Manitowoc National Crane NBT30H-2, Service Manual

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SWING NBT30H-2 SERVICE MANUAL
6-10
03-20-2019 Control # 613-06
Torque Values
Inner Race Torquing
The inner race bearing bolts are located on top of the inner
race (Figure 6-7).
1. Extend and set the outriggers.
2. Fully elevate the boom.
3. Torque all bolts to 80% of the full torque value of 908 Nm
±35 Nm (670 lb-ft ± 26 lb-ft) following a star pattern
sequence as shown in (Figure 6-6) starting with bolt
number 1.
Tools used are the socket, multiplier, backlash adapter,
necessary extensions, and torque wrench.
4. Return to bolt 1 and torque all bolts using the same star
pattern sequence to the final torque of 1213 Nm ±47 Nm
(895 lb-ft ±35 lb-ft). The same tools are used as in
step 3.
Outer Race Torquing
The outer race bearing bolts are located on top of the outer
race (Figure 6-7).
1. Extend and set the outriggers.
2. Fully elevate the boom.
3. Torque all bolts to 80% of the full torque value of 908 Nm
±35 Nm (670 lb-ft ± 26 lb-ft) following star pattern
sequence as shown in (Figure 6-6) starting with bolt
number 1.
Tools used are the socket, multiplier, backlash adapter,
necessary extensions, and torque wrench.
4. Return to bolt 1 and torque all bolts using the same star
pattern sequence to the final torque of 1213 Nm ±47 Nm
(895 lb-ft ±35 lb-ft). The same tools are used as in
step 3.
BEARING CLEARANCE
If a swing bearing exhibits the following symptoms, it may
have reached the end of its useful life.
• metal particles in the grease
• increased drive power required
• noise
• rough operation
• acceleration in the increase in bearing clearance
Measure the internal clearance of the swing bearing to
determine if it needs to be replaced. (Reference National
Crane Technical Support Information TSI #10)
1. Place the boom in the boom rest and set the outriggers.
2. Put a magnetic base dial indicator opposite the boom on
the top of the frame (Figure 6-8).
3. Place the dial on the top of the swing bearing
(Figure 6-8).
4. Power the boom down onto the boom rest.
5. Set the dial indicator at zero.
6. Raise the boom about 3 inches above the boom rest.
7. Record the deflection indicated on the dial.
8. Repeat steps 4 through 7 three times and average the
readings.
9. If the average is greater than 2.3 mm (0.090 in), replace
the bearing.
10. If the average is less than 2.3 mm (0.090 in), repeat the
measurement at every 45° around the total working area
of the crane (Figure 6-9).
a. Measure the deflection at positions 2,3,7, and 8 for
180° rotation and positions 2 and 8 for 360° rotation.
b. Use another crane to support the end of the boom
when the boom is powered down.
c. Locate the dial indicator opposite the boom.
d. Set the dial indicator to zero.
e. Raise the boom about 76 mm (3 in).
f. Record the reading on the dial indicator.
g. Repeat steps d through f three times.
h. Average the readings.
If the average is greater than 2.3 mm (0.090 in) at any
position, replace the bearing.
Top of Swing
Bearing
Top of Frame
FIGURE 6-8
Magnetic Base
Dial Indicator