Best Procedure Weld Technique to build-up Pipe

[bob330]

Hi All,

I was wondering what welding techniques are optimal for building up thinned piping without burning through. In other words, what techniques allow you to lay down good filler with very minimal penetration? I'm looking for information not just on process (GMAW,GTAW,SMAW) but also on other factors affecting penetration like travel speed, etc.

I have read that with stick welding with 6010 electrodes, slow travel speeds actually tend to lead to less penetration which is opposite of what I would have suspected.

Thanks,
bob

 

[metengr]

The minimum thickness that I would permit for weld restoration of thinned tubing or pipe in high pressure service is 0.090". For this thickness, I typically use GTAW to avoid weld metal drape-thru or bowing through the pipe wall.

You have quite a bit of manipulation with the manual GTAW process because of the local heat input that works in your favor. GMAW could also be used for welding on thinned material, but you have to be experienced with GMAW to avoid lack of fusion type weld defects.

 

[metengr]

or bowing

The above should be "arc blowing" not bowing

 

[SJones]

Residual stresses also come into play and a number of people adopt a 'basket weave' deposition sequence with each weld layer deposited in an orthogonal direction to that of the previous layer. It is assumed that the piping in question is not in service. If it is, 5 mm would be the thinnest that I would consider getting someone to weld on. If you do use SMAW, low hydrogen electrodes may offer a cleaner, more sound repair.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[HgTX]

Have you asked on the AWS forum? They are pretty good with the "hands-on" questions.

http://www.aws.org/cgi-bin/mwf/forum_show.pl

Hg



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