V. SUPPLY SYSTEM CONSIDERATIONS
I. Pump Cavitation
A WGI reciprocating power pump is a device to move liquid under specified operating conditions. If the liquid is not arriving at the inlet side of the pump promptly, evenly, and with the least amount of resistance; the pump cannot operate efficiently, nor can it move the liquid through the discharge system smoothly. A poor liquid supply system to the inlet side of the pump will create pump cavitation (where liquid moving through the pump vaporizes rapidly wherever the local absolute pressure falls to, or attempts to fall below, the liquid vapor pressure). Cavitation can cause premature failure of the pump valve, piston or plunger packing, pitting of the cylinder walls, and damage to the pump and system by subjecting all parts to undue stresses. Consider the interactions between a piston and the liquid it pumps. The piston must stay in contact with the liquid through its entire stroke.For reciprocating power pumps, plunger/piston velocity varies sinusoidally with crankshaft position. Maximum velocity occurs approximately at mid-stroke and zero velocity occurs at both ends (full forward position and full reverse position) of the stroke. Under certain inlet conditions, liquid looses contact with the piston and creates a cavity. When the piston slows, and the liquid catches up with the piston, collapsing of the cavity will occur. This cavitation creates shock waves that travel throughout the pump and pumping system, generating noise, vibration and wear.
Even if velocity-matching requirements are met, pressure at the pump inlet must be high enough to prevent gas formation/separation.
