Hydraulic pumps have two functions that are performed during operation, allowing pressure to push liquid into the inlet line from the reservoir to the pump through a mechanical effect created at the pump. Another function it performs is the mechanical action of the pump to supply liquid to the pump outlet, which is then forced into the hydraulic system. Positive displacement and non-positive displacement are classified by hydraulic pumps, although most hydraulic systems use positive displacement. Compared with the volume output of the pump, the slippage of the positive displacement pump is smaller. Now, if the output port is blocked, the pressure in the pump will increase, causing the pumping element or its housing to stop working, or the prime mover of the pump may stop, causing the drive shaft not to break. But continuous flow is produced in non-positive displacement pumps because no positive seal is provided to reduce slippage and this results in a change in pressure top, which indirectly or directly results in a variable output. Examples of non-positive displacement pumps are propeller pumps and centrifugal pumps.
The hydraulic pump can work as an oil pump motor unit because it rotates forward and reverse when powered by pressurized fluid. When looking for a hydraulic pump, some specifications need to be considered, such as housing material, operating specifications, etc. When considering operating specifications, there are two important factors, pump type and pump stage. Types of hydraulic pumps include radial pistons, axial pistons and external gears and vanes. An axially mounted piston for an axial piston pump pressurizes the fluid, and the piston moves through the chamber, pressurizing the fluid by mechanical movement from a power source of the pump. Use a port plate or check valve to direct fluid flow from the inlet tube to the outlet or discharge. Another thing to keep in mind is that most axial piston pumps are multi-piston. In radial piston pumps, as the name indicates, the piston is mounted radially with respect to the axis. It is a variant of an axially mounted piston that uses multiple interconnected pistons, usually in a star pattern.