Hydraulic Pump Power Power = rate of conversion of energy. If a mass m is raised through a height H it gains energy mgH. If it does in time t then the rate of conversion is mgH/t. Q: volumetric flow rate or discharge

Efficiency of the pump Mechanical efficiency; motor efficiency

Fluid can be pushed very hard through a pipe. The only limit is the ability of the pipe to handle the pressure. Suction is not a force, but simply removing an opposing force to the force of air pressure. Rather than thinking in terms of the pump's ability to pull the fluid, the flow is limited by the ability of gravity and air pressure to push the fluid into the pump. The atmosphere pushes down on the fluid, plus, if the pump is below the tank, the weight of the fluid from gravity above the pump inlet also helps. Until the fluid gets to the pump, these are the only two forces providing the push. Friction losses and vapor pressure must also be considered.

Maximum suction height

Whenever the liquid pressure drops below the vapor pressure, liquid boiling occurs, and the final effect will be cavitation: vapor bubbles may reduce or stop the liquid flow, as well as damaging the system. The violent collapse of the cavitation bubble creates a shock wave that can carve material from internal pump components. Additionally, the increase in vibration can cause other mechanical faults in the pump and associated equipment.

The best way of preventing cavitation in a pump is to ensure that the inlet (suction) pressure is not too low. The net positive suction head (NPSH) is the difference between the pressure head at inlet and the vapor pressure:

NPSHA (available) NPSHR (required)