Hello Purav

In the case of your manway, you probably did not do a separate calculation for the flange and blind cover (I am assuming this). However, in PV Elite you can do a calculation for the flange and cover, but you have to do this by adding a body flange to the model. It may look a little odd in the 3D model, but it will perform the calculation without a problem.

I have discussed the issue of bolt stress in another thread on the forum. When you initially assemble the flange and its mating cover (or other flange), you torque the bolts up to get a proper squeeze on the gasket. When you start to pressurise the system, the bolts stress does no really increase - it remains essentially the same. What happens is that the pressure on the gasket decreases.

At the hydrotest, the bolt stress is still about the same, but the pressure on the gasket decreases still further. So, the only thing you need worry about with the hydrotest, is that you do not get leakage.

Another this that may be surprising to you, is that as the design phase, you use PV Elite which gives a bolt allowable stress of around 25 000 psi (172 MPa). But, when the flanges are assembled, the fitter must get the stress up to at least 50 000 psi (344 MPa). That is about the only way of preventing leakage. I learned this when I attended a flange seminar in New Orleans one year.

Don't worry too much about the bolt stress. SA 193 B7 material is almost unbreakable. It is a very fancy high strength steel.