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

Purging is not always as simple as it may at first appear. Even though a pipe/tube is purged to an acceptable  oxygen level, the HAZ will still discolor if too much heat is applied. To get cooling/scrubbing effect there must be flow of purge media. If the purge is introduced into the channel too far away from the actual weld, you may experience lamellar flow where the purge gas that is in contact with this ID walls doesn't move or flow. It is best to introduce purge as near the actual weld as possible and especially on larger bore pipe you will benefit from the use of diffusers to increase a turbulent flow which will help cause the purge gas in contact with the ID walls to carry away heat and help reduce decolorization.

 

 

 

Thanks,

 

 

Chip Frizzell

 

CWI / ASNT NDT Lvl III / NACE CIP Lvl 2 – Certified

 

Price is what you pay – Value is what you get.

Seldom does the lowest price result in the best value!

 

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From: materials-welding@googlegroups.com <materials-welding@googlegroups.com> On Behalf Of muneebslsa@gmail.com
Sent: Saturday, March 2, 2019 6:37 AM
To: materials-weldingmaterials-welding <materials-welding@googlegroups.com>
Subject: Re: Re: [MW:29182] Backing gas as per API RP 582

 

Hi Microbe, 

 

That's right, you sniffed the bottom catch contemplating on the right scenario irrelevant of the case relaxation is not entertained here and as you know the hindrance like at end times had to do something like what you have said, the sequel is something like i had to disagree as a contractor as this is cost impact and unanticipated requirement and at the same year i had to join as owner representative for same client where my italian contractor also did not agreeing with this requirement, so there came a mutual agreement of mock up test, where in both agreement we had to agree something if you get a first 2 to 3 colors can be accepted, other colors cases to be purged, it was made finalized something like that.

 

But for me correction can be very simple and easy when you fabricate with all bosses connections same time purge as you will purge to normal welds and finish it of one time with no hide and seek.

 

Note: mother pipe to wear pad fillet outside welding cases (non purging filler is a futile).

 

 

 

 

---

Regards,

MOHAMED MUNEEB MAHABOOB

 

From: steel_microbe

Date: 2019-03-02 04:37

To: Materials & Welding

Subject: Re: Re: [MW:29179] Backing gas as per API RP 582

Dear Muneeb,

It would be wise for you to do a 'mock-up' of the exact conditions, processes etc. Cut the 'mock-up' in half after completing the welding and assure your-self 

your getting the results you want, If not, modify the conditions, such as  lowering  the amperage, increase the weld  travel speed etc. come -up with a procedure that meets your requirements.

 

 

From: Mohamed Muneeb

Date: 2019-03-01 13:54

To: materials-welding

Subject: Re: Re: [MW:29177] Backing gas as per API RP 582

Dear Suresh,

 

I do not disagree at all and I do agree with chromium depletion 2 to 5 mm where oxidation/heat tints some clients mandates, it was explicit anyhow my scenario it is to be contemplated that 2 inch mother pipe inside inaccessible to passive and end to end connections is far from centre weld, in this even you have fillers or electrodes compatible doesn't need to purge still the question is for mother pipe internal.

 

Hence complete all the attachments / bosses before hydro and considering all the configuration it should be mandated before the project and explicit written procedure should be incorporated/approved and international standard should come in amendment for all welds type and open root should withdrawn.

 

Thanks for understanding.

 

Thanks 

 

Mohamed Muneeb.

On Friday, March 1, 2019 at 1:25:11 AM UTC-6, suresh Fluor wrote:

Dear Mohammed, 

 

I do agree with that there is constrain for it depends on  joint configuration where chromium depletion is effected . Manoj asked that question in his first email " Is it mean that if we do welding with SMAW process back purging is not required?" then answer would be " not required". 

 

Further more experts are enlarged the answers with different scenario's where end to end or open root for piping & fittings etc...

 

In addition to that there is TGX filler wire is available (TGX is manufacturer name ) where purging is not required and It is most suitable for your scenario particularity in field joints but again subjected to accept of PQR qualified with TGX  (as mentioned in the earlier email )

 

Thanks 

 

Suresh 

 

On Fri, Mar 1, 2019 at 12:01 PM munee...@gmail.com <munee...@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 <manoj...@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 <dili...@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 <manoj...@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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