The swing bearing is an anti-friction roller bearing
race contains two grease fittings for lubrication of the
that mates the superstructure to the carrier. The
bearing. The outer race incorporates 156 gear teeth
bearing inner race is bolted to the superstructure and
that mesh with the pinion gear of the swing gearbox
the outer race is bolted to the carrier. The inner
to provide rotation.
Proper identification of bolt grades is important.
When marked as a high strength bolt (grade 8), the
The swing bearing is the most critical maintenance
serviceman must be aware of bolt classifications and
point of the crane. It is here, at the centerline of
that he is installing a high strength heat-treated
rotation, that stresses of loads are concentrated. In
tempered component and the bolt must be installed
addition, the bearing provides the only attachment
according to specifications. Special attention should
between the superstructure and carrier. Therefore,
be given to the existence of lubricant and plating that
proper care of the bearing and periodic maintenance
will cause variation from dry torque values. When a
high strength bolt is removed, or untorqued, the bolt
of the turntable-to-bearing attach bolts - IS A MUST -
must be replaced with a new bolt of the same
to ensure safe and efficient operation.
TORQUING TURNTABLE BOLTS
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
Failure to maintain proper torque of the
loosen in service due to vibration, shock-
turntable bearing attaching bolts will
loads, and temperature changes, there-
result in damage to the crane and
fore, periodic inspection should be
possible injury to personnel.
thereafter, ensuring the bolts are
Maintaining proper torque value for bolts is extremely
important for structural strength, performance, and
KNOW YOUR TORQUE WRENCH! Flexible beam-
cause distortion, binding, or complete separation of
type wrenches, even though they might have a pre-
the superstructure from the carrier.
set feature, must be pulled at right angles and the
force must be applied at the center of the handle.
Force value readings must be made while the tool is
in motion. Rigid handle-type, with torque limiting
Repeated retorquing may cause bolts to
devices that can be pre-set to required values,
stretch. If bolts keep working loose, they
eliminate dial readings and provide more reliable,
must be replaced with new bolts of the
less variable readings.
proper grade and size.