Diagnostic method for predicting maintenance requirements in rotating equipment

• US 20060178854A1
• Filed: 07/07/2004
• Published: 08/10/2006
• Est. Priority Date: 07/07/2003
• Status: Active Grant

• Current Assignee: ArcelorMittal Dofasco GP
• Original Assignee: ArcelorMittal Dofasco GP
• Inventors: Hunt, Kevin Guy, Stulen, James Frederick, Lindsay, William
• Granted Patent: US 7,206,719 B2
• Time in Patent Office: Days
• US Class Current: 702/177
• CPC Class Codes: B21B 28/00 Maintaining rolls or rolling equipment in effective condition lubricating, cooling or heating rolls while in use B21B27/06
• CPC Class Codes: B21B 38/00 Methods or devices for measuring, detecting or monitoring specially adapted for metal-rolling mills, e.g. position detection, inspection of the product control devices or methods B21B37/00
• CPC Class Codes: B21B 38/008 Monitoring or detecting vibration, chatter or chatter marks
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition
• CPC Class Codes: G05B 2219/37434 Measuring vibration of machine or workpiece or tool
• CPC Class Codes: G05B 2219/37435 Vibration of machine
• CPC Class Codes: G05B 23/0283 Predictive maintenance, e.g. involving the monitoring of a system and, based on the monitoring results, taking decisions on the maintenance schedule of the monitored system; Estimating remaining useful life [RUL] preventive maintenance, i.e. planning maintenance according to the available resources without monitoring the system G06Q10/06

Abstract

This invention is a method to determine the condition of rotating equipment, namely drive spindles, to enable the timely maintenance or replacement of same. The method uses an electrical signal from a vibration sensor mounted on part of the drive train to measure the level of vibration energy when the equipment is rotating under loaded and unloaded conditions. The relative vibration under the loaded and unloaded conditions is used as an indicator of equipment condition. Typically there is more vibration under load when the equipment is in good condition. When the level of vibration under the no-load condition matches or exceeds that seen under load, the equipment needs to be serviced or replaced.

Claims

1. A diagnostic method for predicting maintenance requirements in rotating equipment normally operating in loaded and unloaded conditions, the method including the following steps;

coupling a sensor to apparatus associated with said rotating equipment, said sensor being responsive to vibration in said apparatus to generate an electric signal;

obtaining a load signal from apparatus associated with said rotating equipment which is indicative of whether the rotating equipment is loaded;

sampling said electric signal when the rotating equipment is loaded over a predetermined sampling time interval to obtain a loaded electric signal Vl;

sampling said electric signal when the rotating equipment is unloaded over a predetermined sampling time interval to obtain an unloaded electric signal Vμ

; and

periodically displaying the relative magnitude between said loaded electric signal Vl and said unloaded electric signal Vμ

over an extended maintenance period of time, a maintenance inspection being required when the magnitude of the unloaded electric signal Vμ

exceeds the magnitude of the loaded electric signal Vl.

2. A diagnostic method according to claim 1 in which the sensor is selected from the group comprising a velometer and an accelerometer.

3. A diagnostic method according to claim 1 in which the electric signal generated is either current or voltage.

4. A diagnostic method according to claim 1 in which the sensor includes a piezoelectric crystal.

5. A diagnostic method according to claim 1 in which the rotating equipment is a drive spindle for a work roll and the load signal is indicative of whether the work roll is applying pressure to a work piece or whether the work piece has exited the work roll.

6. A diagnostic method according to claim 1 in which the electric signal is sampled during a sampling time interval selected to correspond to a predetermined vibration frequency range.

7. A diagnostic method according to claim 6 in which the predetermined vibration frequency range during which the electric signal is sampled is 0 to 150 Hz for rotating equipment rotating at less than 100 revolutions per minute.

8. A diagnostic method according to claim 6 in which the predetermined vibration frequency range during which the electric signal is sampled is 0 to 200 Hz for rotating equipment rotating at up to 700 revolutions per minute.

9. A diagnostic method according to claim 6 in which the predetermined vibration frequency range during which the electric signal is sampled is 0 to 500 Hz for rotating equipment rotating at more than 1000 revolutions per minute.

10. A diagnostic method according to claim 1 in which the said loaded electric signal Vl is sampled over a time interval of 10 seconds during which the rotating equipment is fully loaded.

11. A diagnostic method according to claim 1 in which the said unloaded electric signal Vμ

is sampled over a time interval of 10 seconds during which the rotating equipment is unloaded.

12. A diagnostic method according to claim 1 in which sampling of the unloaded electric signal Vμ

begins a predetermined period of time after the load signal indicates that the rotating equipment is not loaded.

13. A diagnostic method according to claim 1 in which the loaded and unloaded electric signals Vl and Vμ

correspond to the maximum electric readings taken during said predetermined sampling time interval.

14. A diagnostic method according to claim 1 in which electric readings corresponding to the loaded and unloaded electric signals Vl and Vμ

are averaged during said predetermined sampling time interval to generate an average electric signal.

15. A diagnostic method according to claim 14 in which an alert signal corresponding to the arithmetic ratio R between electric readings corresponding to Vl and Vμ

is generated and displayed visually.

16. A diagnostic method according to claim 15 in which a daily average of the arithmetic ratio R is plotted over time.

17. A diagnostic method according to claim 15 in which the natural logarithmic of the ratio R is plotted over time.

18. A diagnostic method according to either claim 16 or 17 in which the slope of the plot is monitored.

19. A diagnostic method for predicting maintenance requirements in rotating equipment normally operating in loaded and unloaded conditions, the method including the following steps;

coupling a sensor to apparatus associated with said rotating equipment, said sensor being responsive to vibration in said apparatus to generate an electric signal;

obtaining a load signal from apparatus associated with said rotating equipment which is indicative of whether the rotating equipment is loaded;

calculating a range of average maximum and average minimum electric signal readings over a pre-selected sampling time interval for rotating equipment in a loaded condition;

calculating a range of average maximum and average minimum electrical signal readings over a pre-selected sampling time interval for rotating equipment which is not loaded;

calculating the natural log of the ratio of an average loaded to average unloaded range value to define a condition index;

periodically displaying the condition index over an extended maintenance period of time, a maintenance inspection being required when the condition index falls below a predefined threshold.