Would you reject of accept?

Date 10-25-2008 19:58

Im not familiar with ut, but call it as the code reads no more no less, note what you see and if something happens later you will be covered. I dont hate anything more then going and doing a job and calling to 1104 only to have good welds called bad to just because somebody else who looks at your film and thinks that 1/4'' of slag will be the end of the world.

By hvymax

Date 12-01-2008 16:35

If the test is only to be of the top 1/4 then that is what you are testing. You may feel free to bring these to the attention of the CWI but you always follow the procedure first. As a recent CWI I have learned that most of these questions are to discern your ability interpret these and discount anything that is clearly not being tested.

By trapdoor (**)

Date 10-26-2008 06:09

I don't have the latest copy of D1.1 in front of me and am reading from a 2002 compter version that I have.

In table 6.7 note F (in the legend) applies to procedure 5. Note F reads as follows: Weld metal-base metal interface indications shall be further evaluated with either 70°, 60°, or 45"transducer-whichever sound path is nearest to being perpendicular to the suspected fusion surface.

When I do UT of thick parts I always plot out the joint on paper before i do the test and figure out how far I need to scan from the weld toe with each probe angle. I then mark that dimension (plus a couple of inches for good measure) on the part with a paint marker. For example 6" away for a 60° and 9 1/2" away for a 70°. Also when I plot out the weld on paper I am able to ensure full coverage of the joint in the first leg if possible. While I scan the joint if I get any relevant, non rejectable, indications I then mark the location of the transducer and index point and mark the flaw location (surface distance) with a silver verithin pencil (writes through cuplant). Some times on a 14" long weld I'll mark 1 spot other times I'll mark 7 spots. After I have finished scanning the weld per the procedure from table 6.7 I will then use the UT plotter and check to see if any of the indications I marked are in the "weld metal-base metal interface". If any of these indications are clearly in the weld then i ignore them. If there are indications at or near the "weld metal-base metal interface" I will then go through and check these indications with the other probe angles and evaluate. In a nut shell thats how i was trained to do it.

So to awnser your question if you already scanned that area of the weld with the required transducer angle and had no rejectable indications then I would say it is good. But some might say different and I could very well be wrong. I would love to hear someone elses opinion on the matter.

Oh and if you are still a level I you really should bring this sort of stuff up with your supervising level II or III.

By thirdeye (***)

Date 10-26-2008 10:45

trapdoor,

You make some valid points and code interpretations. I use a graph paper spiral notebook to keep my joint sketches in, and have a series of clear overlay sheets with angles, sound paths and surface distances on them. These overlays can slide across the sketch as needed for plotting indications. However one thing I'd like to add...... determining the "actual" BM/WM interface (or fusion zones) is more predictable on thinner joints. Often times on thick joints, the welder may opt to "improve" the bevel with a carbon arc, or may get more western when he/she is backgouging, thus changing the expected interfaces that guys like me may draw on the UT sketch. In other words, the actual joint and fusion zones often times don't look like the joint sketch. If you look closely at the second picture, you can see the fusion zones in that cross section. The interface on the right is pretty close to expected, the one on the left wanders a little more, especially toward the top of the joint. Take a close look at the indication, there is a linear coming off of the left end of it.

By trapdoor (**)

Date 10-26-2008 16:01

thirdeye

Nice pictres. I use the same set up to plot with as well. I also have a smaller slide rule type plotter that stavely makes. These are great tools for UT aspecially when you have geomertical reflectors i.e. backing bars. You make a good point about welders air arcing and changing tha angle of the bevel. Luckily most of the time I am around when they weld large pieces and I make notes on how far they modify the joint before welding. Not being there when the joint is welded can make it almost imposible to get precise with dedermining base metal/weld metal interface indications. But to be safe if an indication is in the suspected base metal/weld metal interface area then I will still scan the indication to be sure. In really thick parts the acceptance criteria is fairly loose compared with thinner material and I rarely find rejects when good welders are doing the work. There is deffinatly alot of things to consider when doing UT on welds and I learn something every day. I in no way consider my self an expert but I do try my best. Thanks for the input.

By CWI555

Date 10-26-2008 16:31

It's been my observation that many UT techs who've only performed AWS UT are unfamilar with echo dynamics and flaw characterization. Observing the wave mechanics via RF signal when something is in question is necessary.

Not to many welding processes don't alter the angle of impingment. If it's fused, it will have an inherent alteration of the original prep angle. Therefore it's near to impossible to rely on actual bevel angle. That is exclusive of the air arcing and other concerns previously mentioned. I would advise that AWS UT techs need to be taught more echodymamics than is currently put out there for that reason.

My opinion for what it's worth,
Gerald

By kipman

Date 10-26-2008 16:48

Well said Gerald. And as Thirdeye points out, in most structural steel cases it really is a wild ass guess as to where the actual fusion face lies. That is why I believe F to Table 6.7 should be read conservatively, i.e. if I have an indication near the anticipated fusion face I evaluate it with 45, 60, and 70 degrees.
This doesn't add much time in most cases, as I only have to do this for evaluation of indications and not for all scanning.
Mankenberg

By hogan

Date 10-27-2008 14:46

I agree that note f would be applicable.

By 803056

Date 12-02-2008 14:33

I still use the plotting method to help me visualize what is going on. The twist is that I use my laptop and my AutoCad program.

I draw the transducer and the sound path as a "block" so that I can move it back and forth along the surface of the cross section of the joint. It makes pin pointing the reflector much easier especially when the base metals are of different thicknesses or there is a weird joint configuration.

Best regards - Al

By jwright650 (*****)

Date 12-02-2008 16:15

Nice tip about using the "block" in Autocad, Al.....I'll have to give that a try.

By jwright650 (*****)

Date 12-02-2008 16:24

Gerald,
About AWS UT techs who primarily UT to D1.1 being not as familiar with other aspecs of UT'ing...I agree, the only time that I ever had to set up a DAC curve was in classes that I've taken over the years. I stumble along and can get through it but I should know it better than I do.

"If it's fused, it will have an inherent alteration of the original prep angle. Therefore it's near to impossible to rely on actual bevel angle." -a simple macro etch will verify this statement real quick. With FCAW the arc diggs pretty deep and it does alter the actual prep quite a bit....so to find something "near" the original joint but not exactly within the groove...yup, it is very possible.

By 803056

Date 12-02-2008 17:00

I don't sell myself as an expert in UT, so forgive me if I ask a couple of stupid questions.

Am I missing something? Isn't the point of knowing the original bevel angle so that you can maximize the reflector produced by incomplete fusion between the weld metal and the bevel face?

The code requires the technician to use the 45, 60, 70 degree wedge depending on the type of joint, thickness of the joint and the area (top, middle, bottom) being interrogated. Acceptance or rejection is based on the code requirements as far as the proper wedge used and the rating of the reflector, but once a reflector is found, don't you "peak" the response by using the transducer that produces the maximum response so you can better characterize the discontinuity and determine the extent of the size, length, orientation, etc. as suggested by Kip?

The difference in the acoustical impedance of the weld and the base metal is unlikely to produce a response unless you have an unusual combination of WM and BM. That being the case, if the weld is sound, i.e., no reflectors, the angle of the transducer is immaterial, no sound will reflect from the weld interface, thus there is no response.

Is my reasoning correct?

Best regards - Al

By CWI555

Date 12-02-2008 20:52 Edited 12-08-2008 15:16

if the weld is sound, i.e., no reflectors, the angle of the transducer is immaterial

The angle is imperative not immaterial. Picture a knife edge. Turn that picture in your mind (or if you have a pocket knife in reality) until your looking at the flat of the blade. Which angle gives you more surface to reflect from? If I impinge on a planar at 45 degrees, and that so happens to be parallel with how the planar is oriented, I am hitting the blades edge. the wave front is going to skip over and below it. If your looking for a lack of fusion, inherently, that angle of the lack of fusion at the WM/BM boundary inherently has a direct impact on detectability. if it's 45 or so from the perpendicular, it can cause a significant loss of sound through redirection/refraction/reflection etc. for straight up straight down D1.1 UT, It's simply Distance gain size. (DGS) Amplitude of response is part of the A-B-C = D formula. If it's +4 or +12 or -4db it's all in db, not is it a crack, is it LOF, or whatever it may be.

but once a reflector is found, don't you "peak" the response by using the transducer that produces the maximum response so you can better characterize

Flaw characterization never comes into the picture. Where understanding echo dynamics comes into the picture is in determining if something is going wrong, where your sound is at, and a host of other matters. Table 6.7 precludes the use of different tranducers, though many procedures do so anyway. If I have a 3" piece, I'd be using 45/70/70 ducers for instances rather than 70/70/70 as you would with 5/16".

So what does the technician do when they hit a free edge bounce in a backing bar that returns? reject because the signal shows up as in the second leg, does he or she recal, change angles, hunt and peek for some phatom indication that doesn't exist? Or do they note the phase change/subsequent conversion of the wave front 180 from propagation and possible constructive or destructive interference that is a clear sign of a free edge rather than a flaw? (that by the way is why I won't buy a scope not capable of RF waveform display. A scan rectified is nice and all that, but there are times when it can hose you)

I for one can think of many structural UT techs that bit the bullet on that one. Including myself 19 years ago when I first tried my hand at D1.1 UT.

Then there is the WM/BM boundary. Every material has a boundary unless they are contiguous/homogenous. It's not unusual to get a minor return out of phase from the HAZ area and or BM/WM interface. Those in particular have to be watched closely as they may or may not be haz cracking (whose angular orientation may or may not be suited for the angle of impingment).

All in all, the only thing the bevel angle does for you is give a starting point.

Regards,
Gerald

By 803056

Date 12-02-2008 21:27

I understand what you are saying, but my point was, if there are no reflectors, i.e., no defects present, the bar is homogeneous, the angle is immaterial. The sound will not return to the transducer if it is attenuated by the bar if it is long enough (or your range is set short enough).

I also said that the reflector is accepted/rejected based on it's rating per D1.1. The characterization is something above and beyond what D1.1 requires, but the client often requests, i.e., is the defect porosity, a crack, etc. How deep is the top edge, how deep is the bottom edge, how long, etc. is always of interest if a repair is required. The welder wants to know what he is looking for before starting to excavate the weld.

I will look into the phase conversion from backing bars that you mention. I haven't tried to use the full unrectified wave when using UT for weld inspections. I'll give it a try.

Thanks for the explanation.

Best regards - Al

By CWI555

Date 12-03-2008 12:58

My point was, you cannot state "no defects present" without taking those factors mentioned into account.

Regards,
Gerald

By 803056

Date 12-04-2008 04:58

Valid point.

Al

By supermoto (***)

Date 12-04-2008 16:14 Edited 12-04-2008 16:24

I may need to make my question more clear. The areas that were not rejectable are for example:

Scanning a T joint 3" thick
-This is a #5
-I would have to use a 45 for the top quarter and a 70 for middle half and bottome quarter.

But my question is that if I see something in the middle half with a 45 and I determine it rejectable by size, not location is it still rejectable or do you leave it according to tables 6.2, 6.3, and 6.7.

This also goes for areas in HAZ doe they stay?

I would have to say I will follow the code but make sure to include the know indications in the UT inspection reports.

By Maxpayne575 (*)

Date 12-04-2008 21:24

Boy, this sure got complicated, echodynamics, RF,

You gave quite a thickness range in your O.P., 3" Tee joint makes it easier. So,

Since F or XF applies, and you say the indication is near the middle, and assuming from the thickness it is a double bevel groove, (TC-U5), you may be looking at the fusion face on the opposite bevel, in which case, yes, you should reject it, because technically you have just applied F. If you can get to face C, you could verify the location of it freom there, with a 45 deg shoe.

Remember, F isn't an option when it's called out, it says "shall be further evaluated...."

As far as AWS UT techs not knowing how to characterize indications, or recognize backing bars, or use a DAC, I refer you to Commentary C-6, and Annex S.

By supermoto (***)

Date 12-05-2008 13:20

I still don't think that you understand the question.

Yes I should have explained a little better but there are many different thicknesses and majority of our CJP are BTC-U4.

Yes I can further evaluate it with another angle or from face C but if I am using a 45 for the top quarter and I see something outside of the top quarter is it rejectable. Sure I can evaluate it with a 60 or 70 and maye even from face C but I still find a true large enough reflector to reject, but it is outside the top quarter, is it still rejectable according to D1.1?

C-6 and Annex S are very informative.

By Maxpayne575 (*)

Date 12-05-2008 20:26

OK, I got ya, here's the rule that I apply with my inspectors. Now keep in mind that whether or not Note F or X-F applies will depend on the thickness.

Here goes. If you are looking at the top quarter with the 45 then ONLY LOOK AT THE TOP QUARTER. I'm not yelling at you, btw.

Now, if note F applies, you will be looking at fusion faces with the appropriate angle anyways, AFTER you've done the 45 70 70 inspection. Now Note F applies for any thickness greater than 1 1/2" butt or Tee weld, period.

Now let me say something without you taking it the wrong way. In your original question, you stated that you are doing a Tee weld which requires a #5 inspection. OK, Look at table 6.7, the only thickness range in a Tee weld that requires a #5 procedure is 2 1/2" to 3 1/2", and also this requires F or XF. That is why I focused my answer on this specific thickness range.

Your question is easy enough to understand, take some time to understand table 6.7, note F, and X.

By hogan

Date 12-05-2008 20:47

Note F and XF apply to thickness and weld type.

By supermoto (***)

Date 12-06-2008 14:30

Thank you. I was not trying to make my question so difficult to understand.

This is the answer I was looking for.

By CWI555

Date 12-08-2008 15:51

Annex S is informative, C is commentary, neither binding unless called for by procedure/contract.
Recognizing backing bars is knowing where your sound is and what it's doing.

As for the commentary:

para 6.27.6 paraphrased; indications in root and fusion face shall be further evaluated with either 70 60 or 45 whichever is nearest to being perpendicular to the expected fusion face. I fail to see where it states evaluation by anything other than a different angle.

The resolution comment in the commentary section under C 6.26.12 is insufficient to say the least and more apt to confuse than help.

If and when "informative" annex S is invoked, AWS still leaves the tech hanging out to dry. Figures S9 through S12 Just don't cut it.
A Level 1 should be able to figure as much out as annex S shows. Especially S9 and S10. I've yet to see the perfectly sperical porosity or slag inclusion, much less the signals portrayed in the figures unless I am on the IIW block. More often than not there is some combination of all.

Therefore, there is nothing "complicated" about it, it should be the norm not the exception.

Regards,
Gerald