US20010001135A1

US20010001135A1 - Condition Analyzer

Info

Publication number: US20010001135A1
Application number: US09/739,760
Authority: US
Inventors: Carsten Aronson
Original assignee: SPM Instrument AB
Current assignee: SPM Instrument AB
Priority date: 1996-07-05
Filing date: 2000-12-20
Publication date: 2001-05-10
Also published as: ES2138942T1; US6725723B2; EP0909430B1; US6499349B1; SE9602694D0; PT909430E; EP0909430A1; ATE207228T1; US20030018439A1; EP1124204A3; DE909430T1; US20010001136A1; CN1223735A; ES2138942T3; DE69707459T2; EP1124204A2; WO1998001831A1; CN100481137C; SE9602694L; DK0909430T3

Abstract

The invention relates to a method for evaluating the condition of a machine (100) with a measuring point (90), which method is performed by a movable analysis apparatus (30). The method comprises the steps of producing a condition value, by means of measuring at the measuring point, which condition value is dependent on the actual condition of the machine, and storing the condition value in a writable information carrier (120) which is placed by, or in the vicinity of, the measuring point (90) so that the condition value subsequently can be used as a reference condition value. The invention further relates to an apparatus for performing the method and a device for co-operating with the analysis apparatus and for mounting by a measuring point on the machine (100).

Description

TECHNICAL FIELD

1. The present invention relates to a method for generating a condition value for a measuring point on a machine having a measuring point, and a system for performing the method.

STATE OF THE ART

2. Machines with moving parts are subject to wear with the passage of time, which often causes the condition of the machine to deteriorate. Examples of such machines with movable parts are motors, pumps, generators, compressors, lathes and CNC-machines. It is known to, more or less regularly, investigate the operating condition of such machines. The operating condition can be determined by measuring the amplitude of vibrations in the bearings and by measuring temperature changes on the casing of the machine, which temperatures are dependent on the operating condition of the bearing. Such condition checks of machines with rotating or other moving parts are of great significance for safety and also for the length of the life of such machines. It is known to perform such measurements on machines completely manually. This ordinarily is done bv an operator with the help of a measuring instrument performing measurements at a number of measuring points on a machine. The measuring data obtained by means of the measuring instrument for each measuring point is noted down on a pre-printed formula. For a machine it can be necessary to have a number of measuring points in order to later be able to determine the overall operating condition of the machine. For example, three measuring points are often used for the measurement of vibrations of a motor, in such a way that the vibrations are measured in three mutually perpendicular directions, i.e. in the X-direction, in the Y-direction and in the Z-direction. The operator must note down each measured value on the formula. It is furthermore necessary for the operator to evaluate the measured values so that he can make a judgement on whether the measured amplitude measurement values indicate a change for a measuring position so that the machine can be serviced if the measured values indicate wear. This places a large demand on the professional knowledge of the service personnel of which vibration and temperature measurement values are acceptable and which measurement values are not acceptable.

3. In order to identify damage to bearings it is known to use a shock impulse measuring apparatus by means of which damage to bearings can be determined in machines with rotating machine parts. In order to perform such measurements at a measuring point, the diameter of the shaft and the rotational speed of the shaft are set on a measuring scale. These values, which are set by hand function as a reference level. If the measured values measured by means of the measuring instrument are greater than the reference level, this can be indicated by means of a warning lamp or by means of a sound signal.

4. It is known from EP-0 194 333 to provide each measuring point with identity data which is automatically readable by means of a separate reading probe. EP-0 194 333 also describes that the characteristic data values for the measuring point are readable at the measuring point so that the above described reference value can be generated automatically. The reference value is consequently calculated in a standardized and unambiguous way from the characteristic data values. Consequently, according to this known technique, the one and the same reference value is valid for all bearings with a certain shaft diameter and a certain rotational speed.

5. EP-0 211 212 describes a measuring instrunent for detecting and evaluating data representative of the condition of a machine. The described measuring instrument has a measuring probe which is combined with a sensor probe for reading a measuring point code, whereby the measuring probe and the code, sensing probe are provided in a common mobile casing.

DESCLOSURE OF THE INVENTION

6. The problem which is to be solved by means of the present invention is to provide a method which permits an increased accuracy in detecting changes of the condition of a machine.

7. This problem is solved according to the invention by means of a method for evaluating the condition of a machine with a measuring point, which method is performed by a movable analysis apparatus comprising the steps of:

8. producing a condition value, by means of a measurement at the measuring point, which condition value is dependent on the current condition of the machine; and

9. storing the condition value in a writable information carrier (120) which is placed on, or in the vicinity of the measung point 90 so that the condition value subsequently can be used as a reference condition value.

10. According to a preferred embodiment, the reference condition value is produced depending on a measured value, such as a vibration measured value measured in connection with the final inspection of a newly manufactured machine, and on relevant interpreting information, such as shaft diameters and rotational speeds for a rotatable shaft on a machine. With the object of providing a determination of whether some measurable condition change is present, a method according to the invention is performed which comprises the steps of:

11. a) producing a condition value, which condition value depends upon the actual condition of the machine at the measuring point; and of

12. b) acquiring a reference value, indicating the condition of the machine at the measuring point at an earlier time point, from an information carrier which is placed by, or in the vicinity of the measuring point.

DESCRIPTION OF THE DRAWINGS

13. In order to make the present invention easy to understand and produce, it will be described with reference to the appended drawings:
14.FIG. 1 shows a schematic block diagram of an embodiment of a condition analyzing system according to the invention.
15.FIG. 2A shows an embodiment of a sensor unit which comprises an interface for communication with an information carrier at a measuring point.
16.FIG. 2B shows an embodiment of a device at a measuring point comprising an information carrier and an interface for communication with the interface according to FIG. 2A.

PREFERRED EMBODIMENTS

17.FIG. 1 shows a schematic block diagram of an embodiment of a condition analyzing system 10 according to the invention. The condition analyzing system comprises a sensor unit 20 for producing a measured value dependent on movement and more precisely, dependent on vibrations.
18. The sensor unit 20 is connected to an analysis apparatus 30 via a conductor 32. The analysis apparatus 30 comprises a non-volatile memory 40, a microprocessor 50 and a read/write memory 60. A computer program is stored in the read memory 40, and by means of this computer program the function of the analvsis apparatus 30 is controlled. When it is written below that the microprocessor 50 performs a certain function, it shall be understood that the microprocessor runs a certain part of the program which is stored in the memory 40.
19. The microprocessor 50 is connected to a display unit 62. By means of the display unit 62 a user of the condition analyzing system is informed of the condition of the current measuring point in clear text. The production of a condition value is described more closely below. The display arrangement can cornprise, on the one hand a screen, on the other hand a printer unit, so that the user can have the condition value from the measuring point printed out if so desired.
20. According to a preferred embodiment the analysis apparatus 30 comprises a screen 62 on which relevant information is shown during the measuring, and a diskette station 64 in which a diskette is introduceable. In this way the user with the help of the analysis apparatus 30 collects the condition values for a plurality of measuring points and save all the information on a diskette removably introduced into the diskette unit 64. The microprocessor 50 is further connected to an information port 66, by means of which the apparatus 30 can be connected to a separate information processing unit.
21. The analysis apparatus 30 is equipped with an interface 70 for the exchange of data, with a device 80. When the system is operative, the device 80 is firmly mounted on or at a measuring point 90 on a machine 100 with a movable part 110. A measuring point can comprise a connection coupling firmly attached to the casing of the machine to which the sensor unit is removably attachable. The connection coupling can, for example, be formed of a bayonet coupling. A measuring point can cornprise a threaded recess in the casing in which the sensor unit is screwable. In the last case the sensor unit 20 comprises corresponding threads so that it can be introduced into the recess like a screw.
22. Alternatively, the measuring point is marked on the casing of the machine only with a painted mark.
23. The machine 100 exemplified in FIG. 1 has a rotating shaft 110 with a certain shaft diameter d₁. Shaft 110 in the machine 100 rotates at a certain speed of rotation V₁when the machine is in use.
24. The apparatus 80 comprises an information carrier 120 which is equipped with information on the identity of the measuring point and interpreting information. The information carrier is furthermore equipped with at least one condition value K_refwhich can be used as reference for determining a possible chance in the condition.
25. The identity information can be formed of, for example, the identity number of the measuring point or of a data string which identifies both the machine 100 and the measuring point 90. The machine 100, which is only partly shown in FIG. 1, can comprise a number of measuring points and a number of moving parts so that the condition of different parts of the machine can be determined individually. The interpretation data stored in the measuring point device 80 can comprise a first computer word indicating the above mentioned shaft diameter d₁, and a second computer word indicating the speed of rotation V₁. The information carrier 120 is connected to an interface unit 130 for exchanging information with the interface unit 70 of the analysis apparatus 30. An operator transports the portable analysis apparatus 30 to the measuring point for which the condition value is to be determined and attaches the sensor unit 20 to the measuring point 90. According to one embodiment the sensor unit 20 is provided with a change-over switch (not shown) which closes in dependence of the sensor unit being brought into contact with the measuring point 90. When the change-over switch closes, an activating signal is produced which, via the bus 32 is delivered to the microprocessor 50 and thereby activates the microprocessor to perform an analysis routine. An actual condition value is determined bv the analysis routine, and a reference value Kref acquired from the information carrier 120. The reference value K_refindicates the condition value for the individual machine for the same measuring point at an earlier point of time. The reference value K_refis stored in the information carrier in the same way as described below.
26. When the machine is new from the factory or when a bearing for a rotatable shaft 111 is renovated or exchanged, a condition value K_reffor each measuring point 90 of the machine 100 is determined.
27. The condition reference value for the measuring point is determined according to a preferred embodiment by producing a measured value indicating the vibration or temperature of the machine at the measuring point and, in a known way, with the help of interpretation information, such as shaft diameter and speed of rotation of the shaft, transforming the measured value into a condition value. Because this condition value K_refis produced when the corresponding machine part is new or newly renovated, possible later condition changes can be advantageously determined by comparison with the reference K_ref.
28. When the apparatus 30 is used to produce the reference condition value K_ref, a keyboard is connected to the information port 66 and the microprocessor is instructed to perform a reference-producing routine. The reference-producing routine involves the microcomputer 30 acquiring a measuring value from the sensor unit 20 and the display unit 62 showing a request for the operator to input the interpretation information which applies for the measuring point.
29. The interpretation information can be inputted, for example, via the keyboard or by means of a diskette which is introduced into the diskette station 64.
30. The microcomputer calculates the actual condition value K_refindicating the condition of the individual measuring point depending on the measured value and the inputted interpretation information.
31. Both the condition reference value K_refand the inputted interpretation information determined in this way are delivered to the information carrier 120 via the interface 70.
32. Alternatively, the interpretation data as well as the reference value K_refcan be delivered to the diskette unit 64 or the display unit screen 62 in order to be inputted to the information carrier 120 in another way.
33. According to a preferred embodiment of the invention the device 80 comprises a readable and writable memory 120 which can exchange information in both directions with the interface 130. According to one embodiment the device 80 comprises a photoelectric cell which provides the power supply to the memory 120 and the interface 130.
34. Because the device 80 in the above described way is applied with a condition reference value which is individual for the machine and for the measuring point, later condition measuring can give advantageously accurate indications about changes in the condition. This means that the analysis apparatus does not have to be provided with any information at all about the machine or its measuring point, and despite this it is still possible to achieve an accurate evaluation of whether any changes in the condition have occurred. This is of considerable advantage, for example, during the checking of the condition of machines fixed to the floor in a large manufacturing industry, where the number of machines and measuring points is very large. It further provides a very good security as the risk of mixing of the data in a data base is eliminated by the reference condition value being stored directly at the measuring point.
35. A method for determining a possible change in the condition is usually performed with a certain regularity by maintenance personnel. A first example of when such a process can be performed, according to the invention, is when a machine has just been installed after delivery. In this situation there is already a condition reference value in the information carrier which has been generated and stored there in connection with the final inspection at the manufacturer of the machine.
36. When the installator has just installed the machine, the process is performed for determining a possible change in the condition with the purposed of verifying that the installation is correct and that the condition of the macnine has not deteriorated during the transport from the manufacturer.
37. The method comprises the steps of:
38. producing a measured value which depends on a movement of the machine;
39. acquiring interpretation information from an information carrier which is mounted by the measuring point;
40. producing an actual condition value, indicating the actual condition of the measuring point on the machine, dependent on the measured value and the interpretation;
41. acquiring a second condition value, indicating the condition of the measuring point at an earlier point of time, from the information carrier;
42. producing a relation value dependent on the actual condition value and the second condition value, which relation value indicates a change in the condition.
43. This process can be performed by the microprocessor 50 by it running an analysis routine which is stored in the memory 40.
44. The analysis routine comprises the step of the microprocessor 50 requesting measured values from the sensor unit 20. According to one embodiment of the invention the sensor unit comprises an accelerometer 140 with a piezo-electric element. When the measuring point 90 vibrates, the sensor unit 20, or at least a part of it, also vibrates and the accelerometer 140 then produces an electrical sional of which the frequency and amplitude depend on the mechanical vibration frequency and the vibration amplitude of the measuring point 90, respectively. The electrical signal is delivered to the analog-digital converter 34 which with a certain sampling frequency f_sconverts the analog signal to consecutive digital words in a known way. The microcomputer 50 stores a series of digital words which correspond to a time sequence of the electrical signal in the memory 60, and then performs an analysis of the signal sequence, whereby the frequency and amplitude of the signal is determined. Consequently, a measured value for the vibration amplitude A_vand the vibration frequency f_vis determined. The microcomputer then take the interpretation information and the reference value K_reffrom the device 80 by reading information from the interface 70.
45. According to one embodiment, the interface 130 on the device 80 comprises an opto-transmitter which transfers data serially to the interface 70 in the form of trains of pulses of infrared light.
46. The device 80 can be activated depending on an information request which is received via the interface 130. Alternatively, the device 80 comprises a detector element which senses if the sensor unit 20 is applied to the measuring point 90 and then activates the device 80 to send information to the interface 130.
47. In this way the microcomputer receives information on the identity of the measuring point and interpretation information, such as the diameter value d₁and the rotational speed value V₁.
48. With knowledge of the interpretation information d₁resp. V₁, each measured vibration amplitude value A_vcan be easily converted to an actual condition value K_a. A predetermined interpretation algorithm is stored in the memory 40 and starting from an amplitude value A_vand interpretation information, such as d₁and V₁, the microcomputer produces a corresponding condition value K_adependent thereon. Such an interpretation algorithm is based on an embodiment of a method for producing a condition value described in the Swedish Laid-Open Document 339 576.
49. According to one embodiment, the interpretation algorithm is based on the machine classification standard ISO 2954.
50. The actual condition value K, produced and the reference condition value K_refacquired from the information carrier 120 are delivered to the screen 62 so that the operator can judge if the two values correspond. If K_ais essentially similar to K_refthe condition is essentially unchanged. If there is a discrepancy between the two values, then this indicates that the condition of the machine has changed.
51. Because the actual condition value K_aaccording to the invention can be compared with an earlier measured condition value K_reffor the same measuring point, an extremely accurate indication of changes is achieved. In this way, advantageously well-judged decisions can be made on when maintenance is required, which in turn leads to that the life length of the machine can be increased.
52. According to a preferred embodiment, the microcomputer produces a relation value in dependence of the actual condition value K_aand the reference condition value K_ref.
53. By dividing the value K_awith the reference K_ref, a relation value is achieved which gives a percentage change of the condition of the machine part or parts to which the measuring points relate. According to another embodiment the relation value is produced as the difference between the value K_aand the reference K_ref.

Claims

What is claimed is:

1. A portable vibration monitor, comprising:

a housing;

a sensor unit;

a transducer coupled to said sensor unit, wherein said transducer is substantially enclosed within said housing, and wherein said transducer has as an output an analog signal representative of vibrations present in a piece of vibrating machinery contacted by said sensor unit;

an analog to digital converter coupled to said output of said transducer, and configured to digitize said analog signal;

a processing circuit configured to receive said digitized analog signal and to produce digital data comprising a value indicative of the degree of bearing wear derived from said digitized analog signal, and

an interface circuit configured to receive said digital data from said processing circuit and to transmit said digital data to a device external to said housing.

2. The monitor of

claim 1

, wherein the processing circuit further produces a vibration parameter comprising velocity.

3. The monitor of

claim 1

, wherein the processing circuit further produces a vibration parameter comprising enveloped acceleration.

4. The monitor of

claim 1

, wherein the processing circuit further produces a vibration parameter comprising a frequency domain spectrum.

5. A method of monitoring the condition of a machine, comprising the steps of:

storing data indicative of bearing service or bearing assembly in a memory located proximate to a measuring point on a machine;

mechanically coupling a transducer to said measuring point;

processing an output of said transducer to produce data indicative of one or more characteristics of vibrations of said machine; and

storing said data indicative of one or more characteristics of vibrations of said machine in said memory.

6. The method of

claim 5

, additionally comprising the step of subsequently retrieving said data from said memory.

7. A handheld probe for monitoring the condition of machines, said handheld probe comprising:

a housing;

a piezoelectric transducer within said housing;

electrical circuitry within said housing;

a probe comprising a coupler for connecting to a device located at a measuring point on a machine, wherein said probe is mechanically coupled to said piezoelectric transducer; and

a contact located proximate to said probe, said contact coupled to said electrical circuitry so as to transmit electrical signals between said electrical circuitry and one or more devices external to said housing, whereby both an electrical and mechanical coupling between the device at the measuring point is made when said probe is connected to said device.

8. The handheld probe of

claim 7

, wherein said probe comprises a threaded portion adapted for engagement with a probe receiving location on the machine.

9. An interface between a vibration measuring point on a machine and a digital data processor, said interface comprising:

a portable, housing;

a probe having a first portion external to said housing which is configured to mechanically couple to said vibration measuring point, said probe additionally comprising a second portion coupled to a vibration transducer;

a circuit in said housing translating an analog electrical signal output from said transducer into digital data;

wireless communication circuitry within said housing receiving said digital data, and for wirelessly transmitting said digital data.

10. A method of monitoring the condition of a machine, the method comprising the steps of:

contacting a measuring point on said machine with a portable probe comprising a vibration transducer;

converting an output of said transducer to first data indicative of one or more characteristics of vibrations of said machine; and, electronically evaluating said data by determining the rate of change of the value of said data.