A-B-C

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

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

Atmospheric pressure added to gauge pressure.

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

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

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

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

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

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.

Used to connect and align the pump to the motor with registered fits. (imperial dimensions. Called the D frame adapter in the metric system)

A non-seal pump with the shaft, bearings and rotor contained in a can to prevent product leakage. Limited to pumping clean lubricating liquids.

Fluid flow measured in gpm, liters/min, M3/hr. etc.

The compound formed when carbon combines with an element. The carbides of metal are very hard and are often used as a mechanical seal face.

Used as a restrictive bushing in flushing applications, a thermal barrier in high temperature applications, a disaster bushing in an A.P.I. gland and to support a deflecting shaft in many mechanical seal applications.

A common mechanical seal face material chemically inert to most fluids with the exception of oxidizers, bleaches, halogens and a few other fluids.

A self-contained assembly containing the seal, gland, sleeve, and both stationary and rotating seal faces. Usually needs no installation measurement. Must be used if impeller adjustments are made. Cartridge seals are the standard for A.P.I. seal applications.

Cavities or bubbles form in the fluid low-pressure area and collapse in a higher-pressure area of the pump, causing noise, damage and a loss of capacity.

The pump is suspended on feet attached to the sides of the volute instead of the bottom. Used in higher temperature (> 100?C) pumping applications.

The metric system unit of viscosity.

The kinematic unit of viscosity. Viscosity in centipoises divided by the liquid density at the same temperature gives kinematic viscosity in centistokes.

Moves liquid with centrifugal force. Available in circular and volute configurations.

Sometimes called a cyclone separator. Uses centrifugal force to throw solids out of the fluid. Does not work very well in slurry seal applications.

A hard, chemically inert seal face material that includes products refereed to as silicone carbide.

When a liquid flashes into a vapor, solidifies, crystallizes, cokes etc.

Occurs in the 300 series of stainless steel. Caused by a combination of tensile stress, chlorides and heat. No one knows the threshold values.

Forms when chrome forms with carbon in the heat affected zone during the welding of stainless steel. The use of low chloride stress corrosion carbon stainless steel is recommended in these applications.

The passivated layer that forms on the 300 series of stainless steel.

Used with centrifugal pumps that circulate fluid rather than build head or pressure.

The pump impeller is mounted directly on the motor shaft. There is no separate bearing case.

A hard coating is plated or welded to a softer base material. Presents problems with different thermal expansion rates, the hard coating can “heat check” or crack. Not recommended as a seal face material.

The elastomer changes shape when it has been exposed to too much heat. Round O-rings come out square.

One seal is located inside the other, with a common hard face shared by both of them. Because of its large radial space requirement the seal is usually limited to mixer type applications.

When the parts share the same centerline they are concentric to each other.

Condensed steam.

A natural circulation of fluid. The hot fluid (lighter) rises and the cool fluid (heavier) sinks.

Used to contain fluid between two mechanical seals. An enclosed heater or cooler can be used to control the barrier or buffer fluid temperature. Pressure or level gages can indicate which seal has failed.

Surrounds the stuffing box of the pump to control the temperature of the fluid in the stuffing box. Usually molded into the back plate.

Corrodes at a rate of less than 0.002 inches (0.05 mm) per year.

Used to connect the pump to the driver. It transmits torque and compensates for axial growth, but not for radial misalignment.

Any object made of an elastic material has a natural period of vibration. When a pump rotor or shaft rotates at any speed corresponding to its natural frequency, minor unbalances will be magnified. These speeds are called the critical speeds.

Very cold temperatures.

Directs the pumped liquid to the discharge piping.