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The pole spacing for the yoke lift test listed in D1.5 2010, in this case DC 4-6", is this inclusive to the minimum and maximum pole spacing for the actual test? It was my understanding that the lift test qualified the equipment being used and the Pie Gauge qualified the pole distance sensitivity of the induced flux field?
The Pie field indicator should be used to verify field direction. Here is an excerpt from ASTM E709 that clarifies why the Pie field indicator is not used to verify sensitivity:
“Pie” Field Indicator—The magnetic field indicator
shown in Fig. 14 relies on the slots between the pie shaped
segments to show the presence and the approximate direction
of the external magnetic field. Because “pie” field indicators
are constructed of highly permeable material with 100 %
through wall flaws, indications do not mean that suitable field
strength is present for the location of relevant indications in the
part under examination.
Ramon
Thanks Ramon
I can see that part of the problem I have is that I have an out dated version of ASTM E709. This version is in total contradiction with the statement you presented. Injected after the first sentence states "A suitable field strength is indicated when a clearly defined line of magnetic particles forms across the copper face of the indicator (the slots are against the piece) when the magnetic particles are applied simultaneously with the magnetizing force. Failure to obtain an indication can result from: (1) insufficient magnetic field or (2) the magnetic properties of the material being examined, or both."
The material is nothing special just A36.
Mark
Mark,
It is always helpful to have the latest and greatest standard. Just from my observations it seems that newer versions aren't issued unless there are content changes. I've included a couple of more items from E709-08 that touch on the subject of Process Controls below, however the most recent version is 2014 so there have been additional updates.
Excerpt from E709 regarding the yoke lifting force check:
20.3.7 Electromagnetic Yoke Lifting Force Check—The
magnetizing force of a yoke (or a permanent magnet) should be
checked by determining its lifting power on a steel plate. See
Table 3. The lifting force relates to the electromagnetic strength
of the yoke.
As far as checking for adequate field strength ASTM E709 Table 2 also recommends a daily system performance check using a test piece or ring specimen, a sample of a Magnetic Particle Performance Verification Plate can be found in Figure 13.
Excerpts from E709 describing system performance checks that are relevant to yoke and prods:
20.8.1 Production Verification Parts with
Discontinuities—A practical way to evaluate the performance
and sensitivity of the dry or wet magnetic particles or overall
system performance, or both, is to use representative verification
parts with known discontinuities of the type and severity
normally encountered during actual production examination.
However, the usefulness of such parts is limited because the
orientation and magnitude of the discontinuities cannot be
controlled. The use of flawed parts with gross discontinuities is not recommended. (Warning—If such parts are used, they
must be thoroughly demagnetized and cleaned after each use.)
20.8.2 Fabricated Test Parts with Discontinuities—Often,
production verification parts with known discontinuities of the
type and severity needed for evaluation are not available. As an
alternative, fabricated verification specimens with discontinuities
of varying degree and severity can be used to provide an
indication of the effectiveness of the dry or wet magnetic
particle examination process. If such parts are used, they
should be thoroughly demagnetized and cleaned after each use.
20.8.3 Test Plate—A magnetic particle system performance
verification plate, such as shown in Fig. 13 is useful for
checking the overall performance of wet or dry techniques
using prods and yokes. Recommended minimum dimensions
are ten inches per side and nominal thickness of one inch.
Discontinuities can be formed by controlled heating/cooling,
EDM notches, artificial discontinuities in accordance with
14.2.2 or other means. (Warning—Notches should be filled
flush to the surface with a nonconducting material, such as
epoxy, to prevent the mechanical holding of the indicating
medium.)
Ramon
Thank you Ramon
Here is my problem. These are not production parts but welds. The code is Bridge code AWS D1.5. The question and what I am being tasked with is the requirement for pole spacing on any given size weld length. What is allowed. Do to the restrictions of both ASTM E709 AND AWS D1.5 I cannot demonstrate that I can generate the required field strength to be in compliance with the code unless I use 4-6" based on the lift force test. The inspector (3rd party) is requiring me to do so. Technicians are not required to carry 50Lb NIST traceable plates. The yoke has met that requirement but my question is still has ASTM E709 and AWS D1.5 somehow established that this pole spacing is the only acceptable spacing based on the lift force test? Here is an example, what if I can use the same equipment to pull a 50lb plate @ 8 and 10" spacing? I did that with this yoke just out of curiosity.
Still the question I have is what the requirement of the D1.5 code.
Mark
to add to what AL has already stated about the lift test:
ASTM E709 20.3.7 and Table 3 gives the lifting forces required for Current Type and Yoke Leg Spacings
ASTM E1444 7.3.4 Dead Weight Check - Yoke and Table 1 for Required Verification Intervals
The lift test is used to verify the yoke is working properly by producing the required field strength to lift the required weight.
The pie gage with produce indications even when the legs of the yoke are held in the air and the pie gage placed between them. It has nothing to do with the strength of the field induced in the material. The pie gage will produce indications even when placing the legs of the yoke against a piece of aluminum.
Best regards - Al
The Pie gage is for verifying magnetic field "directions" rather than strength. See ASTM E1444 6.2.5 and Figure 1
Thank's for all your comments.
Sensitivity was a poor choice of words on my part. The Pie gauge does only verify the field direction. Getting back to the requirements of the lift test. Which in this case is a 6 month verification pulling a 50lb plate in DC @ 4" and 6" spacing. My question now, are both ASTM E709 and AWS D1.5 stating that unless I use that particular range in that type of current I cannot generate enough field strength to locate a relevant indication?
I better review the test requirements, I thought it was 40 pounds for a DC yoke.
Al
Al, it changed to 50# for DC 4"-6" spread a while back.....I think it used to read 40# at a 2"-4" spread.(if memory serves me right)
See, one can learn something new every day.
Al
2-4" is the AC requirement.
548272, yeah the A/C requirement has always been 10# at 2-4", it was the DC that changed a while back.
For those who may not know, a 1/4" thick plate 12" x 12" is right at 10#, if you need an inexpensive lift plate to verify the A/C side of your yoke. All you need to do is verify it on a calibrated scale that is traceable back to a NIST standard and you are all set.
I know I am the real newbie here when it comes to MT procedures, BUT, just because the 'calibration' of the yoke is at that spread does not mean that all testing of components has to be done at that spread??!! Or did I totally miss something in my classes thus far?
Otherwise, why do they bother to make the legs adjustable?
Anyway, that appears to me to be the question here in that the TPI is requiring leg spread to be the same for testing as it was for calibration of field strength.
He Is In Control, Have a Great Day, Brent
I believe the lift test for AC is #10lbs. at equal leg space.
Brent
Just to share...here in Smokey, there was a discussion on whether correct yoke leg distance was applied during the test and the technician normal answer was "you can verify the yoke markings on the tested surface". This become an instant hit that once you saw the yoke markings on the surface it means MT had been performed.
One day I've encountered a technician doing MT on inside the tank, he did not know that I'm observing his testing. He was spraying the black ink and pretending using the yoke on the surface while the yoke electric plug was inside his coverall pocket. When I asked him on why his yoke was not electrically connected. He put on a brave face and quickly walk away. He immediately disappeared and when he came back to work the next day, he claimed that he was using a permanent magnet at the time of testing
.
Hello Joey,
On that note, I know Magna Flux as a battery unit (DC) that is small and light weight and sometimes can be hard to notice depending upon how the battery is being transported and how the technician is dressed. A sweet little unit but limited as it is only DC and rather pricey compared to my AC unit from Parker.
My main interest was in the contention that one must use the legs of the yoke at the exact same dimensional spread that the verification of magnetic field strength is done to. I don't remember that from my recent studies but have not had time to research and confirm either yea or nay.
My second interest was in actually getting an answer to the OP's actual question. I don't thing anyone has yet to really get down and dirty and 'YES' or 'NO' to the question of 'is this the way it must be done'. That is: must the legs be at the same spacing for both calibrated verification and for field testing? And this brings me to a follow up question: Must the flat of the feet make total firm, flat, contact with the test piece or can they make a more limited contact to establish the magnetic field? Again, this would fall into the same question because if they are not flat, the field won't be as strong and may not pick up the 10 or 50 lb verification block. But just because the magnet is able to pick up the block verifying the ability of the magnet is it required to establish the full strength field while testing under every conceivable field condition?
Now, Al would seem to be saying 'NO' in his response. And I understand how, not only in NDT equipment verification but many things, calibration, verification, certification are all totally different from actual working conditions. But let's answer the OP's question with a direct yes or no, IF POSSIBLE. I also know that Job Specs, Contract Documents, and a wide variety of codes that one can be working to changes things on us from time to time. But this seems like it should have a simple one word answer to me.
Thank you for your story though Joey. One of those inspections 'oopps' that we don't really like to admit happen but inspectors are no more or less human than the welders who try to hide things and cut corners or the contractors who try to buffalo their way around code requirements with 'I never had to do that before' when you just told them the same thing on a different job 2 months ago.
He Is In Control, Have a Great Day, Brent
Brent, I don't think it is a normal practice to perform the NDT without the establised procedures. So by right the OP's question can (should) be found on the MT procedure.
There should have an agreement between the customer and NDT contractor on proposed MT procedure. Some company will require the NDT contractor to do the mock up test to see if their proposed procedures will produce acceptable results.
Absolutely true. Just as for the welding contractor who must submit the WPS's prior to work beginning. CWI's are to have a model program for much of the inspections work and submit it and get it approved (many should take note of that comment because I know you don't have one. It is from IBC chapter 17 as well as some great items of interest in AISC SDM Q5 I believe.). And, NDT people are also to have their program set up with procedures that encompass their work by their Level III who is either an employee of their company or on retainer as a permanent consultant for them.
These programs are where a lot of the things come from that I harp about that cause confusion because the person implementing them doesn't realize they aren't code and don't apply to every situation. They are methods of my companies procedure and how I make sure I accomplish my job but none of the codes told me to do it that way. But if my program says I am going to do it, I have to do it. Same with AISC and other outfits that audit preapproved fabrication shops. What you often get caught on is something in your QC manual that didn't have to be there and is a real pain but when the manual was written someone thought it sounded good and would impress customers. Now you have to do it and prove how it is being done.
These items, Contract documents, and codes all work together and yet each serves it's own purpose.
But at the same time, there is nothing in any code that requires the NDT tech to set the spacing at a particular spacing to accomplish MT on a project. There is no way, a majority of the time, that a TPI should be telling the tech that the job must be accomplished at that leg spacing based upon the codes specification of a calibration/verification technique. He has stepped over his lines of authority- UNLESS, it is definitely in someone's QC manual with their Level III's established operating procedures.
And, to be fair, we don't have, once again, ALL the information. Only a limited view from the OP's perspective.
He Is In Control, Have a Great Day, Brent
The lift test simply verifies the yoke in proper working condition.
It is no different than checking the intensity of a black light at 15 inches.
Both tests, the black light and the yoke, simply verifies the machine meets some minimum requirement. The chances are the light will not be held exactly 15 inches away from the test surface and the yoke will not be used with the legs adjusted to 4 inches apart.
Al
Al,
To make sure I kept my yoke leg spacing correct, I painted two circles on my lift plate to place the yoke legs in to make sure I had the correct spacing while verifying the yoke.
Thanks Everyone
I appreciate all the comments posted. While I check into this further I guess the only answer is to simply give the man what he wants and move on.
Mark
If you read E 709 it says that the system performance check be performed once a day. The standard has multiple options to perform that check:
Use of the "magnetic particle performance variation plate", shown in figure 13 in E709-11, which the standard specifically says is useful for checking the performance of wet and dry techniques using yokes and prods. You can buy one here.
http://www.phtool.com/store2/proddetail.asp?prod=E709%2EMP%2ECS%2ESD25968Use of "production verification parts with discontinuities" however they caution you against using parts with gross discontinuities.
Use of "fabricated test parts with discontinuities"
This is how you verify your technique, e.g. leg spacing, and the ability to detect critical discontinuities although it seems that for field inspection of welds that this portion of the standard is conveniently ignored by most.
Ramon
Interesting? Why would you say ignored by most? I have down loaded the latest version of ASTM E709-14 but have not looked it over. I do think that system performance check is not applicable here. At least not with this situation. Checking on it though, I might be wrong.
I think it applies if you strictly adhere to the standard. That's what the code references right? The reason I say that it is ignored by most is because I have only seen one company use the plate to check system performance. But you can't deny that it doesn't require it in the standard.
Ramon
Ramon,
I'm going to play devil's advocate: I didn't see it so it didn't happen!!
I don't think that is a standard I would like to hang my hat on.
He Is In Control, Have a Great Day, Brent
Just a cautionary note. When using a yoke and a long string of extension cords, there can be a considerable voltage drop. The voltage drop can reduce the current supplied to the yoke. Insufficient voltage and current will reduce the lifting capacity of the yoke and it will reduce the intensity of the magnetic flux. A lift test "on-site" can be performed to verify the "system" is performing up to specification.
As for the articulated legs; the legs should be adjusted to maximize the contact surface between the ends of the legs and the surface to be tested. It is one of those things I check for when witnessing someone performing a MT using a yoke.
Best regards - Al
Al
I agree that there can be a line loss due to the length of the power cord. Sometimes that is unavoidable particularly when working out of certain model man lifts on a field site. In this case I do not think that was an issue. The work was done at the fabricators facility and the cord length was no longer than 25'.
The TPI had no issue on how the technician conducted the test or that anything other than 4-6" of pole spacing was being used at any time, these are relatively small welded components. Or that the technician was not following their companies MT procedure. How this all started was that on the initial field report submitted the technician listed a general pole spacing of 3-8" as stipulated in their procedure. The TPI did not accept this general over all range and stated that the technicians procedure was not in compliance with the D1.5 code. The report was revised to list the actual spacing used for each piece under test. The TPI was satisfied with that.
I am going to read through both ASTM E709 and E1444 over the weekend. I now have many more questions as to how a field technician can verify this without carrying a variety of test plates and test standards?
Thanks
Mark
Just as a follow up for those interested.
I reviewed AWS D1.5 2010, ASTM E1444/E1444M-12 and ASTM E709-14. My conclusion is that the TPI is correct in that the pole spacing specified in the code book pertaining to the lift force test is proportional to detecting relevant indications. The Pie Gauge has no practical use, at least in this application, and is to be used only for demonstration purposes.
Since the bridge code book only references one type of verification test, the lift force test, using any type of test plate with known defects, shims or QQI's etc... wouldn't be acceptable unless agreed upon. In my particular situation this would be impossible and there is no way to fabricate a suitable test standard with every defect in every conceivable geometric direction.
One question that I still have is that in AWS D1.5 2010 section 6.7.6.2 states " The yoke method shall be in conformance with ASTM E709, and the standard of acceptance shall be in conformance with 6.26."? ASTM E709-14 is the "Standard Guide for Magnetic Particle Testing". There is no reference to ASTM E1444/E1444M-12 which is the "Standard Practice for Magnetic Particle Testing". This publication also states in section 1.1 "This practice establishes the minimum requirements for magnetic particle testing used for the detection of surface or slightly subsurface discontinuities in ferromagnetic material. Guide E709 can be used in conjunction with this practice as a tutorial."?
Where it comes to the lift force check in both AWS D1.5 and ASTM E709, which are identical, the ranges are AC 2-4" @ 10lb, DC 2-4" @ 30lb, DC 4-6" @ 50lb. In ASTM E1444 section 7.4.4 "Dead Weight Check" the ranges are AC 2-6" @ 10lb, DC 2-4" @ 30lb, DC 4-6" @ 50lb.
My question now is why is the code book referencing a "Standard Guide" which is considered a "tutorial" by the "Standard Practice".? Also, if the lift force and dead weight checks establish a criteria with regards for flux density in order to reveal a relevant indication then why are they different in the AC range?
Mark
That would be best answered by the D1 committee.
You will have to submit a technical inquiry to the committee and inhale a long slow breath of fresh air because it will be a long while before you will receive a response. Just don't make the mistake of holding your breath waiting for their response. You WILL die!
I waited 5-years for my most recent response and it was another year before it was published in Inspection Trends and the Welding Journal (I think I saw it in the WJ). I believe I have four inquiries still pending. Maybe they will be addressed by the up coming edition of D1.1.
I understand why it can take such a long time for the committees to issue a response. The implications of a response can have far reaching consequences. I expect the most recent response will result in a change in the 2015 edition of D1.1 and possibly the next edition of D1.5. The bottom line is that they have to give careful consideration before rendering a decision. It is worth the wait.
Until a decision is rendered by the committee, the Engineer is the individual that has the authority to provide a resolution to such questions on a job by job basis.
Best regards - Al
Al
Thank's for the info. I think I'll send an inquiry to the ASNT committee also.
Mark
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