reflections

Date 01-18-2008 21:58

howdy. would appreciate some info from you, we are getting indications from a ut inspection on through wall full pen welds on tangential pipe/nozzles on a 63mm vessel. the indications show exactly in the same spot on tangential nozzles protruding through the vessel wall. and are only indicated when transducer is exactly perpendicular to the pipe/nozzzle along the circumference of the vessel line on the oblique side. the indication also would put the inclusion/shadow inside the parent metal of the pipe/nozzle somewhere around the i.d. of the pipe. we have these about two out of three time on an average and it seems to clear up when repaired but we do not find anything within the removal of of the inclusion. this leads me to believe that it is an anomaly and it is reflecting if the inside of the nozzle and it is a false indication of an inclusion and indicating the inside of the pipes wall. we have 48 of these to do and do not want to be chasing ghosts so i appreciate your input and will give more information if asked and will try to provide what i can. i am only a welder and i have only assisted the ut guys and night will have a limited scope of understanding of the intricate details about ut testing but will be try to get the answers or at least be able to provide the info as i observed.
thanks in advance.
darren

By CWI555

Date 01-19-2008 01:10

"it seems to clear up when repaired " There before repair, gone after. That would lead me to believe it's real. However; I can't tell you anything with confidence without joint design, materials, etc. I will comment that you used the word inclusion several times, and inclusion by definition is something included. If in fact there is a real indication, (which I suspect it is) It's not a guarantee that you will see it on excavation. Further information will require more details.

Regards,
Gerald

By g32141

Date 01-19-2008 04:22

If the indications go away when you fix them what does that tell you?
They were real.
Sometimes with lack of sidewall fusion they became bigger because of the added heat without getting rid of the original defect. The defect propogates and gets bigger.

By darren

Date 01-19-2008 06:18 Edited 01-19-2008 06:23

they reassessed things today and inserted a probe down the pipe and all of the rejections have now been cleared as it was the id of the pipe they were seeing.i wasn't there to see the procedure but there were a lot of people at the meeting and a senior inspector cleared up the issue. no repairs. still no ut failures in my file so im happy

the reason they indications went away after repair is because they used a different inspector to ut the repairs and he did not indicate a reflection.
the design was pipe at 45 degrees at the 135 degree mark on the can. can is 4' diameter and 2.25 inches thick ,pipe was 2" xxheavy
it is restricted chemistry for h2s sour service gas in china. i don't remember its exact specs from print
thanks
darren

By 803056

Date 01-19-2008 13:40

Is anyone sure it was the first inspector that was wrong?

Al

By darren

Date 01-19-2008 20:32 Edited 01-19-2008 20:49

three different inspectors found the same reflection only one of them realized it was the i.d. of the pipe/nozzle. in hindsight the one inspector said he should have realized something was wrong when the inclusion was the exact size/diameter as the i.d. of the pipe, he was laughing as he said it. most of the inspectors that we have work very well with us welders and we all work together to get a better product out. i and most of the bosses like it when they call things the hard way instead of easy because it makes a better product and us better welders, and lets face it reputation is everything.
darren

By CWI555

Date 01-19-2008 22:58 Edited 01-20-2008 03:21

Given your description, I'd be careful about buying this off. It may in fact be real yet. Simply pushing a boroscope down and seeing a root is not sufficient evidence it has gone away.
It may in fact be nothing, but I'd damn sure not buy it off on a visual given your description. I suggest mapping the area of concern out ultrasonically, and re-examine.
If in fact it is a flaw, there should be a phase reversal at the interface of the flaw, with a subsequent back-wall reflection from the root area if your root is as large as your making out. For that, use the RF display on the scope.

If in fact it was the root, and the root is fine, then I'd be questioning the abilities of your UT techs. You shouldn't have three of them coming up with the same wrong answer.

Regards,
Gerald

(edit) if by inserting a probe down the pipe you mean they put the transducer in the pipe and scanned from the I.D. that for sure is no guarantee it's gone, as it would have an inherent change in impingment properties. (/edit)

By 803056

Date 01-19-2008 23:10

Good advice.

Al

By g32141

Date 01-20-2008 03:04 Edited 01-20-2008 03:35

That's well worded.

Even a surface breaking root defect might not be visible to the naked eye. It could still have a portion of good metal above the defect.

TKY joints require a special type of training to be able to interpret the results too.

Your indication is either root geometry being wrongly interpreted or it is a real defect. My guess is a real defect since it goes away after being repaired.

Now you have 3 different UT guys in the mix. Were all of them in on this meeting you had to tell their side of the story? It seems like you hired 2 companies and the 1st 2 ut guys were with the same comapny and the 3rd ut guy was from the 2nd.

Two say it is bad and one says it is ok and you go with the lone guy saying everything is ok based on a visual using a borescope. Not a smart move.

The reason that "shadows" happen is because there is something in front of the light not allowing it to pass through to the ground. Something real and physical that blocks energy.

The same thing happens in radiography. Someone says it's a "shadow" but then it vanishes after they repair it. Sounds like to me that your production people are grasping at straws and going with the 3rd guy who said everything is ok.

The reason you see shadows on an piece of x-ray film is because it is the opposite of what you normally see a shadow as. More light (x-ray energy) hits the ground (x-ray film) which means there is physical thing (metal) not blocking the sun (x-rays) from reaching the ground (x-ray film).