Terex Fermec 760, Service Training

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HUSCO UNLOADER VALVE OPERATION
Oil from P2 enters the Valve, flows through the Check Valve & combines with the flow from the Steer Priority
Spool & exits through Port EF to the Loader & Backhoe ControlValveS. A drilling in the Block feeds oil from
EF back to the end of the Unloader Spool, through the orifice in the center of the spool, through the Spring
Chamber to the Relief Valve & Solenoid Valve. When pressure in EF Exceeds 3000 PSI (207 Bar) the Relief
Valve opens & oil begins to flow from EF through the orifice in the Spool through the relief valve to tank.
The pressure drop created across the orifice & acting on the end of the Spool exceeds the force of the Spring,
allowing the Spool to shift, opening P2 to Tank. When pressure in EF falls below the setting of the Relief
Valve, it closes, the flow through the Orifice stops, pressure equalizes at each end of the Spool, the spool is then
shifted to its original position by the spring. Oil from P2 passes through the Check Valve again to
combine with the flow from P1 to give full flow to the Hydraulic Control Valves. Similarly, when the
Solenoid valve is energized the oil flows along the same path, causes pressure drop across the orifice and the
spool shifts across & opens P2 to Tank.
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