00-C-2821
operation in commercial applications, without overheating or excessive wear.
When specified (see 6.2), the crane shall be equipped with an auxiliary load
hoist drum of adequate size for pile driving or jib boom hoistline operations.
The auxiliary load hoist drum shall be powered either by the power plant or
hydraulic power means and be independent from the boom hoist drum. The
auxiliary drum shall be engaged by a friction type clutch or hydraulic control,
and shall be operable through linkages and control lever from a position within
reach of the operator while seated.
3.7.7 Power load lowering. The primary load hoist and the secondary load
hoist drums shall be equipped with a powered reversing drive, and suitable
control features to provide precision controlled power lowering of loads by the
main hook line and secondary hook line. The drum brakes shall have a safety
device that will automatically set the brake during loss of power. The powered
load-lowering mechanism shall be actuated by a control conveniently located
within the revolving upperstructure engine compartment, and shall be capable of
lowering all rated loads with the manufacturer's recommended reeving. The
powered load-lowering mechanism shall be capable of lowering the loads at a
smooth, steady and variable, controlled rate of speed, without jerking,
bouncing, or slipping the load. Extended use of the powered load-lowering
mechanism shall not result in clutch or brake failure by fading, grabbing,
cracking, internal rupture, breakage, permanent deformation, or any malfunction.
Clutch and brake lining temperatures shall not exceed the maximum recommended by
the manufacturer of the lining. The powered load-lowering mechanism shall be
capable of being disengaged to allow load free-falling, when required, and also
be capable of being disengaged, when not in use, so as not to interfere with
normal crane operations. When specified (see 6.2), both the primary load hoist
and the secondary load hoist shall be equipped with an automatic brake that will
activate when the control lever for either primary or secondary hoist is
returned to neutral. The automatic brake shall include an on-off feature to
permit selection of the automatic brake mode or free-fall mode with manual
brakes.
3.7.8 Boom hoist and Power lowering. The crane boom hoist shall be
power-controlled and shall raise the boom with capacity load. The boom hoist,
equipped with a safety ratchet or other positive holding device, shall safely
suspend the boom with recommended reeving without attention from the operator,
shall provide for power lowering under the operator's control, and shall make
gravity lowering (free spooling) of the boom cable impossible under any
circumstance. The boom hoist and power lowering shall be controlled by a
hydraulic valving system or clutches. The boom hoist clutch shall be of the
friction or electromagnetic type, readily accessible for adjustment and repair,
and sufficiently large to eliminate slippage under 115 percent of rated load.
The hydraulic valving system or clutches shall be controlled by either
mechanical linkage, air, manual effort applied through hydraulic linkage, or by
full power hydraulics.
3.7.9 Controls. All crane controls, lockouts, and indicators shall be
located within easy reach of the operator in the operator's cab, and shall be
readily accessible under all conditions of operations. All controls shall be
clearly marked as to their use and function. When specified (see 6.2), dual
controls located in the upperstructure cab shall be provided to permit the crane
operator to start and stop the carrier engine, operate the carrier brakes,
clutch, steering, shifting the carrier transmission between the neutral,
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