A glossary of terms should get you started on cavitation-free pumping systems.

Condensate Pump: A condensate pump returns condensate to the boiler in applications where this cannot be done by gravity. The pump must be located so that condensate flows into the receiver by gravity.

Condensate Return Unit: A prepackaged system usually consisting of a tank, pump and a float switch that is used to pump condensate back to the boiler or boiler feed unit.

Boiler Feed Unit: A prepackaged system consisting of a tank, pump and makeup water line that returns condensate to the boiler.

Boiler Feed Pump: A pump that is governed by a control that monitors the actual boiler water level. It only adds water to the boiler when the boiler needs it. The pump controller is mounted on the boiler.

NPSHR and NPSHA: These acronyms are short for net positive suction head required and net positive suction head available. NPSHR curves for centrifugal pumps are needed because all centrifugal pumps operate at a lower pressure in the impeller eye than the pressure existing at the pump suction flange. The curve identifies the pressure over and above fluid flashpoint or vaporization pressure, which is needed at the pump impeller eye and takes into account decreased pressures within the pump.

Cavitation: Cavitation is usually due to oversizing of the pump or can also be caused by an excessive suction lift on the restricted suction line and results in the liquid being pumped exploding into vapor within the pump casing. This exploding is due to the fact that at cavitation, a pump develops a partial vacuum within the casing causing the liquid being pumped to break into vapor within the pump. Cavitation occurs both on closed and open systems depending on system pressurization.

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