(1) Main relief valve
(2) Signal limiter relief valve
The load sensing signal limits the maximum system pressure. When the load sensing signal pressure is increased, the system pressure increases.
The relief valve for the load sensing signal controls the maximum load sensing pressure that is sent to the pump controls. During normal operation, the relief valve for the load sensing signal limits the load sensing signal pressure to a maximum of 31000 ± 500 kPa (4500 ± 75 psi).
When the load sensing signal pressure is greater than the pressure setting of the relief valve for the load sensing signal, the poppet is moved upward against the spring force. Load sensing signal pressure flows to the tank.
When heavy lift is activated, the solenoid valve for heavy lift on the pilot manifold is energized., Pilot hydraulic oil is sent to the top of the relief valve for the load sensing signal.
Pilot hydraulic oil pushes the spool in the downward direction, which compresses the spring in the relief valve for the load sensing signal. The maximum load sensing signal pressure is increased to 35500 to 36000 kPa (5150 to 5220 psi).
To adjust the maximum load sensing pressure, turn the adjustment nut inward or turn the adjustment nut outward.