Another thing to add to that thought. There is a reason API 620 appendix U, ASME code case 2235, and others now allow levels of "planar" defects.
For instance, RT criteria per Section VIII div 1 UW51 is 0 planar defects. (cracks, lack of fusion). Whereas UT allows a specific area of planars.
RT will not see cracks and lack of fusion as efficiently as UT will. This is the primary reason for the differences in acceptance criteria.
On the other hand, if voluminous defects such as porosity and slag are found, Standard UT will be diffused by these types of indications. This is where
RT once surpassed UT. However; with the advent and use of phased array and other more advanced techniques, the gap for detection of this type
of indication has been closed. Speaking of boiler tubes, and other small diameter tubes, UT was once unable to perform this inspection adequately,
this to has been handled by advanced techniques.
All in all, the clock is ticking on the usefulness of RT as UT gains more and more acceptance in the industry, which is in no small part supported by
recordable graphics displays in 3 dimensional format. Some of the die hard RT types are still hanging on to it, but at the end of the day, the risk
of RT are beginning to be outweighed by the benifits of UT. RT's coffin is in the making, after all, why go through the headache of licenses, regulatory
matters, and health risk when a viable alternative exist that presents none of those concerns?
I will leave it with a quote from an ASME code interpretation that speaks directly to the shifting mindsets currently taking hold in the industry:
Interpretation: VIII-1-04-95
Subject: Section VIII, Division 1 (2001 Edition, 2003 Addenda); UW-11(a) and Code Case 2235-6
Date Issued: May 31, 2006
File: BC04-1455
Question (1): Is it the intent of Code Case 2235-6 that when portions of the vessel meet the requirements
of UW-11(a) for full radiography and portions meet the requirements of Code Case 2235-6 for using ultrasonic
examination in lieu of radiography, the vessel nameplate be stamped with "RT-1"?
Reply (1): Yes, provided the extent of examination, joint efficiencies, and the Code Case are noted on the
Manufacturer's Data Report and the nameplate is marked under the Code Symbol stamp by applying "UT."
Question (2): May a vessel nameplate be stamped "RT-2" per the rules of UG-116 of Section VIII,
Division 1 when a complete vessel satisfies the requirements of UW-11(a)(5) and when the spot radiography
requirements of UW-11(a)(5)(b) have been applied, but when ultrasonic examination in accordance with the
provisions of Code Case 2235-6 has been used in lieu of radiography?
Reply (2): Yes, provided the extent of examination, joint efficiencies, and the Code Case are noted on the
Manufacturer's Data Report and the nameplate is marked under the Code Symbol stamp by applying "UT."
Regards,
Gerald
Gerald,
I too have followed the industry trends as UT has become more "accepted" as a test method by various Code bodies, DOT and customer specifications etc. The code case you mentioned as well as UT being used on things like cross country pipelines (which were always considered RT territory) are good examples. I'm sure there are many other industries where this is taking place too.
Sadly, even though ASME, API etc., are allowing provisions for using UT, the final okay still requires AI, engineer, or customer approval. In my neck of the woods RT is very popular but the quality of RT technicians is in a downward spiral causing a confidence issue that is bleeding over into other NDT methods. 50% of my clients use out sourced RT contractors on a regular basis, some have 250K to 500K annual RT budgets and there is not one that is totally satisified with the service they are receiving. Granted, there are some issues with availability of crews in general, but until some of the issues with incorrect techniques, mis-intrepetation, missed defects etc. is corrected in a trusted method like RT, I'm not sure how soon UT will be able to replace it.
~thirdeye~
The sooner the better in my opinion. I've a lot more faith in UT than RT.
Me too.
I used to be a radiographer and I am happy that I was provided with the opportunity to switch to become an AUT hand.
I have been on jobs where RT comes in behind us after we call cracks. I have seen the film that was shot and talked to the radiographers and there was nothing on the film for them to see but clean weld. They even cut the welds out and macroed them to be sure. The one radiographer said to me I can't even begin to imagine how many cracked welds I have buried under my belt.
There is a market for boiler tubes and I am sure that someone is working on a solution. I can imagine that once they get it right just about every weld will be a reject.
The computerized UT has permanent records as well which was a major factor in not using UT. They don't deteriorate like x-ray film and you can put thousands upon thousands of welds on an external hard drive. You'd need a box truck for that much x-ray film.
The downside is the prep time as far as cal blocks being made, the surface needs to be prepped more etc. RT can just show up and slap a film on a weld and blast it no matter how dirty it is or if the coating isn't cut back and with different wall thicknesses. We need a little more time. If everything is ready I can scan a couple of welds and either clear them or reject them faster than I could go into the darkroom and load a single film.
I don't miss the days of monitoring barriers in a paper mill when I watched a guy with a cart full of scaffolding actually grab our sign, read it and then ram his cart through it breaking it. Or having to talk to the state NRC people because my helper told someone that crossed our barrier that his teeth or hair might begin to fall out any second.
I doubt that RT will completely die out. There will always be people who need to see inside of something without breaking it open. But as far as cross country pipelines consider it extinct.
I'm contemplating allowing phased-array UT in place of RT on a D1.5 job. Any advice for how to set up criteria, etc.? I don't want to just use an ASME code; the idea is to reject the same flaws that would have been rejected with a combination of RT and conventional UT under D1.5.
I do have a contact at Olympus. Does anyone have someone I might contact at ASME to find out how they managed to get comfortable with going the no-RT route?
Hg
I believe if you call the new york office of ASME and get in contact with Wayne Hembree, he could probably steer you in the right direction.
The biggest problem that we see here in NY is the shortage of qualified UT techs. I would love to see UT replace RT but there are some situations where RT is the viable alternative even with all of its drawbacks. Part of the problem with UT, is employer based certification programs. Testing isnt standardized from employer to employer, which is the reason that here in NY, you have to pass our test before you do UT on our bridges. We see guys come in to take our test that dont have a clue what they are doing.
We have to have outside certs be it ASNT, CGSB or PCN since we work all over the world. Only in the states are they allowed to work under company or union cert. Hopefully that will change.
We were shut down in Brazil because they didn't think that the ASNT and PCN certs meet the requirements of some ISO regultation. It was finally resolved and we were covered.
Do you need to take a NY DOT test if you have an outside cert? I used to do a lot of bridge work RT and UT.
I'm not impressed those of PCN origin. I've had two of them tell me at different times when looking at the RF waveform that it's a "TOFD" signal, and both wanted to argue that TOFD "was the first time it was ever used". They never heard of a delta test, nor many other things I'd expect of someone with a central cert. All in all, they were a bit to much on the arrogant side for the amount of ignorance displayed.
As for changing, it's in progress. It's called ISO standardization. People are kicking and screaming, but it's coming, just will take a while.
Well I have no idea what the delta test is. I didn't invent the thing. I do know what an RF signal is because I used it to check babbit bearings. That's how the TOFD signal is diplayed in the A scan.
The nuke guys use it alot with hand units. I won't even get involved in a pissing match with them. Hands down they are way better hand scanners.
I'm a pipeliner. I like this type of job.
At the same time I worked with a few that went back to working that way instead of pipelining. It suited them better.
I have seen and heard of plenty of people who are arrogant. It can and will get you run off. But at the same time you need a thicker skin than most.
We require that anyone performing UT on New York State Bridges must pass our test. Its a three part test, same as most places with a general, specific with questions coming from the New York State Steel Construction Manual and then the practical. The practical is tough, you MUST understand where your sound is in order to be able to pass. New York City does not require the cert and they have paid the price in the past.
Dave
When do you put on this this test? Can I show up and take it for free since it is a DOT test? I'd like to take it.
The test is given anytime, and yes its free. You would need to call Bob Cosgrove to schedule a test. His number is 518-485-7253.
The system would have to be set up according to that code.
If you're going to scan D1.5 you'll need to conform to that as a minimum if it is allowed. You can add to it but not take away. Not sure how it would work but in pipeline they actually use job material to make calibration blocks according to the code.
AWSs uses IIW blocks. The wedges I am using are actually wider than the IIW block where you check for distance and sensitivity.
It can and will work out faster safer but there is a lot of leg work. At the present time we are not allowed to scan transitions but they can be done. You'd need a special cal block for that.
Check these guys out.
www.utscan.com
talking about x-ray test I don't know if this is BS or what so I just soon ask. I have never done a x-ray weld test yet but was told that if your root is maybe not 100% on a pipe that if you run stringer passes that the stringer passes could hide any defects you may have in your root and maybe will not show up on X-ray this is tig welding a pipe from root to fill and cap. or is it just harder to pick up on and the person reading the x-ray just may not see it as easy. I was always taught stringers were stronger then one big weave and this person also said he thought a bend test was harder to pass then an x-ray.
Can anyone shed a little light on this subject??
Thanks
Chris
chris2698,
To some degree, an as-welded surface can "mask" the image in a radiograph since the image of the cap is directly in line with the image of the root. For example, adding higher stringers to the cap directly over an area where you suspected something like a concave root or internal undercut may hide that condition to some degree as the additional weld metal would balance out the density (darkness of the film) in that area. Concave areas show up darker than the surrounding weld, higher or additional stringers on the cap, if placed correctly, would provide additional weld metal in that area, which in turn would change the image on film. Trying to hide something like incomplete penetration is almost impossible.
Most codes have provisions for grinding the surface of the weld if there is concern that something will mask the radiographic image. In the old days, the caps I hated were the 1" wide, figure 8 pattern weaved ones which had several densities on the films. My favorite ones would have to be a rolled-out one pass cap with 7018.
You will hear many theories on destructive (bend tests) verses nondestructive weld tests (like an x-ray test). One thing to consider right off the bat is the number and size of the bend coupons verses the length of weld that is radiographed.
~thirdeye~
thirdeye and Richard Cook thanks I have always kinda wonderd about the stringer passes. I haven't had to take a x-ray weld and I'm not saying I want to learn a method of how to beat the system but was currious about it, someday I may have to take a x-ray test
Well those days are over. You can't hide that stuff from AUT. I even told the welders that. I told the forman not to change guys out because they went for almost a month witout e wedling defect. They went to .618" pipe and they had one guy that really screwed the entire crew's repair rate in 2 days. The foreman asked me if it was the welder.
I don't know. It's either the welder or the the grinder. I can't know. I mention things like if he he put a new grinder on that side of the pipe. The foreman knows what he did and he isn't complaining. He knows who he has where.
I doubt it was a welder problem since he was on the crew that went a month without repairs. I bet it lies with the grinder.
Be careful, I hope you are as good as you are representing yourself. I've run across many individuals that were for all intent and purposes, "monkeys" at the controls. It sounds like you might be otherwise.
There are four sets of variables in most process'
1) Material or object under exam
2) Technique
3) Equipment
4) operator
In each of these are conditions and circumstances that would affect the required outcome. Remember the new equipment these day's are computor based, so "garbage in garbage out". Now don't miss understand me I believe in this new equipment and it is great. But don't think for one minute that any of it is fool proof. This equipment has it's application but not in all areas and what the future brings is yet to be seen.
This new equipment does eliminate some variables, which is great, but not all.
That brings me back to the importance of assuring highly qualified operators/technicians. And again if the individual that is buying the services is not familiar with the process, can be "impressed with your intelegence" or they can be baffled with "bull crap".
good luck
I would have to echo the be careful statement here. I've seen it done. AUT is performed on tank welds, piping welds, and many other forms.
AUT utilizings many different modes of transfer as well. I do consider it a very good method when properly deployed with proper training and simulation mockups, however; not everyone does this.
There are ways to screw with the AUT operator, and if that operator doesn't have a very good understanding of the waveforms employed, he or she will never know they have been had. This is why I find disturbing the lack of that understanding among some of the european counter parts who have their "AUT" certs, and a large part the same for the U.S. ones. They also need a better than average understanding of welding methods and basic metallurgy. All of which apply to manual types as well. This gets into two different classifications:
Operator: This type simply runs the machine. Their training doesn't explain why the UT waveforms are doing what they are doing, but rather, goes on the assumption that the operator doesn't need to know. There are a lot of these types out there in AUT. They know from training and their operations manual to set the blocks up in a certain way, to set the tracks just so, watch for lift off, and all things related. However; put a manual scope in their hands to proof up what they find, and they are lost. Further; if that machine does something not covered in the manual, they are lost. If they get a phase reversal from haz crack just outside their gate, They wouldn't know what it was and would let it go. (I've seen that very thing happen). Just to list a few.
Technician: Has a good understanding of echodynamics, can pick up old analog scopes, or new digitals, and cal up and use equally. The can also pick up on those phase reversals without refering to the op manual, and in general, uses the machine as a tool for fact gathering, rather than as a crutch.
My comments earlier about two operators are classic examples of that. They did not understand how those grey and black lines came to be and what the machine was doing to create them. To them; the RF screen was a TOFD screen. They were never trained to read the echodynamics of that RF display. The only thing they knew to do was match an expected response from the TOFD scan window to the RF display for conformation and if it didn't match up, they would ignore it as irrelevant. In short, they don't even watch the scan as it's taking place, but rather, depend on the machine to do it for them. That last part is the biggest problem with it. A monkey can be trained to push the right buttons for an expected response as witnessed by the chimps NASA put into space, but a true technician will be able to read it no matter how much the machine lies to them and can react appropriately when the machine meets up with something outside of normal operating parameters as exemplified by the apollo 13 mission. (especially applicable to those set ups trying to utilize secondary creep)
Having said all that; I am a strong believer in UT of all forms, but there are still many wanna be's out there for my comfort. Those wanna be's give us all a bad name.
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