Dears,

If I have to design Bolted Flange as per App-2, whart is the thumb Rule for selecting size and no of bolts to have optimum flange thickness. If it is to be done with try and error method from what size and Nos should I start?

Is there any rule to control the value of G (Eff. Gasket Dia) to get optimum thickness.

Regards,
Pradeep

Well as a first guess u may select flange geometery to the nearest standard flange size.

If your optimum flange thickness is the thinnest which is allowed by App. 2, the bolts in the App. 2 calc should be as small as possible to keep your area Am small (Am = Ab). This again will keep your design bolt load W for the gasket seating small.
Regarding to the optimum G, please have a look at the lever arm hG in Fig 2-4 sketch (6). Keep it small (as well as hD and hT).
Michael