Rotating bearing analysis and monitoring system

• US 7,606,673 B2
• Filed: 04/30/2007
• Issued: 10/20/2009
• Est. Priority Date: 05/01/2006
• Status: Expired due to Fees

• Current Assignee: Dynamic Measurement Consultants, LLC
• Original Assignee: Dynamic Measurement Consultants, LLC
• Inventors: Judd, John E.
• Primary Examiner(s): Dunn; Drew A
• Assistant Examiner(s): Cherry; Stephen J
• Application Number:
  US12/297,368
• Publication Number:
  US 20090093975A1
• Time in Patent Office: 904 Days
• Field of Search: 702/34, 702/41, 702/56, 702/61, 702/81, 702/94, 702/145, 702/177, 702/181, 702/182, 702/183
• US Class Current: 702/56
• CPC Class Codes: G01H 13/00 Measuring resonant frequency

Abstract

A method of analyzing vibrations of a rolling element bearing installed in a rotating machine includes accessing vibration data corresponding to the bearing to be analyzed, determining a degraded condition factor BD for the bearing, selecting an expected designer-determined mean-time-to-failure MTTF of the bearing operating under a design load in the operating environment of the rotating machine, selecting a forecast time period, calculating a reduced mean-time-to-failure RMTTF of the bearing using the expected designer-determined mean-time-to-failure MTTF and the degraded condition factor BD, calculating a probability of failure of the bearing in the forecast time period using the reduced mean-time-to-failure RMTTF, accessing cost data corresponding to a cost of failure of the bearing in the rotating machine, calculating a financial risk from the calculated probability of failure in the forecast time period and the cost data, and displaying the financial risk for the selected time period.

Claims

1. A method of analyzing vibrations of a bearing installed in a rotating machine comprising the steps of:

accessing vibration data corresponding to the bearing to be analyzed;

determining a degraded condition factor BD for the bearing from the vibration data;

selecting an expected designer-determined mean-time-to-failure MTTF of the bearing operating under a design load in the operating environment of the rotating machine;

selecting a forecast time period;

calculating a reduced mean-time-to-failure RMTTF of the bearing using the expected designer-determined mean-time-to-failure MTTF and the degraded condition factor BD;

calculating a probability of failure of the bearing in the forecast time period using the reduced mean-time-to-failure RMTTF;

accessing cost data corresponding to a cost of failure of the bearing in the rotating machine;

calculating a financial risk from the calculated probability of failure in the forecast time period and the cost data; and

displaying, on a computer display, the financial risk for the selected time period.

2. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 1 wherein the step of determining a degraded condition factor BD for the bearing from the vibration data comprises determining a plurality of discriminants from the vibration data and using the plurality of discriminants to calculate the degraded condition factor BD for the bearing.

3. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 2 wherein at least one of the plurality of discriminants is selected from a group consisting of a low frequency energy LF discriminant, a high frequency energy HF discriminant, a crest factor CF discriminant, a kurtosis K discriminant, an envelope demodulation ED discriminant and a peak acceleration P discriminant.

4. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 3 wherein the plurality of discriminants used to calculate the degraded condition factor BD includes the high frequency energy HF discriminant.

5. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 1 wherein:

the degraded condition factor BD for the bearing varies from a minimum to a maximum; and

wherein the step of calculating a reduced mean-time-to-failure RMTTF of the bearing using the expected designer-determined mean-time-to-failure MTTF and the degraded condition factor BD comprises setting the RMTTF equal to the expected designer-determined mean-time-to-failure MTTF when the degraded condition factor BD for the bearing is at the minimum and setting the RMTTF equal to the forecast time period when the degraded condition factor BD for the bearing is equal to the maximum.

6. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 5 wherein the reduced mean-time-to-failure RMTTF linearly varies from the expected designer-determined mean-time-to-failure MTTF to the forecast time period as the degraded condition factor BD for the bearing varies from the minimum to the maximum.

7. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 5 wherein the selected forecast time period corresponds to the selected designer-determined mean-time-to-failure MTTF and varying the forecast time period varies the selected designer-determined mean-time-to-failure MTTF.

8. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 1 wherein the step of calculating a probability of failure of the bearing in the forecast time period using the reduced mean-time-to-failure MTTF comprises calculating a probability of failure POF within a time period t using a reduced mean-time-to-failure RMTTF according to the equation:

POF=1−

(e raised to the minus (t/RMTTF) to the 3/2 power).

9. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 1 further including the step of determining a dynamic force factor DF from the vibration data and wherein the step of calculating a reduced mean-time-to-failure RMTTF of the bearing comprises calculating a reduced mean-time-to-failure RMTTF of the bearing using the designer-determined mean-time-to-failure MTTF, BD and DF.

10. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 9 wherein the steps of determining a degraded condition factor BD for the bearing and determining a dynamic force factor DF from the vibration data comprise determining a plurality of discriminants from the vibration data and using the plurality of discriminants to calculate the degraded condition factor BD and the dynamic force factor DF for the bearing.

11. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 10 wherein at least one of the plurality of discriminants is selected from a group consisting of a low frequency energy LF discriminant, a high frequency energy HF discriminant, a crest factor CF discriminant, a kurtosis K discriminant, an envelope demodulation ED discriminant and a peak acceleration P discriminant.

12. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 10 wherein the degraded condition factor BD is calculated from a high frequency energy HF discriminant, a crest factor CF discriminant, a kurtosis K discriminant, an envelope demodulation ED discriminant and a peak acceleration P discriminant and the dynamic force factor DF is calculated from a low frequency energy LF discriminant and a percentage of the high frequency energy HF discriminant.

13. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 11 wherein the plurality of discriminants used to calculate the dynamic force factor DF includes the low frequency energy LF discriminant.

14. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 13 wherein the plurality of discriminants used to calculate the dynamic force factor DF includes the low frequency energy LF discriminant and a percentage of the high frequency energy HF discriminant.

15. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 9 wherein the selected forecast time period corresponds to the selected designer-determined mean-time-to-failure MTTF and varying the forecast time period varies the selected designer-determined mean-time-to-failure MTTF.

16. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 9 wherein the step of calculating a probability of failure of the bearing in the forecast time period using the reduced mean-time-to-failure RMTTF comprises calculating a probability of failure POF within a time period t using a reduced mean-time-to-failure RMTTF according to the equation:

POF=1−

(e raised to the minus (t/RMTTF) to the 3/2 power).

17. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 1 further including the step of calculating and displaying a probability of failure within a short term time period using RMTTF where the short term time period is less than the forecast time period.

18. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 1 further including the steps of:

accessing cost data corresponding to a cost of replacing the bearing in the rotating machine; and

displaying a comparison between the cost of replacing the bearing and the financial risk for the selected time period.

19. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 1 further including the steps of:

accessing cost data corresponding to a cost of replacing the bearing in the rotating machine; and

displaying a warning based on a comparison between the cost of replacing the bearing and the financial risk for the selected time period.

20. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 1 further including the step of accessing vibration frequency exclusion data and wherein the step of determining a degraded condition factor BD for the bearing from the vibration data comprises determining a degraded condition factor BD for the bearing from vibration data that excludes a range of vibration frequencies specified by the vibration frequency exclusion data.

21. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 20 wherein the vibration frequency exclusion data defines vibration frequencies corresponding to a variable frequency drive.

22. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 20 wherein the vibration frequency exclusion data defines vibration frequencies corresponding to a gear system.

23. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 1 further including the steps of:

accessing additional vibration data corresponding to at least one additional bearing to be analyzed;

determining a degraded condition factor BD from the additional vibration data for each additional bearing;

selecting an expected designer-determined mean-time-to-failure MTTF for each additional bearing;

selecting a forecast time period for each additional bearing;

calculating a reduced mean-time-to-failure RMTTF for each additional bearing using the degraded condition factor BD for each additional bearing;

calculating a probability of failure in the forecast time period for each additional bearing using the reduced mean-time-to-failure RMTTF for each additional bearing;

searching for bearings having a probability of failure above a specified level; and

displaying information about the bearings having a probability of failure above the specified level.

24. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 1 further including the steps of:

accessing additional vibration data corresponding to at least one additional bearing to be analyzed;

determining a degraded condition factor BD from the additional vibration data for each additional bearing;

selecting an expected designer-determined mean-time-to-failure MTTF for each additional bearing;

selecting a forecast time period for each additional bearing;

calculating a reduced mean-time-to-failure RMTTF for each additional bearing using the degraded condition factor BD for each additional bearing;

calculating a probability of failure in the forecast time period for each additional bearing using the reduced mean-time-to-failure RMTTF for each additional bearing;

accessing cost data corresponding to a cost of failure of each additional bearing;

calculating a financial risk for each additional bearing;

searching for bearings having a financial risk above a specified value; and

displaying information about the bearings having a financial risk above the specified value.

25. The method of analyzing vibrations of a bearing installed in a rotating machine according to claim 1 further including the steps of:

accessing additional vibration data corresponding to at least one additional bearing to be analyzed;

determining a degraded condition factor BD from the additional vibration data for each additional bearing;

selecting an expected designer-determined mean-time-to-failure MTTF for each additional bearing;

selecting a forecast time period for each additional bearing;

calculating a reduced mean-time-to-failure RMTTF for each additional bearing using the degraded condition factor BD for each additional bearing;

calculating a probability of failure in the forecast time period for each additional bearing using the reduced mean-time-to-failure RMTTF for each additional bearing;

calculating an expected remaining bearing life for each bearing;

searching for bearings having an expected remaining bearing life less than a specified duration; and

displaying information about the bearings having an expected remaining bearing life less than the specified duration.

26. A computer program product for analyzing vibrations of a bearing installed in a rotating machine comprising:

a computer usable medium having computer readable program code means embodied in said medium for accessing vibration data corresponding to the bearing to be analyzed;

computer readable program code means for determining a degraded condition factor BD for the bearing from the vibration data;

computer readable program code means for selecting an expected designer-determined mean-time-to-failure MTTF of the bearing operating under a design load in the operating environment of the rotating machine;

computer readable program code means for selecting a forecast time period;

computer readable program code means for calculating a reduced mean-time-to-failure RMTTF of the bearing using the expected designer-determined mean-time-to-failure MTTF and the degraded condition factor BD;

computer readable program code means for calculating a probability of failure of the bearing in the forecast time period using the reduced mean time to failure RMTTF;

computer readable program code means for accessing cost data corresponding to a cost of failure of the bearing in the rotating machine;

computer readable program code means for calculating a financial risk from the calculated probability of failure in the forecast time period and the cost data; and

computer readable program code means for displaying the financial risk for the selected time period.