Hydrostatic Head to be Considered to Carry Out ASME Code Calculation.

Especially in vertical vessels containing liquids, the pressure at the bottom of the vessel is greater than at the top, on account of liquid height (or head). The vessel needs to be able to withstand this greater pressure. Hence it should be taken into account in design calculations. (There may be exemptions for horizontal or short vertical vessels, but I don't know what the current codes say.)

Perhaps your college or employer should invest in a copy of the local code, so that you can give brief quotations of sections where questions arise. This would enable other parties to give better answers.

• Yes, hydrostatic head must be taken as a case of calculation, and this is very very important especially for high elevated columns, where the weight of liquid column used in hydro test must be taken into consideration in addition to the MAWP. At many times of calculations you can find that the thickness of column at base is more thicker than the thickness at top of column for the same MAWP.

• Another case of calculation to be taken into consideration is the case at operation where the vessel is filled with certain liquid (with certain density) level to be clear at Vessel Datasheet, where you have to find the pressure at every section due to weight of liquid column.

• Also, a lot of times of calculations, I found that the class/rating of flanges at base is higher than that class/rating at top, e.g. at base the class #300 and at top #150.

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