MULTIPLE DISCRIMINATE ANALYSIS AND DATA INTEGRATION OF VIBRATION IN ROTATION MACHINERY

• US 20040138832A1
• Filed: 01/11/2003
• Published: 07/15/2004
• Est. Priority Date: 01/11/2003
• Status: Active Grant

• Current Assignee: DMC SPA, Dynamic Measurement Consultants, LLC
• Original Assignee: Dynamic Measurement Consultants, LLC
• Inventors: Judd, John E.
• Granted Patent: US 6,763,312 B1
• Time in Patent Office: Days
• US Class Current: 702/56
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence

Abstract

A system and method for monitoring and analyzing vibrations in a rotating machine having rolling bearing elements where the method comprises providing an accelerometer to detect an acceleration signal indicative of machine vibration, filtering the vibration signal for signal frequencies indicative of bearing surface defects and converting the RMS value of the signal frequencies to a first DC voltage, determining the RMS value of the acceleration signal and converting the RMS value to a second voltage; determining the peak value of the acceleration signal, determining the ratio of the peak value to the RMS value of the acceleration signal and converting the ratio to a third DC voltage; determining the square of the peak value of the acceleration signal, determining the ratio of the squared peak value to the value of the second voltage to provide a fourth DC voltage indicative of the ratio; detecting a signal at the resonant frequency of the accelerometer, demodulating the detected signal at the resonant frequency and converting the resultant low frequency energy indicative of bearing defects to a fifth DC voltage; and summing the first third, fourth and fifth DC voltage signals in predetermined weights to obtain a signal indicative of the condition and degradation state of bearings in the rotating machine. A low frequency signal combined with a weighted portion of the high frequency energy signal is also detected from the accelerometer signal that provides an indication of the life reducing dynamic forces exerted on the bearing and converting it to a DC voltage indicative of a dynamic force factor on the life expectancy of the bearings. This dynamic force factor signal may be combined with the bearing degradation factor signal to provide a Life Expectancy Factor signal along with a Weibull Probability of Failure display.

Claims

1. A method of monitoring and analyzing vibrations in a rotating machine having rolling element bearings to determine machine bearing condition comprising the steps of

a. providing an accelerometer to detect an acceleration signal indicative of machine vibration;

b. determining the RMS value of said acceleration signal to provide a first signal;

c. filtering the acceleration signal for signal frequencies indicative of bearing surface defects, and converting the RMS value of said signal frequencies to a second signal;

d. determining the peak value of the acceleration signal, determining the ratio of said peak value to the RMS value of the first acceleration signal and converting said ratio to a third signal;

e. determining the square of the peak value of the acceleration signal, determining the ratio of said squared peak value to said first signal and converting said ratio to a fourth signal;

f. detecting a signal at the resonant frequency of the accelerometer, demodulating said resonant frequency signal and converting the low frequency component energy of the demodulated components to a fifth signal; and

g. combining said second through fifth signals in predetermined weights to obtain a voltage value indicative of the condition of the bearings in the rotating machine.

2. The method of claim 1 wherein the combining of said four signals is by multiplication.

3. The method of claim 1 wherein the combining of said four signals is by addition.

4. A method of monitoring and analyzing vibrations in a rotating machine having rolling element bearings to determine machine bearing condition comprising the steps of

a. providing an accelerometer to detect an acceleration signal indicative of machine vibration;

b. filtering the vibration signal for signal frequencies indicative of bearing surface defects and converting the RMS value of said signal frequencies to a first voltage signal;

c. determining the RMS value of the acceleration signal;

d. determining the peak value of the acceleration signal, determining the ratio of said peak value to the RMS value of the acceleration signal and converting said ratio to a second voltage signal;

e. determining the square of the peak value of the acceleration signal, determining the ratio of said squared peak value and converting said ratio to a DC voltage;

f. detecting a signal at the resonant frequency of the accelerometer, demodulating said signal at the resonant frequency and converting its low frequency energy to a third DC voltage signal; and

g. combining said first voltage signal and at least two of said second, third and forth voltage signals in predetermined weights to obtain a voltage value indicative of the condition of the bearings in the rotating machine.

5. The method of claim 4 further including the further step of filtering the accelerometer signal for low frequencies below about four times the rotational speed of the machine, which are indicative of dynamic forces on the machine bearings to provide a dynamic forces factor signal and combining the dynamic forces factor signal with the bearing degradation signal in a weighted relationship to obtain a life expectancy signal indicative of the expected remaining life of the bearing under test.

6. The method of claim 5 comprising the further step modifying the dynamic forces factor signal a factor indicative of the rigid or flexible mounting method of the machine.

7. A method of monitoring and analyzing vibrations in a rotating machine having rolling element bearings to determine the dynamic forces acting on the bearings comprising the steps of

a. providing an accelerometer to detect an acceleration signal indicative of machine vibration;

b. filtering the accelerometer signal for low frequencies below about four times the rotational speed of the machine, which are indicative of dynamic forces on the machine bearings, converting said low frequencies to a first voltage signal; and

c. filtering the acceleration signal for the high frequency impact energy signal frequencies indicative of bearing surface defects and converting the RMS value of said signal frequencies to a second voltage signal; and

combining a portion of said second voltage signal indicative of Hertzian fatigue with said first voltage signal to derive a third voltage signal indicative of the dynamic forces on the bearings.

8. A system for monitoring and analyzing vibrations in a rotating machine having rolling element bearings to determine machine bearing condition comprising

a. an accelerometer mountable to the machine to sense vibrations and provide an acceleration signal indicative of machine vibration;

b. first means receiving the acceleration signal determining the RMS value of said acceleration signal and providing a first signal indicative thereof;

c. a first filtering means for filtering the acceleration signal for signal frequencies indicative of bearing surface defects and converting the RMS value of said signal frequencies to a second signal,

d. first means for determining the peak value of the acceleration signal and determining the ratio of said peak value to the first signal and converting said ratio to a third signal;

e. second means for determining the square of the peak value of the acceleration signal, determining the ratio of said squared peak value to said first signal and converting said ratio to a fourth signal;

f. detecting from the acceleration signal a signal at the resonant frequency of the accelerometer, demodulating the signal at the resonant frequency, and converting the demodulated signal to a fifth signal; and

g. means for combining said second through fifth signals in to obtain a signal indicative of the condition of the bearings in the rotating machine.

9. The system of claim 8 where each of said second through fifth signals are derived in a channel receiving the acceleration signal and each of said channels includes scaling means for making each of said second through fifth signals of equal value for a predetermined condition of a bearing under inspection.

10. The system of claim 9 wherein said means for combining is an arithmetic unit which sums the second through fifth signals, multiplies the sum by the reciprocal of the number of channels and subtracts the resultant product from a reference value to obtain a value indicative of the existing condition of degradation of the bearing.

11. The system of claim 9 wherein said means for combining is an arithmetic unit which multiplies the values of the second through fifth signals and further multiplies the product by {fraction (1/10)}⁻

n, where n is the number of channels.