Valve design question re: Pressure on bonnet

[packdad]

Let's say you have a valve with a bonnet that bolts to the body. It's a gasketed connection with the gasket located within the bolt circle. When the pressure force on the bonnet is considered during valve design, do you assume design pressure only within the diameter of the gasket, or do you take it all the way out to the bolt circle (or to the edge of the flange)?

I would think, since gaskets are prone to leak and are not really pressure boundary components, that you'd have to assume design pressure beyond the gasket for design purposes, but I'd like to hear if this is, in fact, true.

 

[abscott]

Packdad,
There are many different bonnet joint designs and more gasket designs and materials than you can imagine. Without knowing the specifics it is had to give you an answer.

The most complete bonnet-joint analysis technique may be found in the ASME, Boiler & Pressure Vessel Code, Section III, Components. This technique was established for nuclear components and may be "over-kill" for your needs. Most all gasket analysis programs extend the hydraulic pressure loading to the middle of the gasket face.

The joint analysis is performed for normal operating pressure and the hydrostatic test pressure required at assembly.

My suggestion is to contact your gasket manufacturer and they will provide you with the correct technique for analyzing the bonnet joint.
Hope this helps,
ABScott