Re: [MW:29138] RE: 28982] Backing gas as per API RP 582

Slag in SMAW or FCAW only covers the weld and not areas adjacent to weld (i.e. HAZ and heat tint area in Stainless steels). This may not be an issue on the outside of your SS piping but it will affect the corrosion resistance of the surface which is in contact with process fluid (i.e. inside the pipe). Therefore, if your material, especially stainless steels, is used for its corrosion resistance characteristics, and heat of welding reduces its corrosion resistance (which normally it does), I recommend you to use back purging. 

But in these cases, back purging may not be required:

• in cases where stainless steel is not used for its corrosion resistance (e.g. cryogenic applications).
  
• in cases where you will apply "proper" pickling (and passivation) which removes affected layers.
  

Please Remember, if you are using welding processes other than SMAW/FCAW, back purging shall be done to protect weld metal (and obviously, it will also protect areas adjacent to the weld).

 

Regards

Ramin  Kondori

Sr. QA/QC & Welding Engineer

-----------------------------------------------------------

PG-Dip. in Welding Engineering (IWE  AT  0070)

BSc. in Civil Engineering (IUT)

BGAS Painting Inspector

ASNT Level I&II

                        

On Mon, Jan 28, 2019 at 9:23 AM PGoswami <pgoswami@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:pgoswami@quickclic.net,pradip.goswami@gmail.com

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Manoj John
Sent: January 27, 2019 8:04 PM
To: materials-welding@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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