Eaton Cooper Power NR Series Maintenance Instructions Manual

Contents

Shop repair proceduresThe operations described in this section should beperformed under the cleanest conditions possible. Therepair work, except for bushing replacement, will besimplified if the work bench is arranged so the mechanism/head assembly can be inverted (bushings down). No specialtools are required for any of the repair procedures.BushingsBushing maintenance generally consists of a thoroughcleaning and a careful examination for chips, cracks, orother mechanical damage during the periodic maintenanceinspection. Bushings must be replaced whenever damage isdiscovered.The Type NR oil switch bushings are oil-filled. The specialfixtures and procedures required to assemble thesebushings is beyond the scope of normal shop maintenancerepair. Therefore if a bushing is in any way damaged, thecomplete bushing assembly must be replaced. Refer toFigure 8 and proceed as follows:1. Disconnect the appropriate bushing lead from thebottom end of the bushing rod.2. Remove the three hex head capscrews and bushingclamps that secure the bushing to the head casting andlift out the complete bushing assembly.3. Remove and discard the lower bushing gasket.4. Twist off the split aluminum ring from the old bushingand install on the new bushing assembly if ring is ingood condition; replace ring if damaged.ote:N The clamping ring cushions and distributes thepressure between the porcelain and the clamps. DONOT OMIT.5. Install the new bushing assembly into the head usinga new lower bushing gasket. Position the bushing withthe stud-end of the terminal pointing outward.6. Position the clamping ring with the split centeredbetween two clamping bolts.7. Reassemble the bushing to the head casting. Tightenthe clamping bolts evenly, a little at a time, to a torqueof 3-7 ft-lbs.ote:N Clamping forces must be applied gradually andequally, in rotation, to each bolt. This results in anevenly distributed gasket pressure.8. Reconnect the lead to the bushing rod.ContactsThe Type NR oil switch has an open-type, double-breakcontact arrangement as shown in Figure 6. Dependingupon the extent of damage, the stationary and movingcontacts only, the moving contact and arm assembly, or thecomplete contact box assembly may be replaced.Figure 4. Bushing removal.Aluminum ClampingRingBushingGasketBushingClampFigure 5. Open-type double-break contact arrangement ofType NR oil switch.StationaryContactsMoving Contacts6TYPE NR OIL SWITCH MAINTENANCE INSTRUCTIONS MN230001EN February 2016