nitrogen purge blk steel pipe S.M.A.W. welding

[downhillbill]

gov spec requiring nitrogen purge while weld is being performed.gov spec ref's to ASME B31.1 and B31.9. Weld procedure QW-482 smaw, joint design vee,backing none,base metal (QW-403) P-# 1,,GRP # 1,Spec SA 106 GR-B,base metal .0625 to .436 all dia with in T range,,filler metals QW404,spec. no. SFA 5.1, AWS E6010 uphill& spec no 5.5 AWS E7018 uphill etc..???Why would nitrogen purge be used for this procedure ? Cannot find "code" ref that supports the use of nitrogen purge for these circustances. Reply to....
billvidmar@cobbmechanical.com

 

[deanc]

This may be an engineering requirement to help reduce internal oxidation during welding. It could give you better internal weld quality as well. Ask a GOOD Welding Eng.

 

[PVRV]

1. deanc is correct. Nitrogen purging is utlized to reduce oxygen
presence as an example mothballing to avoid corrosion and
TIG welding to ovoid oxidation of the root pass.

2. Nitrogen Purging is not a welding parameter applicable to SMAW
or any other welding process that ulizes coated welding
consumables or flux. (As far as I am concerned) However,
I would agree that it does good.

3. Nitrogen Purging is required while welding any pipeline with
traces of hydrocarbons as a safety measure.

General:

If the weldment quality was of grave importance XX18 electrode should of been used exclusively.

Cheers,

 

[sayee1]

Its funny that E6010 has been permitted for the root and still nitrogen purge has been asked for. Like PVRV said Exx18 or Exx16 should have been suggested for the root, especially since uphill welding is suggested for the root. I would have called for GTAW welding in case the quality/corrsosion resisitance of root were so critical! E6010 is inferior to the Exx18/6 in terms of diffusible hydrogen in weld metal(Remember cellulosic coated E6010 is expected to have 5-8% mositure in coating and is hence non-low hydrogen) as well as the strength is 60 ksi as compared to the 70 ksi of E7018/6. One error in your post downhillbill is that E7018 -is SFAF /A5.1 and not 5.5 as mentioned by you! Thanks and regards
Sayee Prasad R
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