AIR-COOLED HEAT EXCHANGERS (FINFANS); "Flat Diameter" on U1

[ALO_Inspector]

Hi y'all,
I'm an Inspector in Oil & Gas and i specialize in RBI on refinery equipment. For inventory calcs i have to put in the dimensions of equipment and i've noticed on U1s for air cooled heat exchangers (finfans), under the dimensions for the header boxes there is "Flat Diameter" & length. I am trying to get a better understanding of flat diameter and what it means and how it is calculated. See attached image

 

[EdStainless]

Pull the appropriate design guide for these (HTRI or HEI or whatever) and look up how they define it.

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P.E. Metallurgy, consulting work welcomed

 

[Rputvin]

Do you have a drawing of the unit? A standard unit of this type has a copper coil and piping headers, but they can be designed in a number of ways including using a tubesheet and box header similar to a shell-and-tube heat exchanger without the shell.

This is from the U1 on one of our ASME air-cooled heat exchangers. The tubesheets and corresponding box headers measure 15-7/8" x 66-1/16" at the gasket face, rounded to 15.9"x66.1"

"Diameter" is a bit misleading in this case of a rectangular head.

 

[ALO_Inspector]

Hi EdStainless! Thanks for replying! Could you be more specific? This is out of my wheelhouse and i need more direction. I looked up HTRI and it seems that's Heat Transfer Research, Inc and they have modeling software? Most of the equipment i analyze is built way before modeling software, for instance this is a Litwin design built in 1977. I thought this would have been defined in ASME Sec 8 Div 1, or in API STD 661 but it's not. Are there any specific documents i could look up and find?

 

[ALO_Inspector]

Hi Rputvin! Thanks for replying! Yes i agree, "diameter" is decieving in this case, as this is a rectangular header box as well. The dimensions of this header box are 3.75" depth x 7.75" tall x 88.625" length. But on the U1, it gives 9" as the "flat diameter" and 88.625" length. Yours is the same way, 15.9" "diameter" and 66.1" length. But where does the 9" "diameter" and the 15.9" "diameter" on yours come from? How is it calculated?

 

[Rputvin]

We're using the tubesheet/header face dimension for that Flat Diameter. This is the pressure boundary between the "body" and "head" of the vessel.

You have two dimensions to define the rectangular face instead of one dimension for a true diameter. We're at a flat diameter of (15.9"x66.1"). You have two heads called out at 9"x88-5/8" and 3-3/4"x7-3/4" - I would assume the 9x88 is your tubesheet/header interface, and the 3.75x7.75" is a smaller end plate, perhaps on the other end of the unit?

A drawing might help clear that up, though.

 

[SnTMan]

Looks to me like the short x long dimension of the box header, inside dims presumably.

Regards

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[ALO_Inspector]

Hi Rputvin! ok, so they're simply saying this head is a flat plate with X & X dimension, and i was reading too far into it. Thanks! unfortunately there are no drawings for this equipment other than an inspection iso showing where cmls are to be taken, but no dimensions.