Hydraulic Charge Pump 101: The Basics You Should Know

There is a wide range of closed loop hydraulic applications used in a variety of industries. From large tractors and harvesters to small self-propelled lawn mowers, the one thing these things often have in common is an HST (hydrostatic transmission) with a hydraulic charge pump.

This particular pump is typically a gear-type pump that is used for fixed or positive displacement to charge or feed fluid through the HST system loop. It can either be integrated directly into the HST system or be a separate stand-alone pump that is attached to the HST system.
 

The charge pump provides several key functions for the HST system, including:

• Replace/Replenish Fluid: In closed loop systems, case drain oil from the pumps and motors return to tank and therefore the oil returning to the pump from the motor(s) needs to be topped up so as to prevent pump cavitation and this is the primary function of the charge pump.
• Maintains Back Pressure: HST systems require inlet pressure to be maintained constantly in order for the system to function correctly. Charge pumps do this and can be customized to fit specific inlet pressure PSI levels as needed for your HST system.
• Auxiliary Control Functions: Charge pumps can occasionally be used to provide sufficient power to perform other functions, like operating remote hydraulic servo controls or hydraulic brakes.
• Filtration: Many HST pumps will have a built in filter on the charge pump inlet manifold so that the charge pump pushes the oil through the filter prior to it reaching the main pump. This way all the drain oil is filtered and over time all the oil in the circuit is cleaned.

If you are designing a new HST system or need replacement charge pumps, or other hydraulic parts, pumps, motors, and components, please feel free to contact White House Products Ltd. at +44 (0) 1475 742500 today!