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About Hydraulic Pumps
Hydraulic pumps are extremely basic and capable devices
designed to move liquid by pressure or suction. Hydraulic pumps are used
to transfer energy and are powered by an energy source that initializes
the pump but has no part in the pumping action itself. The kinetic energy
of the fluid is used to force a small part of liquid that is under high
pressure to a reservoir, called the pump outlet, which is at a higher
level. Commonly, a small diameter piston is pushed against an uncompressible
fluid, such as oil. The smaller piston causes the oil to move a second,
larger piston on the opposite side of the system, multiplying the force.
Hydraulic multiplication factors make pumps useful in many applications
that require great strengths, including automobile braking systems, dump
trucks and construction shovels/excavators.
Hydraulic pump manufacturers produce hydraulic pumps in different varieties,
sizes, flow rates and power ratings. If the cylinder of the hydraulic
pumps is expected to constantly raise a heavy weight, a single piston
pump or double-acting pump is appropriate. In applications that initially
have little to no resistance but require high force later on, a two-speed
dual piston pump will suffice. Hydraulic pumps with a 4-way valve are
ideal for applications that call for a double-acting cylinder, which
exerts force in either direction. Hydraulic pump manufacturers may need
to know the weight of the load being lifted by and the piston diameter
of the cylinder, the number of cylinders lifting the load and the travel
length (stroke) of the cylinder, in order to determine the appropriate
type of pump for the application.
Pressure capacities are important factors when purchasing from hydraulic
pump manufacturers. The load is actually what causes the pressure on
the fluid, not the pump itself. The rotary action of the pump simply
moves the fluid, causing flow. Hydraulic pumps pressure rating is determined
by the capability of the pump to withstand pressure without internal
leakage or damage to the pump components. If simple or moderate work
is expected, low- and medium-pressure pumps will do just fine. On the
other hand, if a pump will be used for large construction equipment,
a high pressure system will most likely be necessary.
It is difficult to predict when hydraulic pumps will fail. However, new
diagnostic technology has been developed that claims to do just that.
The discharge pressure of hydraulic pumps is directly measured to accurately
predict failure and the remaining life of the pump. This technology improves
on the common detection methods of using vibration signals, which are
affected by environmental interference, by measuring the ripples on the
surface of the fluid, which are not affected by external sources. By
easily extracting a “feature signal” from the pump discharge
pressure in real time, it is able to predict failure within 50 to 100
hours, which leads to improved safety and significantly reduced or eliminated
downtime. The system can be economically integrated into new or existing
hydraulic pumps without much modification.
Featured
Articles
http://www.maintenanceworld.com/Articles/insider/hydralicPump.htm
http://forms.danfoss.com/journal/prev_articles/98-3-1wh.htm
http://www.insidersecretstohydraulics.com/variable-hydraulic-pump.html
Types of Hydraulic Pumps
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are energy-saving pumps that are operated by a compressed air source
and require no energy to maintain system pressure. In both the single-
and two-stage air hydraulic pumps, air pressure is simply converted
to hydraulic pressure, and they stall when enough pressure is developed.
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have pistons that make the strokes in the same direction along the centerline
of the cylinder block.
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are non-positive displacement pumps that are used in hydraulics requiring
a large volume of flow. Centrifugal pumps operate at fairly low pressures
and are either diffuser or volute types.
- use hydraulic cylinders to provide electric power to machinery.
- are pumps whose output can only be altered by changing
the drive speed.
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are pumps that operate at extremely high pressures. High pressure pumps
operate in the range of 3,000 to 70,000 psi.
- have intermeshing gears that displace fluid, creating mechanical power.
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are manually operated to pressurize a hydraulic system. Hydraulic hand
pumps are often used to calibrate instruments.
- convert hydraulic energy to mechanical power.
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require virtually no maintenance, as they have only two moving parts.
Water from an elevated water source enters one of two chambers through
a relatively long, thick pipe, developing inertia as it moves down to
the second chamber, which starts the pump.
- use hydraulic power to move water from one place to another.
- discharge liquid in a constant flow.
- discharge liquid volumes at separate periods.
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use pistons that are arranged in a design similar to wheel spokes and
are situated in a small cylindrical block.
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depend on reciprocating motion in order to transmit fluid from the inlet
side to the outlet side.
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are a type of positive-displacement pump that use rotational motion
to transfer liquids from the pump inlet to the outlet.
- are pumps in which the clamps and cylinders are
quickly extended by high flow at low pressure in the first stage of
operation. In the second stage, piston pumps build pressure to a preset
level and then maintain that level.
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are composed of two separate pump assemblies that are contained in a
single housing.
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have cylinder sizes that are changeable.
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