ASME NTIW Tubesheets calculation

[ReddeV]

Sorry for the repost... I probably made a mistake and posted it in the "Compress area" before.

I'm trying to apply for ABSA CRN approval some HX I manufacture.
Such units have NTIW tubesheets and are excluded by the scope of UHX per UHX-10.
I calculated those tubesheets according to TEMA R, feeling confident that this could be the soultion, but the Revisor rejected the calculation since NTIW models are excluded from TEMA too.
TEMA RCB-7.3 (1) mention such configuration, but obviously desn't give any solutions, leaving all the issue in the hand of the inspector.
Now the ABSA revisor "suggested" to calculate the tubesheets with the following approach
1. calculate the perforated area with TEMA R considering the radius passing throught the outmost tube
2. calculate the unperforated areas with UG-34, considering the tubesheet as an un-stayed flat end.

I consider such approach not only overly conservative, but especially for the point 2 something not applicable.

UG-34 considers the pressure only by one side. So which pressure should I consider in my calculation? The shellside or tubeside one?
Furthermore which sketches do I use? The one welded to the shell or the other one with the flanged extension bolted?
If I consider the flanged one I would calculate an unstayed plate retained only by the bolts. That's not corrected since it doesn't consider the other side welded. In such way I would calculate some kind of "floating" end.

So now I need to find a good solution in compliance with U-2(g) and I would like to avoid the FEA calculation for now.

Any suggestions?

Thanks in advance

ReddeV

 

[SnTMan]

ReddeV, ASME Part UHX calculations are routinely used for NTIW designs even though strictly speaking it is not wthin the scope. Previous discusion has been held, see thread794-264299 for example.

However, your reviewer has kicked that approach. As to your further questions I would try to get some guidance from him.

Perhaps he would accept the tubesheet calculated per UG-34 using for E the ligament effiency from Part UHX or UG-53.

Regards and good luck,

Mike

 

[ReddeV]

Thank you very much SnTMan, I really appreciate your suggestion.

Just one thing is not so clear for me.

In the UG-34 which sketch(es) shall I consider in my calculations?

My tubesheet is welded to the shell by one side according to Fig. UG-34 Sketch (h) and has flanged extension on the other side for the cover.

If I consider sketch (h) I should consider the shell side pressure only, correct?

Otherwise on the other side (the flanged one) I have tubeside pressure greater than the shell side one.
So it would be more conservative to consider this side in my calculation but I don't even know which sketch should be considered.
The sketch (k) would refer to a flat end not welded but only tightened by the bolts and that's not correct(even if in this way I could consider the right mean gasket diameter in my calcs).

I don't have a solution for this.

The right configuration of my tubesheet is the one considered as Sketch (b) of Fig. UHX-13.1

Could you please help me once more?

Thank you and Regards

Andrea

 

[SnTMan]

ReddeV, there is no clearly applicable figure in UG-34, therefore I would make the reviewer specify or otherwise reach some agreement with him. He is the party that needs to be satisfied in the end.

Otherwise any calculation performed is potentially just an exercise.

Regards,

Mike

 

[ReddeV]

SnTman, yes you're right... he's the party that needs to be satisfied, but unfortunately I alredy asked him some clarifications about another concern and the answer was something like "do it yourself"

Ok... I will try to submit this new calc considering sketch (h) and maybe the delta of pressures between shell and tube sides (or at least the max pressure which is the tube side one) and wait for his new concerns.

In the meantime let me thank you

Regards

Andrea

 

[SnTMan]

ReddeV, I would recommend the higher of the two pressures.

Sorry your reviewer won't adopt a position.

Again, good luck.

Regards,

Mike

 

[TJOrlowski]

Somewhat off topic: I think I know exactly which reviewer at ABSA is looking at ReddeV's heat exchanger. We are currently experiencing a similar bottleneck with one of our designs that already holds CRN approval in multiple other provinces.

It is. . . time consuming.

-TJ Orlowski