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[go-fish]

I am a little confused about tank min. liquid level. How is minimum liquid level of hydrocarbon tanks determined? Is it dependent on:-

1) Outlet nozzle size and Table 5.6a, Column 8 of API 650 plus additional liquid height in order to maintain the outlet nozzle always submerged.

OR

2) If the inlet nozzle is bigger than outlet nozzle then Table 5.6 a, Column 8 of API 650 plus additional liquid height applied to inlet nozzle size so that both inlet and outlet nozzle are always submerged. Inlet nozzle may be required to be submerged in order to avoid splash filling at the start of the filling operation which could lead to static electricity.

OR

3) NPSHr for the transfer pump as min. liquid level will be the level required to avoid cavitation.

OR

4) For floating roof tanks, minimum level of floating roof allowed to maintain clearance with mixers (if used) assuming that the roof is required to be floating on the liquid surface even in minimum liquid level position. This would generally give the highest min. liquid level of the above cases.

[Technical Bard]

The answer is all of the above, if they are applicable in a given case. You must check each of them and pick the largest value to set the minimum liquid level in the tank.