Open-loop: Pump-inlet and motor-return (via the directional valve) are connected to the hydraulic tank.Ore processing plantThe term loop applies to feedback; the more correct term is open versus closed "Artificial sand washercircuit".

Closed-loop: Motor-return is connected directly to the pump-inletChina cement mills. To keep up pressure on the low pressure side, the circuits have a charge pump that supplies cooled and filtered oil to the low pressure sideJaw breakers. Closed-loop circuits are generally used for hydrostatic transmissions in mobile applications.

Advantages: No directional valve and better responseRotary dryers, the circuit can work with higher pressure. The pump swivel angle covers both positive and negative flow directionRotary dryer. Disadvantages: The pump cannot be utilized for any other hydraulic function in an easy way and cooling can be a problem due to limited exchange of oil flow. High power closed loop systems generally must have a 'flush-valve' assembled in the circuit in order to exchange much more flow than the basic leakage flow from the pump and the motorraymond mill, for increased cooling and filtering. The flush valve is normally integrated in the motor housing to get a cooling effect for the oil that is rotating in the motorhousing itself.