Manitowoc 999 Service And Maintenance Manual

Reference Only
Manitowoc Published 05-16-17, Control # 233-03 1-31
999 SERVICE/MAINTENANCE MANUAL INTRODUCTION
1
FREE FALL MODE (OPTIONAL)
See Figures 1-21, 1-22, and 1-23
The front drum, rear drum or both drums can be equipped
with free fall option. In Standard mode - free fall, left brake/
clutch pedal operates front drum while right brake/clutch
pedal operates rear drum when lowering the load. When
hoisting in free fall, front drum handle or rear drum handle
operates the same as in full power mode.
The PC will not allow a selected drum to be switched to free
fall until following steps are performed:
• Bring selected load drum to complete stop.
• Press down selected drum brake/clutch pedal fully until
latched.
• Turn Crane Mode switch clockwise and hold until Drum
1 FFall (front drum) or Drum 2 FFall (rear drum) appears
on digital display screen.
• Turn crane mode switch counterclockwise to confirm
selected free fall drum.
• Drum FFall On appears on digital display screen and
yellow free fall light is on for selected drum.
The following description is for front load drum while
operating in free fall. Operation of rear drum is the same,
except for different drum, brake, pawl and brake/clutch.
Hydraulic connections between drum pump and motor form
a closed-loop system. Load drum brake (1) and drum pawl
(2) are released with low-pressure side hydraulic fluid. Left
travel charge pump supplies pilot flow to shift drum motor
servo (3). A pressure sender (4) in high-pressure side of
each load drum circuit provides system pressure information
to the PC.
Changing of closed-loop fluid occurs through leakage in
motor and external sequence/flow valve (5). Sequence/flow
valve opens at 200 psi (14 bar) and removes 6 GPM (23 L/
min) of hot fluid from system by dumping fluid in the motor
case.
Drum pump and motor case drains are connected together
and routed to system drum brake/clutch housing. Case drain
cooling fluid enters the center of brake/clutch housing and
exits at top of housing. From brake/clutch-housing outlet the
cooling fluid enters a filter assembly (16) before returning to
tank.
When front load drum rotates, the speed encoder (6) sends
an input signal to the PC. The PC sends an output signal that
enables rotation indicator (7) in on top of control handle. As
drum rotates faster, rotation indicator pulsates faster
indicating rotational speed of drum.
Drum Brake and Pawl Switch
When front drum (8) brake switch is in on - park position,
front drum hoist brake release solenoid HS-16 is disabled so
brake is spring-applied to drum. Front drum pawl in solenoid
HS-19 is enabled and pawl is engaged. Front drum pump
does not stroke in response to control handle (9) or brake/
clutch pedal (10) movement.
When front drum brake switch is placed in off - park position,
front drum brake remains spring-applied to load drum until
the PC releases the brake. The PC sends an output signal to
enable front drum pawl out solenoid HS-20. The pawl is
disengaged from drum. Load drum control handle circuit to
the PC remains open.
Free Fall Brake/Clutch Operation
See Figures 1-21, 1-22, and 1-23
An engine mounted auxiliary fixed displacement, two-output
pump (11) supplies hydraulic fluid at 3,000 psi (207 bar) to
inlet ports of brake/clutch valve manifold (12). Hydraulic fluid
flows through front drum free fall enable solenoid HS-18 of
brake/clutch valve to tank when free fall is disabled.
Hydraulic fluid is returning to tank at 6 gpm (23 L/min).
System pressure is not high enough to release spring-
applied brake/clutch (13).
When solenoid HS-18 is enabled, hydraulic fluid is ported to
front drum brake proportional valve HS-17. HS-17 receives a
variable voltage signal from the PC from brake/clutch pedal.
It uses this variable voltage to control the pressure being
applied to the brake/clutch.
A pressure sender (15) in brake/clutch valve manifold
provides system pressure information to the PC. Free fall
manifold relief valve (14) is set to 3,000 psi (207 bars).
When brake/clutch is spring-applied, the shaft is engaged
with drum planetary gears. In full power, the drum is powered
from the motor shaft through planetary gears to rotate the
drum. Free fall brake/clutch shaft, attached to third planet
gear carrier, does not rotate when raising load.
When springs are hydraulically released, brake/clutch shaft
and planet gear carrier are free to rotate, allowing drum to
free fall. Brake/clutch pedal pressure controls drum speed as
the PC controls releasing spring pressure to friction discs
and outer plates.
NOTE: Brake/clutch pedal can remain applied during full
power mode as brake/clutch pedal is disabled until
the PC selects free fall.

Manitowoc 999 Specifications

General

Brand	Manitowoc
Model	999
Category	Construction Equipment
Language	English