If there where water in it, you would have to have your range set to cover the entire circumference of the pipe. Keep in mind the velocity of water is 1480 m/s and the velocity of mild steel is approximately 5960 m/s. It's a lot faster in the steel. time wise the steel is just about 4 times faster for time of flight. If the velocity of the scope is set for steel (assuming longitudinal) then as far as the scope is concerned it's clock is calcing the T based on the velocity of steel and is not going to take into account that it's traveling through a much slower medium, and therefore will report only what was put in. If it is assumed this is an 250mm ID then you have that amount of water at 1480 to account for.
In effect for every 25mm of water, the scope when set for steel would have to have 100mm of range. on the 250mm ID full of water, it would have to 1100 range set in order to pick up the opposite wall O.D.
If the tech whomever it is did not take this into account, he would have no idea if there was water or not, as the reflection cooefficient would give him a reflecting from the backwall, but not show the opposite wall because there was not enough range to display it.
It sounds like water in it to me, or it could also be partitially full, or there could be something solid left behind in the line.
If it is water, about 175mm of it would equal a half value layer if memory serves me correct. That would kill the shot as the HVL for steel is about about 12mm for 180KV at 3ma constant potential (again if my memory serves me correct).
I have not done the UT or RT myself, my brother just called and asked for advice and ideas.
I dont know what kind of UT they has performed, but the lvl II guy is pretty experienced in both RT and UT. According to my brother the tech did adjust quite alot during the examination.....well knowing water might be the issue.
My first thought was the line was full of water or something solid left behind, like a backing ring or something simillar.
They knocked on the pipe with a hammer and it indicated a ^ringing^ sound - well as much as a DN300 can ^ring^ when being close to supports, etc....
They followed the line all the way to a vessel, on which they opend the vent (no air or water pressure) and shot the weld just below......same result.
Seeing as its an eastern european contractor (no offence) it could very well be something left behind in the pipe.
I think they use 4mA, not that it would matter in this case.
3.2
I would suggest the expansion of the range for the UT. Even experienced hands trip up on that one frequently. If he's already done it, then it's nothing but a phone call.
They went home, telling the contractor to air-blow the line :)
I will update tomorrow.
3.2
are they sure of the material type perhaps the pipe has a repair sleeve inside, Could be full of solids.
If its real old maybe its a lead pipe JK.
it sounds to me like it is solids in the line, it might be quicker to just cut it open and find out what is really inside of it.
You may be right, but cutting open a line before all NDE options are exhausted is a bit premature. If the sound is not reaching the opposite wall, then it is something other than a liquid. considering that they moved upstream to another weld and had the same problem, would make solids a questionable cause, but if no sound is pinging the other side, there isn't much else that it can be.
DID they remove the lead cap form the target?
MDK
Yes.
Water.
3.2
Sorry for my late update.
Thanks. Was it eventually detected by UT?
Hi All!
Interesting Post! I asked this question to a few of my more educated work colleagues and they all said that 'water' in the line would cause this! As regards the UT method of detecting this in the first place, well, opinions were divided! Yes it can be done, however the cost and skill levels involved far out-weighted the common sense idea of blowing out the line and then cutting the offending weld!
Regards
I would lay two paychecks the UT hand didn't have enough range and or amplitude. As for another comment about the cost, it's not really that costly.
I agree with CWI555. This is no more difficult that a thickness/lamination scan. Something every level I should be able to do. As stated previously, you need to know where your sound is going and set your range appropriately.
Any of you guys ever find a file in an x-ray? lol
Yup, files, hammers, skids. :-) The skids were sabatoge though, and in one instance the hammer may have been.
jrw159
I can see how easy it can happen. We picked up 2 40 footers welded together on a pipeline once and I heard something sliding down the inside of the pipe. Ahhhhh sit, that's where I left that dam file. lol It got left in the open end of the pipe where the fitter was prepping the bevel before it went in the hole.
Welding rods (stuffed down boiler tubes by some disgruntled types) Boots (not attached), various hand tools, among other things found in pipe and tube. Found a 1911 in 12" of concrete (Shot at the request of police). X ray of tires for bonding (dunno who remembers the maypops that came out on Ford SUV's a while back). If you've been in field RT, you see a lot of odd things.
I was on a small pipeline job in a residential area, the welders had welded some 6" spools and left them laying out for the weekend. We went to RT them on Monday. When I ran the film I could see something odd while developing. A cat had climbed inside and died. Laying right across a weld.
That must of been one rough root pass!!
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