The Difference Between Hydraulic Piston Pump and Hydraulic Gear Pump

Hydraulic pumps come in different forms to suit a range of application requirements from industrial molding presses to heavy off-road equipment. One hydraulic system can be very different from another. For one system, a hydraulic piston pump may be the best solution, while a hydraulic gear pump may be better suited for a different system.

1. What is a hydraulic piston pump?

Hydraulic piston pumps are powered by hydraulic drives and employ a reciprocating positive displacement design to manage fluid flow. Cylindrical elements in the piston or cylinder block create a vacuum created by the drive mechanism, which draws in fluid. The cylindrical chamber is pressurized by distributing energy into the fluid, compressing and forcing it towards the outlet of the pump.

The basic design produces about 4,000 psi, but pumps are available for working pressures up to 14,500 psi. There are many different models that can displace a specific amount of fluid. Some allow you to adjust the displacement per revolution, which can make them more energy efficient. Piston pumps are relatively complex and expensive in design, but are useful in energy efficient applications that require high pressure and effective oil flow control.

2. What is a hydraulic gear pump?

A hydraulic gear pump is a lower cost option, but it is very durable and there are many options. Typical pressure ratings are around 3,000 psi, but many displacement sizes and pressures can be found. Some hydraulic gear pumps are rated up to 4,500 psi, although additional valves are required in systems that require regular flow adjustment.

Hydraulic gear pumps work by drawing fluid between their meshing gears. Adjacent gear teeth form cavities enclosed within the housing and pressure plate. A partial vacuum is created at the inlet where the gears disengage, allowing fluid to fill the space and travel along the outer edges of the gears; when the gear teeth mesh again, the fluid is pushed out of the pump.

3. The main difference between hydraulic piston pump and hydraulic gear pump

Both hydraulic piston pumps and hydraulic gear pumps use hydraulic oil to transfer energy or generate mechanical force. Hydraulic piston pumps rely on reciprocating motion. Rotational force is generated along the axis. Fixed and variable displacement pumps are available, as well as different types of pumps including axial, inline, bent axis, plunger and radial pumps, each with their own unique method of propelling fluid.

Hydraulic gear pumps, on the other hand, move fluid through closely aligned gears that create suction to draw in and discharge fluid. Depending on the application requirements, pumps with internal or external gears can be used. Lobe, progressive cavity and vane pumps are just some of the types available. One disadvantage of using gear pumps is the need for additional equipment to control the desired displacement, since they only operate on a fixed displacement.