John,
You can remove the purge gas after the root pass but it is advisable to leave it until the second pass (hot pass) is complete. If you were to burn through two layers with your third pass then the parameters are to high on your WPS. Purging throughout the entire weld is costly especially on large diameter joints unless your client has made this request and is willing to pay for it.
Thank you,
Ken
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of John Hardcastle
Sent: Saturday, October 16, 2010 1:14 AM
To: materials-welding@googlegroups.com
Subject: [MW:7587] Purge Gas
When can we remove backing gas purge from non-ferrous pipe joints.
Can we remove the gas purge once the root run is complete, or once the root and first hot pass is complete.
We leave the gas purge on until the joint is capped and i am sure this is wasting gas.
| John Hardcastle |
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| Fabrication Manager |
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| Euro Mechanical Contractors Company Factory |
| P.O. Box 46153 |
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| Phone: +971 2 550 08 99 |
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| Mobile: +971 50 4445873 |
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| Email: jhardcastle@euromechanical.com |
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