G3524 and G3532 Tandem Maintenance{7002} Caterpillar

G3524 and G3532 Tandem Maintenance{7002}

Usage:

Engine:: G3512 (S/N: 7NJ135-497); G3516 (S/N: 4EK904-2221); G3524 (S/N: 7SZ207-221); G3532 (S/N: 8BZ304-386)

Introduction

The following service and maintenance must be performed in addition to the maintenance specified in the relevant service manuals for tandem generator sets to provide reliable operation.

Product Improvement

Install the bearing temperature RTD if not already present using the included O-ring.
If provided, discard the included ferrule.

Monitor the bearing temperatures and take action as detailed in ""On-going Product Monitoring & Control" ".

Technician Qualifications

Each technician working on tandem generator sets needs to have the following knowledge and skills prior to working on a tandem generator set installation.

Alignment of a tandem generator set
Generator hub removal and installation
Generator bearing replacement
Shock pulse measurement (optional, but highly recommended)
Insulation testing techniques (including temperature compensation)
Generator drying
Coupling rubber inspection & replacement
Generator bearing to sleeve gap measurement
Installation auditing
Generator and package end-play determination & correction
Vibration measurement
Creating trend charts to predict required maintenance, service, and repairs
Generator bearing failure analysis

Installation Audits

As practical, audit each installation paying particular attention to the following items:

Cool air supply to the generator air intake and the generator coupling. Generator air intake temperature, measured in the airflow in front of the intake screen, should be less than 10°C higher than the outside ambient temperature and always less than 40°C. The air around the protective screen around the generator coupling should also be less than 40°C.
Proper airflow through the engine room, from the rear of the generator to the front of the engine.
Laminar recirculating airflow from the generator exhaust back into the generator intake. This recirculation can occur if other objects impede the airflow in the building in front of the generator. Generator stator failures can occur due to localized overheating of the insulation system caused by this recirculation. The airflow usually consists of a thin layer of very fast flowing, very hot air.
Measure the package endplay by measuring the location of the coupling star (inner element bolted to the generator hub) with respect to the outside edge of the ring holding the rubber boots in place. This measurement must be completed after the generator stopped running without changing the generator rotor or engine crankshaft positions. If this measurement is less than 7.5 mm or greater than 12.5 mm schedule a more detailed investigation.

Installation Check

The following must be done any time an engine or generator is moved or loosened from the base. If these items were not done in the past, do them now.

Generator Set Package Vibration

Perform a complete package vibration check on generator sets per the instructions in Engine Data Sheet, LEKQ4023, "Linear Vibration". The same engine locations must be checked on both engines.

Alignment

Perform a complete package alignment per the instructions in Special Instruction, REHS0445, "Alignment Procedures for G3500 Tandem Generator Sets".

Caterpillar Coupling (5N-3765) Position

The position of the hub on the generator shaft determines whether the coupling can float freely, i.e. the package has adequate endplay. See Appendix A-15 for instructions.

Package Endplay

The generator endplay must be checked with the generator coupled to the engine. See Appendix A-1 for instructions. If the generator endplay is insufficient when coupled to the engine, the generator must be uncoupled to check the endplay of the loose generator.

Generator Endplay

Check generator endplay with the generator decoupled from the engine. Generator endplay is necessary to allow the generator bearings to operate without thrust load. See Appendix A-2 for instructions.

Caterpillar Coupling (5N-3765) Boot Rubber Deformation

Over time, the rubber boots used with the Caterpillar coupling may deform due to the transmitted torque. The deformation will show whether the coupling is in an extreme position during operation (the star is moved all the way forward to the flywheel or all the back to the retaining ring). Deformed rubber boots in the Caterpillar coupling can inhibit free axial movement, but generally the deformation is already in the normal operating position. See Appendix A-16 for instructions.

On-going Product Monitoring & Control

Generator Bearing Temperature

The generator bearing temperatures should be monitored continuously by a control system capable of taking action when the alarm or shut down temperature is reached. See Appendix A-8. Set the controls to shut down the generator set when the shutdown temperature is exceeded.

The published temperature set points (Alarm at 85 °C (185 °F) and Shutdown at 95 °C (203°F)) are maximum values. Lower temperature set points can and should be used when practical for improved protection and should be set as follows:

Improved temperature set points can be established by monitoring the bearing temperature during operation when the ambient temperature is at its highest.
Set the alarm temperature to 5 °C (9°F) to 10 °C (18°F) higher than the highest normal operating temperature recorded and the shutdown temperature 10 °C (18 °F) above the alarm temperature. These new set points must be lower than or the same as the published limits.

Shock Pulse Measurement

Bearing shock pulse measurements are a good indicator of the bearing condition. It can be used as a diagnostic tool or set up for continuous monitoring. For example, PrufTechnik supplies a hand held tester, VibScanner, for diagnostics and a more permanent installed instrument, Vibrex, for continuous monitoring.

If a unit is operating while the shock pulse or any of the other indicators are marginal, then that unit should be monitored on a regular basis such that service can be scheduled if required.

The Base and Max shock pulse measurements are made at the same time.

The base shock pulse measurement indicates the lubrication performance. Typical examples are insufficient or too much grease. Long term continued operation without correction might result in bearing failure. See Appendix A-4 for details and instructions.

The Max shock pulse measurement indicates the relative mechanical condition of the bearing surfaces. Abnormal readings mean the bearing has mechanical damage to the races, balls, and/or rollers sufficient that a bearing failure is likely to take place. The root cause of the damage can only be determined through failure analysis of the bearing system. Until the repairs can be made, we recommend frequent monitoring. The urgency of the scheduled repairs can be determined by using a trend chart to predict the future. See Appendix A-5 for details and instructions.

Annual Product Maintenance

Generator Coupling

Caterpillar Coupling (5N-3765)

Remove boots and determine wear. See Appendix A-16 for instructions. Replace boots if average wear exceeds 2.0 mm (0.08 inch).

Note: The Caterpillar coupling has three rubber elements that absorb the torque fluctuations as the package is operating. These rubber elements are called rubber boots.

Centa or Ringfeder Coupling

Inspect exposed rubber (generator side), probably easiest using a borescope or small mirror. Replace rubber element if diagonal 45° cracks are visible on the face of the rubber or if the rubber shows bulging.

Clean any fluids off the coupling rubber and eliminate the source of those fluids. The coupling may need to be removed for cleaning and repairs.

Engine Coupling

Annual inspection is necessary if the generator coupling is a Centa or Ringfeder coupling otherwise inspect every other year. No significant wear has been observed if the generator coupling is the Cat coupling.

Caterpillar Coupling (5N-3765)

Remove boots and determine wear. See Appendix A-16 for instructions. Replace boots if average wear exceeds 2.0 mm (0.08 inch).

Generator bearing to sleeve gap

If the gap between the generator bearing outer surface and the bearing sleeve exceeds 0.10 mm (0.004 inch), the bearing and the sleeve must be replaced. See Appendix A-6 for details.

Generator bearing rotation during prolonged periods of not running

To prevent generator bearing flat spotting and to maintain the oil film on the generator bearing surfaces, it is necessary to periodically turn the generator rotor. Ideally this is done every 2 to 3 months. It is not necessary to run the generator set for this purpose. Barring-over of the engine a few times does turn the rotor sufficiently to satisfy this need.

Generator insulation testing

Perform at least annually, quarterly in severe environments, and always near the end of an extended period of inactivity.

Insulation Test

Measure insulation resistances and temperatures of all generator windings (main rotor, main stator, exciter rotor and stator, and PMG stator-if present). Infinity readings are not acceptable. Use a tester with sufficient range. The insulation tester resistance range needs to exceed 50 GigaOhm.

Enter temperature compensated insulation resistances on trend charts. If any of the trend charts show an abnormal decline, the root cause must be investigated and resolved prior to the generator set returning to operation. Items to investigate include insulation cleanliness, moisture content, and physical winding damage.

Compare temperature compensated insulation resistance measurements to the population at large to identify potentially at-risk generators.

Polarization Index (PI)

Measure polarization index (PI) of main stator and main rotor windings. The polarization index is the 10 minute insulation resistance reading divided by the 1 minute insulation resistance reading with both readings taken during a continuous 10 minute test. If the PI of either the stator or the rotor is less than 2.0, then dry the generator until the PI returns above 2.0. See Special Instruction, SEHS9124, "Cleaning and Drying of Electric Set Generators" for drying instructions.

Note: Depending on the method used, the drying process can take multiple weeks to complete.

Shock Pulse Measurement

Bearing shock pulse measurements are a good indicator of the bearing condition. It can be used as a diagnostic tools as part of the annual maintenance or just prior to overhaul. For example, PrufTechnik AG supplies a hand held tester, VibScanner, for diagnostics.

If a unit is operating while the shock pulse or any of the other indicators are marginal, that unit should be monitored on a regular basis such that service can be scheduled.

The Base and Max shock pulse measurements are made at the same time.

The Base shock pulse measure indicates the lubrication performance. Typical examples are insufficient or too much grease. Long term continued operation without correction might result in bearing failure. See Appendix A-4 for details and instructions.

The Max shock pulse measurement indicates the relative mechanical condition of the bearing surfaces. Abnormal readings mean the bearing has mechanical damage to the races, balls, and/or rollers sufficient that a bearing failure is likely to take place. The root cause of the damage can only be determined through failure analysis of the bearing system. Until the repairs can be made, we recommend frequent monitoring. The urgency of the scheduled repairs can be determined by using a trend chart to predict the damage progression. See Appendix A-5 for details and instructions.

Bearing Temperature Sensor

The generator bearing temperature sensors must be checked for proper operation. See Appendix A-7 for instructions.

Bearing Temperature Differential

Checking the bearing temperature differential is another method to verify proper operation of the bearing system. See Appendix A-9 for instructions.

Generator Set Package Vibration

Package vibration levels taken annually need to be compared with the original vibration levels. The root cause of any discrepancy must be investigated. Perform a complete package vibration check per the instructions in Engine Data Sheet, LEKQ4023, "Linear Vibration on Generators". The same engine locations must be checked on both engines.

Generator Exciter Rotor Fit

Check the generator exciter rotor for tightness. See Appendix A-18 for instructions.

Appendix

If the result in any of the following cases is marginal, the Interim Corrective Action (ICA) or Permanent Corrective Action (PCA) must be performed. If the result is not acceptable, the PCA must be performed.

Appendix A-1 - Package End Play

The following procedure is used in order to check the forward movement and backward movement of generator rotor from normal operating position with the coupling in place.

Note: The following procedure must be completed immediately after a shutdown.

The position of the rotor after shutdown is the same as the running position, so this is the reference of the measurements.

Measure the limits from the running position by moving the generator rotor forward and backward.

Note: Make sure the rotor is moved completely forward and backward for these measurements.

Refer to the following list for rating the package end play referenced from the original stop position.

Normal

Greater than ... 2.00 mm (0.08 inch)

Acceptable

Greater than ... 1.00 mm (0.04 inch)

Marginal

Greater than ... 0.50 mm (0.02 inch)

Less than ... 1.00 mm (0.04 inch)

Not Acceptable

Less than ... 0.50 mm (0.02 inch)

If the measurement is Marginal or the measurement is Not Acceptable, refer to the following lists for the corrective action.

Interim Corrective Action if marginal

Monitor the generator end play on a monthly basis.
Schedule a Permanent Corrective Action.

Permanent Corrective Action

Determine the cause for the lack of end play and correct.

Note: Refer to the following list for possible causes:

Wear in the coupling rubber boot.
Hub is in the wrong location
Sleeve Failure
Bearing Failure
Lack of generator end play

Appendix A-2 - Generator End Play

The following procedure is used in order to check the forward and backward movement of generator rotor from normal operating position unconstrained by coupling.

Note: The following procedure should be completed immediately after shutdown. Maintain the gauge position reference from the previous package end play measurement.

Measure after the Package End Play by removing the coupling boot retaining ring.
Verify that the coupling is not the limiting factor when the rotor is moved.

Measure the limits from the running (reference) position.
Note: Make sure rotor is moved completely forward and backward for these measurements.
Refer to the following list for rating the Generator End Play
Normal
Greater than ... 2.00 mm (0.08 inch)

Acceptable
Greater than ... 1.00 mm (0.04 inch)

Marginal
Equal to or Greater than ... 0.50 mm (0.02 inch)
Less than or equal to ... 1.00 mm (0.04 inch)

Not Acceptable
Less than ... 0.50 mm (0.02 inch)

If the measurement is Marginal or the measurements Not Acceptable, refer to the following lists for the corrective action.
Interim Corrective Action
- Monitor the generator end play on a monthly basis.
- Schedule a Permanent Corrective Action.
Permanent Corrective Action
- Determine the cause for the lack of end play and correct.

Note: Refer to the following list for possible causes for a lack of end play:

Bearing Failure
One or both of the generator bearings are in the wrong location.

Appendix A-3 - Bearing Position

The following procedure is used in order to check the bearing position.

Check the distance from the shaft shoulder to the bearing.
Refer to the following list for rating the Bearing Position.
Normal and Acceptable
The bearing is located against the shoulder ... 0.00 mm (0.0000 inch)

Not Acceptable
Greater than ... 0.00 mm (0.0000 inch)

If the measurement is Not Acceptable refer to the following lists for the corrective action.
Permanent Corrective Action
- Replace the bearing
- Investigate the cause and resolve the cause.

Appendix A-4 - Shock Impulse Base

Note: The Shock Pulse Base measurement should be performed with the generator set running at full load for 10 minutes prior to the measurement (at full load).

The Shock pulse measurement must be taken exactly under bearing on the bearing housing with the generator set running.

Note: Multiple readings should be taken for better accuracy. Use reading average.

If a unit is operating while the shock pulse or any of the other indicators are marginal, then that unit should be monitored on a regular basis such that service can be scheduled if required.

Take a measurement under the bearing on the bearing housing with the generator set running.
Refer to the following list for rating the Shock Impulse Base.
Normal
Less than ... 5 dB

Acceptable
Less than ... 5 dB

Marginal
Greater than ... 5 dB
Less than ... 10 dB

Not Acceptable
Greater than ... 10 dB

If the measurement is Marginal or the measurement is Not Acceptable, refer to the following lists for the corrective action.
Interim Corrective Action
- Lubricate the bearing if the bearing is not double-shielded.
- Investigate the causes for the high dB level.
- Continue to monitor the bearing.
- Schedule a replacement of the bearing if there is no improvement.
Permanent Corrective Action
- Investigate the cause and resolve the cause.
- Replace the bearing.

Appendix A-5 - Shock Pulse Maximum

Note: The Shock Pulse Maximum measurement should be performed with the generator set running at full load and for 10 minutes prior to the measurement (at full load).

The Shock pulse Maximum measurement should be taken exactly under bearing on the bearing housing with generator set running.

Note: Multiple readings should be taken for better accuracy. Use the highest reading.

Take a measurement under the bearing on the bearing housing with the generator set running.
Refer to the following list for rating the Shock Impulse Maximum.
Normal
Less than ... 20 dB

Acceptable
Less than ... 20 dB

Marginal
Greater than ... 20 dB
Less than ... 35 dB

Not Acceptable
Greater than ... 35 dB

If the measurement is Marginal or the measurement is Not Acceptable, refer to the following lists for the corrective action.
Interim Corrective Action
- Closely monitor the bearing.
- Schedule a bearing replacement.
Permanent Corrective Action
- Replace the bearing.
- Investigate the causes for the deterioration of the bearing.
- Replace the sleeve.

Appendix A-6 - Bearing to Sleeve Gap

Note: The Bearing to Sleeve Gap must be checked after shutdown. Additionally, the Bearing to Sleeve Gap must be checked at the top of the Bearing.

Take a measurement at the top of the bearing on the bearing housing after the generator set has been shutdown.
Refer to the following list for rating the Bearing to Sleeve Gap.
Normal and Acceptable
Less than ... 0.070 mm (0.0028 inch)

Marginal
Greater than ... 0.070 mm (0.0028 inch)
Less than ... 0.100 mm (0.0039 inch)

Not Acceptable
Greater than ... 0.100 mm (0.0039 inch)

If the measurement is Marginal or the measurement is Not Acceptable, refer to the following lists for the corrective action.
Interim Corrective Action
- Monitor the Bearing to Sleeve Gap for any changes.
- Schedule a Bearing Replacement.
Permanent Corrective Action
- Replace the bearing and sleeve.
- Check the coupling.

Appendix A-7 - Bearing Temperature Sensor

Note: The Bearing Temperature Sensor must be checked when the generator set running at full load and stabilized.

Is the reading steady with the generator set running at operating temperature?
Refer to the following list for rating the Bearing Temperature Sensor.
Acceptable
A stable reading that is equal to or greater than the following degrees above ambient ... 10 °C (18 °F)

Not Acceptable
An unstable reading or a reading that is within the following degrees of ambient temperature ... 10 °C (18 °F)

If the measurement is Not Acceptable, refer to the following lists for corrective actions.
Corrective Action
- Check bearing to sleeve gap and correct per instructions if necessary.
- Check for proper RTD hole alignment between the bracket and the sleeve. If found non-conforming, replace and notify Caterpillar. Replace temperature sensor, inserting it until the tip contacts the bearing.
- Replace the temperature sensor and mount it using the rubber ring.

Appendix A-8 - Bearing Temperature

Note: The Bearing Temperature Sensor must be checked with the generator set running at full load and stabilized.

Measure the Bearing Temperature with the generator set having operated long enough for bearing temperatures to have stabilized.
Refer to the following list for rating the Bearing Temperature.
Normal
Less than ... 25 °C (45 °F)

Acceptable
Less than ... 85 °C (185 °F)

Marginal
Greater than ... 85 °C (185 °F)
Less than ... 95 °C (203 °F)

Not Acceptable
Greater than ... 95 °C (203 °F)

If the measurement is Not Acceptable, refer to the following lists for corrective actions.
Interim Corrective Action
- Continue to monitor the Bearing Temperature.
- Schedule a Permanent Corrective Action.
Permanent Corrective Action
- Investigate root cause and correct.
Note: Refer to the following list for possible causes of the excessive Bearing Temperature:
- Poor air circulation in the engine room
- Pending bearing failure
- Too little grease
- Too much grease
Note: Use shock pulse measurement to help with diagnosis.

Appendix A-9 - Bearing Temperature Differential

Note: The Bearing Temperature Differential must be checked when the generator set running at full load and stabilized.

This measurement is the difference between the bearing temperature and the ambient temperature that is measured at the generator air intake for the rear bearing and at the screen of the adapter bracket for the front bearing.

Measure the Bearing Temperatures with the generator set having operated long enough for the bearing temperatures to have stabilized.
Refer to the following list for rating the Bearing Temperature Differential.
Normal
Greater than ... 20 °C (36 °F)
Less than ... 25 °C (45 °F)

Acceptable
Greater than ... 10 °C (18 °F)
Less than ... 25 °C (45 °F)

Marginal
Greater than ... 25 °C (45 °F)
Less than ... 30 °C (54 °F)

Not Acceptable
Less than ... 10 °C (18 °F)
Or Greater than ... 30 °C (54 °F)

If the measurement is Marginal, perform the Interim Corrective Action.

If the measurement is Not Acceptable, perform the Permanent Corrective Action.
Interim Corrective Action
- Continue to monitor the Bearing Temperature Differential.
- Schedule a Permanent Corrective Action.
Permanent Corrective Action
- Investigate root cause and correct.
Note: Refer to the following list for possible causes of the excessive Bearing Temperature:
- Poor air circulation in the engine room
- Impending bearing failure
- Too little grease
- Too much grease
Note: Use shock pulse measurement to help with diagnosis.

Appendix A-10 - Ambient Temperature

Note: The Ambient Temperature must be checked with the generator set running at full load and stabilized.

Measure the Ambient Temperature.
Refer to the following list for rating the Ambient Temperature.
Normal
Less than ... 40 °C (104 °F)

Acceptable
Less than ... 30 °C (86 °F)

Marginal
Greater than ... 30 °C (86 °F)
Less than ... 40 °C (104 °F)

Not Acceptable
Greater than ... 40 °C (104 °F)

If the measurement is Not Acceptable, refer to the following lists for corrective actions.
Interim Corrective Action
- Continue to monitor the Ambient Temperature.
- Investigate the root cause.
Permanent Corrective Action
- Investigate root cause and correct.
- Continued operation with the proper power deration is an acceptable solution.
Note: Refer to the following list for possible causes of the excessive Ambient Temperature:
- Inadequate airflow from outside.
- Poor air circulation in the engine room

Appendix A-11 - Temperature at the Generator

Note: The Temperature at the Generator must be checked when the generator set running at full load and stabilized.

Measure the Temperature at the Generator air inlet and at the protective screen in the coupling area.
Refer to the following list when checking the temperature at the generator.
Normal
Greater than ... 40 °C (104 °F)

Acceptable
Less than ... 30 °C (86 °F)

Marginal
Greater than ... 30 °C (86 °F)
Less than ... 40 °C (104 °F)

Not Acceptable
Greater than ... 40 °C (104 °F)

If the measurement is Not Acceptable, refer to the following lists for corrective actions.

Interim Corrective Action

Continue to monitor the Temperature at the Generator.
Investigate the root cause.

Permanent Corrective Action

Investigate root cause and correct.

Note: Refer to the following list for possible causes of the excessive Temperature at the Generator:

Inadequate airflow from outside.
Poor air circulation in the engine room.

Appendix A-12 - Generator Stator Temperature

Note: Maximum temperature of the three phases measured after 4 hours of operation at full load.

Measure the Generator Stator Temperature.
Refer to the following list for rating the Generator Stator Temperature.
Normal
Less than ... 145 °C (293 °F)

Acceptable
Less than ... 145 °C (293 °F)

Marginal
Greater than ... 145 °C (293 °F)
Less than ... 155 °C (311 °F)

Not Acceptable
Greater than ... 155 °C (311 °F)

If the measurement is Not Acceptable, refer to the following lists for corrective actions.
Interim Corrective Action
- Operate at no load to reduce stator temperature. Once back to normal, derate to keep the temperature acceptable.
- Investigate the cause of the high temperature.
Permanent Corrective Action
- Determine root cause and correct.

Appendix A-13 - Interior to Exterior Temp Differential

Note: The Interior to Exterior Temp Differential must be checked with the generator set running at full load and stabilized.

Measure the Interior to Exterior Temp Differential.
Refer to the following list for rating the Interior to Exterior Temp Differential.
Acceptable
Less than ... 10 °C (18 °F)

Marginal
Greater than ... 10 °C (18 °F)
Less than ... 15 °C (27 °F)

Not Acceptable
Greater than ... 15 °C (27 °F)

If the measurement is Not Acceptable, refer to the following lists for corrective actions.
Interim Corrective Action
- Continue to monitor the Interior to Exterior Temperature Differential.
- Verify generator operating temperature.
- Investigate the root cause.
Permanent Corrective Action
- Investigate root cause and correct.

Note: Refer to the following list for possible causes of the excessive Interior to Exterior Temp Differential.

Inadequate airflow from outside.

Appendix A-14 - Vibration

Use standard Caterpillar vibration measurement points. Evaluate against published criteria.

Measure the Vibration.
Refer to the following list for rating the Vibration.
Acceptable
Less than the following per order ... 0.13 mm (0.005 inch)
Less than the following value overall ... 0.20 mm (0.008 inch)

Not Acceptable
Greater than the following value on any order ... 0.20 mm (0.008 inch)
Greater than the following value overall ... 0.13 mm (0.005 inch)

If the measurement is Not Acceptable, refer to the following lists for corrective actions.
Interim Corrective Action
- Identify the source.
- If possible, fix the problem.
- Schedule a Permanent Corrective Action soon.
Permanent Corrective Action
- Identify the source and correct the problem.
- Implement a process to avoid future problems.

Appendix A-15 - Caterpillar Coupling Position

Note: This measurement must be taken after running the generator set.

Measure the distance from the outside edge of the plate that is holding the rubber boot in place to the inner element surface.
Refer to the following list for rating the distance:
Normal
End to end movement greater than ... 7.0 mm (0.28 inch)

Acceptable
Greater than ... 7.5 mm (0.30 inch)
Less than ... 12.5 mm (0.49 inch)

Marginal
Greater than ... 7.0 mm (0.28 inch)
Less than ... 7.5 mm (0.30 inch)
Or Greater than ... 12.5 mm (0.49 inch)
Less than ... 13.0 mm (0.51 inch)

Not Acceptable
Less than ... 7 mm (0.28 inch)
Greater than ... 13 mm (0.51 inch)

If the measurement is Not Acceptable, refer to the following lists for corrective actions.
Interim Corrective Action
- Monitor the end play.
- The permanent Corrective Action can be postponed if the distance is marginal.
Permanent Corrective Action
- Reposition hub on generator shaft.
- Check the end play.
- Check the condition of the bearing.

Appendix A-16 - Coupling Boot Wear

Check the indentation into the rubber by the teeth to the new rubber boots.

Refer to the following list for rating the distance:

Normal

Acceptable

Less than ... 2.0 mm (0.08 inch)

Not Acceptable

Greater than ... 2.0 mm (0.08 inch)

If the measurement is Not Acceptable, refer to the following lists for corrective actions.
Corrective Action
- Replace the boots.

Appendix A-17 - Coupling Housing Wear

Check Visible wear from the teeth or the rubber on either the housing that is bolted to the flywheel or on the ring holding the boots in place.
Refer to the following list for rating the distance:
Normal - No wear
Acceptable - No visible wear
Not Acceptable - Visible wear

If the measurement is Not Acceptable, refer to the following lists for corrective actions.
Interim Corrective Action
- Investigate the cause.
- Look into the condition of the front generator bearing and its bearing sleeve. Are they frozen together due to fretting?
Permanent Corrective Action
- Replace coupling boots.
- Determine root cause and address the issue.

Appendix A-18 - Exciter Rotor Fit

Components can be moved on the shaft, wear is visible, heat sink bolts not tight.

Check the components.
Acceptable - There is no movement. There is no wear. The bolts are tight.
Not Acceptable - There is movement, or there is visible wear, or the bolts are loose

If the measurement is Not Acceptable, refer to the following lists for corrective actions.
Corrective Action
- Replace damaged or loose components.
- Insert spacers if necessary.
- Tighten.