HELP!!! Chill Ring on 6" Schedule 80 Pipe w/100% xray

Date 03-07-2008 05:01

Howdy men.

My buddy and I recently took a 6G-R Pipe test with a chill ring using 1/8" E-6010 all the way out. Sounds simply, right? WRONG. We were positive we knocked this test out of the ball park. The both looked great and we can't think of anything we'd have done any different.

We were told the xray revealed that there was slag showing up, yet both of us cleaned our beads and ground out are restarts. However, I noticed that there was a small gap between the edge and the chill ring when I was welding in my root pass. We're using 1/8" rod and the gap is at very least 1/4" maybe a little more.

They are allowing us to re-test, however, like I said earlier, I can't think of anything I would have done any different. We not only ground out our re-starts but we wired wheeled the crap out of each pass and used dental tools and files. So is it possible that the gap between the chill ring and the edge is blowing slag underneath where we can't get to? If so, then how do we keep that from happening? We don't get to prepare our coupons so closing the gap isn't an option.

Any suggestions you can give us would be a big help.

By nevadanick (**)

Date 03-07-2008 05:42

are you running a weave or two stringers on the root ?

By Superflux (****)

Date 03-07-2008 06:03

You didn't say where the indication was located....1) I would not accept a coupon with gap between the chill ring and pipe I.D. This can lead to undercutting of the pipe ID. To seat the chill ring tight, you drive a small center punch or similar device to spread it tight to the pipe. 2) With that wide of a gap, undercutting with slag entrapment is definately a possibility, and I'm guessing (typically the problems are on the bevel farthest from the restriction ring? down hill side of the 6G?) the indication is where you can't see so good.
If the problem is indeed in the root pass, might want to back off on the heat (due to that "crack of dawn gap") just a smidgen. Another thing is, the restriction ring plays tricks on the mind and hands and tends to make you unconsciously veer away from it, ie. bad rod angle.
Hope this helps, and don't drink away your sorrows tonight...hang over shakes make for uneven stack of dimes.
Good luck tomorrow!

By js55

Date 03-07-2008 15:39

1/4" gap between a chill ring and the bevel edge is significant.
Superflux is right chill rings are split rings. Spread it until you have a tight fit all the way around. The gap between the chill ring ends should be understood by inspection.

By nevadanick (**)

Date 03-08-2008 04:56

i guessed that he meant 1/4 root opening, not a 1/4 gap between the ring and the bevel

By pipewelder_1999 (****)

Date 03-07-2008 22:44 Edited 03-08-2008 06:04

The "Gap" at the backing ring may very well hold some slag however that slag is not what shows up in a radiograph.

It is the internal undercut that is not filled in with weld. Regardless of the fit of the backing, allowing the root to properly fill in will help eliminate this issue.

Slag inclusions ,which are normally dark on film. are not dark because it is there. Its dark because there is no steel there. If the gap between backing and pipe were smaller you would have less chance of undercutting the internal surface.

Both of the illustrations below would look nearly identical on film. A radiograph cannot tell you if there is slag filling a void.

Be sure to pause on the sides long enough to let the weld fill in. Its easy to think because there is backing, hotter is better. That may not be the case.

Even with fill passes the leading cause of trapped slag is NOT the slag that was left but the contour of the weld prior to depositing an additional pass. A radiographer cannot tell the difference between a void in the metal that has trapped slag or one that does not.

Have a nice day

Gerald Austin
http://weldingdata.com/slag_nonfusion.htm