UPS 120, UPS 150, UPS 250, UPS 300, UPS 301, UPS 500, UPS 600, UPS 750 and UPS 900 Uninterruptible Power Supplies Caterpillar

Replacement of the Bearing for the Flywheel

The bearings for the flywheel on the UPS must be changed due to wear and vibration. Consult the Operation and Maintenance Manual for the appropriate maintenance interval for replacing the bearings on your product.

There are several indications of bearing wear. Replace any bearing with indications of wear.

• Vibration

• Temperature

• Increase in operational noise level

Note: Bearings are always changed as a top and a bottom set. The bottom bearing is changed first. The top bearing is changed second.

Prior to Beginning

The flywheel cabinet must be at the following specifications:

• Off-line

• De-energized

• Flywheel at zero RPM

You will need to have the appropriate replacement parts and tools in order to change the bearing.

Required Tools

Illustration 1	g01280654
(1) Comm/Accel assembly screw (2) Comm/Accel PWA (3) Comm/Accel O-Ring (4) Rotor retaining bolt (5) Bearing bolt (6) Toothed rotor wheel (7) SAE hex plug (8) Upper bearing cartridge (9) Shim pack (10) Black O-Ring (11) SAE hex plug (12) Flywheel housing (13) SAE hex plug (14) Black O-Ring (15) Shim pack (16) Lower bearing cartridge (17) Rotor retainer (18) Polished rotor retaining bolt (19) Load cell (20) Load cell bolt

Bearing service is always performed on both the upper and lower bearings.

Note: Change the lower bearings first.

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When servicing or repairing electric power generation equipment: Make sure the unit is either locked out or tagged DO NOT OPERATE. Remove all fuses. Make sure the generator engine is stopped. Make sure all batteries are disconnected. Make sure all capacitors are discharged. Make sure residual voltage in the rotor, stator and the generator is discharged. Failure to do so could result in personal injury or death.

The following steps must be done before performing maintenance on internal components.

Shut down all inputs to the MMU cabinet. The customer will have an unprotected load.

1. Use "Control-X" in "UPSView" to apply the brake if the flywheel is not at zero rpm.

2. Place the key switch to the MMU cabinet into the BYPASS position.

3. With the flywheel rpm at zero, put the UPS in MAINTENANCE BYPASS, if available. If the maintenance bypass is unavailable, then the UPS must be shut down. Follow the appropriate shutdown or the appropriate bypass procedure for the system configuration.

   Refer to Systems Operation, Testing and Adjusting, RENR9988, "SMS System Shutdown" in order to find the appropriate shutdown or the appropriate bypass procedure.

   Refer to Systems Operation, Testing and Adjusting, RENR9988, "MMS System Shutdown" in order to find the appropriate shutdown or the appropriate bypass procedure.

4. Discharge the DC bus. Allow the DC bus to purge below 24 VDC.

5. Open the doors of the cabinet by using a hex key on the upper and lower latches.

6. Discharge the capacitors. Allow the capacitor banks in the UPS to purge for 5 minutes.

7. Remove the frame rail (49) from the lower cabinet.

   The lower frame rail is held on by 14 bolts. Refer to Illustration 2.

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   Illustration 2	g01270504
   Bolts for the lower frame rail (21) Bolt (49) Lower frame rail

8. Remove the metal cover over the upper bearing of the flywheel.

9. Refer to section "Determine the Configuration of the Lower Bearing" in order to determine the type of lower bearings that are being removed.

Determine the Configuration of the Lower Bearing

There are three different procedures for the lower bearings. The procedure that follows is determined by the type of bearings in the system.

The lower bearings are the following types:

• Hall effect probe system bearings

• Load cell type 1 bearings

• Load cell type G3 bearings

Read the following sections in order to determine the type of lower bearing. Follow the installation and the removal instructions in the appropriate section.

Hall Effect Probe System Lower Bearings

The Hall Effect sensor can be upgraded to the load cell sensor with new bearings. Refer to Systems Operation, Testing and Adjusting, "Attachments" for information in upgrade kits.

The system uses Hall Effect probes to determine the weight of the flywheel on the lower bearings.

The Hall Effect probes do not contain a load cell that is attached to the lower bearing. The center of the lower bearing is flush with the outer edge of the lower bearing.

The center of the bearing contains four socket head bolts and the outer edge contains eight socket head bolts.

Note: Hall Effect probe bearings are typically found in hardware prior to version 2.4.

Refer to Illustration 3 for a drawing of a Hall effect probe lower bearing.

Removal and Installation

Follow the instructions in section "Hall Effect Probe System Lower Bearing Removal and Installation".

Hall Effect Probe System Lower Bearing Removal and Installation

Illustration 3	g01280942
Hall Effect probe system lower bearing (22) Outer bolts (23) Inner bolts (24) Center flush with edge

Illustration 4	g01270607
Hall Effect probe system lower bearing components. (14) Black O-Ring (15) Shim pack (16) Lower bearing cartridge (17) Rotor retainer (18) Polished rotor retaining bolt (22) Outer bolts (23) Inner bolts (25) Static drain O-Ring (26) Static drain

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Illustration 5	g01270616
Removing plugs. (13) SAE hex plug

1. Remove the three 1 inch SAE hex plugs (13).

   Note: If only two SAE hex plugs (13) are present, the ball valve assembly is installed. Caterpillar recommends replacing the ball valve assembly with a third 1 inch SAE hex plug (13).

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   Illustration 6	g01270622
   Shims for the rotor (47) Rotor shims

2. Insert the three shims (47) for the rotor into the three openings on the bottom of the flywheel case.

   Note: The short tabs of the three shims (47) for the rotor must face outward from the center of the flywheel. Make sure that the tabs rest on the pole ring inside the flywheel case.

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   Illustration 7	g01270627
   Shims for the rotor in place (cutaway view) (47) Rotor shims

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   Illustration 8	g01270631
   Inserting shims for the rotor (13) SAE hex plug (47) Rotor shims

3. Disconnect the cables that are attached to the bottom of the flywheel housing. The cables lead to the board of the flywheel.

   The parts that the cables lead to are the following parts: bearing thermistor, flywheel connector and vacuum cable.

   Note: Do not disturb the post of the armature or the connections to the field coil.

4. Remove the static drain (26) assembly by removing the four 6/32 inch socket cap bolts (23), using a 7/64 inch Allen wrench.

5. Remove the polished 3/8 inch lower retaining bolt (18) and the lower retainer with a 9/16 inch socket.

6. Verify the placement of all four of the shims for the rotor. Some movement may have occurred.
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   Illustration 9	g01270634
   Placement of the feeler gauge (48) Feeler gauge

7. Take measurements with the four feeler gauges (48) between the edge of the bearing cartridge (16) and the flywheel case at 90 degree increments.

8. Record the measurements for reference later.

9. Remove the eight 5/16 inch socket cap bolts (22) from the bearing cartridge (16) with a 1/4 inch Allen wrench. Remove the bolts in a star pattern. Turn the bolts a 1/4 turn until the bolts are loose.
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   Illustration 10	g01270651
   Bearing puller (28) Center bolt (45) Bolt

10. Install the bearing puller onto the bearing cartridge (16) with the two Allen head bolts (45).
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    Illustration 11	g01270652
    Bearing puller and shims in place (28) Center bolt (45) Bolt (47) Rotor shim

11. Install the two guide pins (46) into two opposing bolt holes in the bearing.
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    Illustration 12	g01270657
    Guide pins (46) Guide pins

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    Illustration 13	g01270660
    Bearing puller and guide pins in place (28) Center bolt (45) Bolt (46) Guide pins (47) Rotor shim

12. Carefully turn the center bolt (28) of the bearing puller by hand until the center bolt (28) contacts the journal of the rotor.

13. Turn the center bolt (28) in order to extract the lower bearing cartridge (16).

    Note: Take care to stop the bearing from falling when the bearing comes free.

14. Remove the brass shims from the bearing.

    Note: Make sure that the shims for the bearing are removed from the flywheel housing. Feel with your finger in order to be sure.

15. Measure the brass shim pack (15) thickness with a vernier caliper. Record the results for reference. Verify that the caliper is accurate to .001 inch. Measure the shims individually. Measure the shims as a group.
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    Illustration 14	g01270673
    Measuring shim pack thickness

16. Remove the bearing puller from the bearing cartridge (16).

17. Record the height of the bearing that is stamped on the face of the bearing.
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    Illustration 15	g01270678
    Bearing height in inches

18. Compare this height to the height on the original bearing face.

19. If the new height is less than the original height, subtract the difference from the original shim pack (15). If the new height is greater than the original height, then add the difference to the original shim pack (15).

    Adjust the thickness of the shim pack (15) according to the results. The adjustment ensures that the rotor rests in the correct position. Refer to the following examples.

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    Table 2

    Example 1
    New height of the bearing	1.997
    The previous height of the bearing	1.995
    Difference	.002
    Add .002 to shim pack
    Example 2
    New height of the bearing	2.029
    The previous height of the bearing	2.032
    Difference	.003
    Subtract .003 from shim pack

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    Illustration 16	g01270716
    Install the new O-ring for the bearing. (14) Black O-ring

20. Remove the O-ring (14). Lubricate the O-ring (14). Reinstall the new O-ring (14) with high vacuum grease.

21. Insert the new bearing with the required number of shims that were determined in steps 15 through 19.

22. Install the bearing installer.
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    Illustration 17	g01270724
    Bearing Installer (28) Center bolt (29) Washer (30) Outer nut (31) Spacer (32) Threaded shaft

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    Illustration 18	g01270727
    Bearing installer in bearing cartridge (30) Outer nut (32) Threaded shaft

23. Tighten the 3/8 inch center bolt (28) for the bearing installer with a 9/16 inch socket.

24. Hand tighten the outer nut (30) on the bearing installer.

25. Use an 11/16 inch open-end wrench to tighten the outer nut (30). Use an 1 1/2 inch open-end wrench to hold the center bolt (28), until the bearing seats completely on the journal of the rotor.

26. Insert the bolts and start threading the eight 5/16 inch socket cap bolts (22). Thread the bolts loosely.

27. Insert the four feeler gauges (48) in the locations that were defined in Step 7.

    Note: If a feeler gauge (48) does not go back into place, tighten the opposing bolt. Reinsert the gauge. Loosen the bolt when the feeler gauge (48) is installed.

28. Remove the two guide pins (46).

29. Remove the bearing installer.

30. Tighten socket cap bolts (22) to 27 N·m (20 lb ft) in a star pattern.

31. Clean the threads of the bottom retainer bolts.

    Note: If the bolt head shows wear, replace the bolt. A smooth surface is important for proper operation.

32. Place a single drop of Loctite 232 Low Strength Retaining Compound onto the threads of the bottom retainer bolt.

33. Insert the 3/8 inch bottom retainer bolt with the bottom retainer lip toward the journal of the rotor.

34. Tighten the bottom retainer bolt with a 9/16 inch socket.

35. Tighten the bolt to 38 N·m (28 lb ft).

36. Remove the O-ring (25) for the static drain (26). Lubricate the O-ring (25) for the static drain (26). Install the new O-ring (25) for the static drain (26). Measure the static drain (26). Adjust the static drain (26). Install the static drain (26) with four bolts (23).

    Follow the procedure in Systems Operations, Testing and Adjusting, RENR9988, "Static Drain Install Procedure" in order to measure the static drain and adjust the static drain.

37. Remove the feeler gauges (48).

38. Remove the three shims (47) of the rotor.

39. Apply new grease to the outer side of 1 inch O-ring. Do not remove the O-rings from the plugs.

40. Install the three 1 inch plugs (13).

41. Reconnect any cables that were disconnected.

    Changing the Lower Bearing is complete. Refer to "Determine Upper Bearing Configuration" to determine the procedure for the upper bearing replacement.

Load Cell Type 1 Lower Bearings

Type 1 load cell systems use load cells to determine the weight of the flywheel on the lower bearings.

The load cell systems contain a load cell that is attached to the lower bearing. The load cell is raised with respect to the lower bearing.

The center of the bearing contains six socket head bolts and the outer edge contains eight socket head bolts.

There is a notch on one side of the load cell.

Type 1 load cells are typically found in hardware systems 2.4 and above.

Refer to Illustration 19 for a drawing of a Hall Effect Probe lower bearing.

Removal and Installation

Follow the instructions in section "Load Cell Type 1 Lower Bearing Removal and Installation".

Load Cell Type 1 Lower Bearing Removal and Installation

Illustration 19	g01271783
Type 1 load cell lower bearing (22) Outer bolts (23) Inner bolts (33) Center bolt (34) Notch

Illustration 20	g01281144
(14) Black O-Ring (15) Shim pack (16) Lower bearing cartridge (17) Rotor retainer (18) Polished rotor retaining bolt (19) Load cell (20) Load cell bolt (22) Outer bolts (23) Inner bolts (26) Static drain (35) Mounting bolt for static drain (36) Mounting washer for static drain (37) Load plate (38) Load cell shim

1. Remove the three 1 inch SAE hex plugs (13).
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   Illustration 21	g01270616
   Removing plugs. (13) SAE hex plug

   Note: If only two SAE hex plugs (13) are present, the ball valve assembly is installed. Caterpillar recommends replacing the ball valve assembly with a third 1 inch SAE hex plug (13).

2. Insert the three shims (47) for the rotor into the three openings on the bottom of the flywheel case.

   Note: When the shims (47) are inserted into the casing for the rotor, the short tabs of the three shims for the rotor must face outward from the center of the flywheel. Make sure that the tabs rest on the pole ring inside the flywheel case.

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   Illustration 22	g01270622
   Shims for rotor (47) Rotor shims

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   Illustration 23	g01270627
   Shim for the rotor in place (cutaway view) (47) Rotor shims

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   Illustration 24	g01270631
   Inserting shims for the rotor (13) SAE hex plug (47) Rotor shims

3. Disconnect the cables that are attached to the bottom of the flywheel housing. The cables lead to the board of the flywheel.

   The cables connect to the following parts: bearing thermistor, flywheel connector and vacuum cable.

   Note: Do not disturb the post of the armature or the connections to the field coil.

4. Remove the six socket cap bolts (20) that connect the load cell (19) to the bottom bearing with the 1/4 inch Allen wrench.

   Note: Do not remove the two recessed bolts on opposing sides of the load cell (19).

   Note: Remove the bolts slowly and remove the bolts evenly. Remove the bolts in a crisscross pattern. Make sure that the movement of the load cell (19) stays vertical. Make sure that the load cell (19) will not bind in the housing.

5. Remove the load cell (19) from the bottom bearing.

6. Remove the polished 3/8 inch lower retaining bolt (18) and the lower retainer using the 9/16 inch socket.

7. Take measurements with the four feeler gauges (48) between the edge of the bearing cartridge and the flywheel case at 90° increments.
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   Illustration 25	g01270634
   Placement of feeler gauge (48) Feeler gauge

8. Record the measurements for reference later.

9. Remove the remaining two 5/16 inch socket cap bolts from the bearing cartridge with a 1/4 inch Allen wrench.
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   Illustration 26	g01270651
   Bearing puller (28) Center bolt (45) Bolt

10. Install the bearing puller onto the bearing cartridge with the two Allen head bolts (45).
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    Illustration 27	g01270652
    Bearing puller and shims in place (28) Center bolt (45) Bolt (47) Rotor shim

11. Install the two guide pins (46) into two opposing bolt holes in the bearing.
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    Illustration 28	g01270657
    Guide pins (46) Guide pins

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    Illustration 29	g01270660
    Bearing puller and guide pins in place (28) Center bolt (45) Bolt (46) Guide pins (47) Rotor shim

12. Carefully turn the center bolt (28) of the bearing puller by hand until the center bolt (28) contacts the journal of the rotor.

13. Turn the center bolt (28) in order to extract the lower bearing cartridge (16).

    Note: Take care to stop the bearing from falling when the bearing comes free.

14. Remove the brass bearing shims from the bearing.

    Note: Make sure that no shims for the bearing remain in the flywheel housing. Feel with your finger in order to be sure.

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    Illustration 30	g01270673
    Measuring shim pack thickness

15. Measure the brass shim pack thickness with a vernier caliper. The measurement should be accurate to 0.02540 mm (0.001 inch). Record data for reference. Measure the shims individually. Measure the shims as a group.

16. Remove the bearing puller from the bearing cartridge (16).

17. Record the height of the bearing that is stamped on the face of the bearing.
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    Illustration 31	g01270678
    Bearing height (in.)

18. Compare this height to the height on the original bearing face.

19. If the height of the new bearing is less than the height of the original bearing, subtract the difference from the original shim pack.

20. If the height of the new bearing is greater than the height of the original bearing, add the difference to the original shim pack (15).

    Adjust the thickness of the shim pack (15) according to the results. The adjustment ensures that the rotor rests in the correct position. Refer to the following examples.

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    Table 3

    Example 1:
    New bearing height:	1.997
    Old bearing height:	1.995
    Difference:	.002
    Add .002 to shim pack
    Example 2:
    New bearing height:	2.029
    Old bearing height:	2.032
    Difference:	.003
    Subtract .003 from shim pack

    Note: For the procedure on measuring shim pack, refer to "Hall Effect Probe System Lower Bearing Removal and Installation" Step 17.

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    Illustration 32	g01270716
    Install new bearing O-Ring (14) Black O-ring

21. Remove the O-ring (14). Lubricate the O-ring (14). Reinstall the new O-ring (14) with high vacuum grease.

22. Insert the new bearing with the required number of shims that were determined in Steps 15 through 20.

23. Install the bearing installer.
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    Illustration 33	g01270724
    Bearing Installer (28) Center bolt (29) Washer (30) Outer nut (31) Spacer (32) Threaded shaft

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    Illustration 34	g01270727
    Bearing installer in bearing cartridge. (30) Outer nut (32) Threaded shaft

24. Tighten the 3/8 inch bearing installer center bolt (28) with a 9/16 inch socket.

25. Hand tighten the bearing installer outer nut (30).

26. With an 11/16 inch open-end wrench, tighten the outer nut (30) with a 1 1/2 inch open-end wrench until the bearing seats completely on the journal of the rotor.

27. Insert the two 5/16 inch socket cap bolts. Start threading two 5/16 inch socket cap bolts in opposing bearing bolt holes. The socket cap bolts should be threaded loosely.

28. Insert the four feeler gauges (48) in the locations that were defined in step 10.

29. Remove the two guide pins (46).

30. Remove the bearing installer.

31. Tighten socket cap bolts to 27 N·m (20 lb ft) in a star pattern.

32. Clean the bolt threads for the bottom retainer.

    Note: If the bolt head shows wear, replace the bolt. A smooth surface is very important for proper operation.

33. Place a single drop of Loctite 232 Low Strength Retaining Compound onto the threads of the bottom retainer bolt.

34. Insert the 3/8 inch bottom retainer bolt with the bottom retainer lip toward the journal of the rotor.

35. Tighten the bottom retainer bolt with a 9/16 inch socket.

36. Tighten the bolt to 38 N·m (28 lb ft).

37. Install the yellow cable for the bearing thermistor.

38. Verify the static discharge drain (26) angle on the load cell with an angle block. If the angle does not match the block, adjust the angle of the static drain.

    Follow the procedure in Systems Operation, Testing and Adjusting, RENR9988, "Static Drain Install Procedure" to measure the static drain and adjust the static drain.

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    Illustration 35	g01270895
    Static discharge drain angle block

39. Remove the O-ring (14). Lubricate the O-ring (14). Install the new O-ring (14) for the new load cell (19).

40. Insert the load cell (19). Attach the load cell with six 5/16 inch hex head bolts (20).

41. Tighten with a 1/2 inch socket wrench.

42. Tighten the socket cap bolts to 27 N·m (20 lb ft) in a star pattern.
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    Illustration 36	g01270959
    Bottom bearing in place

43. Remove the feeler gauges (48).

44. Remove the three shims (47) from the rotor.

45. Apply new grease to the outer side of the 1 inch plug O-rings. Do not remove the O-rings from the plugs.

46. Install the three 1 inch plugs.

47. Reconnect any cables that were disconnected.

    The lower bearing change is complete. Refer to section "Determine Upper Bearing Configuration" in order to determine the procedure for the upper bearing replacement.

Load Cell Type G3 Lower Bearings

Load Cell Type G3 systems use newer style Load Cells to determine the weight of the flywheel on the lower bearings.

The load cell systems contain a load cell attached to the lower bearing. The G3 load cell covers the entire lower bearing.

There are six socket head bolts (22) and two empty holes around the outer edge of the load cell (39) and the bearing assembly.

G3 load cells are typically found in hardware systems 3.0 and above.

Refer to Illustration 37 for a drawing of a G3 Load Cell lower bearing.

Removal and Installation

Follow the instructions in section "Load Cell Type G3 Lower Bearing Removal and Installation".

Load Cell Type G3 Lower Bearing Removal and Installation

Illustration 37	g01270904
Load cell type G3 system lower bearing components. (22) Outer bolts (39) Load cell (covers entire bearing)

Illustration 38	g01281309
(14) Black O-Ring (15) Shim pack (16) Lower bearing cartridge (17) Rotor retainer (18) Polished rotor retaining bolt (19) Load cell (20) Load cell bolt (22) Outer bolts (26) Static drain (35) Mounting bolt for static drain (36) Mounting Washer for static drain (37) Load plate

For removal and installation instructions, refer to "Hall Effect Probe System Lower Bearing Removal and Installation". Follow steps 1 through 47.

Refer to "Determine Upper Bearing Configuration" to determine the procedure for the upper bearing replacement.

Determine Upper Bearing Configuration

There are two different procedures for the upper bearing. The procedure that follows is determined by the type of remote position sensor RPS assembly that is installed in the system.

The RPS assembly types are the following types:

• Magnetic RPS assembly

• Optical RPS assembly

Read through the following sections to determine the type of RPS assembly that is being dealt with. Follow the upper bearing removal and installation methods that are referenced in the appropriate section.

Magnetic RPS Assembly

Magnetic RPS Assemblies use a magnetic pickup to determine the position of the rotor.

The magnetic sensor has the following parts:

• Upper PWA

• Hex head bolt

• Metal two-piece rotor wheel and spacer

Refer to Illustration 39 for a drawing of a Hall Effect probe lower bearing.

Follow the instructions in section "Magnetic RPS Assembly Upper Bearing Removal and Installation".

Magnetic RPS Assembly Upper Bearing Removal and Installation

Illustration 39	g01271262
Magnetic RPS system upper bearing components (4) Rotor retaining bolt (5) Bearing bolt (10) Black O-Ring (15) Shim pack (38) RPS sensor screw (39) RPS sensor (40) RPS sensor O-Ring (41) Rotor (42) Rotor spacer (43) Upper bearing cartridge

Illustration 40	g01281686
(41) Rotor (42) Rotor spacer

Repeat step 1 through 33 in section "Load Cell Type 1 Lower Bearings"

1. Install the hex head 3/8 inch upper retainer bolt (4). Install the rotor wheel (41) and the spacer (42) using a 9/16 inch socket.

2. Tighten the upper retainer bolt (4) 38 N-m (to 28 lb-ft).

3. Reconnect any cables that were disconnected earlier.

4. Check continuity from the upper retainer bolt to the casting of the flywheel. There should be less than 5 ohms between the two.

5. Verify that the proper gap is between the magnetic pickup and the rotor wheel. Refer to Systems Operation, Testing and Adjusting, RENR9988, "Hall Probe Flywheel Telemetry Calibration Procedure".
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   NOTICE
   Always use an electrostatic discharge wrist strap when handling the RPS.

6. Use the three screws (38) to install the RPS.

7. Connect the following parts: flywheel connector, upper bearing thermistor and sensor ribbon cable.

8. Refer to section "Bearings Change Post-Removal Steps".

Optical RPS Assembly Upper Bearing Removal and Installation

Optical RPS systems use an optical method to determine the position of the rotor.

The optical sensor has the following parts:

• Upper PWA with a fiber optic cable

• Socket head bolt

• Plastic one-piece rotor wheel

Refer to Illustration 41 for a drawing of an Optical RPS Sensor.

Illustration 41	g01271287
Optical RPS assembly (4) Rotor retaining bolt (39) RPS sensor (44) Rotor wheel

Follow the instructions in section "Optical RPS Assembly Upper Bearing Removal and Installation".

Optical RPS Assembly Upper Bearing Removal and Installation

Illustration 42	g01271283
Optical RPS system upper bearing components (4) Rotor retaining bolt (5) Bearing bolt (10) Black O-Ring (15) Shim pack (38) RPS sensor screw (39) RPS sensor (40) RPS sensor O-Ring (43) Upper bearing cartridge (44) Rotor wheel

Illustration 43	g01281714
(44) Rotor wheel

1. Disconnect the following parts: thermistor for the upper bearing, the RPS sensor ribbon cable and the upper flywheel connector.

2. While wearing an electrostatic discharge wrist strap, remove the three 6X32 inch socket cap bolts (38) holding the optical RPS sensor in place using a 7/64 inch Allen wrench.

3. Lift straight up on the RPS sensor (39) in order to remove the sensor.

   Note: Be careful to not drop any screws in the flywheel.

4. Place the sensor in an environment that is free of static.

5. Remove the 3/8 inch socket cap bolts (4) for the rotor retainer with an Allen wrench.

6. Remove the rotor wheel (44).

7. With the four feeler gauges (47), take measurements between the upper bearing cartridge (43) and the casting of the flywheel at 90° increments.

8. Record each measurement.

9. Remove the feeler gauges.

10. Remove the eight 5/16 inch bearing cartridge socket cap bolts (5) with a 1/4 inch Allen wrench. To tighten the socket cap bolts (5), turn the socket cap bolts a 1/4 turn, in a star pattern.

11. Install the bearing puller onto the bearing cartridge (43).
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    Illustration 44	g01271268
    Bearing puller and guide pins installed (28) Center bolt (45) Bolt (46) Guide pin

12. Install the two guide pins (46) in two opposing bolt holes of the bearing.

13. Turn the center bolt (28) of the bearing puller by hand. Turn the bolt until contact with the journal of the rotor is made.

14. Turn the center bolt (28) in order to extract the upper bearing cartridge (43) with a 1 1/2 inch open-end wrench.

15. Remove the brass bearing shims from the bearing.

    Note: Make sure that no shims for the bearing remain in the flywheel housing. Feel with your finger in order to be sure.

16. Measure the brass shim pack thickness with a vernier caliper. The measurement should be accurate to .001 inch. Record data for reference. The shims must be measured individually. The shims must be measured as a group.
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    Illustration 45	g01270673
    Measuring shim pack thickness

17. Remove the bearing puller from the bearing cartridge.
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    Illustration 46	g01270678
    Bearing height in inches

18. Record the height of the bearing that is stamped into the face of the new bearing cartridge.

19. Compare this height to the height on the original bearing face.

20. If the new height is less than the original height, subtract the difference from the original shim pack.

21. If the new height is greater than the original height, then add the difference to the original shim pack.

    Adjust the thickness of the shim pack according to the results. The adjustment ensures that the rotor rests in the correct position. Refer to the following examples.

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    Table 4

    Example 1:
    New bearing height:	1.997
    Old bearing height:	1.995
    Difference:	.002
    Add .002 to shim pack
    Example 2:
    New bearing height:	2.029
    Old bearing height:	2.032
    Difference	.003
    Subtract .003 from shim pack

22. Remove the O-ring (10). Lubricate the O-ring (10). Install the new O-ring (10).

23. Insert the new bearing with the required number of shims (15).

    Note: For the required number of shims, refer to Table 4.

24. Install the bearing installer. Refer to "Load Cell Type G3 Lower Bearing Removal and Installation" step 22, Illustration 33.

25. Tighten the 3/8 inch center bolt (28) of the bearing installer with a 9/16 inch socket.

26. Hand tighten the outer nut (30) of the bearing installer.

27. Insert the four feeler gauges (47).

28. Hold the threaded shaft (32) with an 11/16 inch open-end wrench. Tighten the outer nut (30) with a 1 1/2 inch open-end wrench until the bearing seats completely.

29. Remove the bearing installer.

30. Remove the two guide pins (46).

31. Insert the eight 5/16 inch socket cap bolts for the bearing.

32. With a torque wrench, tighten the eight socket cap bolts in a star pattern to 27 N·m (20 lb ft).

33. Remove the feeler gauges (47).

34. Clean the bolt threads of the upper retainer.

    Note: If the bolt head shows wear, replace the bolt. A smooth surface is very important for proper operation.

35. Place a single drop of Loctite 232 Low Strength Retaining Compound onto the threads of the bottom retainer bolt.

36. Install the 3/8 inch socket cap bolts for the upper retainer and rotor wheel using a 5/16 inch Allen wrench.

37. Tighten the upper retainer bolt (4) to 38 N-m (28 lb-ft ).

38. Reconnect any cables that were disconnected earlier.

39. Check continuity from the upper retainer bolt to the casting of the flywheel. There should be less than 5 ohms between the two.

40. Install the RPS sensor (39) with three screws (38). Refer to Systems Operation, Testing and Adjusting, RENR9988, "Rotor Position Sensor (RPS) Assembly" for more information.
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    NOTICE
    Always use an electrostatic discharge wrist strap when handling the RPS Sensor.

41. Connect the following parts: flywheel connector, upper bearing thermistor and sensor ribbon cable.

42. Go to the section "Bearings Change Post-Removal Steps".

Bearings Change Post-Removal Steps

Perform the Hall Effect probe or the load cell procedure, depending on the system configuration.

Hall Effect Probe System

1. Replace the metal shield over the flywheel upper bearing.

2. Replace the frame rail for the bottom cabinet.
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   Illustration 47	g01271376
   Reattach the lower rail bolt. (21) Bolt (49) Lower frame rail

3. Close and Lock the doors of the cabinet by using a hex key on the upper and lower latches.

4. Put the UPS into on-line mode via UPSView.

5. Calibrate the vibration sensor zeroes in accordance with the calibration procedure Systems Operation, Testing and Adjusting, RENR9988, "Vibration Sensors Calibration".

   Note: The calibration pertains only to firmware prior to 3.22.

6. Calibrate " RPS Advance" set point. Use the procedure Systems Operation, Testing and Adjusting, RENR9988, "RPS Advance Setpoint Calibration".

7. Turn the key switch of the MMU cabinet to the ON-LINE position.

   The change for the bearing is complete.

Load Cell Systems

1. Replace the metal shield over the upper bearing for the flywheel.

2. Replace the frame rail (49) of the bottom cabinet.

   Only four bolts need to be reattached. Refer to Illustration 47.

3. Close and lock the doors of the cabinet by using a hex key on the upper and lower latches.

4. With UPSView, update the installation date of the bearings in the UPS firmware for each flywheel bearing that was replaced.

   "Op. Params > Op. Group 8: > Bearing Install Day"

   "Op. Params > Op. Group 8: > Bearing Install Month"

   "Op. Params > Op. Group 8: > Bearing Install Year"

5. Put the UPS into on-line mode via UPSView.

6. Enter the value for the "Load Cell Offset" in the "Op. Params > Op. Group 7: > Load Cell Offset" menu in UPSView.

7. Enter the value for the "Load Cell Calibration Factor" into the "Op. Params > Op. Group 7: > Load Cell Cal. Factor" menu in UPSView.

8. Enter the value for the "Load Cell Serial Number" into the "Op. Params > Op. Group 13: > Load Cell Serial Num." menu in UPSView.

9. Calibrate the "Vibration Sensor Zeroes" in accordance with the calibration procedure Systems Operation, Testing and Adjusting, RENR9988, "Vibration Sensors Calibration".

   Note: This calibration pertains only to firmware prior to 3.22.

10. Calibrate RPS Advance setpoint. Use the procedure Systems Operation, Testing and Adjusting, RENR9988, "RPS Advance Setpoint Calibration".

11. Turn the key switch of the MMU cabinet to the ON-LINE position.

    The change for the bearing is complete.