I am assuming that you are talking about a closed loop circuit. In a closed loop the pump circulates the oil to the motor (high pressure side) and then back to the pump (low pressure side). The flow can be reversed for forward and reverse as in mobile equipment - (most likely crusher flight drive in your application). The charge pressure relates to the pump (it is a pump that is in tandem with the main pump) and the charge pressure is set to overcome system back pressure from the motor return circuit.

All closed loop circuits will leak oil and require this oil to be replaced. A hot oil flush valve is also normally in the system to dump oil back to tank for cooling purposes. The charge pump will replace that leaked and flushed oil back into the circuit through the return (low pressure side) of the pump / motor circuit. The Charge Pressure is the pressure set on the charge pump relief valve.

The charge pressure is also a great troubleshooting indicator in a closed loop circuit. ie: A low charge pressure reading is usually an indicator of exessive leakage at the pump or the motor. ■

Originally Posted by taiwofatimehin

This term charge pressure also means Feed Pressure or charge line pressure, this is a term used in a closed-loop hydraulic system for the pressure that feeds the closed-loop circuit, since the pumps and actuators are in closed look and can't suck from the tank directly.

The video belows explains how a closed-loop hydraulic circuits works and the function of the charge/feed pressure system.

I don't believe the video you chose is accurate for what is termed a charge pump as there is a separate pump (feed) not connected to the main pump and is showing the low pressure side at close to the high pressure side. This would be very hard on the system to hold it at full system pressure when the feed pump is running and the circulating pump swash plate is in neutral.

In a true charge pressure circuit it only needs to be at the same pressure as the low pressure side to perform correctly. The return oil drain through the case of the main pump and back to the tank. When the swash plate is in neutral the A & B ports of the circulating pump are maintained at the charge pressure and not the full system pressure as shown in your example.

This video explains a charge pressure system on a closed loop.

https://www.youtube.com/watch?v=P1vv0gA6sBs ■