Method and apparatus for analyzing rotating machines

• US 5,115,671 A
• Filed: 07/13/1990
• Issued: 05/26/1992
• Est. Priority Date: 07/13/1990
• Status: Expired due to Fees

• Current Assignee: Life Systems, Inc.
• Original Assignee: Life Systems, Inc.
• Inventors: Hicho, Michael D.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): Arana, Louis M.
• Application Number:
  US07/552,421
• Time in Patent Office: 683 Days
• Field of Search: 73/488, 73/496, 73/506, 73/507, 73/570, 73/660, 340/670, 340/671, 340/683
• US Class Current: 73/488
• CPC Class Codes: F04C 2270/125 Controlled or regulated
• CPC Class Codes: F04C 28/28 Safety arrangements; Monitoring
• CPC Class Codes: F16C 19/52 with devices affected by abnormal or undesired conditions
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence
• CPC Class Codes: G01M 13/045 Acoustic or vibration analysis
• CPC Class Codes: G01N 2291/2696 Wheels, Gears, Bearings

Abstract

A vibration transducer (22) is mounted to a rotating machine (20) for sensing vibration thereof. An output electrical signal from the vibration transducer is analyzed to generate a level display (18) of vibrational displacement per unit time, a speed display (22) indicative of rotational speed, and a bearing condition display (20) indicative of bearing condition, all displays derived directly from the vibration transducer signal. The electrical signal is transformed (36) into a frequency spectrum that has an amplitude for each of a plurality of narrow frequency ranges or bins. Each frequency bin has a characteristic center frequency and a predefined width or band of frequencies. A speed analysis program (38) identifies a set of at least first, second and third order related frequency bins, i.e. frequency bins whose center frequencies are an even multiple of each other, that have a significantly high amplitude and provides the lowest bin center frequency as a control signal to the speed display. A bearing condition analysis program (40) eliminates the bins that are integer multiples of the running speed and lower frequency, e.g. less than third order, identifies sets of bins with relatively large amplitudes that are integer multiples of each other, and selects the set of bins with the largest amplitude as being controlling of bearing condition. After elimination of frequencies not indicative of bearing condition, the bearing defect frequency remains. The amplitude of this frequency is displayed on bearing condition readout (22). The amplitude indicating the severity of the bearing defect.

Claims

1. A method for determining a running speed of a rotating machine whose rotating elements are enclosed in a housing, the method comprising:

sensing, from a vibration transducer input means in contact with said housing, mechanical vibrations of the rotating machine;

converting the sensed vibrations into an electrical signal;

filtering the electrical signal to obtain and select frequencies of the electrical signal;

converting the filtered electrical signal into a frequency spectrum;

selecting frequency components of the frequency spectrum characteristic of the running speed, and components that are random, spurious and caused by other effects;

eliminating the components that are random, spurious and caused by other effects;

calculating the running speed from the selected running speed characteristic frequency components.

2. The method of claim 1 wherein the step of selecting the frequency components includes:

identifying frequency peaks within the frequency spectrum;

identifying corresponding first, second, and third order sets of the frequency peaks;

identifying corresponding frequency peaks of greater than the third order;

and wherein the calculating step includes;

calculating an estimated running speed from a one of the first, second, and third order related sets;

confirming the estimated running speed with a previously calculated final running speed;

comparing the confirmed estimated running speed with a running speed corresponding to the greater than third order frequency peaks;

selecting one of the greater than third order frequency peak running speed and the estimated running speed, as a representation of the final running speed.

3. An apparatus for determining running speed of a rotating machine whose rotating elements are enclosed in a housing, the apparatus comprising:

a vibration transducer input means in contact with said housing for converting sensed mechanical vibrations into an electrical signal;

an analog-to-digital convertor means for converting the electrical signal into a digital signal;

a transform means for transforming the digital signal into a frequency spectrum;

a selecting means for selecting frequency components of the frequency spectrum characteristic of running speed and frequency components that are random, spurious and caused by other effects;

an eliminating means for eliminating the frequency components that are random, spurious and caused by other effects;

a converting means for converting the selected running speed characteristic frequency components to obtain an indication of the running speed.

4. The apparatus of claim 3 wherein the selecting means includes:

a refining means for selectively combining portions of each selected components with adjacent frequency components to resolve the selected components into a greater number of frequency components each with a narrower frequency range;

an identifying means for identifying sets of the refined frequency components that are first, second and third order related as having center frequencies that are even multiples of each other;

a running speed estimating means for estimating an estimated running speed from the center frequencies of one of the first, second, and third order related sets;

a confirming means for confirming the estimated running speed with a previously known final running speed;

means for identifying a set of higher order frequency components related to the first, second and third order related sets, the higher order frequency component sets having a higher frequency greater than the third order related set;

comparing means for comparing the confirmed estimated running speed with the higher order frequency components of the higher order frequency component set;

selecting means for selecting one of the higher order frequency components and the estimated running speed, as a representation of the final running speed.

5. A method for determining a running speed of a rotating machine from a sensed vibration of the rotating machine, the method comprising:

converting the sensed vibration into an electrical signal;

filtering the electrical signal to obtain and select frequencies of the electrical signal;

converting the filtered electrical signal into a frequency spectrum;

selecting frequency components of the frequency spectrum characteristic of the running speed, and components that are random, spurious and caused by other effects by,

identifying frequency peaks within the frequency spectrum,

identifying corresponding first, second, and third order sets of the frequency peaks, and

identifying corresponding frequency peaks of greater than the third order;

eliminating the components that are random, spurious and caused by other effects;

calculating the running speed from the selected running speed characteristic frequency components by,

calculating an estimated running speed from at least a one of the first, second, and third order related sets, and

confirming the estimated running speed with a previously calculated final running speed;

comparing the confirmed estimated running speed with a running speed corresponding to the greater than third order frequency peaks;

selecting one of the greater than third order frequency peak running speed and the estimated running speed, as a representation of the final running speed.

6. An apparatus for determining running speed of a rotating machine from sensed vibrations, the apparatus comprising:

p1 a vibration detector means for converting the sensed vibrations into an electrical signal;

an analog-to-digital convertor means for converting the electrical signal into a digital signal;

a transform means for transforming the digital signal into a frequency spectrum;

a selecting means for selecting frequency components of the frequency spectrum characteristic of running speed and frequency components that are random, spurious and caused by other effects;

an eliminating means for eliminating frequency components that are random, spurious and caused by other effects;

a refining means for selectively combining portions of each selected components with adjacent frequency components to resolve the selected components into a greater number of frequency components each with a narrower frequency range;

an identifying means for identifying sets of the refined frequency components that are first, second and third order related as having center frequencies that are even multiples of each other;

a running speed estimating means for estimating an estimated running speed from the center frequencies of one of the first, second, and third order related sets;

a confirming means for confirming the estimated running speed with a previously known final running speed;

means for identifying a set of higher order frequency components related to the first, second and third order related sets, the higher order frequency component sets having a higher frequency greater than the third order related set;

comparing means for comparing the confirmed estimated running speed with the higher order frequency components of the higher order frequency component set; and

,

selecting means for selecting one of the higher order frequency components and the estimated running speed, as a representation of the final running speed.

7. A method for determining a running speed of a rotating machine enclosed within a housing, the method comprising:

sensing mechanical vibrations of the rotating machine with a vibration detector in contact with the housing of the rotating machine;

converting the sensed mechanical vibrations into an electrical signal;

filtering the electrical signal to obtain and select frequencies of the electrical signal;

converting the filtered electrical signal into a frequency spectrum ranging approximately from 0 Hz to 1000 Hz.

selecting frequency peaks of the frequency spectrum ranging from about 0 Hz to about 1000 Hz characteristic of the running speed, and components that are random, spurious and caused by other effects;

eliminating the components that are random, spurious and caused by other effects;

calculating an estimated running speed from at least one of the frequency peaks;

confirming the estimated running speed with a previously calculated final running speed;

comparing the confirmed estimated running speed with a running speed corresponding to a highest obtained frequency peak of the frequency peaks; and

,

selecting one of the highest obtained frequency peak representing the running speed and the estimated running speed, as a representation of the final running speed.

8. An apparatus for determining running speed of a rotating machine enclosed within a housing, the apparatus comprising:

a vibration detector means in contact with the housing for converting sensed mechanical vibrations into an electrical signal;

an analog-to-digital convertor means for converting the electrical signal into a digital signal;

a transform means for transforming the digital signal into a frequency spectrum ranging approximately from 0 Hz to 1000 Hz;

a selecting means for selecting frequency peaks of the frequency spectrum characteristic of running speed and frequency components that are random, spurious and caused by other effects;

an eliminating means for eliminating the frequency components that are random, spurious and caused by other effects;

a running speed estimating means for estimating an estimated running speed from center frequencies of at least one of the frequency peaks;

a confirming means for confirming the estimated running speed with a previously known final running speed;

means for identifying a highest obtained frequency peak of the frequency peaks;

comparing means for comparing the confirmed estimated running speed with the highest obtained frequency peak; and

,

selecting means for selecting one of the highest frequency peak and the estimated running speed, as a representation of the final running speed.