Method and apparatus for real-time, on-line monitoring of wear in machinery

• US 4,766,373 A
• Filed: 02/20/1987
• Issued: 08/23/1988
• Est. Priority Date: 10/17/1983
• Status: Expired due to Fees

• Current Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Original Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Inventors: Waggoner, Clinton A., Chambers, Keith W.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Snow, Walter E.
• Application Number:
  US07/016,791
• Time in Patent Office: 550 Days
• Field of Search: 324/204, 324/227, 340/631, 73/861.05, 73/861.11, 73/64
• US Class Current: 324/204
• CPC Class Codes: G01N 27/74 of fluids G01N24/00 takes precedence
• CPC Class Codes: G01N 3/56 Investigating resistance to wear or abrasion
• CPC Class Codes: G01N 3/567 by submitting the specimen to the action of a fluid or of a fluidised material, e.g. cavitation, jet abrasion G01N3/565 takes precedence
• CPC Class Codes: G01N 33/2858 Metal particles

Abstract

The specification describes a method and an apparatus for detecting and quantitatively assessing wear of a machine having ferromagnetic components subjected to wear during operation resulting in the production of ferromagnetic particulate wear debris, and a lubrication system utilizing a lubricating fluid, in which the wear debris becomes entrained, for lubricating the components. The method comprises the steps of passing a sample stream of the lubricating fluid at a predetermined rate of flow axially through the core of an inductance coil of a sample oscillator for producing a time varying signal which deviates from a predetermined value in proportion to the mass of ferromagnetic material contained in the fluid passing through the core, monitoring the rate of change of signal and activating an indicator when the rate of change of the signal exceeds a predetermined level.

Claims

1. A method of monitoring the rate of wear of a machine having ferromagnetic components which wear during operation resulting in the production of ferromagnetic particulate material, said machine having a lubrication system utilizing a lubricating fluid, in which said material becomes entrained, for lubricating said components, said method comprising the steps of:

passing a sample stream of said lubricating fluid at a uniform rate of flow axially through an inductance coil of an RF oscillator operating at a base frequenty arranged such that the frequency of the output signal of said oscillator deviates from said base frequency in proportion to the mass of the ferromagnetic material in the fluid passing through the coil;

periodically accumulating ferromagnetic particulate material at a site in said sample stream upstream of said coil for a predetermined time interval;

releasing material accumulated thereat at the conclusion of said interval; and

integrating with respect to time the frequency transient in the oscillator output signal resulting from said the passage of said accumulated material through said inductance coil to provide a signal proportional to the concentration of ferromagnetic particulate material in said lubricating fluid; and

comparing said proportional signal with a predetermined threshold to provide an indication of the rate of wear of said machine.

2. A method as defined in claim 1, further including the step of monitoring the rate of flow of said lubricating fluid through said coil and adjusting said flow rate so as to maintain it within predetermined limits.

3. A method as defined in claim 1, further including the steps of calculating the concentration of ferromagnetic particulate material in lubricating fluid flowing through said coil on the basis of the difference between the frequency of said output signal and said base frequency and activating an indicator when the calculated value exceeds a predetermined threshold level.

4. A method as defined in claim 1, further including the steps of determining the average value of said oscillator output signal over a predetermined time interval and activating an indicator when the value of the signal output by said oscillator exceeds said average value by a predetermined amount.

5. A method as defined in claim 1, further including the step of determining a wear severity index and activating an indicator when said index exceeds a predetermined value.

6. A method as defined in claim 2, said step of monitoring the rate of flow of said fluid including the steps of accumulating ferromagnetic particulate material in said stream at two separate sites upstream of said coil for equal predetermined intervals of time, releasing accumulated material at said sites into said stream in predetermined timed sequence, detecting the time interval between the arrival of said accumulations at said coil and converting said detected time into a flow rate.

7. A method as defined in claim 6, wherein said accumulations are released simultaneously.

8. A method as defined in claim 6, wherein the accumulation at a proximal site is released in advance of the accumulation at a distal site.

9. A method as defined in claim 5, wherein said step of determining a wear severity index includes the steps of determining the concentration of coarse and fine particles in said stream and determining the ratio one of said concentrations to the other of said concentrations.

10. A method as defined in claim 7, wherein said step of determining a wear severity index further includes accumulating both coarse and fine particles at a first predetermined site upstream of said coil for a predetermined time interval at a first trapping current, accumulating both coarse and fine particles at a second site spaced from said first site upstream of said coil for a predetermined time interval at a second trapping current and releasing the accumulations at said sites in predetermined timed sequence.

11. A method as defined in claim 9, wherein said step of determining a wear severity index further includes accumulating both coarse and fine particles at a single site upstream of said coil for a predetermined time interval at a first trapping current and releasing the accumulation, accumulating at the same site both coarse and fine particles for a predetermined time interval at a second trapping current and releasing the accumulation.

12. A method as defined in claim 1, said method further including the step of mixing said oscillator output signal with a reference signal having a reference frequency for producing a signal having both sum and difference frequencies and demodulating said signal to provide an IF output signal at the difference intermediate frequency.

13. A method as defined in claim 12, said integrating step including counting the number of cycles of said IF output signal during a second predetermined time interval subsequent to the conclusion of said time interval and within which said accumulated material passes through said coil, and converting the resultant count to signal representative of the concentration of ferromagnetic material in said fluid stream.

14. A real-time, on-line apparatus for monitoring the rate of wear of a machine having ferromagnetic components which wear during operation resulting in the production of ferromagnetic particulate material, said machine having a lubrication system utilizing a lubricating fluid, in which said material becomes entrained, for lubricating said ferromagnetic components, said apparatus comprising:

means defining a fluid flow passage having one end adapted to be connected to said machine for taking a sample of said lubricating fluid from said machine and another end adapted to be connected to said machine for returning said sample to said machine, said passage having a portion thereof formed of nonmagnetic material;

sensing means including an RF oscillator having an inductance coil disposed about said portion of said passage means, said oscillator being adapted to operate at a base RF frequency and produce an RF output signal, said coil being arranged such that the frequency of said RF output signal deviates from said base RF frequency in proportion to the mass of ferromagnetic particulate material entrained in the fluid passing through said coil;

means for accumulating ferromagnetic material in said sample stream upstream of said inductance coil; and

electrical circuit means for;

(a) integrating with respect to time the frequency transient in said RF output signal resulting from the passage of said accumulated material through said coil to provide an integrated output signal;

(b) comparing said integrated output signal against a predetermined threshold and providing a second output signal representative of the rate of wear of said machine; and

(c) controlling said accumulating means so as to activate said accumulating means for predetermined timed intervals at predetermined increments of time whereby to accumulate ferromagnetic particulate material at said site and deactivate said accumulating means at the end of said intervals whereby to release any accumulation at said site into said fluid passage.

15. An apparatus as defined in claim 14, said means defining a fluid flow passage including a housing having an interior chamber, a non-ferromagnetic electric insulator means defining said fluid flow passage, said inductance coil being disposed within said chamber and wound about said insulator means within said housing, and means disposed within said housing for radially supporting said passage means along the length thereof.

16. An apparatus as defined in claim 14, said accumulating means including an electromagnet responsive to said electrical circuit means for accumulating and releasing said ferromagnetic particulate material.

17. An apparatus as defined in claim 16, said electromagnetic having a cylindrical tubular core of magentic material defining a further portion of said passage and an electrical winding disposed about said core and electrically connected to said circuit means.

18. An apparatus as defined in claim 14, further including a reference oscillator for producing a time-varying signal having a nominal reference frequency, a mixer for combining said time-varying signals and for producing a signal having both sum and difference frequencies and demodulating said signal to provide an IF output signal having a difference intermediate frequency, said electrical circuit means being responsible to said IF output signal.

19. An apparatus as defined in claim 14, said electrical circuit means further including means for maintaining a constant rate of flow through said passage means.

20. An apparatus as defined in claim 14, said electrical circuit means further including means for monitoring the rate of flow of fluid through said passage and providing an indication of a change in said rate of flow.

21. An apparatus as defined in claim 14, said accumulating means being an electromagnet, said apparatus further including a second electromagnet for accumulating ferromagnetic particulate material in said passage, said second electromagnet being disposed upstream of said first mentioned electromagnet;

said electrical circuit means being operable to control the electrical current flow through said electromagnets whereby one of said electromagnets may be operated at a first trapping current for accumulating fine ferromagnetic particulate material thereat and the other of said electromagnets may be operated at a second and different trapping current for accumulating coarser ferromagnetic particulate material thereat; and

said electrical circuit means being further operable to deactivate said electromagnets in predetermined times relation and provide a signal proportional to the ratio of the concentration of fine and coarse ferromagnetic particulate material.

22. A method of monitoring the wear of a machine having ferromagnetic components subjected to wear during operation resulting in the production of ferromagnetic particulate material, said machine having a lubrication system utilizing a lubricating fluid, in which said material becomes entrained, for lubricating said components, said method comprising the steps of:

passing a sample stream of said lubricating fluid at a predetermined rate of flow axially through an inductance coil of an RF oscillator operating at a base frequency arranged such that the frequency of the output signal of said oscillator deviates from said base frequency in proportion to the mass of the ferromagnetic material in the fluid passing through said core;

periodically accumulating ferromagnetic particulate material at a site in said sample stream upstream of said coil for a predetermined time interval;

releasing material accumulated thereat at the conclusion of said interval;

detecting the change of the frequency of said output signal from said base frequency;

monitoring the rate of flow of said lubricating fluid through said core and adjusting said flow rate so as to maintain it within predetermined limits, said monitoring step including the steps of accumulating ferromagnetic particulate material in said stream at two separate sites upstream of said core for equal predetermined intervals of time, releasing accumulated material at said sites into said stream in predetermined timed sequence, detecting the time interval between the arrival of said accumulations at said core and converting said detected time into a flow rate.

23. An apparatus for monitoring the rate of wear of a machine having ferromagnetic components subjected to wear during operation resulting in the production of ferromagnetic particulate material, said machine having a lubrication system utilizing a lubrication fluid, in which said material becomes entrained, for lubricating said ferromagnetic components, said apparatus comprising:

means defining a fluid flow passage having one end adapted to be connected to said device for taking a sample of said lubrication fluid from said device and another end adapted to be connected to said device for returning said sample to said device, said passage having a portion thereof formed of nonmagnetic material;

an RF oscillator having an induction coil disposed about said portion of said passage means, said oscillator being adapted to operate at a base RF frequency and product an RF output signal, said coil being arranged such that the frequency of said RF output signal deviates from said base RF frequency in proportion to the mass of ferromagnetic particulate material entrained in the fluid passing through said core;

means for accumulating ferromagnetic material in said sample stream upstream of said inductance coil;

electrical circuit means for monitoring the change of the frequency of said signal and producing an output signal when the change of the frequency of said signal exceeds a predetermined value and controlling said accumulating means whereby to activate said accumulating means for predetermined timed intervals at predetermined increments of time whereby to accumulate particulate at said site and to deactivate said accumulating means at the end of said intervals whereby to release any accumulation at said site into said fluid passage; and

means responsive to said circuit means output signal for providing an indication of a wear condition;

means for monitoring the rate of flow of fluid through said passage and providing an indication of a change in said rate of flow, said means for monitoring the rate of flow of fluid through said passage including;

first means for accumulating ferromagnetic particulate material in said passage upstream of said coil;

second means for accumulating ferromagnetic particulate material in said passage upstream of said coil;

control means for activating and deactivating said first and second accumulating means;

means responsive to the output of said oscillator for detecting the peak position with respect to time thereof produced in response to accumulated material released by said accumulating means and flowing through said core;

timer means responsive to said peak positions for determining the time interval between the peak positions and producing a signal representative of said interval; and

means responsive to said interval representative signal for producing a signal representative of the flow rate of said fluid in said passage.