Fire Case on Internal Shell of Jacketed Vessels

[skearse]

This is something that one of the other guys that do our PSV sizing have gone back and forth on a bit, and I wanted to get input from some others.

When calculating the exposed wetted area for a jacketed vessel (jacket can be any type-half pipe, dimpled, etc.), do you guys either (a) exclude the jacketed area or (b) apply an appropriate adjustment to the F factor when calculating the exposed wetted area for the shell? Obviously, the most conservative case is to use the entire wetted surface of the shell, as if it weren't jacketed at all, which is how some of our calcs have been performed. But, I would think that some form of "credit" may be appropriate for the jacketed surface of the vessel. Not talkign about the jacket itself here, just the internal shell of the vessel.

Thanks in advance all.

 

[chemicalengineerthai]

Do not compromize or too optimize in the safety system.....

a) Take maximum level alarm high hieight or any specified for max and calculate wetted area, if you do not have take about 80% is good enough.

b) If you need to cover uncertainty in your operating envelop, should take max F.