Section 4 – FLY-JIB MOMENT LIMITER CONTROL Mini-Crawler Crane M A E D A
4-168 1/2019 MC405C-3
Items of Moment Limiter
Restriction for Operation
Operation Control by Moment Limiter
Moment limiting is just for emergency.
Operations depending on it may cause hazards
such as auto stop.
Always try to avoid automatic stop of crane
operation.
DANGER! In the case of automatic stop of
crane operation due to over-load, operations
as below are strictly prohibited which may
cause hazards such as tipping of crane or
breakage of boom.
• Boom lowering • Boom extending • Hoist
hook up
Under conditions as below, moment limiter shall
control operations:
(1) Restrict operation under over-load condition.
(2) Working radius restriction by optional control
by an operator.
(3) Restriction by over winding detector.
(4) Restriction of slewing and boom angle range
in pick and carry mode.
(5) Restriction of boom working radius in fly-jib
mode.
All the operators and maintenance technicians
should read this standard manual carefully for
thorough understand before actual operation,
inspection and maintenance.
Restriction in Fly-Jib Mode
In fly-jib mode, practicable working radius is
restricted.
See "Working Radius/Lifting Height for Fly-jib" on
page 3-28.
DANGER!
• Any crane operation under conditions that
moment limiter's load capacity display
indicates 90% or higher must only be
practiced carefully in decelerated mode with
low engine revolutions. If engine is in high
revolutions or crane is operated in
accelerated mode, lifted load may bounce
and exceed its range which may result in
hazards such as tipping of crane or
breakage of the boom.
• In fly-jib mode, main-boom angle is
restricted within safe operation range. Any
operation beyond the range shall result in
boom breakage or crane tipping. Be careful
and confirm the correct angle during crane
operations.
Boom Angle Restriction
Operation range of fly-jib mode is restricted by
main-boom angle, regardless of the extended
length. Keep operation within the range.
[Operation range: 76° to 55°]
Detail of restriction is as specified below:
1. Boom angle 72° to 57° (Safety range)
While main-boom angle is within this range,
indicators below on moment limiter control
panel shall light simultaneously:
• Boom angle upper limit LED (18) (Orange)
• Boom angle lower limit LED (6) (Orange)
This shows normal operating condition.
Fig. 4-503
2. Boom angle 76° to 72° (Pre-warning range
of boom angle upper limit)
While main-boom angle is within this range,
indicator below on moment limiter display
will flash.
• Boom angle upper limit LED (18)
At the same time the warning buzzer beeps
to warn the operator and others that the
boom is reaching its limit. (Boom angle
lower limit LED (6) light flashes.)
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