UG-101 (p)

[jakov11000]

Hello,

I have a brazed heat exchanger that consists of multiple flat plates brazed together. Such brazed flat plates form multiple channels. The exchanger looks like a box - like a square. Construction is too complicated to be evaluated per UG-34 or any other paragraph of VIII-1. Therefore UG-101 is used. Now, we have used UG-101 (p) for MAWP determination, since these are all flat plates. We are being challenged by a jurisdiction in Canada. They say that UG-101(p) is not applicable to end plates. According to them UG-101 (p) is applicable to inner plates but not to end plates.

I am assuming they would like us to use UG-101(m) and that would result in much lesser MAWP.

Please let me know your opinion - would UG-101(p) be applicable for end plates as well.

Thanks in advance.

 

[TGS4]

Please explain to me how "burst"/4 would result in a lower MAWP as compared to "no excessive deformation"/3?

 

[jakov11000]

TGS4,

Yes, you might be right. No "excessive deformation" does not really specify what the deformation should be, and it might result in the same MAWP as UG-101(m).

But let's focus on UG-101(p) only, would you think that it would be applicable in our case?

 

[TGS4]

I think that a reasonable argument could be made that UG-101(p) could be applicable in your case. Which jurisdiction? And how are they arguing that this is not applicable?

 

[jakov11000]

TGS4,

Well they are focused on the word COLLAPSE. Which acc to them would be for external overpressure or internal vacuum only. Our unit is designed for internal overpressure. Now, in ASME VIII-1 I was only able to find some reference to collapse in Appendix 23 where it says "(a) Test three full size specimens to failure (visible collapse)by external hydrostatic pressure." Anyway even if collapse means external pressure only, our pressure envelope consists of flat plates, and for those internal overpressure or internal vacuum does not make any difference.

It is Alberta.

So, what would be your opinion on this?

Thanks,
jakov11000

 

[TGS4]

I would point out the terminology in Division 2 where collapse is generally in reference to plastic collapse, which is for internal pressure.

This seems like a silly nitpicking to me.

 

[MillerSu]

Jakov11000,
Pls. go through UG-101(p) again. there is a related clause which is UG-28(i). UG-28 is "thickness of shells and tubes under external pressure". My opinion is collapse means the failure mode of vessels which are under external pressure. If your design is not suffer external pressure, this clause is not applicable for you. Actually, my work is plate fin heat exchanger design. it is brazed in a furnace too. the MAWP is determined by UG-101(m). hope it is helpful for you.

 

[jakov11000]

Thanks guys!

MillerSu,

They have accepted UG-101(p). I argued that flat end plates have the same failure mode regardless of the side where the pressure acts (internal overpressure or internal vacuum). Same is with UG-34 and UG-39.