Zoomlion ZT20J, Service And Maintenance Manual

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4-4
d) Place a small bucket or bottle in front of the floating cylinder exhaust valve and insert the cleaning
tube.
e) Loosen the exhaust valve and slowly unscrew it counterclockwise. Air is exhausted from the top of
the floating cylinder. Use a small bucket or bottle to catch the hydraulic oil that flows out. Close
and tighten the exhaust valve at the same time.
f) Find the exhaust valve on the opposite side of the floating cylinder and repeat the above steps.
4.2.2 Swing axle lock test
Locking system testing must be performed quarterly when components of the locking system are
replaced or improper system operation conducted.
Note: before starting the floating cylinder test, make sure the boom is fully retracted, lowered and
centered in the middle of the two drive wheels.
a) Place a 3.94 inch /10 cm block with a rising ramp in front of the left front wheel.
b) Start the engine from the working platform controller side.
c) Place the drive lever in the forward position and very carefully climb on the ascending ramp so that
the left front wheel is at the top of the block.
d) Drive the telescopic cylinder very carefully, with the boom extended at least 3.33 feet /1 m.
e) Position the drive lever in the reverse gear position and drive the mechanical device away from the
block and ramp.
f) Ensure that the left front wheel is locked on the ground.
g) Drive the telescopic cylinder very carefully to return the boom to the stowed position. The floating
cylinder should be released and allow the wheel to rely on the ground, and it may be necessary to
activate the system to release the cylinder.
h) Repeat the above steps to operate the right front wheel.
i) If the function of the floating cylinder is abnormal, contact the qualified personnel to correct the
malfunction, then perform other operations.
4.3 Chassis Angle Sensor System
The chassis angle sensor system is used to measure the angle of the turntable relative to the chassis. The
control system reads the sensor reading and compares the reading to a preset turntable angle value.
When the unit is in the stowed position, the equipment can travel at the highest speed, but when the tilt
angle of the turntable is greater than 5 °, the control system limits the travel speed to the low driving
speed mode. When the unit is in the stowed position and the tilt angle of the turntable is greater than 3 °,
the boom function can only be operated in the turtle speed mode. When the device is in the working
position, the travel function is disabled. Therefore, when a safety accident occurs during operation, the
device must be returned to the stowed position to continue driving the device.