6-9
Published 10-01-2020 Control # 699-00
GRT9165 SERVICE MANUAL SWING SYSTEM
SWING BEARING
Description
The swing bearing is an anti-friction roller bearing that mates
the superstructure to the carrier. The bearing inner race is
bolted to the superstructure and the outer race is bolted to
the carrier. The inner race contains two grease fittings for
lubrication of the bearing which are hosed to two fittings at
the front of the turntable center section. The outer race also
contains two grease fittings and incorporates gear teeth that
mesh with the pinion gears of the swing gearboxes to
provide rotation.
Maintenance
General
The swing bearing is the most critical maintenance point of
the crane. It is here, at the centerline of rotation, that
stresses of loads are concentrated. In addition, the bearing
provides the only attachment between the superstructure
and carrier. Therefore, proper care of the bearing and
periodic maintenance of the turntable-to-bearing attach bolts
IS A MUST to ensure safe and efficient operation.
Torquing Turntable Bolts
General
Maintaining proper torque value for bolts is extremely
important for structural strength, performance, and reliability
of the crane. Variations in torque can cause distortion,
binding, or complete separation of the superstructure from
the carrier.
Proper identification of bolt grade is important. When marked
as a high strength bolt (grade 8), the serviceman must be
aware of bolt classifications and that he is installing a high
strength heat-treated tempered component and the bolt
must be installed according to specifications. Special
attention should be given to the existence of lubricant and
plating that will cause variation from dry torque values. When
a high strength bolt is removed, or un-torqued, the bolt must
be replaced with a new bolt of the same classification.
Torque the capscrews to recommended values, refer to
Fasteners and Torque Values, page 1-16.
NOTE: Zinc flake coated bearing bolt heads are stamped
with the suffix “ZF” as a visual identifier.
When a high strength bolt is removed, or un-torqued, the bolt
must be replaced with a new bolt of the same classification.
Before performing the following procedure refer to Torque
Wrenches, page 1-16 on the proper use of a torque wrench.
DANGER
Failure to maintain proper torque of turntable bearing
attaching bolts will result in damage to the crane and
possible injury to personnel.
CAUTION
Repeated re-torquing may cause bolts to stretch. If bolts
keep working loose, they must be replaced with new bolts
of the proper grade and size.
DANGER
It is mandatory that bearing attaching bolts be inspected
for lack of torque and retorqued, as required, after the first
300 hours of crane operation. The bolts may loosen in
service due to vibration, shock-loads, and temperature
changes, therefore, periodic inspection should be
accomplished every 500 hours thereafter, ensuring the
bolts are properly torqued.
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