I am looking at the API QUTE procedure API UT 2. On page 6, it says for the 1/2 V-path, use the 70 degree transducer and for the full V-path, it lists both 60 and 45 degree transdcuer.
Questions: Does this mean to use all 3 (70, 60 and 45) when scanning a weld or is only 2 required (70 and either the 60 or 45)? And if you are to use either the 60 or 45, by what criteria do you decide which one to use?
- The 1/2V 70 is good for root conditions i.e. cracks, IP and is less subject to be fooled by root condition as it skims over the root concavities better than the 45. The 45 would be good but dure to weld crowns it often doesn't reach the root until 3/2 V.
- The 60 is best for LOFs, as it is near nornal to the +/- 30 degree weld prep.
- The 45, at full V, is a solid performer for OD cracks at the toe.
Further, plotting of reflector location is a very good practice.
1st my apologies to David as my message is off-topic in that I have no idea about API QUTE requirements - but I have made a mental note to check it out at some future point.
2nd to Emil,
Truth is Emil, its been some time since I tested welds by manual ultrasonics, but I have to query your statement that a 70 degreee angle is best for root examination. The practicality, apart from thin-wall welds (<12mm wt say), will be that the beam spread at the sound path distance required for root assessment will make the task difficult.
My method has always been to use the shortest beampath possible to assess the root in order to minimise beam spread. (I would use 24mm or 1 inch probes if available and suitable). So generally for welds 15 - 25 or 30 mm use a 60 degree and 25 or 30 mm and greater a 45 degree for root assessment. Cap width is a deciding factor. As for probe utilisation I would use all effective probes up to maximum of 1 1/2 skips. If it requires greater than that stand-off distance in order to interrogate weld metal or fusion face then I would not bother using it, e.g. 45 degree on 10mm wall thickness.
Conversely I use a 70 degree even on thicker material for under-cap defects, or on thin to medium thickness welds as a general non-parallel "sweep" scan to detect any pattern changes. I hope I havent been doing it all wrong in the past!
I also don't know the API QUTE procedure David but maybe the following comments will be useful to you.
Most regularly utilised norms explain in one way or the other - sometimes vaguely - which angles to use with with which thickness ranges or they specify as in EN 1714 how many angles to use with a certain thickness range and a particular examination class. It should not be left up to the level 2 technician to have to "choose" which angles or frequencies he or she should use. This information should be included in a procedure specifically written for the object being examined or, at the very least, a general procedure from the ndt company detailing exactly which probes to use. This applies not only to probe choice but also to examination class (which examination class to use when not specified by the client).
Working, in the field, directly from a norm is asking for trouble and every inspection company should have work or company specific procedures available for their techs.
From a practical standpoint, Nigel is quite right, the choice of probe angle (and frequency) depends on wall thickness and/or type of weld preparation. Try looking at a tig welded root in a weld 40mm thick with a 70 degree 4MHz probe. You won't find much. All probes have their plusses and their minusses, we shouldn't generalise too much.
Thanks for the reference to API UT 2 which I have read now and I like it! Simple, direct, clear (sorry!), reasonable, not prescriptive by any means.
Section 8.3. technique application seems to partly answer your questions. 8.3.2. clearly allows use of BOTH 45 and 60 if the configuration calls for that. Emil clearly shows at
times its best to use them both = and naturally always then 70 at half-skip maximum, but preferably (for me) if feasible a 60 or 45 for critical root scan. My advise to you is if you are uncertain which probe to use (60 or 45) then use them both - it should result in a more thorough, though slightly slower, inspection.
Hmm, i like it so much I think I'll adopt it as my general UT procedure when I start my own company - hahahaha!!!
I agree with your comments about the 70S, subject to the following -
- API legend has it the the 70 sees everything of importance BUT it doesn't "plot" well, so to ignore the 70 is to ignore an easy detection assessment. To rely on it solely leads to miss-characterization based on location.
- I personally am a fan of the snub-nose 53-55 degree shear wave, as it is in the regime that is crack-sensitive (unlike 60) and gets better root access. Some companies frown on belt-sander modification to equipment and the archaic 45-60-70 fans limit doing the right thing.
Given the only 45, 60 and 70 choices I'll stick to my earlier post as the stock 45S typically won't get 1/2 V root access on thinner stuff and I am not a 60 degree fan for cracking.
Fascinating modification Emil - the "snub-nose 53/55", you sound like a sniper modifying his weapon to draw a truer bead on his target! And I must confess to being, until now unwittingly, an "archaic 45-60-70 fan" for manual UT! I take consolation in being a bolshevik on that score though!
I can appreciate that a more than 30% gain in SOD from weld CL coupled with a "snub-nose" (love it!) will significantly increase root access in manually welded materials below 30mm w.t. whilst maintaining a reasonable beam spread.
Mind you talk of applying a belt-sander to probes does make me (and I suspect many others) wince - what method do you use precisely?
It depends on which manufacturers probes you use, Krautkrämer WB and MWB probes have re-shoeable soles which means with a little creativity, you can produce vitually whatever angle you prefer from the standard probe by machining the sole to the required angle (don't forget snells law) and at the end of the job you just re-shoe the probe with perspex.
Perspex soles can be bought commercially - very expensive. You can also buy a small sheet of perspex from a diy shop very cheaply and cut it to size. If you do this you can buy thicker perspex than the standard which has the extra advantage of bringing the index point forward as well as a longer life.
Back in the day (seems like I say that a lot) we had a significant problem in ½ inch (T) single vee piping butt welds and a real concern for ID connected, root adjacent IGSC cracks. Unfortunately the nominal 45S commercial probes fell just shy of sweeping the root at the ½ V path. If we could just find ¼ inch more!
We were aware of the preferred use of shears between ~35 57 degrees as per Krautkramer and more recently Andrew Cunningham (in this forum). We were also aware that some probes, i.e. early MSW-QCs, were a tad longer in the front than necessary. Working with flat files, belts sanders and, IIW and notched pipe calibration blocks we tweaked an additional ~ .3 inches of coverage and covered the root at the ½ vee. We stopped customization at ~55 degrees and stopped snubbing/chamfering when the standing wave, back at the insertion signal, began to interfere.
Also worthy of note - the 60 degree strains (per Krautkramer and Cunningham and observation) to see the ID corner trap and this was used as an evaluation input a perceived or potential 60 degree corner trap equaling or exceeding the response a 55 degrees might NOT be a crack (normalized to SDH sensitivity). Similarly, if an indication looked to be a crack, the 60 should not see it very well. THIS NOT A RULE, JUST ONE OF MANY INPUTS CONSIDERED IN THE EVALUATION PROCESS.
Please forgive me for the thread hi-jack, though I think you will have picked up more from these guys than you could have imagined! My advice however is dont tamper with your probes when doing the API exam - conform to the norm, use all 3 probes if the material thickness warrants the 45 degree as well as the 60 and 70 and do your tinkering away from prying eyes when you have passed the exam - if you are going to sit it.