Grove
Published 1-20-2017, Control# 483-02
11-25
CD5515-2/YB5515-2 SERVICE MANUAL
STRUCTURALS
11
Mast Bearing Bolts
Very high stress is put on the mast bolts during crane
operation. It is important that these bolts be checked at
regular intervals.
Check the torque on the bolts after the first week or 50 hours
of operation, whichever occurs first, and then every month or
250 hours of operation, whichever occurs first. Make a
record of any loose bolt. If any bolt does not hold to correct
torque after the second check, remove and replace the bolt.
A loose bolt indicates possible failure of the bolt.
The correct torque on each unplated bolt should be 754 to
816 Nm (556 to 602 lb-ft).
Use the torque sequence shown in Figure 11-20 when
checking the torque on the bolts.
NOTE:
Use only special Class 12.9 unplated bolts for
replacement of the mast bolts. Order the bolts from
your Grove distributor, see your parts manual.
If a broken bolt is found, replace the bolt and also
replace the bolt on each side of the broken bolt.
The proper torque will not be obtained without the
hardened steel washers under the bolt heads on
the outer (mast) bolt circle.
Inspection for Bearing Wear
Because of conservative design parameters, static loading
and slow intermittent rotation, there are very few mast
bearings that ever see their full design use.
However, the mast bearing does have moving internal parts
that are prone to wear if not maintained properly. As the
bearing wears, there will be free-play or movement in the
bearing. Some of the symptoms of mast bearing wear are:
a.
Metal particles in the grease around the seal.
b.
Increased drive power required.
c.
Noisy rotation.
d.
Rough rotation.
If one or more of the above symptoms are present, the
following procedure should be used to test the bearing for
excessive wear.
1.
On a level, hard packed surface, set the machine up on
its outriggers.
2.
With the boom forward, fully extended and in a
horizontal position, place a dial indicator on the swing
gearbox cover and mast as shown in Figure 11-21.
3.
Set the dial indicator to zero.
FIGURE 11-19
p0220
Access Hole
FIGURE 11-20
a0495
Swing Mechanism
Reference Only
