The pipe specs in our refinery does not allow to use slip on flanges.
One of the problems that occurs is the difficulty to UT and inspect the internal weld while the piping is on service.
We use SW flanges up to 2" anything over that is WN.
The hydrostatic pressure is equal to the density of the fluid times the height of the column, The pressure at any point does not depend on the volume but on the height and on the density. Example: height of vessel equals 30 ft. and the fluid is water (i.e. density = 62.4 lb/cu.ft.) thus pressure...
