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Back Gouging on Single "V" Butt Joint

07/26/2017 1:32 AM

Q1:We are doing Single V Butt Joint welding with ER80S-G for Root & Hot pass and then SAW(EA2-A2) welding on Plate(25 mm Thk).After welding we are doing Backgouging .Clarification required how much depth back gouging is accepted.After doing LPT we have to gouge more due to weld defect.and due to back gouging it is becoming double V. Kindly advice.

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#1

Re: Back gouging on Single "V"Butt Joint

07/26/2017 3:18 AM

<...accepted...> Consult the body doing the acceptance. It won't be CR4!

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#2

Re: Back gouging on Single "V"Butt Joint

07/26/2017 3:20 AM

1.-There is no depth, nor minimum nor maximum, established in Codes, standards and specifications. The backgouging should be done until finding sound metal.

2.- According to ASME IX QW-254 (SAW)

Joint configuration is Nonessential variable (QW-402.1/4/10 and 11)

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#7
In reply to #2

Re: Back gouging on Single "V"Butt Joint

07/27/2017 8:09 AM

GA.

My recollection of the code as well, both CWB and AWS.

The welding symbol should have BGTSM in the tail.

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Safety - Hazmat - New Member United States - US - Statue of Liberty - New Member Engineering Fields - Chemical Engineering - Old Hand

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#3

Re: Back Gouging on Single "V"Butt Joint

07/26/2017 11:02 AM

The real question: Why is this back-gouging after welding being done in the first place? Is this some sort of welding inspection practice?

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#4
In reply to #3

Re: Back Gouging on Single "V"Butt Joint

07/26/2017 11:22 AM

James, also for me is strange the mentioned root pass. In my opinion, Using SAW process this pass is not require. Weld all with SAW and after backgouging to sound metal on the other side of the plate. But, maybe , it's a question of the approved WPS

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#5
In reply to #4

Re: Back Gouging on Single "V"Butt Joint

07/26/2017 11:45 AM

It is not a topic in my wheel-house. I will ask my boiler welder here about this and see what he has to say.

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#9
In reply to #5

Re: Back Gouging on Single "V"Butt Joint

07/27/2017 3:45 PM

Back gouging is used when an absolutely 100% sound full penetration is required. I fist saw it on submarine rib structural welds. There was a vee prep on both sides of the rib, but it was still normal to find HAZ cracking around the root pass and in some cases a failure to get burn through on the root pass of the first side. In those cases, back gouging was used to remove lack of penetration or HAZ cracking and the second side was filled in. The end result is a structural weld that has no linear indications, inclusions or porosity and the structural integrity and fatigue life of the joint is vastly improved.

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#6
In reply to #3

Re: Back Gouging on Single "V"Butt Joint

07/27/2017 2:05 AM

Thanks for your reply.

As the weld penetration is not so good and to avoid weld defect,It has become regular practise to backgouge after welding for but weld.But during gouging and LPT test they gouge more and also the joint configuration is changing.

Also the width of weld is becoming more after welding with SAW welding.How to calculate weld width requirement afetr welding.

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#8
In reply to #6

Re: Back Gouging on Single "V"Butt Joint

07/27/2017 9:19 AM

It sounds like your practices are leaving a lot to be desired in strength, reliability, and productivity in your facility. Maybe it is time to take a hard look at this process with an eye toward setting it aright?

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