RT - ASME Spot Examination

Date 07-18-2008 02:00

Good day all,

I have a question regarding the interpretation of the UW-52 section of ASME Section VIII - Div. I which is about spot examination of welded joints.

Here in the workshop i am looking at nozzle to flange welds of OD 60,3mm x 8,74mm. These are for a heat exchanger and there are four of them for this one vessel.

Now here is the quote from the code:
"One spot shall be examined on each vessel for each 50ft (15,2m) increment of weld or fraction thereof for which a joint efficiency from column (b) of Table UW-12 is selected. However, for identical vessels or parts, each with less than 50ft (15,2m) of weld for which a joint efficiency from column (b) of table UW-12 is selected, 50ft (15,2m) increments of weld may be represented by one spot examination."

So now that the plot is set, here are my questions:

- if these 4 nozzles belong to the same heat exchanger, are these 4 nozzles to be accounted for one increment of weld and thus, only one spot examination (taken randomly on one of the 4) is enough for all ?

- or each nozzle being a different weld seam, each nozzle have to have one spot examination ?

I hope to be clear enough so that it is understandable.

If you can show me the light, it would be greatly appreciated. I have to say the vocabulary in these standards is sometimes tricky and could be open to various interpretations ...

Thanks in advance !

Vinc'

By new tito (***)

Date 07-18-2008 12:35

May want to check under UW-11 also. I believe your pipe diameter excludes you from RT requirements.

By chang

Date 07-19-2008 01:10

Ok, but hypothetically, if the size were to be big enough, would it still require one RT spot on each separate nozzle or not ?

By cryogenicshaun (**)

Date 07-18-2008 12:59

Are you using RT-2, 3, or 4? I am taking it that this is a Category B weld?

I agree with new Tito. Category B and C butt welds in nozzles and communicating chambers that do not exceed NPS 10 or 1-1/8 in thickness do not require radiographic examination.

By chang

Date 07-19-2008 00:28

[quote]Are you using RT-2, 3, or 4? I am taking it that this is a Category B weld?[/quote]

I am not sure about that RT 2,3 or 4 ... im not a RT inspector, i am just checking the procedure.

The welds are category C. And indeed, UW-11 states it is not required to perform RT on these babies. Nevertheless, the code on this project also mixes with the customer's order specification and the drawings mention spot RT. It is a contradiction, but in this case, im usually going for the most stringent, so I can't be "wrong" in the end.

Thanks for your thoughts, im going to read more about that.

By cryogenicshaun (**)

Date 07-19-2008 01:48

The RT-2, 3, and 4 has nothing to do with the RT inspector. It is radiographic requirements to determine joint efficiency. I don't have my code book in front of me right now to tell you exactly where to look for this. I can't remember if it's UG or UW. I would like to say it's in UW-16 or somewhere around that area. What efficency are you hoping to acheive? Is this going to be a National Board registered vessel? Table UW-12 may help also. I would say that in the event that these were of size to require RT, that you would calculate how much weld that you have and do 1 spot for every 50 ft increment of weld for that category weld joint. Even if that means you only have to RT 1 spot on 1 weld.

If your customer is requesting this, then you need to do it. Alot of customers like to go above and beyond the code. Your best bet, in my opinion, would be to just shoot 1 spot on each nozzle to satisfy their specifications. You may even consider contacting them and asking them to clarify this for you. If they are requiring more NDE than the code calls for, charge them for it if it's a significant amount.

I'm not sure if this was any help to you, but I'm sure that you will find the answer here.

By chang

Date 07-20-2008 06:25

Cryo:
"that you would calculate how much weld that you have and do 1 spot for every 50 ft increment of weld for that category weld joint. Even if that means you only have to RT 1 spot on 1 weld."

Thats the part i dont get ... Considering i have only 4 nozzles and that altogether its far from reaching 50ft, then it means only 1 spot randomly taken from one nozzle only would be sufficient for that category of weld ?

That is just weird to me, but if thats what it is, then be it ...