Vacuum Distillation Column Flange weight more than column weight?

[plantprowler]

I was just estimating the approximate weights of a vacuum distillation column (for a initial analysis & not a final design). The column is expected to be 1200 mm OD / 8 mm thick / 4000 mm long.

If I look up the Class 150 flange size (slip on) I get 1511 mm OD-flange / 108 mm thk with 44 bolt holes of 41 mm dia. That gets me an approximate weight of 500 kg per flange.

i.e. The combined weight of the flanges would be more than that of the column itself.

Just wanted opinions. Is this a possible / typical situation? Or am I likely to be doing something stupid. MOC is SS304.

Are there flanges thinner / smaller than Class 150 typically used? This seems to be the lowest class in the Tables.

 

[racookpe1978]

you have 8 mm thick steel wall for a 4 meter tank, right? Simple rolled steel walls. Fairly short.
The PV walls work like a pipe against internal pressure.

But the the class 150 flanges are 1.5 meter in diameter, right? 108 mm thick = 4 inches.

Of course they will be heavier. You have a cantilevered flat standardized plate that is crossing a larger area than the entire round tank.

Those (two) flanges must be bolted to two mating bolt rings that will also be 1.5 meter in dia, by the way.

 

[marty007]

If you want to use standard flanges, then yes, that's rather common.

If however you're concerned with weight, maybe it's time to take a look at custom flanges. Often for low-pressure applications, a custom designed plate flange can end up much lighter than a standard flange.

 

[SnTMan]

plantprowler, yes, custom flanges as marty007 says.

I am curious, which flange standard are you referring to? You mention slip-on, but the common standard for larger flanges, ASME B16.47, contains only weld necks.

Regards,

Mike

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

 

[racookpe1978]

Do you really, really need a bolt-on FLAT flange plate as the endplate?

If weight matters, and not just buying something of of the rack, then order a dome end. Even a dome end welded to a flange ring (order two slip-on flange rings: one for the tank, one for the dome) will use less "flat plate weight".

For a gravity-filled horizontal tank at room temperature that was permanently vented, I ordered a 42 inch ring, and used a ordinary flat plate as the cover. Drilled the mating holes out of the flat plate. It would never see anything more than the head pressure of the liquid inside.

What pressure? What fluid? What temperature? What code requirements does your client need to meet?

 

[plantprowler]

If you want to use standard flanges, then yes, that's rather common.

Perfect. This is what I wanted to know. Yes, I think it will have to be custom flanges in this application.

I just wanted a sanity check that my calculations showing std. flanges heavier than the column itself weren't stupid.

 

[plantprowler]

@racookpe

The flange is not an end plate but merely joins sections of the column together. Vaccuum column so no pressure requirements. Max T is 150 C.

 

[Duwe6]

Major Quibble; pressure is External, and up to 14.7 psi. Not a trivial item.

 

[plantprowler]

Major Quibble; pressure is External, and up to 14.7 psi. Not a trivial item.

Indeed. All I meant was no high *internal* pressure requirements.