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1.Equipment Information

Equipment Type: Doubly-fed induction generator

Rated Speed: 1800 rpm

Associated Measurement Point for This Case: 3# Motor Drive End Horizontal 5H

2.Alarm and Analysis Process

Equipment Alarm Events:

2.1Analysis Process

2.1.1Explanation of Trends and Indicator Parameters:

Recent sustained increase in low-frequency acceleration vibration across multiple gearbox measurement points.

77#Wind Turbine/Gearbox high-speed shaft output side horizontal (5H)/128k acceleration waveform (2-20000)_equipment multi-trend

2.1.2Time-domain, frequency-domain, envelope demodulation, and other evidence explanations

Time domain waveform shows clear rotational frequency interval impacts.

77#Wind Turbine/Gearbox high-speed shaft output side horizontal (5H)/128k acceleration waveform (2-20000)_Time Domain Waveform

Spectrum reveals bearing inner race fault frequency with rich rotational frequency sidebands.

77#Wind Turbine/Gearbox high-speed shaft output side horizontal (5H)/128k acceleration waveform (2-20000)_Spectrum Analysis

3.Diagnosis Conclusion and Recommendations

3.1Diagnostic Conclusion

September  24,  2022,  11:13  -  Diagnostic  Conclusion  Push:

1.Gearbox high-speed shaft bearing inner race spalling

2.Cage wear

3.Noticeable recent degradation

3.2Recommendations

1.Immediate on-site inspection required to verify actual equipment condition.

2.Long-term operation in this state carries failure risks.

3.Specific checks needed:

Abnormal noise from gearbox high-speed stage

Metal debris in lubrication filter

Bearing damage inspection to be scheduled

4.On-site Maintenance Process

2023-01-27 02:40:

1.Secondary reminder issued for bearing degradation

2.Urged inspection of gearbox high-speed stage noise and filter condition

2023-03-07 21:17:

1.Site team confirmed gearbox maintenance preparation

2.Committed to documenting process with photos

2023-03-09 09:58:

Maintenance photos received showing:

1.Extensive inner race spalling

2.Broken cage

3.Evenly distributed pitting wear on rolling elements

5.On-site Maintenance Photos

On-site inspection photos confirmed high-speed shaft bearing inner race spalling, cage fracture, and rolling element pitting wear.

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6.Post-Maintenance Verification

After maintenance: Significant reduction in gearbox vibration acceleration and stable operation restored

77#Wind Turbine/Gearbox high-speed shaft output side horizontal (5H)/128k acceleration waveform (2-20000)_Trend Analysis

Elimination of impact characteristics in time domain waveforms

77#Wind Turbine/Gearbox high-speed shaft output side horizontal (5H)/128k acceleration waveform (2-20000)_Time Domain Waveform

7.Customer feedback form

Feedback form_1

8.Monitoring fault range

Timely and effective collection of equipment operational status data (such as vibration and temperature) is constrained by network connectivity and data transmission time, as well as by interference from the equipment's inherent characteristics and production processes. At the same time, the analysis and diagnosis of equipment status are based on changes in vibration effects caused by faults in rotating components. Therefore, the condition monitoring system cannot guarantee coverage of all types of faults. The monitoring system, configured according to the measurement point scheme recommended by Party B, can monitor the following fault range and descriptions:

9.Notes

1.If the client of this report is unable to provide basic unit parameters (such as: drive chain diagrams, gearbox structural diagrams, gearbox gear counts, relevant bearing models and brands), it will affect the accuracy of the analysis and diagnosis；

2. This report is based on the analysis, diagnosis, and maintenance recommendations of Ronds’ technical professionals and is for reference only. The specific maintenance and repair measures must be decided by the client；

3. This report is not to be used as evidence for any claims, litigation, or other legal purposes；

4. The client is obligated to keep the analysis report confidential and may not provide the report to any third party, print it as promotional material, or publish it on public information platforms without the written consent of the entrusted party.

1.Equipment Information

Equipment Type: Doubly-fed induction generator

Rated Speed: 1800 rpm

Associated Measurement Points for This Case: Main shaft horizontal (1H), Main shaft axial (1A)

2.Alarm and Analysis Process

Severe main bearing damage detected during routine monthly inspection.

2.1Analysis Process

2.1.1Explanation of Trends and Indicator Parameters:

·Stable low-frequency acceleration trends at both shaft ends

·No significant recent degradation

1#-/1H/256k acceleration waveform (2-20000)_equipment multi-trend

2.1.2Time-domain, frequency-domain, envelope demodulation, and other evidence explanations

After applying a low-pass filter (100Hz) to the low-frequency acceleration time-domain waveform, distinct periodic impacts appeared, with an impact interval of approximately 5.926Hz, which corresponds to the characteristic frequency of main shaft raceway defects.

1#-/1H/256k acceleration waveform (2-20000)_Time Domain Waveform

In the frequency spectrum, there was a notable increase in energy below 500Hz, with the presence of 5.918Hz and its rich harmonics.

1#-/1H/256k acceleration waveform (2-20000)_Spectrum Analysis

3.Diagnosis Conclusion and Recommendations

3.1Diagnostic Conclusion

September  27,  2022,  11:25  -  Diagnostic  Conclusion  Push: The main shaft bearing exhibited moderate to severe damage, primarily characterized by pitting and spalling on the raceways, pitting and spalling on the rolling elements, and cage wear. A gradual deterioration was observed in the recent period.

3.2Recommendations

The equipment is currently in a monitorable operational state, and it is recommended to schedule an inspection at an appropriate time. 1. Monitor for abnormal noises and temperature changes at the main shaft position. 2. Open the cover to inspect the bearing damage and consider replacing the bearing as soon as possible.

4.On-site Maintenance Process

2022-11-01 17:49

On-site inspection revealed severe damage to the main shaft. Due to COVID-19 restrictions in Xinjiang, spare parts could not be delivered to the site. However, due to downtime limitations, the turbine could not be shut down. Replacement was planned to be carried out immediately after the pandemic situation improved.

2023-04-19 11:41

It was reported that the main shaft bearing had been replaced. Wear was observed on the rolling elements, and the cage had sunk.

5.On-site Maintenance Photos

It was reported that the main shaft bearing had been replaced. Wear was observed on the rolling elements, and the cage had sunk.

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severe wear was evident on the rolling elements.

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the cage had sunk, leading to increased clearance between the rollers.

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due to the bearing not being cut open, the extent of raceway damage could not be visually assessed.

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6.Post-Maintenance Verification

After replacing the main shaft bearing, the low-frequency acceleration vibration trend at the main shaft measurement points significantly decreased and remained stable.

1#-/1H/256k acceleration waveform (2-20000)_equipment multi-trend

The chaotic impacts in the low-frequency acceleration time-domain waveform disappeared, and the peak impact amplitude significantly reduced.

1#-/1H/256k acceleration waveform (2-20000)_Time Domain Waveform

In the frequency spectrum, there was a notable decrease in energy in the low to mid-frequency range, and the spectral line gaps disappeared.

1#-/1H/256k acceleration waveform (2-20000)_Spectrum Analysis

Envelope demodulation of the low-frequency range did not reveal any significant bearing damage frequencies.

1#-/1H/256k acceleration waveform (2-20000)_Envelope Demodulation

7.Customer Feedback

Feedback form_1

8.Monitoring Fault Range

Timely and effective collection of equipment operational status data (such as vibration and temperature) is constrained by network connectivity and data transmission time, as well as by interference from the equipment's inherent characteristics and production processes. At the same time, the analysis and diagnosis of equipment status are based on changes in vibration effects caused by faults in rotating components. Therefore, the condition monitoring system cannot guarantee coverage of all types of faults. The monitoring system, configured according to the measurement point scheme recommended by Party B, can monitor the following fault range and descriptions:

9.Notes

1.If the client of this report is unable to provide basic unit parameters (such as: drive chain diagrams, gearbox structural diagrams, gearbox gear counts, relevant bearing models and brands), it will affect the accuracy of the analysis and diagnosis；

2. This report is based on the analysis, diagnosis, and maintenance recommendations of Ronds’ technical professionals and is for reference only. The specific maintenance and repair measures must be decided by the client；

3. This report is not to be used as evidence for any claims, litigation, or other legal purposes；

4. The client is obligated to keep the analysis report confidential and may not provide the report to any third party, print it as promotional material, or publish it on public information platforms without the written consent of the entrusted party.

1.Equipment Information

Equipment Type: Doubly-fed induction generator

Rated Speed: 1750 r/min

Associated Measurement Points for This Case: Gearbox Intermediate Shaft Vertical 4V, Gearbox Intermediate Shaft Axial 5A

2.Alarm and Analysis Process

Equipment Alarm Event

2.1Analysis Process

2.1.1Explanation of Trends and Indicator Parameters:

The overall acceleration trend at the gearbox intermediate shaft monitoring point is stable.

F001/gearbox intermediate shaft axial 5A/256k acceleration waveform(0.1-2000)_trend analysis

The overall velocity value shows a gradual increase.

F001/gearbox intermediate shaft axial 5A/16k acceleration waveform(10-1000)_trend analysis

2.1.2Time-domain, frequency-domain, envelope demodulation, and other evidence explanations

Periodic impacts at intervals corresponding to the intermediate shaft rotation frequency are visible in the time domain waveform.

F001/gearbox intermediate shaft axial 5A/256k acceleration waveform(0.1-2000)_time domain waveform

In the low-frequency spectrum, secondary meshing and its harmonics with intermediate shaft rotation frequency sidebands are observable.

F001/gearbox intermediate shaft axial 5A/256k acceleration waveform(0.1-2000)_spectrum analysis

Impacts at intervals corresponding to the intermediate shaft rotation frequency are visible in the velocity time domain waveform.

F001/gearbox intermediate shaft axial 5A/16k acceleration waveform(10-1000)_time domain waveform

F001/gearbox intermediate shaft axial 5A/16k acceleration waveform(10-1000)_time domain waveform

F001/gearbox intermediate shaft axial 5A/16k acceleration waveform(10-1000)_spectrum analysis

3.Diagnosis Conclusion and Recommendations

3.1Diagnostic Conclusion

May  23,  2023,  14:17  -  Diagnostic  Conclusion  Push: Moderate tooth surface damage and tooth breakage on the gearbox intermediate shaft pinion, with gradual deterioration.

3.2Recommendations

1. Arrange for an immediate inspection of the on-site equipment to assess the actual condition, as prolonged operation in this state poses a risk of failure.

2. Monitor for abnormal vibrations and noises from the intermediate shaft gears, monitor oil temperature and pressure, check for metal particles in the filter elements, and promptly inspect the tooth surface damage on the intermediate shaft.

4.On-site Maintenance Process

1、2023-05-25 15:28

From Anhuang: The early warning regarding the gearbox intermediate shaft tooth breakage on one of the wind turbines at Datang Qianfo Ridge Wind Farm was accurate. The turbine has been shut down for repairs. Thank you for the early warning, which helped prevent a more severe failure.

2、2023-07-28 10:23

The gearbox intermediate shaft gear has been replaced due to tooth breakage.

5.On-site Maintenance Photos

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6.Post-Maintenance Verification

After maintenance, there is a noticeable decrease in acceleration and velocity vibrations.

Trend for low-frequency acceleration total value

Trend for velocity total value

The periodic impact features at intervals corresponding to the intermediate shaft rotation frequency in the time-domain waveform have disappeared.

Time domain waveform_low-frequency acceleration

Time domain waveform_velocity

The intermediate shaft rotation frequency sidebands around secondary meshing and its harmonics in the frequency spectrum have disappeared.

Spectrum__low-frequency acceleration

Spectrum_velocity

7.Customer Feedback

Feedback form_1

8.Monitoring Fault Range

Timely and effective collection of equipment operational status data (such as vibration and temperature) is constrained by network connectivity and data transmission time, as well as by interference from the equipment's inherent characteristics and production processes. At the same time, the analysis and diagnosis of equipment status are based on changes in vibration effects caused by faults in rotating components. Therefore, the condition monitoring system cannot guarantee coverage of all types of faults. The monitoring system, configured according to the measurement point scheme recommended by Party B, can monitor the following fault range and descriptions:

9.Notes

1.If the client of this report is unable to provide basic unit parameters (such as: drive chain diagrams, gearbox structural diagrams, gearbox gear counts, relevant bearing models and brands), it will affect the accuracy of the analysis and diagnosis；

2. This report is based on the analysis, diagnosis, and maintenance recommendations of Ronds’ technical professionals and is for reference only. The specific maintenance and repair measures must be decided by the client；

3. This report is not to be used as evidence for any claims, litigation, or other legal purposes；

4. The client is obligated to keep the analysis report confidential and may not provide the report to any third party, print it as promotional material, or publish it on public information platforms without the written consent of the entrusted party.

1.Diagnosis Conclusion

There is significant damage to the planetary gear in the gearbox, possibly in the form of spalling or broken teeth, posing a risk of sudden failure.

2.Recommendations

Arrange for an inspection as soon as possible, focusing on the damage to the planetary gear in the gearbox.

3.Analysis Process

3.1Explanation of Trends and Indicator Parameters

The overall trend of the total acceleration value of the gearbox is relatively stable.

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3.2Time-domain, Frequency-domain, Envelope demodulation, and Other Evidence Explanations

The impact intervals of the planetary gear rotation frequency can be observed in the 3H low-frequency acceleration time-domain waveform.

m64#(DT064) \ Gearbox Internal Ring Gear 3H \ 256k Acceleration Waveform (0.1-2000 Hz). Sampled Values _ Multi-Time-Domain Waveforms

Comparing the low-frequency acceleration frequency spectrum of the 3H measuring point of the gearbox on March 4th and February 25th, a significant increase in energy at the bottom of the low-frequency band can be seen.

m64#(DT064) \ Gearbox Internal Ring Gear 3H \ 256k Acceleration Waveform (0.1-2000 Hz). _ Multi-Spectrum

After order analysis, a large number of first-order planetary gear rotation frequency sidebands can be observed near the first-order meshing frequency.

m64#(DT064) \ Gearbox Internal Ring Gear 3H \ 256k Acceleration Waveform (0.1-2000 Hz). _ Spectrum Analysis

Envelope demodulation also reveals many harmonics of the first-order planetary gear rotation frequency.

m64#(DT064) \ Gearbox Internal Ring Gear 3H \ 256k Acceleration Waveform (0.1-2000 Hz). _ Envelope Demodulation

4.Description of Maintenance Process

1.On February 27, 2021, Ronds Diagnostics Engineer pushed the conclusion to the site: There is significant damage to the planetary gear in the gearbox, possibly in the form of spalling or broken teeth, posing a risk of sudden failure. Recommendation: Inspect the unit as soon as possible, focusing on the damage to the planetary gear in the gearbox.

2. On March 2, 2021, the Ronds follow-up personnel contacted the site to inquire about the reason for the shutdown and whether it was a maintenance action. The site feedback indicated that they were conducting a semi-annual inspection recently, not a repair. No abnormalities were found visually on the abnormal unit, and the endoscope was already being prepared and would be available at the earliest this week. Endoscopic inspections would be performed on several units.

3. On March 8, 2021, the Ronds follow-up personnel tracked the endoscopic inspection situation at the site. The site feedback indicated that the endoscopic inspection results showed no problems, and the endoscopic report had not yet been issued. The wind turbine was also inspected while running, and no problems were found. The diagnosis had been re-evaluated.

4. On March 16, 2021, the site feedback indicated that the report had not yet been issued, and the manufacturer currently stated that no problems were found during the inspection.

5. On August 3, 2021, the site feedback indicated that the gearbox would be replaced at the end of the month, and photos of the planetary gear crack had been sent.

6. On August 3, 2021, photos of the planetary gear crack were sent from the site. The feedback indicated that this unit did not have frequent maintenance faults, and the load was generally not affected by strong wind fluctuations. Now considering that it has been operating for nearly 5 years, this sudden situation seems to have little to do with quality. We have also consulted some information online, and for non-trending damage like this, forged parts may generally be caused by hydrogen embrittlement.

5.Maintenance Signal Verification

The site was shut down for maintenance and has not yet been restarted.

6.Maintenance Photo

7.Monitoring Fault Range

Timely and effective collection of equipment operational status data (such as vibration and temperature) is constrained by network connectivity and data transmission time, as well as by interference from the equipment's inherent characteristics and production processes. At the same time, the analysis and diagnosis of equipment status are based on changes in vibration effects caused by faults in rotating components. Therefore, the condition monitoring system cannot guarantee coverage of all types of faults. The monitoring system, configured according to the measurement point scheme recommended by Party B, can monitor the following fault range and descriptions:

9.Notes

1.If the client of this report is unable to provide basic unit parameters (such as: drive chain diagrams, gearbox structural diagrams, gearbox gear counts, relevant bearing models and brands), it will affect the accuracy of the analysis and diagnosis；

2. This report is based on the analysis, diagnosis, and maintenance recommendations of Ronds’ technical professionals and is for reference only. The specific maintenance and repair measures must be decided by the client；

3. This report is not to be used as evidence for any claims, litigation, or other legal purposes；

4. The client is obligated to keep the analysis report confidential and may not provide the report to any third party, print it as promotional material, or publish it on public information platforms without the written consent of the entrusted party.