Gradall G-550C Operation And Maintenance Manual page 10

G-660C & G-880C GRADALL (Crawler)
SWING, TILT & TOOL VALVES
HOIST, BOOM & TRAVEL VALVES
(Crawler Units)
MAIN CONTROL VALVES
The two main control valves are of the stack type,
where combinations of inlet, circuit, mid-inlet and
outlet sections are bolted together. Where needed,
the main relief valves are located in the inlet sections
or the mid-inlet section. Where needed, the circuit
relief valves are located in the circuit valve section.
SWING, TILT & TOOL VALVE BANK
Oil enters the inlet section and is available for the
swing, tilt and tool valve sections. If the travel is being
used, the 4th valve section (BA) is activated and the
normal dump oil is routed to an inlet port on the
boom control valve. This allows the operator to use
the boom simultaneously with the crawler to help
travel in tough spots.
A. Inlet port.
B. Load check (Not illustrated, but on the
bottom side of each valve).
Dump port
C.
Power beyond passage (to boom valve).
D.
E. Tool circuit relief valves.
F. Main relief valves.
Mid-inlet (From BA valve).
G.
HOIST, BOOM & TRAVEL VALVE BANK
The hoist and R.H. track are fed by one pump section
thru the main inlet section. The boom and L.H. track
valves are fed thru the mid-inlet sections.
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OPERATION & MAINTENANCE