Then the setting of the compensator of the hydraulic press increased, but the setting of the safety valve did not increase. Once the compensator is set up to approach the safety valve, the safety valve will begin to open and flow the oil into the tank. The more compensators are set, the more the safety valve is opened, and the greater the flow back to the tank. The pressure-compensated pump moves to the full stroke and behaves as a fixed displacement pump rather than changing its flow to meet the needs of the system design. Any flow that is not used to move the load is returned to the tank through a safety valve. When the unit is idling, all pump flow is returned to the tank. Since the pressure drop does not work, most of the energy entering the system is converted into heat.

Changing system pressure is not recommeneded. Most hydraulic presses have a designer's recommendation for system pressure, and a number of design criteria are considered to determine the optimal system pressure. In general, increasing pressure is done to speed up the machine, but this is a very inefficient way to achieve this. The flow rate determines the speed of the actuator, not the system pressure. Yes, increasing the pressure will usually increase the flow, but a more effective way is to turn on the flow control or increase the manual volume adjustment. It is generally recommended to set up a system safety valve of about 250PSI above the pump compensator, and there is no designer's recommendation.