need help back welding procedure

By pipewelder_1999 (****)

Date 11-08-2004 12:04

Can you describe the original joint, process, and dimensions of backgouging groove ?

Gerald

By nonoy Date 11-11-2004 13:14

We have a single-V joint, GTAW process, we backweld the other side of the pipe, because we found out that there is no root penetration. so the problem is some our welder did not know how to do the right preparation (using grinder), i mean the joint geometry.

By pipewelder_1999 (****)

Date 11-11-2004 14:29

If you are backgouging, make sure the groove allows for good fusion. Also make sure that the backgouging removes all of the areas with lack of fusion. This could be verified by liquid penetrant examination before welding.

Have a good day

Gerald Austin

By rhoople47 (**)

Date 11-09-2004 20:21

Lack of fusion where? At the root of the back gouge? You are backgouging right? I had the same problem here once. I did a macro etch and discovered the back gouge was deeper than it was wide, not good. We had a lack of fusion on one side or the other of the backgouged groove. I made them backgouge with a little angle to it, to make it look more like a V and that solved it. Hope this helps you too.

By nonoy Date 11-11-2004 13:16

yes your right!! and thanks

By MBSims

Date 11-12-2004 03:34

Nonoy,

Mabuhay! If I understand your question, you have tried to use a GTAW root pass in a stainless steel pipe weld, but it did not penetrate completely through the joint and you had to backgouge and reweld from the inside of the pipe. The joint geometry should have a 37-1/2 degree bevel angle on each side (75 degrees total). The root opening should be 3/32 in. to 1/8 in. and about 1/16 in. land on the end of the bevel. Use a 3/32 in. or 1/8 in. diameter filler wire, depending on the root opening and feed it into the puddle at the root. Here is an illustration that may help:

http://www.tpub.com/content/construction/14250/css/14250_51.htm