Manitowoc Published 10-01-2012, Control # 045-08 4-1
777 SERVICE MANUAL BOOM
4
SECTION 4
BOOM
AUTOMATIC BOOM STOP ADJUSTMENT
Maximum Boom Angle
Boom stop limit switch (2, Figure 4-1) automatically stops the
boom and applies the boom hoist brake when the boom is
raised to Angle A.
Operation
See Figure 4-1 for following description.
When the boom is below the maximum angle, limit switch (2)
is closed and its LED (light-emitting diode) (if equipped) is
ON. The boom hoist can be operated.
When the boom is raised to the maximum angle, actuator (3)
opens limit switch (2) and the LED (if equipped) goes off.
Boom hoist operation stops automatically because the open
limit switch turns off power to the boom hoist electric circuit.
The boom hoist pump shifts to neutral and the holding valves
close to stop boom movement.
Maintenance
At least once weekly, check that the automatic boom stop
stops the boom at the specified maximum angle. If not,
replace any worn or damaged parts and/or adjust the boom
stop.
Once the automatic boom stop is properly adjusted, it should
not require periodic adjustment. Adjustment is required,
however, when:
• The luffing jib is installed or removed.
• Parts are replaced.
WARNING
Falling Attachment Hazard!
If boom fails to stop for any reason, stop engine
immediately. Troubleshoot system to determine problem.
Do not resume operation until problem has been
corrected.
WARNING
Falling Attachment Hazard!
Do not operate crane unless automatic boom stop is
properly adjusted and operational. Do not adjust
maximum operating angle higher than specified. Boom
could be pulled over backwards or collapse, causing
death or serious injury.
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