304 purging question?

Date 01-27-2006 19:22

Today I found myself confused as to IF ss piping (304 specifically) needed to be purged prior to welding. There is a project in the shop, pre-fab of a vapor piping, 2" sch40 304 ss and it is not being purged. Also, the first pass is fusion welded (no penetration whatso ever) and My boss's point of view is that the purging is not required because it is for vapor, and that the client know's that it is not being purged prior to welding; He is telling me also that there are 30 year old installations that were welded the same way and are functional ( he went into detail about engineering economics as to say that It would not be cost effective to purge). I strongly dissagree, but this may be because of my ignorance to some aspects of ss. I have studied guides of ss welding and I don't remember ever seing anything about "not purging".

Appreciate any responses

regards

Raul

By jon20013 (*****)

Date 01-27-2006 19:47

If you don't purge, you WILL have sugering on the ID. No if's and's or but's about it. You must purge if you wish to have a "good" weld.

If your boss doubts, try testing one, weld it as you are doing and then slice it apart and examine the inside.

If you look at AWS D10 Standard for recommendations on welding austenitic stainless steel pipe you will find this requirement.

I'm sure many will follow with better technical responses than mine but there it is; you have to purge on a fully penetrating stainless weld. I don't know how to say it any clearer than that!

What is your position within this company?

In re-reading your post, your Boss and your Client are very obviously "old school" mentality... you are fighting an unwinable battle it seems.

By - Date 01-27-2006 20:28

As usual, I agree with all Jon has said. Please allow me to address this issue, too. You said that you are fusing the 2" Sch. 40 pipe. You did not mention the joint configuration. Is the pipe a square-butt or does it have a standard bevel on each end? If the ends are square-butt ends, you have more problems than just the purge. You are losing a great majority of the strength in that joint by only fusing and making no penetration. If the configuration is beveled and you are butting up the bevels and fusing the first pass with no penetration, you will very likely encounter sugaring unless you are running the heat so low that it is not causing sugar. Either way is not recommended. You said your boss has pointed out that pipe in service has lasted 30 years with no failures. Well, the law of averages are working against you, for sure. I've had car insurance for 40 years and never had a wreck, so I guess I should cancel it.

By raulvidal (*)

Date 01-27-2006 20:43

The Pipe has standard bevel.

And thank You all for your reply

R

By jon20013 (*****)

Date 01-27-2006 21:10

Chuck, thank you kindly for the vote of confidence! I was hoping you would catch onto this thread as there's probably not another single Message Board member who knows more about stainless than you! (I am meaning no offense to the others, simply my enormous respect for Mr. Meadows!).

To the enquirer:

My shop policy states no less than 3 layers of weld must be deposited before removal of purge. This is fairly common practice, as I'm sure many would agree.

Your problems are as much with your welds as your management. You KNOW the right thing to do, thats why you are here asking concurrence!

I continue the recommendation, make a test weld using your "standard practice" cut it apart, show it to your boss. It probably won't make any difference but at least you will have some evidence.

If you have any jurisdictional authority; i.e., Inspector, contact them. My best guess is you are either stuck with a stupid boss or you'll need to find another job.

Incidentally, I asked before but, are you an Inspector at this Project? Please state your position. Also, is this work governed by any standards? ASME, API, AWS? Answering these questions will help provide a better answer in response!

By raulvidal (*)

Date 01-27-2006 22:26

I'm a CWI, and I started looking for a job after "D" event with my boss. I am not Inspecting this work , but I am the NEW "no auhtority" QC Manager( go figure)...
I went so far as to prepare 4 coupons and weld with purge full penetration and weld with out purge. full penetration and ... I realized that I wasted my time with my boss and the welder trying to explain...

When arguing with my boss about purging I asked him If the client "new" he was not purging he looked away while saying yes, and followed whith the engineering economics blah blah blah... I told him that if I arrived at any project and I saw this SAW movie scenario tha tI would call the police.

R

By Zeke

Date 01-28-2006 15:03

I guess he has a phobia of purging. Try a flux cored tig rod. We have had a lot of success with them in situations where a purge was difficult. They are a little expensive, but still cheaper than the time and labor it takes to purge in some cases. I am not saying it is better than purging, but it is better than what you are doing.

Zeke