It is common to do this using UT.
You said ut? like a lam check
UTT consistent with an API 570 program.
Process Safety Management programs are quite common doing this very thing.
It can also be done with RT. This would give you a picture of a larger area than UT but would, in most cases, be more costly and time consuming.
4" line? UT can be done in 2 minutes. Not a problem
Back in my days of erector engineer I've done exactly that work (measure the thickness of a furnace heater tubes in an oil refinery to check whether they were corroded) using UT. Everything went fine. Fine from a technical point of view because UT proved an excellent tool for the job. Too bad for the refinery owner and the heater supplier, because the tubes, that were supposed to be new and unused, proved to be badly corroded and had to be completely replaced, thus creating an unexpected delay.
Giovanni S. Crisi
Sao Paulo - Brazil
It sounds to me like you are doing a hot tap, around here standard procedure is to UTT the center of were the tap will drill and four points around were the pipe will be welded. They also have an RT crew on stand by to check the seam of the pipe if it will be welded across to check to see that the seam is intact. Usually you can get the RT crew that can also do the UTT. As for cost, around here a UTT crew is more expensive than an RT crew.
RT (on stream) is the better choice.
3.2
Hello guys,
If it is a "live" chiller line will it not be full of liquid ?
RT will give you a very poor shot (if any) if it is full of liquid.
Regards,
Shane
Thats why i wrote "on stream"
It is usually done with Co gamma rays.
It will penetrate anything :)
3.2
Water has a nasty habit of attenuating ionizing radiation regardless of the source. There is a reason nuclear plants use water in the spent fuel pools.
RT for this application would be like using a flat head screw driver on a phillips head screw. You may get to work, but it's not going to do the job very efficiently.
I wont argue with you...BUT its done every day worldwide.
3.2
It's done every day world wide needlessly. That fact is changing by the day as well. Most people are starting to clue in they are using the wrong tool for the job.
I agree that LRUT is taking over
Btw contrary to popular belief, Co60 will not penetrate "anything". A few months back a friend of yours ran into that very issue while performing RT according to the post you made.
half value layers for Co60 in water is to the tune of 3.5" or so for the first layer. However, water is different than most materials in this respect. It's coefficient of absorbtion is considerably different, and that gives considerably different values for subsequent layers.
A good friend of mine?
No Co will not penetrate everything, I wrote that to illustrate its power.
I remember....
But that was using X-Rays for weld defect detection.
3.2
It's the same principle. The physics of it don't change.
And the reason RT is not a good option here is......?
3.2
Reasons:
a) to much attenuation in fluids
b) RT requires specialized techniques to perform a task better suited by UT
c) When RT is not required, using it anyway runs the risk of dose to both the crews and public
d) RT must have a linear T change parallel to the beam axis, most corrosion tends to be perpendicular to the beam axis.
Those are just a few reasons.
I agree that Co does expose the crew to a relative high dose of radiation.
3.2
Guys,
Am I missing something here ?
Years ago we had a request to shoot a large amount of boiler tubes to ascertain the depth of SAC corrosion on the internals of the tubes. We took a similar size tube and then had slots machined at 10 different depths on the inside of the tube.
We then radiographed the tube with IR 192 and kept these graphs as reference graphs.
After we shot random shots of banks of tubes we compared the density of the corrosion with the density of the machined slots and it gave us an "approximate" depth of corrosion.
Whenever we have shot pipes with water in in the past the area where the water is is unviewable.
How can you possibly shoot through water and be able to tell if there is internal corrosion or more critically the depth of corrosion ?
Regards,
Shane
Seems like UT thickness testing would be quicker, safer and alot more accurate. Time is money.....Just my 2ยข
you may find that if the inside of the pipe is severly pitted due to corrosion, back wall readings will be difficult to get. The pits create a non parrallel back on the id and the sound will scatter rather that return to the transducer. jm2c
dave
proper selection of transducers can mitigate that condition.
You are correct, I mixed up a few things :(
3.2
Shane,
what does SAC means? You English speaking people of this Forum use plenty of initials, slang, etc., which we, non English speaking chaps, don't understand.
Giovanni S. Crisi
Sao Paulo - Brazil
Stress Assisted Corrosion
Shane,
now that I know what SAC means, tell me: did you find out what was the reason of the SAC corrosion in the boiler tubes?
Giovanni S. Crisi
PS: Thanks, johnnyhy for the help.
Sorry Giovanni,
Wasn't involved in the technical / engineering side of the problem.
I vaguely remember that it seemed to be worse in areas where the ligaments had been welded on.
Regards,
Shane
vernk,
I try to imagine if the surface of 4"dia pipe is wet during welding.
Lamination check here is a must. Groove weld is preferable using GTAW process. Reinforcing plate (if possible) should be installed. Can you show some photo on leak portion?
UT thickness gauging is useful to detect general corrosion. However, localized corrosion may be difficult to locate.
UT scans is the best choice. Radiography may be used also. Especially on those areas that you need not want to remove the insulation.
Regards
Joey
Is lamination check a must?
3.2
yes sir, you can find it in codes
Also on seamless pipes?
3.2
Joey,
Can you please advise which "codes" require a lamination check prior to welding to the outside of a live pipe. I am unaware of any but would be interested to find out which they are.
We were having a discussion on the merits of UT versus RT and it seemed to be the concensus that UT was more suitable than RT,
Regards,
Shane
Shane
Well, not particularly only on live pipe. API 653 clearly stated the lamination check. API 570 states ultrasonic inspection from the external surface can be used to measure wall thickness and detect separation, holes, and blisters. It also allowed the NDE in accordance with the applicable code and the owner/ user's specification.
In weld flaw detection.....what I understand is 0deg probe will be used first before the angle probes 45, 60, 70.
Please correct me if I'm wrong.
Regards
Joey
Forum
