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Up Topic Welding Industry / Inspection & Qualification / ut indication rating
- - By hogan (****) Date 10-05-2007 15:04
i'm looking for some opinions on an ut evaluation. inspected to aws d1.1 static, it is a t connection. 5/8" welded to 2 1/2". i had the welder grind the cap flush because i found an indication that was difficult to maximize due to bolt holes in the scanning area(all of the 3rd leg and a little of the second. there are numerous holes in the 2 1/2", so i could not inspect from face c. the welder got the gap ground and the scanning area was also ground to shinny metal. prior to grinding the indication was a +13. it turned out that i was maximized with the cap there. could not till until the cap was removed. so, that indication was now a +5. this was due to transfer. i had the part lightly sandblasted. the indication was then a +12. i hope i explained this well enough. what should the indication rating be listed as??
Parent - - By jwright650 (*****) Date 10-05-2007 15:31
I'm confused why the indication went from a +5 to a +12 by simply sandblasting.
Parent - - By hogan (****) Date 10-05-2007 15:57
transfer. less sound is transmitted and recieved due to surface condition
Parent - - By jwright650 (*****) Date 10-05-2007 16:24 Edited 10-05-2007 16:26
Did they blast away part of the indication or smooth the edges so that it doesn't reflect as well?  7dBs is alot. Seems to me sandblasting would have had an opposite effect on your rating. Smoother part would not scatter as much sound. Maybe you don't have enough couplant coverage to get sound in and out of the part? Also...Don't forget to check your couple between the transducer and wedge.
Parent - - By hogan (****) Date 10-05-2007 16:30
the indication was in the root. it was never touched. surface condition was the only thing changed. i'm aware of the need for couplect.
Parent - - By NDTIII (***) Date 10-06-2007 04:15
I agree with Hogan. Surface condition can have a big influence on indicaton amplitude. That is easily understandable. No other explanation necessary. That is why some codes require the surface condition of the part to be the same as the calibration block.
Parent - By jwright650 (*****) Date 10-07-2007 00:59
I agree with Hogan too as far as surface condition effecting getting sound into the part, but it seems to have had an opposite effect by just sand blasting...so that's why I was dismissing the surface condition as reducing the size of a reflection.

Hogan, if you say it is a +12 in a 5/8"  thick part with a 70* transducer, then it is a class D indication. I would look at it again from the opposite side of the plate and re-evaluate the root just to confirm the location.
Parent - - By CWI555 (*****) Date 10-06-2007 18:56
I guess maybe I am being a stick in the mud here, but D1.1 ratings go from + to - in decending order with the lower number being more severe. If you went from a +5 to a +12 it would imply that the flaw somehow shrank. Cleaning the part in question would allow sound to impinge without as much attenuation, increasing the energy delivered to the flaw. This would in my opinion be the opposite condition. I.E. going from 5 to a lesser number (1, 5, or -2 etc). Something is not making sense, have you checked your shoe for internal reflections? A positive increase in rating I.E. going from +5 to +12 doesn't make sense.
Parent - - By hogan (****) Date 10-06-2007 20:26
with the surface in the as rolled condition, the indication rating (ir) was +13. after grinding the surface to shinny metal, allowing more sound, the ir was +5. the part was lightly blasted ( nothing close to near white), and the ir was then +12. what i'm looking for is opinions of what the ir should be recorded at. how would you evaluate it and why? thanks for any input.
Parent - - By g32141 (**) Date 10-07-2007 01:11
I would go with the worst case scenario. You can't lose with that arguement unless you never recorded anything in writing.

Blasting leaves the surface rough. If I need a surface cleaned prior to being inspected with UT I would ask that it be wire brushed never blasted.

If I was in your position I would get them to use a flapper wheel on both sides of the weld in the area where the indication was found to get the metal back to a flat uniform surface.

Was the evaluation, cleaning / blasting and re-evaluation  all done at roughly the same time? If it wasn't you should have a UT report that you filled out indicating all of your calibration settings which could indicate a possible difference from your calibrations and if there is not much of a difference you can rule out and eliminate euipment problems. I would guess that it would be the blasting that caused the difference with the indication ratings.

If they will flapper wheel the surface and you get the same results as the first time around you can validate that blasting is not a prefered method of cleaning prior to UT inspection.
Parent - - By CWI555 (*****) Date 10-07-2007 21:37
I think I would have to go with your explaination. You are correct in that blasting typically leaves a rough surface and subsequent lose of energy. If the polished surface yielded a +5 thats what I would go with.

Regards,
Gerald
Parent - - By hogan (****) Date 10-08-2007 13:11 Edited 10-08-2007 13:17
let's assume all inspection has been performed correctly. please no advice on how to properly perform an ultrasonic inspection. why would you apply a more stringent criteria, the flat, ground smooth, and shinny, base metal scan? compared to the as rolled inspection. do we grind all scanning areas prior to inspection? no. i'm not trying to argue, i'm looking for reasoning.
Parent - - By CWI555 (*****) Date 10-09-2007 02:01
Ok, The first think I would say is that it's not applying a more stringent criteria. Assuming as you state that the exam was done properly, after you removed the cap and re-examined the reading at that time was +5. Going behind it and blasting and therefore changing the surface did not make the +5 go away, it only changed the surface so that you lost more energy in the transfer 7 db by the numbers you've quoted. I am not trying to be a smart ass here, but this would be akin to taking an RT shot where the weld surface was to course to properly read, grinding the surface, and seeing a lack of fusion in the subsequent shot, then shooting it again at a slightly different angle which will half the time make a lack of fusion image disappear due to simple orientation of the energy source. Did the LOF go away? no, did the image go away? yes. Does the lack of an LOF image without repair in the third and final shot make the weld good? no. The ethical thing to do is reject it if the worst case findings are reject-able by the referencing code.

For a UT example, it would be like finding a flaw prior to galvanizing, then checking it again after. before it was out, after it was in. Did the flaw go away? no. did the galv create an attenuation issue? yes.

The best course of action is to make sure there are no surface irregularities or geometries that can interfere with the exam before you begin. If there are geometric concerns, work the math and sketch it out before you begin. Scan per code and procedure requirements, and stick to the results of that scan.

S10.6 Weld Joint Type and Groove Design. The weld
joint type and groove design are important factors affecting
the capabilities of UT for detecting discontinuities.
The following are design factors which can cause problems
and should be considered for their possible affects:
(1) Backings
(2) Bevel angles
(3) Joint member angles of intercept
(4) PJP welds
(5) Tee welds
(6) Tubular members
(7) Weld surface roughness and contour.

Point number seven is where you have run into a problem. While appendix S is informative, it does specifically mention weld surface roughness as a concern in the design when it comes to UT. Bottom line is, you went from a rough surface, to a smooth surface, and back to a rough surface. It tells me the surface your working with is partially masking indications through ultrasonic attenuation. Suggest checking with transfer correction check per figure S4 in appendix S.

Regards,
Gerald
Parent - By g32141 (**) Date 10-09-2007 04:01
"Bottom line is, you went from a rough surface, to a smooth surface, and back to a rough surface. It tells me the surface your working with is partially masking indications through ultrasonic attenuation."

Brilliant.

You can't explain it any more simpler than that.
Up Topic Welding Industry / Inspection & Qualification / ut indication rating

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