Shop repair procedures
The operations described in this section should be
performed under the cleanest conditions possible. The
repair work, except for bushing replacement, will be
simplified if the work bench is arranged so the mechanism/
head assembly can be inverted (bushings down). No special
tools are required for any of the repair procedures.
Bushings
Bushing maintenance generally consists of a thorough
cleaning and a careful examination for chips, cracks, or
other mechanical damage during the periodic maintenance
inspection. Bushings must be replaced whenever damage is
discovered.
The Type NR oil switch bushings are oil-filled. The special
fixtures and procedures required to assemble these
bushings is beyond the scope of normal shop maintenance
repair. Therefore if a bushing is in any way damaged, the
complete bushing assembly must be replaced. Refer to
Figure 8 and proceed as follows:
1. Disconnect the appropriate bushing lead from the
bottom end of the bushing rod.
2. Remove the three hex head capscrews and bushing
clamps that secure the bushing to the head casting and
lift out the complete bushing assembly.
3. Remove and discard the lower bushing gasket.
4. Twist off the split aluminum ring from the old bushing
and install on the new bushing assembly if ring is in
good condition; replace ring if damaged.
ote:
N
The clamping ring cushions and distributes the
pressure between the porcelain and the clamps. DO
NOT OMIT.
5. Install the new bushing assembly into the head using
a new lower bushing gasket. Position the bushing with
the stud-end of the terminal pointing outward.
6. Position the clamping ring with the split centered
between two clamping bolts.
7. Reassemble the bushing to the head casting. Tighten
the clamping bolts evenly, a little at a time, to a torque
of 3-7 ft-lbs.
ote:
N
Clamping forces must be applied gradually and
equally, in rotation, to each bolt. This results in an
evenly distributed gasket pressure.
8. Reconnect the lead to the bushing rod.
Contacts
The Type NR oil switch has an open-type, double-break
contact arrangement as shown in Figure 6. Depending
upon the extent of damage, the stationary and moving
contacts only, the moving contact and arm assembly, or the
complete contact box assembly may be replaced.
Figure 4. Bushing removal.
Aluminum Clamping
Ring
Bushing
Gasket
Bushing
Clamp
Figure 5. Open-type double-break contact arrangement of
Type NR oil switch.
Stationary
Contacts
Moving Contacts
6
TYPE NR OIL SWITCH MAINTENANCE INSTRUCTIONS
MN230001EN February 2016
