UT in lieu of RT

By QCCWI

Date 05-13-2005 14:33

Not trying to be smart, but what does the contact say?

By chall

Date 05-13-2005 15:02

My experience has been that when specified, RT must be used unless it is impractical or impossible to be performed. In those case, UT has been approved.

Charles.

By jwright650 (*****)

Date 05-13-2005 16:32

Are saying that the pipe is at high temperature when inspecting or that the pipe while in service will be at a high temperature? The reason I ask is that contact UT testing may not be practical at a high temperature(may melt your transducer/boil out all of your couplant etc...) I use a rule of thumb...too hot to hold your hand on it for a few seconds, too hot to UT.
John Wright

By bkmuduli Date 05-14-2005 06:38

Let me clarify.

The above piping is under fabrication and shall be operated at high temperature after commissioning. Any failure in the piping may lead to fire.

We intend to carry out UT of weld joints in lieu of RT.

Is there any guideline or recommended parctice peertaining to this?

By NDTIII

Date 05-14-2005 09:59

My first question is why do you want to perform UT in lieu of RT? Is it impractical to do RT?
What is your reason? From a technical standpoint, it wouldn't matter, but most codes do specify RT. You may want to ask your client. If it is acceptable to them, then OK.

By Shane Feder (****)

Date 05-17-2005 10:06

Greetings to everyone from downunder,
I have just put in a request to my client for dispensation to use UT in lieu of RT for the steam piping (B31.1)that we are currently fabricating in Northern Australia.
The reason for this is other contractors are working 24 hr shifts on the boilers that our piping is running to and from and we are on a very strict deadline for completion.We have numerous "tie-in"welds that are all over the outside of the boilers and it would be impossible to radiograph these welds while other personnel are still working on the boilers.The clients representative is a bit wary of UT but it is acceptable in the code and I think I have put forward a pretty strong arguement for my case,
Fingers crossed,
Regards,
Shane

By G.S.Crisi (****)

Date 05-19-2005 14:58

May we know what the client's final decision was? If I were the client, my decision would be "yes".
Giovanni S. Crisi
São Paulo - Brazil

P.S.
Shane: you're Australian and you speak better English than Americans do. When I studied English, I was tought that "If I were you" is the gramatically correct expression instead of "If I was you", as Americans say. Is that right?

By Shane Feder (****)

Date 05-23-2005 08:49

Hello Giovanni,
Firstly, the client agreed to my request.
Secondly, I am actually a New Zealander who has been living and working in Australia for the past 10 years.
Thirdly,I personally say "If I were you " but I have also heard "If I was you"spoken here in Australia. ( Must be all the American TV programmes we get down here)
Best regards to all on the forum,
Shane

By billvanderhoof (****)

Date 05-24-2005 06:29

I'm an American (from New Jersey) and I say "if I were you" but I've also heard both. It may have to do with regional speach differences in America. The differences used to be quite pronounced but mass media is slowly stamping them out (something of a shame I think). There are lots of oddities in english- "I could care less" and "I couldn't care less" both mean the same, flammable and inflammable things are both likely to catch fire but excusable and inexcusable are opposites.
Glad I learned english when I was a baby and it was easy.
Bill

By Jim Hughes (***)

Date 05-16-2005 14:29

From strickly a code standpoint yes you can. But when you say in lieu of something it sounds like someone is requiring you to use RT. You would need to check with the client and if you have an engineering group check with them. If you have the authority to make that call then it's up to you. Depending on what size pipe it is, it could get pretty spendy to use the UT process. You could step up the rejection criteria for RT and grade to a higher standard. Just for an example, if the system your building is normal or category M fluid service than grade to severe cyclic condition. Use a D4 film instead of D7. This is just a couple of suggestions.

Jim

By swnorris (****)

Date 05-23-2005 22:34

Assuming RT is specified in the contract documents, you'll need to check with the engineer to see whether he'll allow UT. As you probably know, all NDT methods have advantages and limitations for detecting various types of weld indications. I don't think that RT can detect lamellar indications. Maybe RT is just his preference. Are you trying to avoid the potential radiation hazard or the difficulty or time involved with RT?

By chakra Date 06-13-2005 10:26

UT is better if you are trying to detect side wall LF (lack of fusion). RT is more comprehensive. We always prefer RT unless it is almost impossible to do so.

By Bonniweldor (**)

Date 06-22-2005 02:26

Correctly executed UT is more sensitive to CRACKS. UT's problem, wrt the ASME Code, is that it normally does not create a permanent record. Automated systems may create a record, but these are not expediently adaptable to field applications.

By MBSims

Date 06-22-2005 03:54

Therein lies my concern for the "UT in liue of RT" provisions in B31.1. I think they lost perspective on that one. Just because RT uses a piece of film to provide a means of interpreting examination results and that piece of film can be stored under proper conditions and looked at later, does not mean that a substitute method must also be able to be stored and looked to look at later. If both methods are capable of detecting the same flaw size and distribution volumetrically, then in my mind they are equal. Visual, liquid penetrant or magnetic particle methods do not produce a permanent reference, yet they are permissible. The results can be recorded on a report form for later reference. Report forms are also used for UT and RT. I just don't see the need for the NDE method to produce a permanent reference.

By Shane Feder (****)

Date 06-22-2005 10:27

Marty,
Worked as clients rep on a Dragline build about a year ago (had a few postings on this forum as I was having major dramas with the contractor)
We performed random UT on numerous butt welds from 1"to 8"plate.We were finding a significant amount of defects (generally lack of sidewall fusion)The contractor was arc gouging these welds and then saying they could not find the defects.They were accusing our UT techs of being incompetent.I had known these guys for a long time and had full confidence in their abilities.This turned in to a major contractual shit-fight. If we had a radiograph (ie.permanent record)we would have had a photographic record we could have used as evidence in an industrial court of law if required.
Years ago when I was a pipe welder I was welding some heavy oil drain lines in the 2G position with GTAW. The heat of the weld was melting the oil up above the weld and as I was putting the root runs in I could see the molten metal bubbling with the internal contamination of the oil.The finished root runs looked fine (externally)and I continued to weld out the butts.The welds were UTéd (much quicker than I thought was normal)and I was told they were perfect.
I was very surprised as I was sure the root runs would be full of porosity.
My point is RT creates a permanent record that can always be re-interpreted at a later stage by a more experienced person (if there is conflict) whereas UT is solely reliant on a persons ability to interpret the signals he is viewing on his set.
I have had first hand experience of a weld being inspected by two different UT techs and both having different interpretations of the same weld.
This posting is not meant to be an exercise in UT bashing but purely my opinion (and I stress it is just an opinion)as to why RT is the preferred technique and UT may be used in certain circumstances"ïn lieu of RT"
Regards,
Shane

By Jim Hughes (***)

Date 06-22-2005 18:28

Hello Shane,
UT also can create a record. It can be paper or computer disc. that can be looked at. The job I'm on now as a welding engineer, we are using AIT, which is a auto UT process. This process gives us a 3D view of the weld and it can be printed out or stored on a disc. My original argument against UT from the start is three (3) fold. 1. You have to know the tech. I have been burned a number of times with UT by going in and repairing a weld and not finding enything. Had our corprate level III look at the record and did not see what the tech saw. It was $3000 to repair a P91 weld on the average for that project. Now I know this can happen with RT also but it has happened on jobs that I have been on more often with UT. 2. The UT company must produce a standard and this can get pretty cost prohibitive if you have alot of different materials your working with. 3. The cost of using the UT process compared with RT on alot of piping, i.e we had some 6000 feet of pipe with over 300 welds on the last job I was on, would have been very costly. Now I know that there are times when you just have to use it, but side by side with RT the cost is much higher.
Just some thoughts from my experiance. That and a $1.50 with get you a cup of coffee here in the USA.
Thanks
Jim

By Bonniweldor (**)

Date 06-23-2005 02:37

UT's sensitivity for finding cracks is far greater than an excavation operator's sensitivity for finding the same crack. UT can find cracks that poor metallographic preparation can miss. If a fissing match develops, the situation is simply not being managed correctly. For instance, if you want to prove the existance of a very tight feature, grind excavate while doing PT at sequential depths. This technique has substantiated many discontinuities identified by conventional shear wave UT.

However, for TOFD and phased array, the accusation of voodoo probably still applies. The same, meticulous, excavation and PT technique tooo often finds NOTHING.

PS: I go for UT over RT every chance I get, because cracks are more detrimental to safety and integrity than rounded volumetric defects. RT may find open cracks, if the source orientation is optimal, but it will never find tight cracks.

By Debasis Mitra Date 07-01-2005 11:59

May I refer to para K341.4.2 (Radiographic Examination) of High Pressure Piping as per ASME B 31.3. It very clearly states in sub para (b) that UT shall not be substituted for RT, but may suppliment it. This implies that there exist some reservation in the use of RT and it can not be just changed to UT. It is aggreed that UT has better detectability for planer defect, cracks.
regards
Debasis Mitra
Sr. Engineer
Haldia Petrochemicals Limited

By NDTIII

Date 07-02-2005 03:57

I made a posting in this forum entitles, "NDT in Lieu of Hydrotesting".
There seems to be some confusion with regards to conducting UT exams as a substitute for RT. The older code interpretations say NO, but it seems the new 2002 B31.3 Edition, says Yes. See B31.3, para. 345.9.1(a).

It also states in the 2002 Edition under para 341.4.1(b)(1), that welds shall be fully examined by random radiography or by ultrasonics.

So based on that para. if you are using the 2002 Edition of B31.3, UT would not be considered a substitute for RT.

I'm still waiting for the B31.3 committee to get back to me.

From a technical standpoint, I see no problem if you are performing baseline examinations. But for inservice examinations, you should use the same method used for the baseline, so you can have something to compare your results with should the need arise.

In addition, if you are examining mechanized GMAW welds in the short circuiting mode, you will want to use automated UT. It would be very difficult for RT to detect some of the sidewall lack of fusion that can be encountered.

I have a question for bkmuduli though. Piping is not calssified by B31.3 as high temperature. It is either Category D, Normal, Severe Cyclic or Category M piping. What piping are you asking about?

In any case, you have to go by what the code states as a minimum unless your contract specifications require something else.

By Shane Feder (****)

Date 07-03-2005 22:55

Greetings All,
The original question was whether UT could be used"ïn lieu"of RT for refinery piping.I assume this piping will be in accordance with B31-3 and as NDTIII has explained this code allows either technique so it would not be classed as ïn lieu".The same applies to B31-1.
My reference earlier in this posting to UT ïn lieu"of RT was due to the fact it was a client requirement to use RT and I was requesting dispensation to use a different inspection process.
I have a new question I hope someone can help me with.
ASME IX Welder Qualification requires Mechanical Tests but these may be substituted with RT as per QW 304.If the commitees of B31-3 and B31-1 consider the processes equivalent why is UT not considered as a substitute for welder quals.
The reason I ask is as you can imagine Australia is a huge country and some of the sites we work on can be thousands of miles from civilization.I might have a UT tech on site who could give me an instant result but I have to send the coupons to the nearest laboratory which may take days,
Thanks and regards,
Shane Feder

By Jim Hughes (***)

Date 07-05-2005 13:29

Hello Shane,
Yes, in the Sec. IX 2000 Addenda there is a code case that was passed to permit use of UT for welder qualification. I don't have it in front of me but if you look at the 2000 addenda or later you will find it. If my memory serves me correctly there are some limits. 1. 0.20 inches minimum, 2. pipe must be not less than 4.5 inches outside diameter, 3. thickness cannot exceed 0.062 times the pipe outside diameter. I'm taking some of this off some notes that I had taken when I saw the code case, but for some reason did not note the case number.
Hope that helps.
Jim

By Shane Feder (****)

Date 07-05-2005 23:00

Thanks Jim,
I will have to follow it up and chase the Addenda,
Regards,
Shane

By HgTX

Date 07-20-2005 21:41

"Now I know that there are times when you just have to use it, but side by side with RT the cost is much higher."

Interesting. In the bridge world, RT is considered to be significantly more expensive that UT. Must be the kind of welds and how easy they are to UT.

Hg

By MBSims

Date 07-20-2005 23:19

In a bridge, the number of RT shots is probably extemely high compared to a pipe weld. On large diameter, heavy wall pipe an access port is used to place the source in the center of the pipe. All the film packs are wrapped around the OD and only one exposure is required. So I can see where RT is a bit more expensive for bridges than manual UT. The high cost for UT in lieu of RT on pipe and vessel welds is the imposition of equipment to record the data as a permanent record. This requires UT equipment with position encoders and data aquisition. The UT used on bridges is probably manual scanning with a paper report form. That doesn't mean it is less reliable than automated scanning, just that you don't have a permanent record of the scan that some pencil pusher can review later. My whole point was that RT film is not used because it produces a permanent record, it is needed as part of the examination process. The permanent record is a secondary benefit. I believe that manual UT is an appropriate alternative for RT and that if someone wants to review the examination results or the adequacy of the inspector's procedure/examination technique, then a hold point should be established to witness the UT. Otherwise, the written report, inspector's certification record and cal sheet should be sufficient as a permanent record. Isn't that how PT and MT results are reviewed?

By g32141

Date 07-19-2005 20:18

Most of the major oil companies are using AUT to inspect their pipeline welds. It is much faster than radiography. You can inspect well over 150 welds in a 12 hour shift if there are no equipment problems. A weld can be inspected from start to finish in about 3 minutes and there is a permanent record of the joint. Another major advantage of AUT over RT is that you can get the exact depth of a defect and cut down on rerepairs. This is important because some procedures only let you repair the weld once and if the defect is not removed the weld has to be cut out.
UT is excellent for sidewall fusion defects that RT has a tough time picking up and RT is excellent for defects that UT has a tough time picking up, like porosity. The problem that I have encountered is that welders and their foreman think of UT as Voodoo when in fact these techniques and system have been thouroughly tested ,macros done of the welds and found to be very accurate. They are so accurate in fact that the engineers are able to modify the acceptance criteria for their pipeline joints to suit their purpose.

If you radiograph a weld and then scan it with AUT you will most likely get different results unless the weld is completely spotless and perfect.

By TTONKA

Date 09-01-2005 20:50

In my experience as a Level II UT Inspector - everyone loves you when the welds pass. You save the company time and money compared to RT. But the first time you reject a weld be prepared to hear "He doesn't know what he is doing". Ultrasonic Testing is not an exact science and there are a lot of geometrical problems that can throw off a UT Inspector, but an experienced inspector can make the right call 9 times out of 10.

By AussieNDT Date 09-02-2005 04:36

From my observations radiography is not an exact science.
With radiography it is all too easy to miss significant planar defects
like cracks, lack of side wall fusion etc.
The benefit of ultrasonic is that a good technician can concentrate on an area of concern while he is actually testing. This does not happen with radiography.
Kevin