In a centrifugal pump, mechanical force powers its shaft, and it rotates, turning the impeller with it. The vanes or blades on the impeller impart kinetic energy to the fluid in pump and as the impeller spins, the fluid works its way to the tips of the vanes. The volute increases in size as it extends from the impeller and it gradually reduces the speed of the fluid while increasing its pressure. A discharge opening in the volute channels the fluid out of the pump. Centrifugal pumps are typically constructed of cast iron, aluminum or high grade stainless steel that can withstand harsh conditions or hazardous materials. This kind of pump offers a uniform rate of flow and can accommodate solid and liquid mixtures. At the same time, however, centrifugal pumps cannot function well at high heads, or pressures. Many need to be primed and are prone to becoming air bound, a circumstance in which the pump is too full of air to form a vacuum. If no vacuum forms, then no water will enter the pump.
Centrifugal pumps transport a variety of materials and can be identified by the liquid or gas they handle. Chemical pumps are able to process commercial and industrial abrasives, chemicals and corrosive materials such as bleach, acid, oil, resin and more. Trash pumps are designed to pump hundreds or thousands gallons of water per minute, including water that is polluted with sand, twigs and other debris. Trash pumps are also known as sludge pumps, waste water pumps or sewage pumps, depending on the specific application. In order to impart kinetic energy to thick or viscous material, the impeller has deep vanes and a large volute discharge opening. Water pumps are used in all applications of water transfer, be it commercial, industrial, residential or wastewater. Centrifugal water pumps can be lightweight, general purpose, multipurpose and high-pressure depending on the intended use. Within this category are sump pumps and well pumps. Sump pumps are designed to empty accumulated water from a low-lying surface. They are used for residential and industrial drainage purposes and to prevent flooding. Well pumps are centrifugal pumps that transport water from an underground source to another location inside a building or structure. Depending on the pipe length, the amount of horsepower needed varies; sometimes these pumps are combined with a pressure tank to distribute water to all parts of a building.
Because centrifugal pumps work with a variety of materials, there are different design options that can maximize their usefulness in different situations. Axial flow pumps have a vertical shaft attached to the perpendicular impeller, forcing the liquid upwards by pressure caused by the lifting action of the vanes on the impeller. Jet pumps help enhance the suction ability of an existing centrifugal pump. Submersible pumps are installed underground in a fluid source which is almost always water. They are self-priming pumps because they do not need to remove air from the suction line in order to provide uninterrupted water flow; water is retained and circulated to prevent the pump from becoming air bound. These vertical pumps are usually designed in a close-coupled form where the motor and pump are close to each other so the assembly can be lowered into a drilled well hole. Submersible and vertical pumps are often powered by electricity. The power cord is held safely in a strong and durable casing. Electric pumps are usually hard to service; replacing a battery in an underground pump would be no small feat. Some electric pumps are small and provide minimum power. 12 volt pumps are a quick and low cost way to lift water. The pump diameter for a 12 volt centrifugal pump is often a few inches and the whole assembly can usually be lifted by a single person.
Centrifugal pumps are becoming more powerful and specialized, capable of lifting fluids in the many industries that require it. New technologies and innovations result in new applications and more effective uses. For example, jet pumps are becoming increasingly unnecessary due to the development of submersible pumps. Self-priming pumps are an improvement and help decrease startup time. Hygienic centrifugal pumps are available for situations that necessitate gentle product handling, easy maintenance and a high degree of cleanability. Industrial pumps are now able to deliver head capacities of 500 feet or more in addition to a flow rate of 40,000 gallons per minute. Improvements in filters and suction ability prevent pumps from clogging or slowing down when working with solids in the liquid like in trash pumps. Efficiency is also important; large pumps require massive amounts of power in order for the impeller to rotate at high speeds. Materials also contribute to faster and more efficient pumps. Fluorocarbons and thermoplastics are gaining popularity for seals and parts and the metals already in use are of high grades that resist corrosion, leaking and other forms of damage.
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Centrifugal
Pump and Centrifugal Pump Manufacturers Images Provided by Cortech
Engineering
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Centrifugal Pumps Types
- 12 volt pumps use centrifugal force to increase the pressure of a liquid by converting mechanical energy into rotational kinetic energy.
- are machines that convert mechanical energy into kinetic energy by increasing the pressure of a liquid through centrifugal force.
- are
made of corrosive-resistant materials.
- are directly connected to a power unit but do not have any less gearing
or shafting.
- are self-priming and capable
of handling clear water and water containing small particulate matter
up to .25" in
diameter. Some dewatering pumps are completely submersible and can
operate from any position,
including upside down.
- are a type of radial flow pump in which the fluid enters the impeller
from both sides. Due to the extending of the shaft into the suction
passage, double suction pumps are limited to pumping clear liquids.
- An electric pump is a machine that uses electrical power to increase the pressure of a liquid through centrifugal force.
- is a centrifugal pump that increases water pressure in shallow and deep wells by converting the mechanical energy of an impeller into kinetic energy.
- are designed with wide unblocked passageways and are an intermediate
pump between radial and axial flow pumps. Mixed flow pumps develop
the
pressure partially with centrifugal force and partially with the lift
of the impeller vanes on the liquid.
- ,
which can be either horizontal or vertical, consist of two or more
pumps of similar capacity that discharge into each other in a series.
Progressively
the pumps develop a total head, the sum of the heads that each pump
has developed. A common shaft with several impellers, each with its
own volute, is rotated by a power supply, building up pressure in
stages.
- take in liquid through the center of the impeller and move it out along
the impeller blades at a 90-degree angle to the pump shaft. Radial
flow
pumps develop the pressure only with centrifugal force.
- are centrifugal pumps that retain a small volume of fluid in order to start up without requiring outside attention to clear their passages of air.
- have smaller openings and cannot handle as great of an amount of solids
or large solids as trash pumps can. There is no industry standard
dividing
semi-trash pumps from trash pumps, so both may be referred to simply
as trash pumps.
- are a type of radial flow pump in which the fluid enters the impeller
from one side, and the shaft does not reach into the suction passage.
Single-end suction pumps are used in applications where there are
large
solids, such as rags and trash, that would normally clog the pump.
- are designed to run inside the water source being pumped, eliminating
the suction lift limitations common with other types of pumps. Suction
pumps are ideal for private use, such as in well systems or irrigation.
- are used
to pump water or other fluids from low-laying surfaces.
- are heavy-duty centrifugal pumps that are designed to pump hundreds
or even thousands of gallons of water per minute, which contains
large
solids, such as twigs, sand, mud, soft solids and trash. Trash pumps
have deeper impeller vanes, incorporated with a larger volute discharge
opening, and are used in such applications as construction and agricultural
sites.
- turn the shaft and impeller at two different rpm levels with a two-speed
motor, allowing for optional pump capacity.
- are designed to have only the casing and the impeller submerged in
the pumpage for priming and the support bearings for the rotating
element
in a dry environment. Vertical cantilever pumps have no throttle or
bumper bushings or any rings at the impeller or submerged below the
maximum normal water level, and they are used in applications, such
as a sump or tank, in which it is necessary not to have a bearing
in
the pumpage.
- use centrifugal force to convert mechanical energy into kinetic energy and increase the pressure a liquid as it travel upwards through a pipe.
- are inefficiently designed pumps
in which the impeller is recessed into the volute. However, vortex
pumps are practical in applications
that
require pumping of excessive solids.
- use
an electric motor to move water.
- extract
water from wells.
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Centrifugal Pumps Terms
-
A circumstance in which a centrifugal body is so full of air that a vacuum
can no longer be formed. Without vacuum, water cannot flow into the pump.
- The force
applied by the atmosphere to the surface of the earth. Atmospheric pressure,
the standard of which is 14.7 lbs per square inch, affects the operation
of a pump.
- A term describing
how much water a pump can process. Capacity is typically articulated as
gallons per hour (gph) or gallons per minute (gpm).
- An undesirable
condition in which vacuum pockets form within the pump. The air pockets
eventually implode under pressure, resulting in the pitting of the impeller
and volute surfaces.
- The force
that causes a substance to move away from its center of rotation.
- An apparatus in a discharge or suction line that permits flow
in only one direction so as to prevent reverse flow and isolate the material
being pumped.
- The removal of
unwanted dirty or clear water containing no hazardous materials.
- A stationary casing,
like a volute, that houses the moving impeller. Diffusers are compact
in design, enabling the pump to create higher pressure heads.
- A collapsible
hose that moves the discharged water from the pump.
- Also called
the "outlet," it is the point at which the discharge pipe
or hose is connected to the pump.
- Detachable plugs
for draining water from the pump when it is inactive.
- Acting by motion,
not weight, in contrast to static.
- The head or pressure
force against which the pump operates.
- Also
known as "total suction head," it is the combination of the
static suction lift and the suction friction loss in the suction line.
- Partially or completely
treated wastewater or other liquid that flows out of a septic tank or
treatment unit.
- Rubber molded
around a steel weight that seals off the inlet or outlet, preventing water
from either entering or exiting the pump at the wrong time.
- The required amount
of gallons per minute (gpm) of pump flow. Flow can also be expressed in
gallons per hour (gph) and in million gallons per day (mdg).
- The measure of the pressure
or force exerted by a fluid in a hydraulic system. Also, the height of
fluid above any point, taking into account losses or gains in pressure
due to gravity and friction as water travels through a system, measured
in lbs per square inch (psi) or feet of water.
- A rotating disk with
vanes of varying amounts attached to the "r" drive shaft that
creates centrifugal force within the pump casing of a centrifugal pump.
Impellers can be open or closed.
- The center of
the impeller and the point at which fluid flows into the impeller.
- Pump components
located on the impeller between the eye and the discharge side of the
impeller. Impeller vanes direct the flow of the liquid to the outside
diameter of the impeller.
- The flow, or the rate
of flow, into a pump.
- A device that
forms a seal between the pump and the engine or motor and prevents water
from getting into the engine or motor.
- A measure of the absolute pressure of the liquid at the inlet
of the pump.
- Allowing the pump to
disperse all air from the influent line of a circulating system by causing
fluid to start flowing once again. Priming the pump is usually accomplished
by either manually filing the volute or turning the pump on.
- The body or casing
of a pump, which may be made of plastic, cast-iron, stainless steel or
aluminum.
- Rubber
vibration-dampening devices that are mounted on the engine to prevent
the pump from "walking away."
- Acting by weight not
motion, in contrast to dynamic.
- A plastic
mesh basket that traps debris to prevent its reaching the impeller. Strainer
baskets are located in the strainer pot.
- The housing of
the strainer basket that is located on the influent side of the pump.
Strainer pots serve as a priming chamber.
- A reinforced
hose through which water flows into the suction end of a pump.
- A type
of cavitation resulting from the small size of the impeller or low cutwater
clearance.
- The act of removing air
or gas from a system. Stuffing boxes in vertical pumps must be vented
to prevent the seal faces from running dry.
- The resistance to
flow of a liquid at a particular temperature. High viscosity liquids,
such as motor oil, are thick and tend to flow slower than water, a low
viscosity liquid.
- Stationary casing of
a centrifugal pump that separates air and water and in which the impeller
rotates. Volutes are spiral-shaped in order to facilitate the partial
conversion of the velocity (kinetic) energy into pressure head as the
water leaves the impeller.
- Creates a
"whirlpool effect" that can cause air to be drawn into the
suction of the pump.
- A small opening
located on the underside of the pump at which point the engine joins the
pump. Weep holes provide the means to quick detection of a leak before
water seeps into the oil sump of the engine.
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