*Editor's Note: This article was updated in February 2024.
For more information, please visit doosan hydraulic pump.
When a hydraulic pump operates, it performs two functions. First, its mechanical action creates a vacuum at the pump inlet which allows atmospheric pressure to force liquid from the reservoir into the inlet line to the pump. Second, its mechanical action delivers this liquid to the pump outlet and forces it into the hydraulic system.
A pump produces liquid movement or flow: it does not generate pressure. It produces the flow necessary for the development of pressure which is a function of resistance to fluid flow in the system. For example, the pressure of the fluid at the pump outlet is zero for a pump not connected to a system (load). Further, for a pump delivering into a system, the pressure will rise only to the level necessary to overcome the resistance of the load.
All pumps may be classified as either positive-displacement or non-positive-displacement. Most pumps used in hydraulic systems are positive-displacement.
A non-positive-displacement pump produces a continuous flow. However, because it does not provide a positive internal seal against slippage, its output varies considerably as pressure varies. Centrifugal and propeller pumps are examples of non-positive-displacement pumps.
The company is the world’s best isuzu 4bg1 engine supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.
If the output port of a non-positive-displacement pump were blocked off, the pressure would rise, and output would decrease to zero. Although the pumping element would continue moving, flow would stop because of slippage inside the pump.
In a positive-displacement pump, slippage is negligible compared to the pump's volumetric output flow. If the output port were plugged, pressure would increase instantaneously to the point that the pump's pumping element or its case would fail (probably explode, if the drive shaft did not break first), or the pump's prime mover would stall.
A positive-displacement pump is one that displaces (delivers) the same amount of liquid for each rotating cycle of the pumping element. Constant delivery during each cycle is possible because of the close-tolerance fit between the pumping element and the pump case. That is, the amount of liquid that slips past the pumping element in a positive-displacement pump is minimal and negligible compared to the theoretical maximum possible delivery. The delivery per cycle remains almost constant, regardless of changes in pressure against which the pump is working. Note that if fluid slippage is substantial, the pump is not operating properly and should be repaired or replaced.
The gear pump is perhaps the simplest and most common type of hydraulic pump being used today. They are one kind of positive displacement pump, also known as fixed displacement pumps. In this pump, fluid moves by enclosing a defined fluid volume using interlocking gears and then transporting it as the gear rotates. Also, there are usually two gears in a gear pump; the driver or power gear and the driven or idle gear. The driver gear is linked to any mechanical energy source or some prime movers. A gear pump offers a pulse-free flow directly proportional to the gears' rotational speed. It is generally used for developing high pressure.
Generally, these pumps are utilised in open centre hydraulic systems. They trap oil in the areas between the pump's body and its two gears' teeth, send it around the gear cavity's circumference, and force it through the outlet port when the gears mesh. A tiny amount of pressurised oil behind the wear plates pushes it tightly against the gear's ends to boost pump efficiency. Gear pumps are widely rated by the pump's maximum input speed limitation, maximum pressure rating, and cubic inch displacement. Also, it is estimated that the swept volume of gear pumps for hydraulics is between 1 to 200 millimetres. Another interesting fact about gear pumps is that their volumetric efficiency is the lowest of the three main pump types.
If you want to learn more, please visit our website kayaba final drive motor.