777 SERVICE MANUAL HYDRAULIC SYSTEM
Manitowoc Published 10-01-2012, Control # 045-08 2-15
2
DISC BRAKE OPERATIONAL TEST
There is no physical way to check the disc brakes for travel,
front and rear drums, and swing. An operational test of each
brake must be performed weekly. Figure 2-14 shows brake
and brake solenoid valve locations.
Operational Test
NOTE: For all pumps except swing, system pressure is
preset at 6,000 psi (413 bar). For swing pump,
system pressure is preset at 5,000 psi (345 bar).
Electrical plugs at brake solenoid valves must be
disconnected to stall crane functions during tests
(Figure 2-15).
1. Start engine and allow it to idle.
2. Select and confirm SETUP mode (faulty pressures will
be recorded in any other mode).
NOTE: For load drums, make sure crane is in full power
mode (free fall OFF). In free fall OFF mode, band
brake will release but disc brake will remain
applied.
3. Disconnect electrical plug for brake being checked
(Figure 2-15).
4. Scroll to corresponding diagnostics screen for brake
being checked. Monitor pump pressure and pump
command while moving control handles.
5. For all functions, move control handle in both directions,
one at a time, to check brake operation in both
directions.
6. Slowly move handle for function being checked.
Specified system pressure must be reached before 50%
pump command is reached and brake must not slip.
7. Reconnect electrical plugs at all brake solenoid valves at
completion of operational test.
FIGURE 2-15
Electrical
Plug
Solenoid Valves Right Side Enclosure
P515a
1 2 3 4
Solenoid Function Description
1 Travel Brake (crawler crane only) Controls two brakes.
2 Rear Drum Brake Controls one or two brakes.
3 Front Drum Brake Controls one or two brakes.
4 Swing Brake Controls one brake.
CAUTION
Overheat Hazard!
Do not hold any function on stall for more than 5 seconds.
Damage to system components may occur.
WARNING
Falling Load/Moving Crane Hazard!
If any disc brake slips when operational test is performed,
repair or replace corresponding brake before placing
crane back into service. Loads could fall or crane could
move if brakes are not operating properly.
For load drums with a disc brake on both ends of drum,
repair or replace both disc brakes.
See planetary manufacturer’s manual for disc brake
repair instructions.
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