# Selection principle of hydraulic pump motor

Update:07 Dec 2021
Summary:1. The selection principle of hydraulic pump motorIndex ①Do you need variables: If you need variables, please choose rad...
1. The selection principle of hydraulic pump motor
Index ①Do you need variables: If you need variables, please choose radial piston pumps, axial piston pumps, and single-acting vane pumps.
Indicator ②Working pressure: Generally speaking, the pressure of the piston pump is 31.5MPa, which is high pressure; the pressure of the vane pump is 6.3MPa, which can reach 16MPa after high pressure, which is medium pressure. The gear pump pressure is 2.5MPa, which is a low pressure, but the highest can reach 21MPa, reaching a medium-to-high level.
Indicator ③Working environment: resistance to pollution sources, among which gear pumps have the best anti-pollution ability, followed by vane pumps, and finally plunger pumps.
Index ④Noise: Low noise is mainly internal gear pumps, double-acting vane pumps and screw pumps. Among them, the instantaneous flow of the double-acting vane pump and the screw pump is uniform, without great pulsation.
Index ⑤Efficiency: The axial piston pump has the highest overall efficiency, followed by the vane pump, and finally the gear pump; pumps with the same structure and large displacement have high overall efficiency. Pumps of the same displacement have the highest total efficiency under rated conditions.
2. Selection of hydraulic pump motor size
After determining the type of hydraulic pump motor, we need to calculate the parameters.
The selection of the hydraulic pump motor is usually based on the performance requirements of the hydraulic pump to select the type of the hydraulic pump, and then determine its specific specifications according to the pressure and flow that the hydraulic pump should guarantee.
The working pressure of the hydraulic pump motor depends on the maximum working pressure of the actuator. Taking into account various pressure losses, the maximum working pressure of pump P can be determined by the following formula:
P pump ≥ K pressure * K cylinder
Among them: P pump is the pressure that the hydraulic pump needs to provide, MPa, K pressure is the pressure loss coefficient in the system, taking 1.3~1.5, P cylinder refers to the maximum working pressure required by the hydraulic cylinder, MPa
The output flow of the hydraulic pump motor depends on the maximum flow and leakage required by the system, that is, Q pump ≥ K flow * Q cylinder