Rework to B31.1

[Brew]

We have some 316L sch10 pipe which was to be welded to ANSI B31.1, for a water purification machine running at a max of 300psi. The welds have been rejected based on lack of penetration off a visual inspection by a 3rd party. My line of thinking is that we can achieve full penetration by making another pass over the existing weld, and possibly having to then lay a cover. Assuming this works for punch, does anyone see any problems with this? Thanks for your expertise. BTW, time is of the essence!

[Mike Sherman]

Brew, are you sure it is schedule 10? You will not be able to achieve full penetration by going over an existing weld. You will need to remove the defective area and do it again. Isn't there a written procedure on this job to cover this contingency? How did the inspector perform the inspection? You are welding GTAW right? Is your purge good? How is your root opening? Are you using a good cleaner such as acetone? Please follow up and let me know how this job ends up.

[Brew]

Sch10 w/ GTAW, and 20psi Argon purge on the rejected welds. My top weldor says he can do it, and I've seen him do it before(achieve punch over existing weld). He's a freakin' magician with a Tig torch!
The initial setup was not exactly to code it seems, but full punch was achieved on all the joints, but not all the way around all of them. THAT weldor is now looking for a new job.
I'm trying to keep rework costs to a minimum, while still providing the customer a good product. If we can get full punch without having to cut/grind/dress joints, that's what I want to do IF there are no concerns about heat stresses, or anything else I might be overlooking....
Thoughts?

[Brew]

Oh yeah...we no longer have an inspector, havent had one for over a year, but we are getting one now! These defects were found in the field by the customer, and verified by someone from one of our sister offices. All visual, no destructive or radiographic testing has been done.

[Mike Sherman]

What your proposing is not standard procedure for repairing this type of defect, but it is your job and your call. I am curious, how big is this pipe?

[Brew]

1 1/4", 1 1/2", 2" and 3". Mostly 3".
Mike, I respect your opinion and your skills. Assuming we CAN get punch, why WOULDN"T you do it?

[Guest]

You can only get penetration on this if the first weld was purged clean. If there is any oxidation on the inside you will only be compounding your problem. Another factor is the amount of heat you will have to apply to acheive penetration.

Mike is correct...if you are welding to a spec, then there is a specified repair prodcedure in that spec. Check that out first, to be safe.

[Brew]

So no one sees any inherent problems assuming this method works? Great!
I'll let you know how it pans out. The units are being shipped back to us, we should have them by Monday.
And dont worry. If this doesnt work out PERFECTLY, we will be cutting out the defects and doing it by the book.
Thanks for the feedback.
John

[Mike Sherman]

The reason I wouldn't do what you are proposing is because it isn't the right way to do it. That's it, just a right way and a wrong way. You are going to have to purge the part again and apply a tremendous amount of heat to burn through the original weld, with no guarentee it will be acceptable. Without getting too technical, stainless doesn't like to be heated anymore than necessary. I personally would remove the bad area and do it right. The amount of time involved is not going to be significant to remove the defect, it is only sch. 10 after all. The amount of time to try and weld it, find out it didn't work, then remove the defect, reweld it again, find out you have probably put too much heat into the part (is it still any good?), well it would just be better to do it right the first time. Good luck and please let me know how it turns out.

[Brew]

So what method would you use to remove the defect in a timely manner? I cant see any way except cutting the joint completely, grinding, beveling, and re-fitting everything. Please, please enlighten me. BTW, we are talking about a couple hundred joints here.

[Mike Sherman]

Do the joints have incomplete penetration all the way around or just here and there?

[Brew]

I'm not sure yet. I havent seen anything with my own eyes, not even a picture. I'm assuming its incomplete here and there, but the customer is acting like its all the way around. Could be either, or more likely both.

[Mike Sherman]

Brew, I don't have a copy of B31.1 to look at here, I don't do any work in power plants. Are these parts going into a nuclear plant? On this pipe the walls are all about .109 to .120 right? I would use an .035 cutting wheel to open the defective area up. This thin wall really doesn't require much beveling but it does require a gap. These must be short parts since you can see the inside right? So after grinding out the defect you can clean the inside with a die grinder if necessary also. Put a good purge on them and reweld it. This should be quick and effective. You will have very little grinding or cutting with these thin discs and they will leave a nearly perfect gap.

[Brew]

Thanks for all your help Mike(and yours too Rocky)! Some of the runs are short enough to get to the inside, but some are not. On the longer ones, I think we are going to have to re-do them from scratch, just to be sure. We will have them boroscoped before the customer sees them again, but I cant afford the time to do it twice. Good idea on some of the short runs, tho. Should save us some valuable time.
Yes, it's at a nuke facility.
Again, thanks for your input. It's really helped me keep my head on straight.

[Guest]

I am surprized that you aren't X-Raying them, if they are going to a nuclear facility. Keep us informed...this is interesting!