OPERATING CONTROLS AND PROCEDURES OPERATOR MANUAL 500E2
3-10 Published 07-26-2019 Control # 111-06
HCA SYSTEM OPERATION
Once an over-capacity conditions reached, the HCA will not
allow the operator to move the load to a greater radius.
Pressure Sensing Switch
When trip pressure is reached, the pressure sensing switch
breaks electrical continuity to the work port unloader
solenoid in the main control valve.When power is removed
from this solenoid, the unloader valves allow the oil flowing to
hoist up, telescope out and boom down to flow to tank. This
path to tank will prevent further operation of these functions.
When the overload condition is corrected by hoisting down,
retracting the boom, or raising the boom, the pressure
sensing switch allows the work port unloader solenoids to be
powered thereby allowing the crane to function normally.
During the operation at near capacity loads, care must be
taken to operate the controls smoothly or the system may be
shocked into the dump mode prematurely.
Caution should be exercised when operating near 80° of
boom elevation. If the boom lift cylinder is fully extended and
pressurized above trip pressure, the system solenoid will
deactivate and the boom will remain locked at 80°. To correct
this condition, momentarily actuate the override switch and
boom down approximately 5°. Some units may be equipped
with a Manual Reset Valve Option that can be used to unlock
the unit from 80°. See Controls and Hydraulics Section for
additional description of this system.
The override system consists of a key switch and a
momentary push button switch.The key switch provides
power to the momentary push button switch located on the
console.To momentarily override, activate key switch and
depress push button on console. This will activate the work
port unloader solenoid and return power to hoist up,
telescope out, and boom down functions.The override switch
is not to be used during normal use of the crane or as an aid
in using the crane in an overload or anti-two blocked
condition.
The load range gauge is provided to aid the operator when
operating near the rated capacity of the crane. The gauge
only provides accurate indication when the lift control lever is
in neutral. The gauge movement is not proportional to the
load on the hook. It is not unusual for the indicator to be in
the red area at less than rated load condition when operating
the lift control, especially during boom down operation.
JIB LOAD LIMITING DEVICE
System Description
The jib load limiting device is an electro-mechanically
operated, maximum capacity sensing device that stops all
normal crane functions that cause overload when maximum
capacity of the jib is exceeded. In the event that an over
capacity condition occurs, the jib load limiting device is
actuated by sensing excessive force on a load cell which
causes the boom down, extend out, and hoist up functions to
become inoperative. These are the functions that increase
the over capacity condition. On jibs with a manually
extendable section, a configuration switch operated by the
extension retaining pin distinguishes between an extended
jib and a retracted jib. This system allows for continued
operation of the hoist down, boom up, and boom retract
functions, the functions that normally allow the operator to
bring the load to a shorter operating radius or set the load
down in order to eliminate an over capacity condition. Once
the excessive force on the load cell has been reduced by
bringing the load to a shorter radius or setting the load down,
normal operation can be resumed. This system uses the
work port unloader solenoid in the anti-two-block system as
the hydraulic system dump circuit.
The jib load limiting system has an override switch and
button located on the operator’s console that momentarily
overrides the hydraulic capacity alert, the jib load limiting
device, and the anti-two-block system and restores power to
crane functions. Two indicator lights located on the
operator’s console alert the operator of function power loss
and discriminate between the hydraulic capacity alert and
the anti-two-block or jib load limiting systems as the cause of
power loss. In the event of a two-block or jib overload
condition, an audible alarm will sound in addition to the
lighting of the indicator light.
Do not use the override to continue lifting operations in an
overload or two blocked condition.
System Operation
The jib load limiting device will operate as stated in the
System Description Section. Once an over-capacity
condition is reached, the system will not allow the operator to
move the load to a greater radius. The truck may have to be
repositioned closer to the load in order to set the load at the
desired location.
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