AWWA D100-11 Radiograph Test Location Interpretation

[onealexis]

Hi All, looking for some assistance in interpreting AWWA D100-11 as far as how many radiographic tests are to be performed and in what locations.

We have two water tanks, each with a diameter of 37'. The tank is comprised of 5 bands with full-pen welds at the seams between the bands and also at the individual segments making up each band. The tanks are being constructed one after the other with the same welders. I calculated that we have a total of about 1300LF of weld.

We are using Section 11.5 to determine the number and location of the tests, but among two groups at our office have two different interpretations.

One interpretation of the code is that you take the total number of LF and divide it by 100' and that what you come up with is the total number of tests to be performed, but that those tests need not be taken any higher than 8' (the height of one level of scaffold.

The other interpretation is that the tests should be performed as the work progresses and one test is to be taken in each 100LF of weld (as the work progresses or progressed).

Does anyone have enough experience with this code to say or know? Can you help us understand in a way that will convince the opposite party the interpretation provided is accurate?

Thanks much.

 

[fegenbush]

This is a pretty cut and dry response. The first sentence of 11.5 specifies that the inspection shall be performed as the work progresses and shall be made as soon as possible after all the joints from one scaffold position have been welded.

"As soon as possible" is a fairly vague statement, and it may be possible to schedule the inspection firm to arrive on a schedule such that you are not taking one shot per call-out.

 

[onealexis]

So, do you mean that the first test should be taken as soon as possible, but tests would still need to be performed as work progresses (1 per 100 LF of weld), or do you read it as all of the tests can be performed at that first level of scaffolding or below?

 

[Ron]

The intent is for the testing to progress as construction progresses. This allows for proper corrective action as needed and prevents the need for compromising repairs if they have to be done later.

 

[fegenbush]

Ron is correct. The key is to perform the inspection as the tank is being constructed, not after construction is complete. It is not economical to stop work to wait for the radiography subcontractor unless contractually obligated to do so. It is certainly not economical to call out a crew to perform a single shot.

 

[onealexis]

I agree. So, the question is though, let's say you have a tank with 800 lf of welding, so you need 1 test in the first 10' of weld and then 1 per each 100' thereafter - can the 8 additional tests be taken anywhere? Like in the bottom 8' of the tank, or do the tests need to be 1 within each additional 100 lf of weld - as the work had progressed. The way the code phrases it, it makes it seem to me as if it should be 1 in each additional 100 lf of weld - that's how it reads. But, then the paragraph which opens the section regarding the testing criteria gives the impression (to some people) you can do all of the testing in the bottom 8'.

 

[JStephen]

Standard practice is to scatter them around the tank. It doesn't say "one PER 100' thereafter", it says "one IN 100' thereafter". See Fig. 23 as an illustration (although dealing with Section 14 layout).