Paint removal for UT(min distance)

Date 11-10-2011 00:06

Well, if you are going to UT through the paint, seems like you ought to paint the cal block too so you get your sensitivity right. Not every inspector wants to paint their cal block. Will you have a different cal block for each paint? How many does this take? Who pays for it? Can you sucessfully remove old paint from the block without damaging it? Certainly your sensitivity will vary depending on the paint. And if you cal through paint, you will likely overinspect bare areas. So what to do? Easiest to remove the paint I think.

By jwright650 (*****)

Date 11-10-2011 12:16

I do agree with removing the paint. There are hundreds of beams....4 floors and every column has 4 beams framing to it(except the exterior cols)on every level. I was just exploring an avenue for the erector who has been asked to remove the paint at "all" of these locations. I have to admit this is the first time in my 27 years here that we have ran into this as a problem. We've written a memo to our paint department for future projects describing that we need to hold the paint back not just the couple of inches for the field welder, but also 3 legs distance for the field UT guys. I will also revise our Quality Manual to reflect these same details.

I would have thought that the UT guy in the field could have straight beamed the flange and saw that there is no loss of the backwall and know that he is getting sound into the flange through the paint. Sensitivity may be an issue, but only if you find an indication that needs investigating, and then you could remove the paint in that area and recheck it to see if the indication is worthy of removal or not per Table 2 in Clause 6.

By ozniek

Date 11-10-2011 12:53

Hi John

UT'ing through paint (good quality, well adhering paint) is possible, but is not preferable. This means that most NDT contractors will not want to do this, and many clients will not want this. If removing the paint is going to be an expensive exercise, then I would try to talk to the NDT company and client, and see if some arrangement can be reached. Even if this means that you will have to pay for a cal block that they ruin because they have to paint it, it will in all probability still be much cheaper. In many instances, the additional time that the paint removal and re-application will take, may be a big incentive to the client to try to help you. If they believe that it will be unacceptable due to the criticallity of the application, then you have not lost anything by asking the question.

Regards
Niekie

By jwright650 (*****)

Date 11-10-2011 13:33

Thanks guys for the replies....I'm just miffed at the guy for not even putting on his thinking cap. I know it is not his resposibility, and he doesn't have to care about anyone's problems. I guess that is where I'm different and look for ways and means to adhere to the codes and still perform good, valid inspection even when the circumstances may not be optimal. This kind of hard stance turns me off to the inspection world in a hurry and puts a bad taste in everyone's mouth concerning inspection and gives inspectors a bad rep just as the one's who turn blind eyes to illegal and unethical practices. Like I stated earlier he could straight beam the flange and make sure he sees the backwall echo, then search with the angle beam and as long as there are no indications then leave the paint intact, but when he sees something that needs to be investigated, then have the erector remove the paint in that location and let the inspector re-evaluate the indication to see if it needs to be removed or merely sized and reported on his report. I mean really, with D1.1 you have to scan at quite a bit over your reference level that you are not likely to miss any relevant indications.

I'm going to offer the painted cal block with the same paint millage, and also my suggestions described above, and see what happens. My bet is that he won't even bring it up to the customer and their EOR for discussion.
Thanks again for the replies.

By L51174

Date 11-10-2011 19:29

Hi, as an inspector and as a level III I have run into this quite a bit. Customers always want a work-around to the paint issue. Obviously, you knew the requirements of 6.26.3, so why would you even ask the inspector to UT through paint? Either you can meet fully the requirements of the code or you can't. Not trying to be abrasive, but it seems the requirement was clear to you from the beginning, you were aware of it, so.... provisions should have been made. A UT inspection performed through paint is not a valid inspection, period, if you are claiming to have performed UT IAW D1.1.

The flaw in your argument is where you state "search with the angle beam and as long as there are no indications then leave the paint intact". Well, if the paint is intact, you are not finding everything you would if there were no paint, so right off the bat, you cannot guarantee you're finding every relevant indication. It's the "search", that is the important part. Depending on the paint, the attenuation at the interface could be very significant, or it could be nil. However, unless you can guarantee consistent paint thickness at every weld, which is unlikely, your results may vary. This is one reason, among others, that throughout many revisions of the D1.1, this requirement has remained.

Painting the cal block is a suggestion I hear often, from people who are, well, let's just say UT is not their specialty. This is not the answer either. You may get the EOR to buy off on through paint inspections, IF you can demonstrate, by properly qualifying a procedure, through probability of detection analysis, performed on a painted mock up of typical welds you will encounter, that you can achieve similar results as an inspection on an unpainted surface. However finding a level III to do this may prove problematic.

As an aside, it is not the job of, nor should it be expected, that the level II make this determination. His/Her job is to follow the qualified procedure provided him/her by the level III. If circumstances do not allow for this, then he shouldnt be expected to sign his name to a report where an improvised and unproven procedure, especially on a structural project, has been utilized.

There's my 2 cents, good luck to you.

By jwright650 (*****)

Date 11-10-2011 19:55

>Not trying to be abrasive

I really didn't take your reply as abrasive, and place value what has been written(your two cents...LOL). My last post was written with sour grapes, I suppose due to past experiences on other issues with this inspector. To be very honest, I really haven't given much thought to performing a UT inspection through paint until now, due to the fact that in my 13+ years as a Level II UT for this company, that I haven't had this issue come up. I don't see any paint because all of my inspections are in a shop and are done before any coatings have been applied.

I agree with your assertion that the field Level II should not sign any reports that would be questionable at best. I haven't had time today to check in with the inspector, so none of this has been mentioned to anyone other than right here on the forum and in our office. After reading your reply and digesting some of what has been posted to date, I will not say anything further to the inspector and let him do his job. I was simply being compassionate towards the erector and his concern for having to remove all of that paint for which "in the moment during his phone call" seemed like a silly thing to have to do. I just didn't think it all the way through before ranting and raving...LOL

Thanks again to those who replied in this thread.

By eekpod

Date 12-07-2011 14:24

We use 2"-3" inches as a standard unless the material in really thick (more than 3/4" and up) then I'd make it a little more 4-5".