SYSTEM / Hydraulic System COUNTERWEIGHT REMOVAL / INSTALLATION CIRCUIT (OPTIONAL) 1. When the counterweight hoist/lower control lever (optional) is operated, pressure oil from the pilot pump flows through the counterweight pilot valve and shifts the auxiliary spool in the 5-spool con- trol valve to remove/install the counterweight. 2. Pressure oil from main pump 2 flows into the counterweight removal / installation cylinder through the auxiliary spool from the neutral circuit in 5-spool control valve. 3. When hoisting the counterweight, pressure oil flows into the cylinder bottom through the check valves in holding valve and slow return valve. 4.
When lowering the counterweight, pressure oil is divided into two directions. One flows to the cyl- inder rod side. Another flows to the holding valve. 5. The holding valve is opened by pressure in the rod side and flows return oil from the bottom side. 6. Return oil flow from the cylinder bottom is regu- lated by the slow return valve. 7. Return oil flows to the hydraulic oil tank through the holding valve. NOTE: During counterweight removal and installa- tion operation, flow rates of pumps 1, 2 are minimum.
(Refer to the Pump Control dur- ing Counterweight Removal and Installa- tion in Control System group / SYSTEM.) Holding Valve Pilot Shut-off Valve Lowering Operation Counterweight Removal Cylinder Auxiliary Slow Return Valve T1J1-02-04-011 Main Pump 2 T2-4-24