Materials & Welding: FW: Re: [MW:29170] RE: 28982] Backing gas as per API RP 582

Thursday, February 28, 2019

FW: Re: [MW:29170] RE: 28982] Backing gas as per API RP 582

Please see the extract from API-RP-582, which states clearly that purging is a must for GTAW &GMAW process when Cr-in the steel exceeds 2.25%. SMAW welds NEVER require any purging. Purging usually is the practice for open root welds, where the root requires protection from oxidation, when Chromium is above that specified amount. SMAW welds never require purging as the slag acts to protect the root. That's the very basics of SMAW welding process , where slag metal reaction and separation is the key.

For fillet welds of thicknesses specified below "Heat Tinting " is a possibility. Use of purging gas could help to avoid oxidation and heat tinting for the thickness(2-5mm) as mentioned here. However note use of small diameter (2.4mm) could be useful to avoid heat tinting if the thickness of the component being welded is around 5mm.

Minor heat tints are removable by acid pickling. Depending on the corrosivity of the process media, many clients does insist on this method. In the attached document you'll find some examples of heat tint depending on the "Oxygen" content on the root. For many fillet welds it's not possible to purge, however controlling heat input helps to avoid heat tint. In another word adoption of correct welding practice is essential.

Thanks,

P.Goswami.P.Eng, IWE.

Independent Welding & Metallurgical Specialist

Linkedin: https://www.linkedin.com/in/pradip-goswami-2999855/

Email:pgoswami@quickclic.net,pradip.goswami@gmail.com

Whatsapp:1-905-9793232

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of muneebslsa@gmail.com
Sent: February 27, 2019 3:03 AM
To: materials-weldingmaterials-welding <materials-welding@googlegroups.com>
Subject: Re: Re: [MW:29161] RE: 28982] Backing gas as per API RP 582

You can check the attachments, but anyhow when it comes to thinner membrane regardless of whatever the consequences might be the case for oxidation which is non occurrence when we simply imagine for fillet welds but anyhow socket welds aren't with this case of lap to lap fillets, hence a detailed study of amendment to be incorporate with through and through case studies and failure analysis stipulating clauses shall be ensured in international standards.

Anyhow now the case as per the research is chromium depletion (causing heat tints / discoloration) for thinner membranes especially for fillets, So to be conclude that there should be some detailed studies as per AWS D18.2 / NORSOK STANDARD M-601 especially for fillet welds.

At any cost don't accept the requirement unless owner is providing his clause which is already stipulated in owner's manual or international standards, the research i have ensured is from my previous owner requirement which i did not agree and the international standards which I have quoted is for open root / butt welds.

Thanks.

Regards,

MOHAMED MUNEEB MAHABOOB

From: sandeep kumar
Date: 2019-02-24 11:20
To: Materials & Welding
Subject: Re: [MW:29146] RE: 28982] Backing gas as per API RP 582
To be specific, as you know purging purpose in SS is mainly for shield against oxidation which took place when molten metal kiss the oxygen from atmosphere. Now when you welding a fillet weld the amount of oxidation is corresponding to the amount of heat supplied vs. encounter of molten weld metal to the atmosphere without shielding.

A fillet weld having a configuration without any gap and zero flow of molten metal to the back side will defiantly not require any purging. Its recommended to use a optimized low heat input. I advise you although to put gas backing upto 2 mm thickness as the low heat dissipation in SS can melt through thickness during welding.

Thanks & regards
Sandeep Kumar

On Friday, February 22, 2019 at 6:19:06 AM UTC+3, John Manoj wrote:
Thanks for the reply, Is back purging is required when we do fillet welding on a thin (2mm to 5mm) SS base material, for example some cleat welding or pad welding or socket welding with GTAW or SMAW process.

Expecting a reply.
Thanks,
Manoj

Dear Mr. Goswami,

In 2016 editions of API RP 582 the purging gas requirement given in subcluases (a) (b) (c) but in previous editions purging requirement given in clause

On Mon, Jan 28, 2019 at 9:53 AM PGoswami <pgos...@quickclic.net> wrote:
Manoj,

SMAW never requires back purging. It's the "slag" generated by the process, which protects the weld root. This is just back to basic scenario.
Thanks.

P.Goswami.P.Eng, IWE.
Independent Welding & Metallurgical Specialist
Saudi Aramco: Designated Project Welding Engineer(DPWR)& Quality Management Personnel
Linkedin: https://www.linkedin.com/in/pradip-goswami-2999855/
Email:p...@quickclic.net,pradip.goswami@gmail.com
From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of Manoj John
Sent: January 27, 2019 8:04 PM
To: material...@googlegroups.com
Subject: [MW:28982] Backing gas as per API RP 582

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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