i required how to deside the flange when flange standard is not standard. if we using minimum thickness if you have formula for this please give me reply
Figure out all the details on your bolting/gasketing/torquing
Post that information here
I can give a thickness of the cover plate based on this information and a material.
You could design the cover to ASME, however, I think that will be too conservative for you (particularly with the allowable stresses they use - but that could be adjusted, anyways ................)
But this looks rather like a college question to me. If so, you should be consulting your textbooks and working things out for yourself; (in any case, asking help with coursework contravenes CR4 house rules)