Boom Lowering Control Valves

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Boom Lowering Control Valves

The boom circuit is equipped with boom lowering control valves (or load control valves), which are attached directly to each of the boom cylinders. The boom lowering control valves contain the following major components: -boom head end line relief

-boom lowering control valve spool -orifice

-manual lower

-piston When the joystick is in the HOLD position, the boom cylinders are held in the raised position. Spring force moves spool 1 up and oil is trapped between the head end of the boom cylinders and spool 1.

The boom lowering control valve keeps the boom cylinder from drifting down.

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When the joystick is moved to the BOOM RAISE position, pump oil flows from main control valve to the boom lowering control valve. The boom lowering spool moves down and pump oil flows to the head end of the boom cylinders, which raises the boom.

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When the joystick is moved to the BOOM LOWER position, pilot oil moves the piston down. When the piston moves down, oil from the bottom of the boom lowering spool is directed to tank and the spool moves up. Oil from the head end of the boom cylinders flows to the tank and the boom lowers.