Manitowoc Grove RT770E, Service Maintenance Manual

Page: 82 / 357

HYDRAULIC SYSTEM RT770E
2-42 Published 11/26/2014, Control # 447-05
DUAL ACCUMULATOR CHARGE VALVE
Description
The load sensing dual accumulator charging valve is located
on the inside of the left superstructure side plate. The
purpose of the valve is to provide pressure regulation to the
service brake circuit.
The dual accumulator charge valve consists of a flow divider
spool, cut-in/cut-out spool, check valve and two sequence
valves (see Figure 2-24).
When used with a fixed displacement pump, the flow divider
spool shifts to ensure priority flow to the accumulators until
the cut-out pressure is obtained. The balance of the flow
exits the valve through the auxiliary port (A) to tank. When
used with a LS piston pump, the LS port is connected to the
pump when the accumulator pressure reaches the cut-in
setting [134 bar (1950 psi)]. The pump will deliver the
required charge flow to charge the accumulators. When the
cut-out setting of 160 bar (2320 psi) is reached, the cut-in/
cut-out spool shifts to vent the LS line to tank. The sequence
valves isolate the two accumulators. If one of the
accumulator loses pressure, the other accumulator will
continue to charge and provide flow to the brake circuit when
required.
Maintenance
Removal
1. Tag and disconnect the hydraulic hoses from the valve.
Cap or plug the lines and ports.
2. Remove the three bolts, washers, and lockwashers
securing the valve to the turntable. Remove the valve.
Installation
1. Position the valve on the superstructure with ports A1,
A2, and B3 facing up and secure with three bolts,
washers, and lockwashers. Torque bolts.
2. Connect the hydraulic hoses to the valve ports as tagged
during removal.
3. Start the engine and check for leaks. Make repairs as
needed.
4. Depress the brake pedal several times to cause the
brake valve to charge. Make several turns with the
steering wheel, and swing the superstructure left and
right. Verify the brakes, swing, and front steering work
properly.