ASME VIII, Div 1 Heat Exchanger

[engpes]

I have an ASME VIII, Div 1 heat exchanger vessel that I am running code calculations on. I am trying to determine a flat, welded, integral tubesheet thickness (see attached drawing).

My design pressure is 200 psig at 1000 F. I am having difficulty determining the total area of untubed lanes (AL) per ASME VIII, Div 1. My question is this:

1.) What constitutes an "untubed lane" per ASME VIII, Div 1? Is it any spaces between tubes larger than the pitch? I did find figure UHX-11.2, but it is somewhat vague.

2.) My current design has tie-rods to stiffen the tubesheet. I cannot find anywhere in Section VIII, Div 1 that references tie-rods in regard to adding stiffeness to the tubesheet. Can I account for these in my design?

I am using compress' heat exchanger adder to analyze this vessel. Can anyone assist.

Thank you very much in advance!

 

[engpes]

Sorry, meant to attached this drawing as well. Thanks.

 

[SnTMan]

engpes, if I understand your design:

1) An untubed lane is generally present in multiple tubeside pass heat exchangers, and is roughly as you state. You have no un-tubed lanes present in your design.

2) UG-47 and following paras. apply to stayed and braced surfaces. Unfortunately tubesheet designs that rely on elements other than the shell and tubes to transfer loads between tubesheets are not within the scope of Part UHX. Strcitly speaking, because your tubefield is not "nominally circular", your design is also not within the scope.

Regardless if what Compress will "let" you do, your design falls under U-2(g) rather than Part UHX. You're most likely going to have to perform an alternate analysis that is agreeable to you AI,a nd perhaps your customer.

Might be more practical to thickne the tubesheets and dump the stays.

Regards,

Mike

 

[engpes]

Thank you Sn TMan! If I were to remove the tie-rods, would the space above and below the tubes be considered untubed lanes?

Also, would removing the tie-rods and increasing the thickness of the tubesheet accordingly allow me to fall under the requirements of UHX?

Adding area of untubed lanes will help out with the stiffness of the tubesheet and reduce my required thickness of the tubesheet. (Currently at 1.75" thick).

Thanks a lot!

 

[SnTMan]

engpes, if it were my design, I would not consider the area outside the tubefield an untubed lane, rather I would more likely just ignore it.

And yes, removing the tie-rods would allow your design to fall within the scope of Part UHX, in my opinion.

Couldn't help but notice your BOM calls out 1" tubesheets, while the drawing field seems to say 1/2"

Regards,

Mike