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Up Topic Welding Industry / Technical Discussions / SA-333 Gr.6 Material Failure
- - By welderette (**) Date 03-21-2006 00:50
We are fabricating Chlorine service piping using this material and have run into lamination in the pipe. This caused a sudden rash of rejections in our RT's. We then brought out a UT tech who tested all the pipe associated with the RT failures and in every case he reports that the pipe is laminated. Has anyone else experienced these laminations using this material? We have wholly rejected the work, and are regouping. However this defect was found in a number of different sized pipe, and from different manufacturers. Any insights that anyone may have would be greatly appreciated. Deb
Parent - - By chall (***) Date 03-21-2006 01:54
Generally, laminations do not show up in RT. Since the defect (revealed by UT) shows up in material from more than one supplier, I would look seriously at the UT technician's work.

Charles
Parent - By ssbn727 (*****) Date 03-21-2006 07:35
Hi Deb!
I would have to agree with chall!
I would have the UT tech check a pipe weld or welds (previously verified by someone else) that you KNOW have no laminations in order to find out whether or not there's an equipment problem or something else...
Question: Has the pipe (all that has been UT'd) been sitting around for a long period of time and are there any environmental factors to consider with respect to a possible cause for the laminations?

Respectfully,
SSBN727
Run Silent... Run Deep!!!
Parent - - By 803056 (*****) Date 03-21-2006 14:24
Have you considered performing a macroetch on a section of the rejected pipe to verify the presence of laminations? The macroetch should reveal the lamination when viewed with low power magnification. The lamination may be sever enough that magnification may not be needed.

Best regards - Al
Parent - - By welderette (**) Date 03-21-2006 15:44
Gentlemen, Thanks for your responses, all good things to consider. We came to suspect lamination when one round of RT resulted in 9 failures out of 18 welds. The failures were called as Insufficient Fusion. Straight line discontinuies, parrallel to the weld, always on the bevel edge. These were done by a welder who has never busted a shot. Something was gone wrong, but we went forward and did the 9 repairs .All the repairs were excavated all the way through the root, where our RT tech said they were. Visual inspections on these roots showed "Wedding Bands" we could find no IF and were at a loss to find the defects. When we did the reshots on these welds we had some rejected again. Comparing the film to the original shots we found that the discontinuity was stll there, only larger. It was also noted that two failed welds had the defects situated in a straight line along the longitudinal axis of the same spool of pipe. We then brought in a UT tech from our NDT Contractor.The equiptment appears to be top notch, the tech has years of experience. Once again I am stunned. We have MTR's of course, but this service is Catagory M and we are taking no chances. It is baffling; Macroetch we've considered, but as a production tool the defects would only be evident after the pipe is cut and preped, alot of work wasted to reject the material and get another piece.
I am wondering if this problem (correct me please if I am way off base)could be in some way be related to the normalizing process where gas pockets in the base pipe might somehow expand and cause lamination.
Another question... Does this type of discontinuity in the base material impact the design calcs in terms of minimum wall reduction? I just don't know. Any help, as always appreciated. Deb
Parent - - By jwright650 (*****) Date 03-21-2006 15:51
For an added insurance against what you have ran into, we scan with UT for laminations before alot of material prep has been done, this way if we find one, there isn't alot of shop time/labor wasted in an un-useable piece of material. Ask me why I started doing this on critical pieces... you guessed it, it was one of those hard $$$ learned lessons.
John Wright
Parent - - By welderette (**) Date 03-21-2006 15:58
John Wright, I would love to be able to UT before fabrication, is there a method to do this, aside from manually? We have about 3000 ft of pipe in this system. Thanks, Deb
P.S. I can relate to the hard lesson $$$ learned, and it is one that will not be forgotten ever.
Parent - By tito (**) Date 03-21-2006 16:36
There is a method to scan complete joints of pipe, although I am not very familiar with it. I have seen it used once, but this was long before I came into QC and had no clue what exactly it did at the time. Later on I learned that the machine was used to inspect pipe for defects, and I believe it is referred to as an EMI machine. I think it runs on the eddy current principal.

While writing this I did a google search for "emi inspection", it seems to be used primarily for drill pipe for the oil field. Don't know if it would suit your application.

Parent - By jwright650 (*****) Date 03-21-2006 17:00
I'm hoping some of the other UT folks will chime in here, I'm not familiar with the process, but have seen video of pipe at the pipe mfg being scanned by UT which consisted of several probes around the perimeter with water squirters to serve as the coupling and this arrangement is fixed while the pipe is being flown through at a high rate of speed. The system actually has spray paint that paints the rejectable spots that have signals strong enough to break the gates set up by the UT operator or what ever parameters that were required.
John Wright

PS, Is there a way to buy your pipe from a mfg that already has the UT done prior to you purchasing it? They could furnish the UT reports to maintain in your files.


edit: added a couple links :
http://www.unicorn-automation.co.uk/Theory.htm


http://www.usultratek.com/products/mtscan.htm
Parent - - By tito (**) Date 03-21-2006 16:52
Quote "It was also noted that two failed welds had the defects situated in a straight line along the longitudinal axis of the same spool of pipe."

Is the pipe seamless or welded? I briefly looked at the spec for sa-333 and it seems that grade 6 can be either. By your comment on the "indication" running along the longitudunal axis of the pipe, and if the "indication" were in the same location an one end as it is on the other.....could it be something related to the actual welding of the pipe seam from the mill?

Also I'm not familiar with the term "wedding bands" but assume that you are referring to a ringlike "indication" that runs the entire circumference of the pipe. If I am correct, and this is actually welded (as opposed to seamless) pipe, there could have originally been laminations in the plate that was used to make the pipe.
Parent - - By welderette (**) Date 03-21-2006 17:38
Tito. The pipe is seamless. The wedding band is slang to describe a root that in appearance is perfectly regular in size and contour that closely resembles a wedding band inside the pipe. in short a visually very good weld. Thanks for clarifying the EMI as eddy current, as I have seen this referenced on some MTR's, but do not find it on the MTR for the material in question. The option to request on the PO that material has been UT'd is certainly the avenue that we should have taken; of course the additional cost and lead time was factored in and not anticipating any problems like this; the wrong decision was made. All we can do now is regroup, correct, and go on. As John pointed out a very $$$$$costly learning experience. What may have been saved in purchasing will more than doubly be lost in satisfactorily resolving this problem. The piping manufacturer is coming on site soon. I will update as I learn anything new. In the meantime keep the ideas coming, you guys are so good. Thanks DEB
Parent - By tito (**) Date 03-21-2006 17:50
Let me actually clarify now that I have looked into it.

E-M-I=

Electro-magnetic inspection

It is used to detect longitudinal and transverse flaws in pipe and tubing.
Parent - - By jwright650 (*****) Date 03-21-2006 15:06
I would check the UT operator's calibrations first before ruleing out the laminations. IMHO, a lamination found by straight beam UT is pretty hard to mess up the diagnosis unless it is extremely close to either the top surface or the backwall surface. I'd like to hear more about your findings when you get to the bottom of this.
John Wright
Parent - - By hogan (****) Date 03-21-2006 16:44
a pt inspection of the bevel prep prior to welding could also confirm a lamination
Parent - - By jon20013 (*****) Date 03-21-2006 17:29
Deb;

Here's a thought (it won't help your existing rejects) in my work, for critical applications, we PT every weld prep. If you have laminations that are open to the prep you'll pick them up then. As for your existing, I'm just stumped a bit, this seems like an awful lot of laminations. Have you cut the existing welds and tried exploring by grinding / PT?
Parent - - By welderette (**) Date 03-21-2006 17:59
John we did cut open all 9 of the original rejects, but were not looking at that time for laminations, but fusion type discontinuities, which we never did find. My manager has requested that we cut out a specimen to send out for additional UT to verify findings. I think I will have them cut out the spool with the two defects alligned to each other. That would be a good opportunity to simply polish and look. I'll let you know what happens. Performing PT on weld prep is one solution, although I would rather have verification that the pipe is sound, at whatever cost, and eliminate that one variable. It seems that lamination detection is a fairly common concern, I have run into laminations several times while oxy-fuel beveling pipe. You cannot miss the "blow-out" or the flat plane beneath.
Here, however, especially on the smaller bore pipe the fitters prefer to use abrasive discs for cutting pipe as the results is more square than that bevelled by machine. So I guess torch cutting would also be one way of evaluating the material. Learning , learning, and am grateful for all the help. Deb
Parent - - By jwright650 (*****) Date 03-21-2006 18:05
A tight lamination can be hard to see visually, but many times it will open up after you start welding and get some heat into the material. Then when it is found, you ask yourself, how in the world did I miss seeing that big thing?
John Wright
Parent - - By welderette (**) Date 03-21-2006 18:24
John; Not only "how did I miss this big thing" but the question I am beating myself up with is "how could I have prevented this fiasco?" I think the answer is becoming evident. More input into the purchasing of material and continue learning from the mistake. Now pick up the pieces and go on. Deb
Parent - - By jon20013 (*****) Date 03-21-2006 20:01
Deb; All I can add is that job you've been on up there has been a great experience for you. It never really seems that way while you're waste deep in sh*t, but once you've finished it up, try reflecting back on the number of issues you've managed to overcome and I think you'll be pretty pleased with the experience this job has added to your portfolio...
Parent - - By welderette (**) Date 03-21-2006 20:42
Hey Jon; Thanks for the thought. As I told my boss "this too shall pass"
unfortunately it'll probably pass as a huge gnarly hemeroid. Yes I have learned so much, and still wading through writting the last of the WPS's.
How many inspectors have said "on the next one, I'll do this differently". I am certainly developing a list of pitfalls to be avoided. In the meantime I just have to take one issue at a time and keep on forging.
Big meeting here on Thursday, the manufacturer, a metalurgist, and the UT Inspector will be convening to evaluate this mess. My daily report is getting quite lengthy. By the way are you still coming NW this spring? Be sure to let me know. Deb
Parent - - By jon20013 (*****) Date 03-21-2006 21:17
Yep, Deb you're just going through the growing pains of experience, I'm sure 99% of all the "old-timers" who regularly post in here have said "on the next one I going to watch out for ...." We're planning a trip to Seattle around the end of May, probably including Memorial day just to take a little extra time. It's been 10 years since I've been home and my wife has never seen the Great Pacific Northwest. A must do.
Parent - - By hogan (****) Date 03-23-2006 16:08
if you order materal that has been ut'd, the allowable size of laminations can be larger than you would expect. You would probably want to review acceptance standard.
Parent - By welderette (**) Date 03-23-2006 16:48
Hogan; Thanks for the heads up; as we are now looking for full body UT.
Will do some research on criteria. Deb
Up Topic Welding Industry / Technical Discussions / SA-333 Gr.6 Material Failure

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