Inlets and outlets for the pump are located in a valve in a central hub. An alternative design places inlets and outlets around the perimeter of the pump housing. Radial piston pumps can be purchased as fixed- or variable-displacement models. In the variable-displacement version, the eccentricity of the rotor in the pump housing is altered to decrease or increase the stroke of the pistons.
Rotary vane pumps use a series of rigid vanes, mounted in an eccentric rotor, which sweep along the inside wall of a housing cavity to create smaller volumes, which forces the fluid out through the discharge port. In some designs, the volume of the fluid leaving the pump can be adjusted by changing the rotational axis of the rotor with respect to the pump housing. Zero flow occurs when the rotor and housing axes coincide. External Gear pumps rely on the counter-rotating motion of meshed external spur gears to impart motion to a fluid.
They are generally fixed-displacement designs, very simple and robust. They are commonly found as close-coupled designs where the motor and pump share a common shaft and mounting. Oil travels around the periphery of the pump housing between the teeth of the gears.
This involves the existence of mechanically sealed chambers in the pump. Through these chambers, fluid is transported from the inlet suction port of the pump to the outlet pressure port. The sealed chambers ensure that there is no direct connection between the two ports of the pump. As a result, these pumps are very suitable to operate at high system pressures and are ideal for hydraulics. Hydraulic pumps are manufactured depending on different functional and hydraulic system requirements, such as operating medium, required range of pressure, type of drive, etc.
A large range of design principles and configurations exists behind hydraulic pumps. Consequently, not every pump can fully meet all sets of requirements to an optimum degree. Three different types of hydraulic pumps exist: gear pumps , piston pumps and vane pumps.
Gear pumps have very few moving parts, work smoothly, and operate very well at pressures around bar. Axial pistons are extremely useful for the travel drive and working hydraulics for mobile machines.
Axial pistons have an important components that will change depending on your needs. The pumps can have either a swash plate or a bent axis design. If you have a system that runs at high pressures, you will need to know about radial piston pumps, which are generally made to operate at pressures between and bars.
Inside these pumps, the pistons extend in a radial direction around the drive shaft. They are generally very efficient and have a low noise level. They are often used in presses, machines that process plastics, and machine tools that clamp hydraulics. As the only type of pump that is capable of working at these high pressures, especially at continual operations, radial pumps are an essential part of many hydraulic operations.
Do you need high-quality hydraulic pumps for your system? Are you not sure which pumps will be right for your specific needs? What separates this pump from the traditional gear pump is its built-in pressure relief assembly and an integral three-position, three-way directional control valve. The dump pump is unsuited for continuous-duty applications because of its narrow, internal paths and the subsequent likelihood of excessive heat generation.
With a dump pump, either a two- or three-line installation must be selected two-line and three-line refer to the number of hoses used to plumb the pump ; however, a dump pump can easily be converted from a two- to three-line installation. Many dump bodies can function adequately with a two-line installation if not left operating too long in neutral.
When left operating in neutral for too long however, the most common dump pump failure occurs due to high temperatures. To prevent this failure, a three-line installation can be selected — which also provides additional benefits.
Pumps for refuse equipment include both dry valve and Live Pak pumps. Both conserve fuel while in the OFF mode, but have the ability to provide full flow when work is required. While both have designs based on that of standard gear pumps, the dry valve and Like Pak pumps incorporate additional, special valving. Primarily used on refuse equipment, dry valve pumps are large displacement, front crankshaft-driven pumps.
The dry valve pump encompasses a plunger-type valve in the pump inlet port. As a result, the horsepower draw is lowered, which saves fuel when the hydraulic system is not in use. In the closed position, the dry valve allows just enough oil to pass through to maintain lubrication of the pump. This oil is then returned to the reservoir through a bleed valve and small return line.
A bleed valve that is fully functioning is critical to the life of this type of pump, as pump failure induced by cavitation will result if the bleed valve becomes clogged by contaminates. Muncie Power Products also offer a butterfly-style dry valve, which eliminates the bleed valve requirement and allows for improved system efficiency. Trying to fit a standard gear pump to a dry valve likely will result in premature pump failure.
Live Pak pumps are also primarily used on refuse equipment and are engine crankshaft driven; however, the inlet on a Live Pak pump is not outfitted with a shut-off valve.
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