• With throttle valve fully open, on strating the motor, entire flow rate of oil will be directed to tank. There is no resistance to flow. Hence pressure reading will be zero.

  • While closing the throttle valve, resistance to flow of oil increases and hence there would be some pressure reading.

    Increasing the throttling would increase the pressure reading.

    On fully closing the valve, very high pressure beyond safe working pressure would cause motor's bimetal over load relay to trip (provided it is set properly).

    If overload relay is set wrongly at higher value, then the weakest path of oil would break. Pipe fitting may leak or brust. If this does not happen, then there would be risk of burning or damage to motor winding.

    Always Relief Valve is provided in the hydraulic circuit. It behaves like overload relay and ensure the pressure build up is limited to the set value on the Relief Valve.

  • With relief valve in the circuit, on fully closing the relief valve, the pressure reading would be equal to the set value on relief valve. I.e. 150 bar.
  • When two relief valves is available as shown in the circuit, then the pressure in the system would be limited to the lowest set value. In this case it would be 80bar.
  • When setting on the relief valve 1 is reduced to 50 bar and on relief valve 2 is set at 80 bar then the pressure reading would be 50 bar.
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