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Bolts on a flange?

Bolts on a flange?

Bolts on a flange?

Hi all,

I'm in the process of designing a underwater casing that will go to a depth of 40 meters. The casing a 280mm diameter cylinder and is in two parts joined by two 300mm flanged faces. The casing has to be watertight, so I'm fitting an o-ring between the flanges. The internal pressure of the casing will be 1 atm.

What is the correct way of determining the number of bolts that will be required to fasten together the flanges.
One of my colleges mentioned that there's a formula that is used to determine this. Does anyone know where I can get this information?



RE: Bolts on a flange?

Hi AeroNucDef

Check out the pressure vessel code PD5500 that might help.


RE: Bolts on a flange?

Thanks DesertFox.

RE: Bolts on a flange?


Your welcome

RE: Bolts on a flange?

If you are using a face-seal oring groove, parker ORD5700 catalog gives great info regarding forces needed to compress a given size/composition oring.

that said, your defining factor is likely to be the handling requirements.  Typically, that will dominate your oring compression needs. Also, remember, external pressure will serve to keep your flanges mated.

bolt force is related to preload torque and bolt size, and can be approximated by
T=K*D(bolt)*F, where K relates to friction (among other factors) and generally is between .15 and .2 for a lubricated bolt.  apply a decent safety factor to this to account for any approximation errors.  If you need more precision, there are better approximations out there, but that's beyond my expertise.


RE: Bolts on a flange?

Cheers subsearobot, I'll have a look at the catalog.

RE: Bolts on a flange?

the rule of thumb in inches was "pi spacing, rounded up to the next multiple of 4"
[i.e., 16 bolts on a 16" bolt circle; 20 bolts on an 18" BCD] so ~ 3-1/8" [80mm} between bolts

RE: Bolts on a flange?

Subsearobot "... Also, remember, external pressure will serve to keep your flanges mated..." not necessarily as buoyant force may be a factor.

RE: Bolts on a flange?

The minimum number of bolts is one, if you use v-band clamps on appropriate flanges. They are typically much smaller and lighter than ANSI style bolted flanges.

Mike Halloran
Pembroke Pines, FL, USA

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