Hi,

My current project involves rerating a pressure vessel from 50C to 120C. The vessel was originally designed according to PD5500.

Due to higher temperature the minimum code test pressure comes out to be 79.7barg (the vessel was originally tested at 70barg) and maximum test pressure for flanges is 77 barg. In this case what rehydrotest pressure should be specified 79.7barg or 77barg?

PD5500 calculates the test pressure using the ratio of new and corroded thicknesses in addition to stress ratio. Does it mean that while specifying rehydrotest pressure we need to use the ratio of the current and corroded thicknesses?

Your opinion/suggestion is much appreciated.

MW