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1819 Pickwick Ave, Glenview, IL 60026 | P: 847-729-5300 | F: 847-729 7062 | Sales@MarchPump.Com

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A

Absorbed Power: The amount of power the pump is consuming at a specific flow and head.

Accumulator: Device used in home water applications that stabilizes the pressure in the pumping

system and avoid the pump cycling on and off every time a tap is opened somewhere in a house.

Adapter: Connects and aligns the power end of an A.N.S.I. pump to its wet end.

A.N.S.I. Standard: Set of envelope dimensions for centrifugal pumps here in the U.S.

established by the American National Standards Institute.

Absolute Pressure: Gauge pressure added to atmospheric pressure. Typically measured in kPa.

Affinity Laws: Used to determine 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 center line of the pump is perfectly aligned with the centerline of its driver

(Typically an electric motor).

API Standards: The American Petroleum Institute’s standards for various pieces of equipment

utilized in the oil and gas industries.

Axial Thrust: The axial forces acting in a pump’s rotor.

Axial Thrust Balancing: The method by which axial thrust is balanced to minimize load bearing.

B

Back to Back Impellers: Method of axial thrust balancing in which some impellers are located

on the shaft facing opposite directions.

Back Plate: Feature used in a centrifugal pumps to position the stuffing box and provide the

pump with an impeller wear surface.

Back Vane: Radial vane, designed to balance axial thrust, located on an impeller’s back shroud.

Back Pull Out Pump: Design feature, common to all A.N.S.I. pumps, allowing the pump’s wet

end to be left on the piping while its power end and adapter are removed.

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Back to Back Double Seal: Pair of mechanical seals located on a pump with rotating seal faces

in opposite directions.

Balance Holes: Holes in the back shroud of a pump’s impeller designed to balance its axial thrust.

Balanced Seal: Design in which a pump’s seal face closing area is reduced to lower the closing

force and reduce the heat generated between the faces.

Barrier Fluid: High-pressure fluid circulated between the two seals in a double mechanical seal.

The fluid should enter the bottom and leave the top to prevent air pockets.

Base Plate: The pump and motor are mounted on this unit.

Bellows: Component of a mechanical seal manufactured from either metal or non-metallic

materials to eliminate rolling, flexing or sliding.

Belt Drive: Combination of pulleys and belts and that transfers torque from drivers to pumps.

B.E.P.: Best efficiency point on a pump curve for a specific impeller diameter. It’s the point

where the power coming out of the pump (i.e. water power) comes closest to the power used

from the pump’s driver (i.e. horse power). This is also the point where there is no radial

deflection of the shaft cause by unequal hydraulic forces acting on a pump’s impeller.

Buffer Fluid: Low pressure fluid circulated between the two mechanical seals in a tandem seal.

Bushing: Close fitting support device used to restrict flow between two liquids, thermally

isolate hot liquids, break down pressure or support the rotating shaft.

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. This can also be used as a manual means of flow control.

C

Canned Pump: Sealless pump with a can contained shaft, bearings and rotor to prevent leakage.

Cartridge Seal: Self-contained assembly containing the gland, seal, sleeve and stationary plus

rotating seal faces.

Centrifugal Pump: The most common type of pump. Centrifugal pumps are rotodynamic pumps

that use rotating impellers to increase the velocity of fluid. They are commonly used to move

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liquids through piping systems. Fluid enters a pump impeller along or near to its rotating axis

and is accelerated by its impeller, flowing radially outward into a diffuser or volute chamber,

from where it exits into the downstream piping system. Centrifugal pumps work by converting

rotational kinetic energy, generally from an electric turbine or motor, to an increased static

fluid pressure. The pump’s rotation transmits kinetic energy to the fluid as it’s drawn in from

the impeller eye and is forced outward through the impeller vanes to the periphery. As the fluid

exits the pump’s impeller, the fluid velocity is converted to static pressure because of the

change in area the fluid experiences in the volute chamber. Generally the volute shape of the

pump casing or the diffuser vanes are responsible for the energy conversion. The energy

conversion results in an increased pressure on the pump’s downstream side, resulting in flow.

Chopper Pump: Chopper pumps are centrifugal pumps, equipped with cutting systems so as to

facilitate maceration of solids that are present in the pumped liquid. The main advantage of a

chopper pump is that it prevents clogging of adjacent piping, as all the solids and stringy

materials are macerated by the pump’s chopping system. Chopper pumps are available in a

variety of configurations ranging from submersible to dry-installed designs and they are

generally equipped with electric motors to run the impeller and provide torque for the

chopping system. Due to their high solids handling capabilities, chopper pumps are often used

for pumping sewage, slurries, sludge and other any other liquid that contain tough or large solids.

Close-Coupled: Close-coupled pumps have neither flexible couplings nor pump bearings and

are characterized by rigidly-coupled motors and pump shafts.

Constant Level Oiler: Device used to maintain the correct oil level in a bearing housing.

Cooling Jacket: Located on pump casings or the stuffing box of a pump, cooling jackets are used

to control the temperature of fluids passing through a pump.

Coupling: Feature used to connect a pump to its driver. A coupling transfers torque between

the driver and pump.

Cryogenic Pumping: The pumping of liquid gases at a very cold temperature.

Cutwater: Pump casing feature that directs pumped liquids into the pump’s discharge piping.

Cyclone Separator: Device used in seal flush lines, that utilizes centrifugal force to separate

solids out of the fluid.

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D

D.I.N. Standard: German standard used to define various industrial products including pumps.

Deflection: Displacement or movement of a pump shaft in a radial direction.

Design Duty Point: The capacity at a head or pressure of the liquid being pumped.

Dewatering Pump: Pumps designed for removing unwanted water from an area. They are

typically smaller or truly portable pumps capable of running on a small engine, single phase

power or compressed air, but can be larger or permanently installed as well.

Differential Pressure: Sometimes referred to as: Pump Total Differential Pressure, it described

the difference between the outlet pressure and the inlet pressure.

Discharge Head: When the outlet pressure of a pump is converted to head of liquid.

Double Suction Pump: Pump with impellers that allow liquid to enter on both sides.

Double Volute: Type of centrifugal pump that featured two cut waters designed to decrease

radial loads and minimize shaft deflection when a pump is operating away from its B.E.P.

Dredge Pump: Dredge pumps are submersible centrifugal pumps designed to handle high solid

concentration. The material being pumped, soil, sand or dirt is transported away along with the

water it’s suspended in. Dredge pumps are typically employed to clear out or deepen a waterway

or harbor.

Dry Running: A pump operating without liquid in its seal area.

Dual Seal: Pair of seals running in any one of a variety of configurations: in tandem, back to

back, concentric or face to face.

Ductility: Property of metal that allows a great deal of mechanical deformation without cracking.

E

Elastomer: Rubber-like material that returns to its original shape in less than five seconds when

compressed then released.

End Suction Pump: Type of centrifugal pump sometimes known as volute pump.

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E.P.R. or E.P.D.M: Ethylene propylene rubber is a common elastomer used in the sealing of

water based and higher pH materials.

Eye of the Impeller: Center of an impeller, where fluid enters.

Expeller: Hydro-dynamic pump seal that doesn’t need water to the gland.

External Gear Pump: Type of positive displacement pump used for high pressure industrial

transfer and metering applications on clean, filtered, lubricating liquids. Characterized by a

designed within which two spur gears are housed in one close clearance casing. Liquids are

trapped between gear tooth spaces and the pump’s casing, the rotation of the gears pumps the

liquid.

F

Face Combination: Materials chosen for lapped seal faces. Usually carbon graphite running on

silicon carbide.

Face-to-Face Seals: Two seals running against a common seal face. The barrier fluid pressure is

always lower than stuffing box pressure.

Face Lubrication: Vapor or fluid that exists between a lapped mechanical seal face.

Face Pressure: Sum of the loads on a seal face—including the shaft axial thrust, the spring load

and hydraulic load, divided by the area of the seal face.

Flashing: Rapid change in phase transforming a liquid into a gas.

Flooded Suction: This refers to a situation where the liquid level on the suction side of a pump

is higher than the pump centerline and the liquid flows to the pump by gravity.

Fluorocarbon: This is a genetic term for an elastomer of which Viton (a Dupont product) is a

typical example. The material has good compatibility with hydrocarbons, has high temperature

capability but poor mechanical life.

Flush: Putting an outside liquid into the stuffing box of the pump at a pressure higher than

stuffing box pressure. All of this liquid mixes with and dilutes the pumped fluid.

Foot Valve: Check valves with built-in strainers.

Free Length: Uncompressed axial length of a pump seal.

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Friction Head: This is the head loss due to friction as liquid flows in pipes and fittings.

Fugitive Emission: A release into the atmosphere of a federally designated hazardous chemical.

G

Gasket: Device used between two static surfaces to create a seal.

Gland: The part that holds one half of the mechanical seal and attaches to the stuffing box.

Glandless Pump: Another term for a Sealless Pump.

Grease Seal: Spring loaded elastomer used to seal bearings. Often referred to as a "lip seal".

Grinder Pump: Grinder pumps are waste management devices. Waste from water-using

household appliances (i.e. washing machines, toilets or bathtubs) flows through a home’s pipes

into a grinder pump’s holding tank and once the waste in the tank has reached a certain level,

the pump will switch on, grind the waste into slurry and pump it into the central sewer system.

H

Hard Face: Either a rotating or stationary seal face.

Head: Height at which pumps can displace liquids to. Head also refers to a form of energy. In

pumping systems there are four types of head: pressure head, static or elevation head, friction

head loss and velocity head.

Horizontally Split Pump: Pumps with casings split into two sections in the axial plane. Meaning

that there’s a top and bottom-half casing. Connections are typically on the bottom-half casing

so as to allow removal of the top casing for inspection without needing to disconnect pipework.

Hydraulic Balance: Procedure for reducing a mechanical seal’s face loading by reducing the

seal’s face closing area.

I

I.D.: Standard abbreviation of Inside diameter.

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I.S.O.: International Standards Organization that sets seal and pump and seal standards.

Impeller: Rotating component of centrifugal pumps responsible for transferring energy to fluids

being pumped.

Impeller Eye: The center of the impeller or the point where fluid enters the impeller.

Impeller shroud: The plates located on one or both sides of the impeller vanes. Prevents solids

from penetrating behind the vanes.

Impeller Vane: Located between the eye and the discharge side of the impeller. Directs the

flow of the liquid to the outside diameter of the impeller.

Inducer: A small axial flow vane that attaches to the impeller of a centrifugal pump that reduces

the N.P.S.H. required by a pump. This improvement occurs across a narrow capacity range and

the impact can be detrimental outside of this range.

Induction Motor: The most common type used in industry. Has a slippage of 2 to 5 percent

compared to synchronous motors.

Inline Pump: Mounted in the piping generally between two flanges. No base plate or alignment

required.

Internal Gear Pump: Positive displacement pumps that uses two rotating gears that un-mesh at

the suction side of the pump to create a void which allows atmospheric pressure to force fluids

into the pump.

J

Jacket: The heating or cooling jacket that surrounds the stuffing box of certain pumps.

Joule: Metric unit describing the energy required to move one Newton over one meter.

Jet Pump: Jet pumps are residential water supply pumps that do not require priming, they’re

designed to lift water from wells and allow it to function without a check valve on the suction.

K

Kalrez: Elastomer-like material used to seal most solvents and other aggressive fluids.

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Kilowatt: One thousand watts. The normal unit for power in the metric system.

kPa: Metric unit of pressure. 100 kPa = one atmosphere.

K Factor: Factor that provides the “head loss” for fittings.

L

Labyrinth Seal: Non-contacting seal that utilizes a series of pressure drops to reduce leakage.

Lantern Ring: Device that supplies lubricant to packing ring sets.

Line Bearings: Vertical pump feature that positions rotors radially.

Linear Pressure Drop: Straight line pressure drops across a lapped seal face.

Lobe Pump: Lope Pumps are positive displacement pump typically used in food industry related

applications. They’re specifically designed to handle solids without damaging them. Lobe Pumps

are driven by external timing gears as a result the lobes do not make contact. Liquid travels

around the interior of the casing in the pockets between the lobes and the casing, meshing of

the lobes forces liquid through the outlet port under pressure. They also offer continuous and

intermittent reversible flows and can operate dry for brief periods of time. Typical applications

are in following industries: food, pharmaceuticals, paper & pulp, beverages, chemical and

biotechnology.

Low Flow: Condition that can cause excessive heat to build up inside a pump’s volute chamber.

M

Magnetic Drive: Sealless pump that uses magnetic force to rotate the impeller.

Mating Ring: Alternate name for the hard face of a pump’s mechanical seal.

Mechanical Seal: The joint that seals fluid in a pump and stops it from leaking out at the joint

between the casing and the pump’s shaft.

Metal Bellows: Mechanical seal feature that eliminates the need for a dynamic elastomer and

springs.

Metal Fatigue: Metal breakage caused by the bending of a part beyond its endurance limits.

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Metering Pump: Piston or bellows type pumps used for precise introductions of chemicals into

an existing fluid stream, tank or other liquid handling equipment.

Minimum Flow: Minimum capacity of a pump to prevent mechanical or thermal damage.

Multi-Stage Pump: Multi-stage pumps are designed for use with clear, clean, liquids that

require a significant amount of discharge pressure. They are standard centrifugal pumps with

the discharge of the initial volute discharging directly into the suction of the next volute. The

numerous “volutes” are internal to the pump and typically times the individual volutes are hard

to spot individually. The number of stages depends on the desired Total Discharge Head

required for an application.

N

Negative Pressure: A pressure below atmospheric pressure.

Newtonian Fluid: A liquid whose viscosity does not change when agitated.

Non Overloading Power: Term for the maximum power absorbed by a pump with a specific

impeller diameter and liquid. Pump motors are typically sized at the next size above this level.

N.P.S.H.A: Net positive suction head available to check the cavitation of the pump. The head or

specific energy at a pump’s suction flange less the vapor pressure head of the fluid being pumped.

N.P.S.H.R.: Net positive suction head necessary to keep pumps from cavitating.

O

O.D.: Industry standard abbreviation for outside diameter.

O.E.M.: Industry standard abbreviation for original equipment manufacturer.

Operating Length: Measurement set by pump manufacturers to provide the correct closing

pressure on the two mechanical seal faces.

Operating Point: The point (flow rate and total head) at which a particular pump operates.

Over Hung Impeller: Impeller not supported on either side with bearings.

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P

Packing: Soft rings a mechanical seal replaces to stop leakage. Packing must have a small leak

because it works by using a series of pressure drops to reduce the stuffing box pressure to the

point where said leakage is acceptable. Typically, five rings worth of packing is necessary to do this.

Parallel Operation: This refers to two or more pumps that are discharging to a common header.

It is important that the impeller speed and outside diameters are the same or one of the pumps

may cause other pumps to operate at shut off.

P.D. Pump: Positive displacement pump. It can pump a high pressure or head, but at a low volume.

Performance Curve: Plot of Total Head vs. flow for pump models, speed and impeller diameter.

Pipe Strain: The strain on a pump’s volute chamber caused by the piping.

Positive Displacement Pumps: The collective definition of all pumps that operate by displacing

a body of liquid which periodically increases and decreases the working volume.

Power End: The end of a pump that attaches to its power source.

Precision Bearing: Ball or roller bearing as opposed to a sleeve bearing.

Pressure Gradient: The pressure drop between the seal faces.

Priming: Filling a pump with liquid prior to its operation.

Progressive Cavity Pump: Positive displacement pumps used for fluids too tough for a standard

pump to handle (e.g. – sludge, paste or grease). They consist of one driven metal rotor spinning

within an elastomer lined stator.

Propeller Pump: Propeller pumps are similar to impeller pumps, but fluids being pumped are

not spun in a circular path. Instead, they proceed in a more or less straight direction to the

discharge. There, the pump’s motor sits above its discharge shaft. Their propellers can be

placed below the surface of the liquid, where it will always be primed. Propeller pumps are

typically low-speed but low heads.

Q

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Quench: Introducing a fluid outside the seal to cool the product, dilute any leakage across the

seal faces or isolate a seal face from the atmosphere.

Quill Shaft: Hollow shaft that contains another shaft.

R

Radial Bearing: Bearing that handles most of the radial loads put on a pump’s impeller. In an

end-suction centrifugal pump it’s the bearing found closest to the pump’s stuffing box.

Radial Flow Pump: Centrifugal pump designed for medium head and medium flow or high head

and low flow.

Radial Thrust: The thrust a pump produces in the radial direction (i.e. at 90 degrees to the

center of the shaft), by forces acting on the impeller when operating at a point other than BEP.

Radially Split Casing: Pump casing wherein the casing joint is at 90 degrees to the shaft axis.

Rated Operation: The basis of selection of both the pump and the driver. When rated operation

is specified, it typically exceeds the requirement of the design operation.

Recessed Impeller Pump: Recessed impeller pumps are frame-mounted, end suction, back pull-

out, recessed impeller, tangential discharge pumps specifically designed for applications

requiring the pumping of shear sensitive liquids, bulky or fibrous solids or air or gas entrained

liquids.

Ring Section Pumps: Multistage pumps that feature several identical stage casings arranged in

tandem behind each other. The stage casings are radially split.

Run Out: Twice the distance that the center of a pump’s shaft is displaced from its rotational axis.

S

Sanitary Pump: “Sanitary pumps” term for the materials used during a specific pump’s

construction. Describing words include: “Clean in Place,” “FDA Compliant” and “Food Grade”.

Sanitary pumps are normally built from stainless steel, EPDM, PTFE and other “clean” materials.

Saturation Pressure: Another term for vapor pressure.

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Seal Faces: The lapped faces that provide the primary seal in a mechanical seal.

Self-Priming Pump: Pumps capable of handling liquids on a suction lift because they can

remove air from their suction lines of their own accord. Typically self-priming pumps have to be

primed with liquid before their initial start; nevertheless their design means that subsequent

starts will not require priming. Pumps able to self-prime from dry are limited to diaphragm and

peristaltic type positive displacement pumps.

Shaft Packing: Soft packing located in a pump’s stuffing box to provide a shaft seal.

Shaft Power: The mechanical power absorbed at a pump’s shaft.

Shut off Head: The maximum head a pump can generate with a given impeller outside diameter.

Sleeve Bearing: An anti-friction or non-precision bearing.

Slurry Pump: Slurry pumps are particularly heavy duty pumps designed to handle the

aggressive or abrasive slurry situations often found in the mining industry—where pumped

“fluids” can contain particles of various sizes.

Specific Gravity: The ratio of the mass of a liquid for a known volume to the weight of water for

the same volume.

Specific Speed: Specific speed of a pump is determined by the geometry of a pump impeller.

Static Head: The height of a liquid above a reference point e.g. pump centerline.

Stationary Face: The seal face that does not rotate with the shaft.

Stuffing Box: The portion of a pump that held its packing and now holds its mechanical seal.

Stuffing Box Pressure: The pressure in a pump’s stuffing box between suction and discharge

pressure.

Submersible Mixer: Submersible mixers are devices used to mix sludge tanks and other liquid

volumes. They are typically used in sewage treatment plants to keep solids in suspension in the

plant’s various process tanks or sludge holding tanks. Submersible mixers are operated using

electric motors, which are coupled to the device's propeller, either direct-coupled or via a

planetary gear-reducer. The propeller rotates, creating liquid flow in the tank, which in turn

keeps the solids in suspension.

Submersible Pump: A pump with a motor capable of operating only when it is submersed in a

fluid that is being pumped. A submersible pump can be either AOD or centrifugal type pumps.

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The centrifugal versions are typically used in sewage lift stations, whereas AODs are commonly

used for chemical transfer applications.

System Resistance Curve: Graphed representation of how total dynamic head varies with capacity.

System Head: The head caused by friction in a pump’s piping valves and fittings.

T

Tandem Seals: Seals facing in the same direction with a low-pressure barrier fluid circulating

between them.

Throttling: Procedure for closing a valve on a pump’s discharge side to increase loss of friction.

Total Discharge Head: Measurement equal to the pressure at a pump’s discharge connection

converted to head of liquid.

Total Dynamic Head: Measurement equal to total discharge head minus total suction head

Total Suction Head: Measurement equal to the pressure at the pump suction connection

converted to head of liquid.

Two Way Balance: Procedure for balancing a pump’s mechanical seal in two directions.

U

Unbalanced Seal: Mechanical seal that is not designed to balance the closing force between

seals.

V

Variable Speed Motor: Motor used to control flow in a system by varying its frequency.

Velocity Head: The part of the total head calculation calculated from the formula H = v2/2g.

Vertical Turbine Pump: Vertical turbine pumps are multiple stage centrifugal type pumps with

motors set at ground level and connected via a shaft to the pump below. Often used as

irrigation pumps, vertical turbine pumps can also pump from lakes, rivers and other bodies of

water.

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Viscous Drag Pump: Viscous drag pumps have impellers with no vanes. They rely on fluid

contact with a flat rotating plate rotating at high speeds to move liquids.

Volute Casing: This derives its name from a spiral-shaped casing surrounding the pump

impeller. It converts velocity energy to pressure energy.

Vortex Pump: Vortex pumps are used to handle liquids with entrained or stringy solids.

W

Water Power: Calculated power coming out of a pump using the formula WHP = head x gpm/3960.

Wear Ring: This is used with closed impeller pumps to seal leakage from the high-pressure side

of the pump to the low-pressure side. This may need to be replaced as it wears when the

recommended clearance is doubled or when reduction in pump performance can no longer be

tolerated.

Welded Metal Bellows: Seal design used to eliminate the use of elastomers.

Wet End: The portions of a pump that gets wet from pumping liquid.

Y

Yield Point: Where a pump’s metal material passes from the elastic to the plastic range.