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Up Topic Welding Industry / General Welding Discussion / ut /rt misdirection
- - By darren (***) Date 08-21-2007 10:06
did a repair on someone else's sub arc seam. was indicated by rt backed up by ut was supposed to be at 19 mm deep i went 31mm and real wide deep found nothing. re shot after i filled with 5/32 7018 vert still there exact same as first rt. now had ut done again and it indicates it is 19mm down within the weld i replaced. now i can't wrap my head around this but the rt/ut says it is within the weld i replaced! exact same as first film so it is the same inclusions and i very much trust the radiographer/ut guy. as well the other four repairs i did shot clean and the tech said because the rt was exactly the same that that weld was sound as well just that we didn't remove the incusion that was indicated on the first film. now my question before i go in for a second time is how can it be indicated twice, once within the subarc seam and then within the weld i replaced.
almost having a brain melt over this.
darren
again i very much trust the welding inspector
Parent - - By g32141 (**) Date 08-21-2007 18:50
Well, if it was within the weld you replaced you can rule out the weld defect being marked up wrong.

What was the defect classified as? Lack of sidewall fusion is harder to see during excavation but I doubt it was that because RT would have a tough time picking it up especially with the thickness you are talking about.

Excavating 31 mm deep for a defect at 19 is a bit of overkill don't you think?

Having a mag yoke to check your excavation will help in the future. They save lots of re-repairs.

Give us some more info about the weld.
Parent - By 803056 (*****) Date 08-21-2007 19:13
Turn the UT machine over, they are looking at the screen upside down!  ;)

Al
Parent - - By darren (***) Date 08-21-2007 20:39 Edited 08-21-2007 20:43
the reason i am putting this in the forum is because it makes no sense at all and the tech agrees i was wondering if  some of the very experienced inspectors had any insight about such a thing. again it is not the weld i replaced and it cannot exist in the weld i replaced as it is identical to the original film and it is a fairly complex inclusion. so i am thinking echo or something outside the norm because the weld i put back in is sound. and the inclusion still shows up. as to the excessive nature of 31 vs. 19 i have chased a lot of indications way past what they were designated by the inspector. dig till you find it regardless of the "facts" ive found the inclusions way off from where they were supposed to be. i just repair what i find and i did not find anything within a very large area surrounding the indication so as i was told fill'er up. again it cannot exist where the indications point to so where oh where can it be?
the reason i am using this forum is because even though management and everyone within the decision making command structure says "its not my fault i did my job"
I DO NOT ACCEPT FAILURE, IT IS NOT AN OPTION. DEATH BEFORE DISHONOUR.
what is a mag yoke please?
darren
ps it was a fairly complex chain of slag inclusion
Parent - - By RANDER (***) Date 08-21-2007 21:24
Is the UT scope calibrated? Measuring in the correct units?  Is the Operator Certified? Is He/She familiar with their equipment?  Not all RT techs are great UT techs and vice versa.  Most guys lean one way or the other.  Sounds like you should be questioning the UT tech on this one.  Are they one and the same person?  A Mag Yoke is a portable device used to perform Magnetic Particle testing. (MT)

A picture is worth a thousand words - Your RT film says you've got slag inclusions, Even you can see that......
Your UT exam is a little harder to interpret and you (Not the tech) have less of an ability to correctly interpret the signals into comprehensible information.   Try the UT again.
Parent - By hogan (****) Date 08-21-2007 21:59
try grinding the surface flush and have the ut guy try a strait beam inspection. it is not as sensitive but it should find slag.

also, mag your excavations
Parent - - By g32141 (**) Date 08-21-2007 22:51
I have seen this lots of times. Either the weld repair was mismarked or the repair welder took it upon himself to remark where the repair in his opinion should be.

With UT the indications should be marked up rather precisely.

What was the seam that you fixed? What code was it?

Unless your calibration block for UT is made from the same job material you can expect some depth and or distance variations.

Please explain "a fairly complex inclusion". Slag, copper, tungsten?

The more details that you can give us the more we can help you sort it out.

You also need to shake the since I didn't see anything I'll filler up attitude because that won't fix a defect.
Parent - - By darren (***) Date 08-21-2007 23:26
the inspector is the best of the best i totally trust his examinations the point i am raising is that its not there!
and as a welder i do what i am told i was told by my foreman to filler up, so i did it obviously i don't have that as a motto otherwise why would i be here trying to solve something that is obviously not my fault, on my own time. all the demarcations were done by the inspector and qc dept. i just went in where i was told to.
they were a intermittent line of slag inclusions.
again the reason i am here is to find a solution and get some real time empirical information as to why this is occuring
darren
Parent - By RANDER (***) Date 08-22-2007 02:23
As none of us have access to the film or the scope its hard to say what the problem is Darren.  However, If you give some detail as to material, joint config., thickness of the part, you might get a little more info.  You've got 2 methods telling you "something" is there. Not seeing anything from here I'd say the UT is off in the kind of way that CWI555 mentioned rather than bet on some "Ghost Indications" that both methods are revealing. 

If one method reveals an indication but another method fails to place the indication right where you think it is that is not a great reason to invalidate the results of both tests.  UT willl give you the Best indication of depth if its done correctly.  As you say the Tech is the best you know and hes telling you there are slag inclusions I dont see why you are are questioning the existence of the indication.  What seems to be the real issue is not the existence but the actual location of the indication(s). 

Sometimes when one is the best it's hard to admit being wrong.  I guess I can't really help here other than to say get a second opinion if it's important to you.  And kudos to you for looking into a problem and trying to find a fix instead keeping the blinders on, heading home to a cold beer and forgetting about the whole thing.

Regards,
Robert
Parent - - By CWI555 (*****) Date 08-22-2007 00:13
Sounds an awful lot like your UT technician is reading the auto trig functions instead of plotting out the indication. Using a 70 19 mm should give around a 55mm sound path single leg. Standard RT cannot tell you how deep they are, and can be off considerably on the perpendicular of the shot orientation depending on how high or low the source was placed in regards to the plan of flaw. I'd place even odds the surface distance as marked from the UT tech is wrong, as well as the depth. If the indication came back after excavating 31mm, you obviously didn't get into it, but both rt and ut say it's there.

The UT machine autotrig functions depend on many things, one of which is plugging the proper thickness. If for instance your thickness was 40mm, and the tech had plugged in 20mm from some other exam and did not change it, the machine would think it was in the second leg when it was still in the 1st leg of the sound path. Using this example lets place at 35mm depth. This would place it firmly in the first leg. Sound path distance to flaw would be 102mm, the surface distance to the index point on the transducer would be 92mm back, and again the depth to flaw would be 35mm.

Now changing that around and assuming the flaw was actually picked up in the second leg:
first leg sound path to back surface = 117mm and going back to the flaw another 14.6mm is added total of 131sp on the second leg, using the 2t -(sound path x cos angle) formula the depth again comes up as 35mm.
The machine has no idea that the actual thickness is 40mm. As far as it knows, the thickness is 20mm and all calculations it makes will be based on that.
So as far as the machine is concerned it is the flaw would be at 4.8mm down.

This may or may not be the case, but given the information you've given I'd lay even odds on it. Even the best UT technicians can fall prey to fits of laziness and start relying to much on the autotrig features common in modern scopes.

Regards,
Gerald
Parent - - By darren (***) Date 08-22-2007 08:23
the joint is a circ seam joining the 1.75" shell to a 2.25" head 1/2" double v prep welded with 7018 inside back gouged from the outside back to sound metal and filled with subarc
and it turns out that because of disparity in thickness between the shell and head the indications were off to one side. someone else dug it out today and filled it back up we will see if it turns out clean. i knew it wasn't in the weld i replaced because the first and second films were identical also there were no new or different indications. although it is upsetting to not complete a job even if the indications were out of my control. i am at least relieved that all the weld i put back in from the inside of the vessel 5/32 vert came out clean. still as most of you know in a shop if you don't affect a repair correctly your fault or not the tongues begin to wag.
and as i have stated failure is not an option

three times it was completely back gouged out because the foreman did not listen to the experienced voices in the shop and back gouge a different angle of  bevel the first or second time and put a very inexperienced operator on the job who had her confidence shaken as she was legitimately over her head for the first saw weld and the first and second reweld of the same then five major repairs as well as. had the shop guru come and gouge off the cap and re subarc so it looked professional, should have had him do the whole thing from the beginning.

so to recap, smaw inside /back gouge outside /subarc out side /re back gouge outside /re subarc outside/ re re back gouge outside /re re subarc out side /gouge off cap outside/ re cap outside/ repair five major subarc weld flaws from inside/ one twice because of wrong location indications.
wow when i see it written out like that it makes me think that someone should be called on the carpet for their decision making

i really appreciate the positive well experienced input and thank you for taking the time to respond.
darren
Parent - - By jwright650 (*****) Date 08-22-2007 11:38
Darren,
I've been reading this thread from time to time and skimmed through it pretty quickly, so forgive me if I'm repeating something that has been stated already. Having said that, is your UT guy using more than one angle wedge to look at these indications and from different sides of the weld where possible? I ask this because with the thickness you have, you should be able to verify pretty quickly the location provided the UT guy is figuring using his Sound Path correctly(trig). By using more than one angle and trying to remain in the first leg, he should be able to nail down the location very accurately. If he isn't completely sure where his sound is and using his trig correctly he could be seeing an indication and marking it on one side when it really is closer to the back side or visa-versa(been there and done that, bought the T-shirt :-) ). I too, commend you for looking into this as deeply as you have. There is a reason for what you are seeing(or not seeing) so i wouldn't give up until you solve your questions. Obviously indications do not move around unless it was interpeted incorrectly the first time or the welder put something back in(chances of it being deposited in the same spot are remote, but...). Not having the whole situation sitting in front of me(UT machine, UT tech, weld example, ect...) if is purely a bunch of guessing going on here, but most of us UT guys and welders have made mistakes that sound very familiar to what you are experiencing.
BTW, I would look hard at that sub-arc set-up before doing too many of these joints, if it is giving you guys that much trouble to keep the deposited material clean.

Gotta run...looking forward to reading more about your situation.
Parent - By CWI555 (*****) Date 08-22-2007 18:38
Any UT hand who says they haven't been there and done that is probably lieing, or has just got out of their level I class. I can't think of one tech that hasn't gotten caught by that including myself.
Parent - - By g32141 (**) Date 08-22-2007 16:41
Dissimilar metals within a transition using more than one bevel could throw someone's calculations off. Is the defect on the shell or the head side of the weld?

What type of calblock is the UT guy using?  Is he scanning the weld from the inside and the outside? Any way of getting him to post on here so we can ask him questions?.

How many times are you allowed to repair it?

Hopefully this last time got it. I am curious to see how this ends now.
Parent - - By jwright650 (*****) Date 08-22-2007 16:56
Sorry g32141, I didn't read the part about any dissimilar materials being joined.
Parent - - By g32141 (**) Date 08-22-2007 17:48
The shell and the head are obviously not the same material in regards to velocity. Like a forging to pipe weld. That makes them dissimilar metals.
Parent - - By darren (***) Date 08-23-2007 00:24
your gonna love this
after all that the welding supervisor who laid out the repair twice discovered he had done so IN THE WRONG LOCATION. so internally the reference points went clockwise and the reference points on the out side were counterclockwise by his markings. so the ut tech and rt tech and the inspectors supervisor said no its still there and the WELDING SUPERVISOR transcribed the information into the vessel backwards and that is why we could not find any inclusions. it was all based on the supervisory control and nothing that the ut guy the rt guy or myself did. thats why when the super went in he said it was in the same place as i had already rewelded but it was one film over.
whew i thought i was gonna bust a brain over the whole thing. thanks for all the help.
darren
live and learn

Parent - By RANDER (***) Date 08-23-2007 02:44
Well G32141 is the winner in this case!!!

Human Error whod a thunk it?
Parent - - By ZCat (***) Date 08-23-2007 02:54
I've been welding 30 years. NDT doesn't strike me as being an exact science.
Parent - - By RANDER (***) Date 08-23-2007 02:57
Weeeeeeeelllllll,
The NDE seemed to be on in this case however the gentleman NOT performing the NDE layed out the overlays in the wrong direction.  Not the Techs fault but it speaks volumes for having a tech lay out what he has found.

Yes Interpretation has much to do with it just as welding is more than reading the numbers on a WPS.  Look, Listen and feel the welding process.  Its all the best of ART and Science combined!!!!!
Parent - - By ZCat (***) Date 08-23-2007 03:01
I've had the techs mark the wrong side of the pipe on numerous occasions, especially if it's small pipe and they're just taking one shot of the whole thing, that really throws them off, for some reason.
Parent - - By CWI555 (*****) Date 08-23-2007 21:58
small bore is typically shot with an elipse, and for section 1 I believe it only requires one view. Sometimes they get confused as to which is inner and outer on the shot.
Parent - - By thirdeye (***) Date 08-24-2007 03:04 Edited 08-24-2007 03:14
Actually, it's two views 90° apart.  And you are correct, knowing the offset direction and placement of the location markers will allow you to determine source side and film side welds.

~thirdeye~
Parent - By CWI555 (*****) Date 08-24-2007 03:56
I stand corrected. It's been a while since I've looked at Section I but yes it is two views 90 out.

Regards,
Gerald
Parent - By thirdeye (***) Date 08-23-2007 18:10
That is a good one....It's not that uncommon either.  Glad you posted the follow-up as I have been watching this thread.

In certain circumstances, the OD / ID  or film side / source side differences in the location markers also can cause some confusion.  Along with an overlay, I like to use a centering head for accuracy.

~thirdeye~
Parent - By CWI555 (*****) Date 08-23-2007 21:57
Good to hear, and glad it's resolved
Up Topic Welding Industry / General Welding Discussion / ut /rt misdirection

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