China Piston Pump, Piston Pump - Variable Capacity
The hydraulic positive displacement pump is the heart of the hydraulic system. Although the pump does not generate pressure, it does produce flow. It is also true that flow resistance can also cause stress. Anyone who designs or
troubleshoots a hydraulic system must understand this seemingly simple concept. Although the pumps do not create pressure, they must be able to withstand the stresses exerted by the load and other resistance on the hydraulic
system.
The China Piston Pump states that two types of positive displacement pumps are widely used in mobile hydraulic systems: gears and pistons. The gear pump is rugged, low cost, and has a variety of displacement and pressure capabilities, but is only available as a fixed displacement unit. Piston pumps have a wide range of sizes and pressures, are extremely volume efficient, have variable displacement capabilities and a variety of control options. However, piston pumps are much more expensive than gear pumps and are more susceptible to damage and failure due to contamination and cavitation.
Gear pumps are typically rated at approximately 3,000 psi, but some can be as high as 4,500 psi. Piston pumps typically operate at pressures up to 5,000 psi, some ratings well above this value, and some in the 20,000-30,000
psi range. While some piston pumps are sized to pump hundreds of gallons per minute, most gear pumps have a maximum output of approximately 50 gallons per minute or less.
However, one of the most useful features of piston pumps is their ability to variable displacement. This means that controllers such as pressure compensators, flow compensators or load sensing controllers can reduce pump flow when flow demand is small or insufficient. As a result, the hydraulic system can operate more efficiently because less wasted flow when dumping heat and wasted horsepower on the pressure relief valve.
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