minimum heat input and shown to customer. There was no visual difference between purged and non purged welding as we controlled the heat input, Customer inspector still insisted for purging so we decided to purge with N2 gas and completed the welding. If we check the purging quality with oxygen monitor nobody will accept.

Thanks for the response.

Manoj.

   

On Fri, Mar 1, 2019 at 11:01 AM muneebslsa@gmail.com <muneebslsa@gmail.com> wrote:

Suresh,

It's not that simple as you did not face that scenario.

Gentlemen, 

Here the current topic is for fillets, so reply with explicit as stated in previous email regarding ''chromium depletion'' 2 to 5 mm.

Dear Manoj,

I was to come to your point as the same case happened to me and let all guys just imagine fabricated spools which already installed at site and the pipe configurationis 2 inch schedule 20s, and pipe is 

With elbows leaving no open fittings and an end to end connections there in any centre of a pipe a wear pad to be installed; now how will you purgeover 100 metres continuous installed spools without open fittings...

Contemplate? Mother pipe inside you have to purge for outside zero gap fillet weld?

So in this to purge entire pipe is not possible and after all the fabrication is done, suddenly some client will make a non conformance saying chromium depletion etc...

Now my question is we do not disagree with the metallurgical effects but why we are so late in getting amendment with this new scope without a clear writing and there will be 

different consequences for different configurations that's why in my previous email I clearly wrote it should be incorporated in international standards removing the word open root or underneath purging root side but it should be cleared with all configurations of welds when it comes to the factors chromium depletion below 8 mm or 6 mm or whatever your new discoveries...

 In your case if purging has to be done then it should bring in amendment same like FBE coating before commencing of the project, you know why?

During fabrication we try to complete all the FBE coating spools welding within the fabrication shop as non-accessible areas inside the spools difficult to coat at site, I mean internal coating, so that's why we weld with all the attachments (completing all NDEs all the requirements) prior to spool hydro test followed by that FBE then directly site installation except if any minor modifications at site in rare case spool will be sent to coating shop.

Similar to that owner has to have his requirements and proactive notifications before commencing of the projects and at the early stage of the projects as lesson learnt from previous projects as chromium depletion to be considered for fillets for all configurations for SS and all non-ferrous below 8 mm or 6mm whatever as per the research before completing spool fabrications all attachments to be completed.

You know what? I am damn sure many experts who is mandating this case to be done but if you go back before 5 or 10 years none would had did purging for below 8 mm or 6 mm for fillets that too for attachments weld, let's be honest this is a new requirement(Fillet / all attachments) for SS and non ferrous.

Thanks.

---

Regards,

MOHAMED MUNEEB MAHABOOB

From: Paidi

Date: 2019-03-01 11:03

To: materials-welding

Subject: Re: [MW:29175] Backing gas as per API RP 582

Manoj, 

your Question is simple and answer also very simple as experts are stated in trailing emails..why you so confusing on this ... you are not clear while asking the question I think so . 

Suresh 

On Fri, Mar 1, 2019 at 10:15 AM Manoj John <manojacgnr@gmail.com> wrote:

If we weld an attachment like pad, cleats, supports to pipe line having below 4 mm thick wall thickness with SMAW process 

On Tue, Jan 29, 2019 at 3:27 PM George Dilintas <dilintas@gmail.com> wrote:

Usually root pass is not performed with SMAW. That is the reason 

Στις Δευ, 28 Ιαν 2019, 04:33 ο χρήστης Manoj John <manojacgnr@gmail.com> έγραψε:

Dear Experts,

As per clause 7.3 of API RP 582 Ed. 2016 back purging required for GTAW & GMAW process but no where I could found for other process like SMAW.  Is it mean that if we do welding with SMAW process back purging is not required?

Please share your interpretation.

Thanks and regards

Manoj.

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Thanks  & Best Regards,

Suresh Paidi

 

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