ASME Section VIII Gasket Question

[dredre]

Hello,

I am dealing with a manhole cover for a tank. I would like to find the equation for determining the thickness of a gasket for the manhole. The gasket is typical, rubber and has punched out holes for the bolts, and seals to the outer edge of the manhole. I looked at ASME Section VIII Mandatory Appendix 2, but it states that the calcs are only for bolted flange connections with gaskets that are entirely within the circle enclosed by the bolt holes. Where can I find the equations for my particular situation. I already calculated the minimum bolt load that will maintain a residual compressive load on the gasket area that is greater than the internal pressure of the tank when the total load is reduced by the hydrostatic force. I have enough preload on the bolt, but I am trying to justify using a thicker gasket....

Any suggestions will be appreciated.

Thank you

 

[prex]

There are no rules to determine the thickness of a gasket, except that different thicknesses will give different bolt loads.
In the site below, under Vessels -> EN13445 or BS5500 there are sheets for calculating full face flanges.

prex

http://www.xcalcs.com

Online tools for structural design

 

[gr2vessels]

dredre,
The tank manways are covered by API 650 / API 620. No calculations are required, cover, bolts and gaskets are specified in those Codes, check out the Table 3-13 of API 650.
If your manway is an ASME B16.5 type, the covers are tabulated and there is nothing you can calculate, just select the correct size, bolting and a gasket suitable for the process fluid. The gaskets are covered / tabulated in ASME B16.20, including the thicknesses you are after.
Cheers
gr2vessels