wromero,

The maximum operating temperature and pressure should be given to you by the process department and your design shall follow. In case there is no definition for the maximum condition you will use the normal operating conditions in your design. However, if the system goes higher temperature and pressure that the normal condition, no one will know what will happen without any calculation or stress analysis. You need to inform the precess engineer or client for this issue.

Flange analysis and peq method gives the same ratio. This ratio is very useful if you have many same size and class flanges in the analysis. You can screen flanges in the analysis, and do one flange calculation for the flange with the highest ratio for the same size and class. If the flange calculation passes, all the same size and class flanges pass.

Peq is just a comparison value (for this discussion only), however, flange calculation is a calculation for stress on flange, bolt group, and leak of the connection. If flange calculation does not pass you need to change some parameters including flange class.

Hope it helps,

Ibrahim Demir