Pumps Glossary



Glossary of Pump Terms: A

Adapter: Connects and aligns the power end of an ANSI pump to the wet end.

A.N.S.I. Standard: American National Standards Institute. A set of specifications (envelope dimensions) for centrifugal pumps manufactured in the United States

Absolute pressure: Atmospheric pressure added to gauge pressure.

Affinity laws: They predict how capacity, head and horsepower are affected by changes in the centrifugal pump impeller diameter or shaft speed.

Air ingestion: Air is coming into the stuffing box because of a negative suction pressure.

Alignment: The centerline of the pump is perfectly aligned with the centerline of the driver (usually an electric motor).

Ambient heat/pressure: The heat or pressure in the area where the equipment is located.

Annealing: To soften the metal by heating it to a predetermined temperature somewhere below its melting point.

Atmospheric pressure: At sea level, atmospheric pressure is 14.7 psi.

Glossary of Pump Terms: B

Back plate: Used in some centrifugal pumps to position the stuffing box and provide an impeller wear surface.

Back pull out pump: A design that allows the wet end of the pump to be left on the piping when the power end and adapter are removed. A.N.S.I. pumps are designed this way.

Back to back double seal: The rotating seal faces are facing in opposite directions. The worst possible configuration. In the past this term was used to describe a higher barrier fluid pressure between dual mechanical seals.

Balanced seal: A design in which the seal face closing area is reduced to lower the closing force, and reduce the heat generation between the faces.

Balance Ratio: A 70/30-balance ratio means that 70% of the seal face closing area is seeing the stuffing box pressure and 30% is not seeing the pressure.

Ball bearing: Consists of an inner race, an outer race, and a series of balls between them. Often called a precision or anti friction bearing.

Bar: Metric term for one atmosphere of pressure.

Barrier fluid: The high-pressure fluid that is circulated between two mechanical seals. The fluid should enter the bottom and leave the top to prevent air pockets.

Base plate: The pump and motor mount on this unit. The pump and motor feet closest to the coupling should be doweled to the base plate.

Bearing: Supports the rotating shaft and allows it to turn with a minimum amount of friction. Could be either sleeve or anti-friction type

Bellows: Can be manufactured from metal or non-metallic materials to eliminate flexing, rolling or sliding elastomers in mechanical seal designs.

Bernoulli’s Law: A moving stream of liquid or gas exerts less sideways pressure than if it were at rest. The result is that things seem to be drawn into the stream, but the higher pressure from outside is really pushing them in.

B.E.P.: The best efficiency point. It is the point where the power coming out of the pump (water horsepower) is the closest to the power coming into the pump (brake horsepower) from the driver. This is also the point where there is no radial deflection of the shaft cause by unequal hydraulic forces acting on the impeller.

B.H.P.: Brake horsepower. The actual amount of horsepower being consumed by the pump as measured on a pony brake or dynamometer.

Brinnell hardness: A method of measuring the hardness of metal parts and hard seal faces. Above 350 the standard machining operations of turning, boring, drilling, and tapping become uneconomical.

Buffer fluid: The low pressure fluid that is circulated between dual mechanical seals.

Buna N: Some times called Nitrile. A common elastomer used in the sealing of oil or water. Sensitive to Ozone attack and therefore has a short shelf life.

Bushing: A close fitting support device used to restrict flow between two liquids, thermally isolate a hot liquid, support the rotating shaft, break down pressure etc. Commonly made of carbon or Teflon.

Bypass line: Used to either re-circulate fluid from the pump discharge to the stuffing box, the stuffing box to the pump suction, or the pump discharge to a lower pressure point in the system.