pumps types
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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.