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This Page is designed to give a brief introduction to

common types of pumps. It deciphers between the

two types of pumps and some of their

subcategories. It also contains some data on

specific pump types that can be used to choose the

ideal pump for a specific problem.

What is a pump?

A pump is a device that raises or transfers fluids.

Pumps are selected for processes not only to raiseand transfer fluids, but also to meet some other

criteria. This other criteria may be constant flow

rate or constant pressure. 

What kind of pumps are there?

There are two main categories of pumps and they

are dynamic pumps and displacement. These two

categories also have many subcategories of pumps.

What are pumps used for?

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Pumps are used for variety applications . Here is a

list of a few applications :

 Drainage !sed to control the level of water in

a protected area.

 "ewage !sed in the collection and treatment of 

sewage.

 Irrigation !sed to ma#e dry lands

agriculturally productive. $hemical Industry !sed to transport fluids to

and from various sites in the chemical plant.

 Petroleum Industry !sed in every phase of

 petroleum production, transportation, and refining.

 %edical &ield !sed to pump fluids in and out

of the body.

 "teel %ills !sed to transport cooling water.

What are some important factors in

deciding on the right pump?

The selection of the pump class and type for a

certain application is influenced by system

re'uirements, system layout, fluid characteristics,

intended life, energy cost, code re'uirements, and

materials of construction.

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 Positive Displacement Pumps

Positive displacement pumps are another categoryof pumps. Types of positive displacement pumps

are reciprocating, metering, and rotary pumps.

Positive displacement pumps operate by forcing a

fi(ed volume of fluid from the inlet pressure

section of the pump into the discharge )one of the

 pump. These pumps generally tend to be larger thane'ualcapacity dynamic pumps. Positive

displacement pumps fre'uently are used in

hydraulic systems at pressures ranging up to *+++

 psi. A principal advantage of hydraulic power is the

high power density power per unit weight- that

can be achieved. They also provide a fi(ed

displacement per revolution and, within mechanicallimitations, infinite pressure to move fluids.

- Reciprocating Pumps

In a reciprocating pump, a volume of li'uid is

drawn into the cylinder through the suction valve

on the inta#e stro#e and is discharged under positive pressure through the outlet valves on the

discharge stro#e. The discharge from a

reciprocating pump is pulsating and changes

changes only when the speed of the pump is

changed. This is because the inta#e is always a

constant volume.

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ften an air chamber is connected on the discharge

side of the pump to provide a more even flow by

evening out the pressure surges. /eciprocating

 pumps are often used for sludge and slurry.

ne construction style of a reciprocating pump isthe directacting steam pump. These consist of a

steam cylinder end in line with a li'uid cylinder

end, with a straight rod conection between the

steam piston and the pump piston or plunger. These

 pistons are double acting which means that each

side pumps on every stro#e.

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Another construction style is the power pump

which convert rotary motion to low speed

reciprocating motion using a speed reducing gear.

The power pump can be either single or double

acting. A singleacting design discharges li'uid

only on one side of the piston or plunger. nly one

suction and one discharge stro#e per revolution of

the cran#shaft can occur.

The doubleacting design ta#es suction anddischarges on both sides of the piston resulting in

two suctions and discharges per cran#shaft

revolution. Power pumps are generally very

efficient and can develop high pressures. These

 pumps do however tend to be e(pensive.

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- Metering Pumps

%etering pumps provide precision control of very

low flow rates. &low rates are generally less than012 gallon per minute. They are usually used to

control additives to the main flow stream. They are

also called proportioning or controlledvolume

 pumps. %etering pumps are available in either a

diaphragm or pac#ed plunger style, and are

designed for clean service and dirty li'uid caneasily clog the valves and no))le connections. 

  Rotary Pumps

A rotary pump traps fluid in its closed casing and

discharges a smooth flow. They can handle almost

any li'uid that does not contain hard and abrasive

solids, including viscous li'uids. They are also

simple in design and efficient in handling flow

conditions that are usually considered to low for

economic application of centrifuges. Types of

rotary pumps include camandpiston, internal

gear, lobular, screw, and vane pumps. 3ear pumps

are found in home heating systems in which the burners are fired by oil

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/otary pumps find wide use for viscous li'uids.

4hen pumping highly viscous fluids, rotary pumps

must be operated at reduced speeds because at

higher speeds the li'uid cannot flow into the casingfast enough to fill it. !nli#e a centrifugal pump, the

rotary design will deliver a capacity that is not

greatly affected by

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Disadvantages 

• !sually re'uires

moderate speeds.

• %edium pressurelimitations.

• ne bearing runs in the

 product pumped.

• verhung load on shaft

 bearing.

Advantages 

• nly two moving parts.

• nly one stuffing bo(.

• Positive suction,nonpulsating discharge.

• Ideal for highviscosity

li'uids.

• $onstant and even

discharge regardless of

 pressure conditions.• perates well in either

direction.

• $an be made to operate

with one direction of

flow with either rotation.

• 5ow 6P"H re'uired.

• "ingle ad7ustable endclearance.

• 8asy to maintain.

• &le(ible design offers

application

customi)ation.

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 pressure variations on either the suction or

discharge ends. In services where large changes in

 pressure are anticipated, the rotary design should be considered.

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Dynamic Pumps

Dynamic pumps are one category of pumps under

which there are several classes, two of which are:

centrifugal and a(ial. These pumps operate bydeveloping a high li'uid velocity and converting

the velocity to pressure in a diffusing flow passage.

Dynamic pumps usually have lower efficiencies

than positive displacement pumps, but also have

lower maintenance re'uirements. Dynamic pumps

are also able to operate at fairly high speeds and

high fluid flow rates.

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Centrifugal Pumps

A centrifugal pump consists of an impeller and aninta#e at its center. These are arranged so that when

the impeller rotates, li'uid is discharged by

centrifugal force into a casing surounding the

impeller. The casing is there in order to gradually

decrease the velocity of the fluid which leaves the

impeller at a high velocity. This velocity is converted

to pressure which is needed to

discharge the fluid.

"ome of the advantages of

cenrtifugal pumps are, smooth

flow through the pump and uniform pressure in the

discharge pipe, low costand an operating speed that

allows for direct connection to steam turbines and

electric motor. The centrifugal pump accounts for

not less then 9+ of the worlds pump production

 because it is more suitable for handling largecapacities of li'uids than the positivedisplacement

 pump.

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Axial lo! Pumps

A(ial flow pumps are also called propeller pump.

These pumps develop most of their pressure by the propelling or lifting action of the vanes on the

li'uid. These pumps are often used in wetpit

drainage, lowpressure irrigation, and stormwater

applications. In general, vertical singlestage a(ial

and mi(edflow pumps are used however,

sometimes twostage a(ialflow pumps areeconomically more practical. Hori)ontal a(ialflow

 pumps are used for pumping large volumes against

low pressures and usually employ siphonic action.

4hen higher pressures are involved, these pumps

can be arranged to operate with siphonic action

until the bac# pressure places the hydraulic

gradient above the pump.