The cylinder (item 12) is in mechanical stop and the pump (item 1) is driven by the motor (item 2) to the working regime.
The oil instantly accumulates in the cylinder (item 12) and the pressure rises in the circuit.
The pressure exerted under the poppet valve (item 3) is brought back against the pressure on the same poppet valve via the jet (item 5). This back pressure is limited by the opening of the poppet valve (item 6) to 195 bar. A leak calibrated by the jet (item 5) returns to the tank by the poppet valve (item 6). At this moment, the flow of the pump lifts the poppet valve (item 3) under a pressure of 200 bar (195 + 5) and returns to the tank (item 10).
It should be noted that there is a large pressure difference (ΔP) across the pressure relief valve, which causes a rapid heating of the oil.
5- Pressure relief valve adjustment with fixed displacement pump
- Decrease the pressure relief valve.
- Start the pump, engine working speed (max).
- Operate a directional valve to put a cylinder in abutment.
- Tighten the pressure relief valve by checking the setting on the pressure gauge installed at the pump outlet. If the cylinder moves, stop the adjustment and wait for the stop.
6- Adjustment range
It is imperative to make the adjustment of the pressure relief valve with engine full speed for the pump provide the maximum flow of the installation.
Pressure valves have adjustment ranges. The opening pressure varies depending on the flow through them (Figure E). These pressure differences are due to the springs of the valves and vary according to the manufacturers.
Note: The pilot operated pressure relief valve reduces the setting range compared to the direct acting pressure relief valve.
