FUNCTIONS AND CONTROLS
TB20J Plus Maintenance Manual 137
© Feb. 2023
The maximum working envelope limit function is essen-
tial for the safe operation of the machine, which may af-
fect the stability of the machine. It is recommended to
check the maximum working envelope limit function
every 3 months or after 250 hours of operation.
NOTICE
If the machine operation cannot be accurately
restricted during the test, please immediately lower
the platform to the stowed position, turn off and mark
the machine, and contact a qualified service
technician for inspection and repair.
Horizontal Reach Restriction
A length sensor is used to measure the boom extension
length and limit the boom from further extending when
the boom length exceeds the maximum horizontal
reach.
0kg＜platform load≤300kg (661lb)
1. Start the machine from the ground controller.
2. Move the main boom luffing switch and the jib boom
luffing switch (if equipped) to adjust the main boom
and jib boom (if equipped) horizontal.
3. Move the main boom telescoping switch to extend
the main boom.
4. When the boom extends to 16.1m (52ft) as shown
on the ground controller display (distance from the
center of the slewing bearing to the outermost side
of the platform), the buzzers in the ground controller
and platform controller should sound, the main
boom cannot extend any more nor lift/descend, but
can be retracted, and the turntable is allowed to
rotate.
5. Move the main boom telescoping switch to fully re-
tract the main boom.
300kg (661lb)＜platform load≤454kg (1000lb)
1. Start the machine from the ground controller.
2. Move the main boom luffing switch and the jib boom
luffing switch (if equipped) to adjust the main boom
and jib boom (if equipped) horizontal.
3. Move the main boom telescoping switch to extend
the main boom.
4. When the boom extends to 14.6m (47ft 11in) as
shown on the ground controller display (distance
from the center of the slewing bearing to the outer-
most side of the platform), the buzzers in the ground
controller and platform controller should sound, the
main boom cannot extend any more nor lift/de-
scend, but can be retracted, and the turntable is al-
lowed to rotate.
5. Move the main boom telescoping switch to fully re-
tract the main boom.
Luffing Angle Restriction
The angle sensor is used to measure the luffing angle of
the boom tube. When the boom is elevated/lowered be-
yond the allowable angle range, the angle sensor will
stop the boom from further elevating/lowering.
1. Start the machine from the ground controller.
2. Move the main boom luffing switch to adjust the
main boom to horizontal position, and move the jib
boom luffing switch (if equipped) to adjust the jib
boom to the highest position.
3. Move the main boom luffing switch to elevate/lower
the main boom.
4. When the main boom is raised to the upper limit of
luffing angle (73°±1° shown on the ground controller
display), the boom should be prevented from further
rising.
5. When the main boom is lowered to the lower limit of
luffing angle (-15°±1° shown on the ground control-
ler display), the boom should be prevented from fur-
ther lowering.
6. Move the boom telescoping switch and main boom
luffing switch to adjust the machine to the stowed
position.
NOTICE
The maximum allowable tolerance of the angle
sensor should not exceed 0.5° in the measurement
range.
10.5 OVERLOAD LIMIT FUNCTION
The rated load capacity of the platform is clearly speci-
fied in the Machine Specifications section of this man-
ual, and if the platform is overloaded, the machine
operation should be limited.
The proper functioning of the overload limit system is
essential for the safe operation of the machine, because
its malfunction may affect the stability of the machine. It
is recommended to check the overload limit function
every 3 months or after 250 hours of operation.
Select flat, level, unobstructed and solid ground to per-
form the following tests with the platform unloaded:
1. Start the machine.
2. Fully raise and lower the boom and retract and ex-
tend the boom twice separately to ensure that the
machine has no obvious shaking and abnormalities,
and is properly lubricated.
3. After lowering the platform to the stowed position,
gradually apply load to the platform according to the
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