OPERATION 800D
2-24
Published 5-27-2018 Control # 039-06
HYDRAULIC CAPACITY ALERT SYSTEM
(OPTIONAL)
System Description
The hydraulic capacity alert (HCA) system is a hydraulically
operated, maximum capacity sensing device that will stop all
of the normal crane functions that cause overload when
maximum capacity is exceeded. In the event that an over
capacity condition occurs, the hydraulic capacity alert
system is actuated by sensing excessive pressure in the lift
cylinder which causes the boom down, extend out and hoist
up functions to become inoperative. These are the functions
that increase the over capacity condition. 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 cylinder pressure has been
reduced by bringing the load to a shorter radius or setting the
load down, normal operation can be resumed. This hydraulic
capacity alert system uses the work port unloader solenoids
in the anti-two-block system as the hydraulic system dump
circuit.
The hydraulic capacity alert system has an override switch or
button located on the operator's console that momentarily
overrides the hydraulic capacity alert and anti-two-block
systems and restores power to crane functions. Two
indicator lights located near the override alert the operator of
function power loss and discriminate between the hydraulic
capacity alert and the anti-two-block systems as the cause of
power loss. If crane is equipped with optional audible alert,
an audible alarm will sound in an overload condition. Do not
use the override to continue lifting operations in an
overload or two blocked condition.
The hydraulic capacity alert system provides a load range
gauge at each operator station. This gauge has three colors
on the dial face: (1) Green - OK; (2) Yellow - Caution; and (3)
Red - Overload. The gauge is plumbed directly to the lift
cylinder and the indicator position can be used as an aid in
determining the load condition of the crane. The lift control
lever must be moved from boom up position to the neutral
position to get the most accurate reading when using load
range gauge. Do not use the load range gauge with a jib
or personnel basket.
System Operation
The capacity alert system 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.
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 & Hydraulics Section for
additional description of this system.
On older models, 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
anti-two-block 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.
On newer models, the override key switch and momentary
override button operate independently. The override key
switch (Figure 2-12) overrides the HCA and ATB systems
continuously, restoring power to crane functions so long as
the key in the activated position. The momentary override
button (Figure 2-13) overrides the systems only so long as
the button is depressed.
HYDRAULIC CAPACITY ALERT
ANTI-TWO-BLOCK
OVERRIDE
HOLDING THIS OVERRIDE TO
INCREASE LOADING OR TWO BLOCK
THE CRANE WILL RESULT IN
DEATH OR SERIOUS INJURY
TO CORRECT THE CONDITION CAUSING
THE CRANE SHUTDOWN REFER
TO OWNERS MANUAL
876452
Fo
r
Reference
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