The "Pumping Performance" Formula is now widely accepted as the only reliable way to assess any under-performance by a tanker's pumps during discharge of the cargo. Based on straightforward physics, the formula can be used to determine the flow rates that may be achieved at different back pressures.
The logic is that the discharge pressure for a given system varies proportionally to the square of the flow rate. This can best be explained by an example:
If the bulk pumping rate is 500 mt/hour at 6 Kg/cm² the rate at 7 Kg/cm² can be calculated as: 500 x √(7.0 / 6.0)(7.0 / 6.0) = 540 mt/hour.
This formula is accurate so long as the differences in flow rate are not extreme, and provided an increase in back pressure does not result in significant vaporisation in the suction lines to the pump.
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