OO-C-2764
smooth, steady controlled rate of speed; and a smooth variable, controlled rate
of speed; dependent on engine speed, without jerking, binding, or slipping the
load. A braking device may be used to assist the power lowering mechanism.
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, when not
in use, so as not to interfere with normal crane operations. When specified
(see 6.2), power load lowering shall be furnished on the primary and secondary
load hoist drums.
3.11.4 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 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 snake gravity lowering (free
spooling) of the boom cable impossible under any circumstance. The boom hoist
clutch shall be of the friction or electromagnetic type, readily accessible for
adjustment and repair, sufficiently large to eliminate slippage under 133.
percent of rated load, and shall be controlled by either mechanical linkage,
air, manual effort applied through hydraulic linkage, or full power hydraulics.
3.11.5 Drums. The drums shall be independently driven, convertible,
suitable for use with any of the different front-end operating equipment, and
shall be arranged so as to reduce eccentric pull to a minimum in order to
prevent chafing of the rope. Pitch diameters of drums or drum laggings shall
comply with the requirements of SAE J881. Unless otherwise specified (see 6.2),
the complete drum assembly and mounting shall be designed for free rotation,
when clutches and brakes are not engaged, to allow gravity lowering of the hook
block. The drum shall be equipped with an adequately constructed socket and a
wedge for dead ending the drum rope. Lubricating fittings or other forms of
lubricating devices shall be provided and so arranged to permit lubrication
without unspooling cable.
3.11.5.1 Drum Lagging. The pitch diameters of the primary or secondary
drums or drum laggings shall be not less than 18 times the largest diameter of
the rope used, and not less than 15 times the largest diameter of rope used for
boom hoist drum, conforming to SAE J881. The drums shall have sufficient rope
capacity to accommodate the boom length specified herein.
3.11.5.2 Drum brakes. Load brakes shall be capable, when properly adjusted,
of holding, without slipping, or lowering the rated loads on recommended
reeving. The brakes shall be capable of being locked in the set position.
3.11.5.3 Drum clutches. Drum clutches shall be of the friction or
electro-magnetic type, capable of withstanding rated speed, continuous operation
without fading, accessible for adjustment and repair, and sufficiently large to
eliminate slippage under 133 percent of rated load with recommended reeving. The
primary and secondary load hoist drums shall be operated by clutches controlled
by levers and shall be designed so that once the clutch is engaged, it shall be
held in place by an over-center lock (knuckle in) on the control linkage; if air
controls are used, the valve lever must be capable of latching in place to hold
the clutches in engagement and be able to perform the power lowering tests
7
For Parts Inquires submit RFQ to Parts Hangar, Inc.
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business