OPERATING CONTROLS AND PROCEDURES MLC90A-1/MLC100-1 OPERATOR MANUAL
3-42
Published 12-10-19, Control # 258-05
5. The load can be lowered in one of two ways — with the
free brake pedal or with hydraulic power.
a. To lower a load with the free fall brake pedal —
leave the drum control handle in off (center) and
slowly release the free fall brake pedal to lower the
load at the desired speed.
When free falling a load, the
corresponding free fall icon will
appear in the Crane Operation Status
Bar of the main display.
As the load nears the desired position, increase foot
pressure on the free fall brake pedal to slow down
the load. Then fully apply the brake to stop the load
and hold it in position.
Alternatively, pull the corresponding drum control
handle back from off to slow down the load. When
the load stops moving, the hoist will automatically
transition to power raising.
Be aware that if the free fall brake pedal is fully
released when the drum control handle is
moved to off, the load will begin to lower
uncontrollably. Be sure to latch down the free
fall brake pedal before moving the drum control
handle to off.
Drum slip and brake pedal response can be
adjusted to meet operator need. See Free Fall Drum
Slip and Pedal Response.
b. To lower a load with hydraulic power — with the
desired free fall brake pedal latched down, push the
corresponding drum control handle forward from off.
The drum brake will release and the load will lower
under hydraulic power at a speed in relation to
handle movement.
As the load nears the desired position, slowly move
the drum control handle toward off to slow down the
load. Then release the drum control handle to off to
stop the load. The drum brake will apply to hold the
load in position.
6. If the load will be suspended for any length of time, latch
down the free fall brake pedal and turn on the drum park
switch.
NOTE The drum brakes will apply and free fall for both
drums will turn off automatically (and have to be
turned back on) if:
• The engine is stopped (or power is lost for any
reason)
• When applicable operating limits are reached
• When applicable system faults occur
• When the drum park switches are moved to the
park position
• The operator gets out of the seat
7. To turn off free fall for the desired drum:
a. Latch down the desired brake pedal.
b. Turn off free fall for the corresponding drum using
the free fall enable switch on the right console (see
page 3-15
) or, on past production cranes, by using
the free fall enable screen in the main display.
The corresponding free fall drum icon will disappear
from the Crane Operation Status Bar of the main
display.
c. Park the drum.
d. Depress the locking pin button, and pull out the
desired locking pin (1A or 2A, Figure 3-13
).
e. Rotate the corresponding free fall selector valve
handle (1B or 2B, Figure 3-13
) to the OFF (O)
position.
f. Reinstall the locking pin (1A or 2A, Figure 3-13
).
Free Fall Drum Slip and Pedal Response
Two free fall adjustments can be made for each drum: drum
slip and pedal response.
To adjust drum slip and pedal response, see the Main
Display Manual.
Drum slip can be adjusted to meet the type of operation
being performed:
• For most operations (such as liftcrane), 100% slip
should be selected so that the load line pays out freely
when a load is lowered with the brake pedal.
• For applications like pile driving, adjust slip so the
hammer follows the pile at the desired rate of speed
(load line pays out automatically without having to use
brake pedal).
The corresponding free fall brake pedal can be applied to
stop the drum regardless of the slip adjustment. Likewise,
the corresponding drum control handle can be pulled back or
WARNING
Falling Load Hazard
When operating in free fall, the load will lower
uncontrolled if the free fall brake pedal is not applied when
the drum handle is released to off (center).
When operating either drum in free fall, do not exceed 150
rpm free fall lowering speed.
Exceeding this limit is not recommended and can result in
accelerated wear and reduced free fall brake life. The
brake could slip allowing the load to lower uncontrolled.
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