Manitowoc National Crane NBT40 Series, Service Manual

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6
National Crane
Published 8-01-2017 Control # 287-11
6-9
NBT40 SERVICE MANUAL SWING
a high strength bolt is removed, or un-torqued, the bolt must
be replaced with a new bolt of the same classification.
KNOW YOUR TORQUE WRENCH! Flexible beam type
wrenches, even though they might have a pre-set feature,
must be pulled at right angle 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 devices that can be pre-set to required values,
eliminate dial readings and provide more reliable, less
variable readings.
NOTE: If multipliers and/or special tools are used to reach
hard to get at areas, ensure torque readings are
accurate.
Torque wrenches are precision instruments and must be
handled with care. To ensure accuracy, calibrations must be
made on a scheduled basis. Whenever there is a possibility that
a torque wrench may have been either overstressed or
damaged, it should immediately be removed from service until
re-calibrated. When using a torque wrench, any erratic or jerking
motion can result in the application of excessive or improper
torque. ALWAYS use a slow, even movement and STOP when
the predetermined value has been reached.
If it is reported by the crane operator or suspected that the crane
has been overloaded beyond the capacities specified above the
bold line on the cranes’ capacity chart, then all swing bearing
bolts must be inspected for looseness and re-torqued to
specifications.
Torque the swing bearing bolts according to the procedures
outlined in this section.
When using step wrenches, calculated wrench settings are
valid only when the following conditions are met.
1. Torque wrenches must be those specified and forces
must be applied at the handle grip. The use of handle
extensions will change applied torque to the bolt.
2. All handles must be parallel to the step wrench during
final tightening. Multiplier reaction bars may be
misaligned no more than 30 degrees without causing
serious error in torque.
3. Multiplier bar handles must be propped or supported
within the outer 1/4 of the handle length, or serious
under or over tightening will occur.
Swing Bearing Bolts
The inner race of the bearing is secured to the turret by 36, 1
inch
8 bolts (Figure 6-5). The outer race of the bearing is secured to
the carrier frame by 36, 7/8 inch, Grade L9 bolts (Figure 6-5).
Tools Required
A complete set of special tools required to torque the swing
bearing bolts is listed and shown in (Figure 6-4).
Inner Race Torquing
The inner race bolts
(Figure 6-5)
can be accessed through the
access holes underneath the bed (1, Figure 6-6).
1. Extend and set the outriggers. Fully elevate the boom.
2. Torque eight bolts (Figure 6-5) to 470 lb-ft ± 20 lb-ft (637
Nm ±27 Nm) using the following sequence pattern; 1,
19, 10, 28, 6, 23, 15, and 33. Tools used are the socket,
multiplier, backlash adapter, necessary extensions, and
torque wrench.
3. Return to bolt 1 and torque all bolts sequentially in a
clockwise direction to the final torque of 857-929 lb-ft
(1161.9- 1259.6 Nm). The same tools are used as in
step 1.
FIGURE 6-4
Torque Wrench 3/4 inch Drive
3/4 and 7/8 inch
sockets
Extension
Reference Only