Acoustic vibration detection of fluid leakage from conduits
First Claim
1. A method for determining the occurrence of an event in an elongated conduit comprising the steps of:
- providing first and second sensor means operably connected to said conduit for generating signals related to sensing at least one of axial or torsional vibrations of said conduit in response to said event;
recording said signals as a function of time;
determining the time difference between arrival of vibrations which generate signals at said first sensor means and said second sensor means, respectively, by(1) subjecting a plurality of multiple point consecutive time records for each signal to fast Fourier transform analysis of the time domain data to produce auto spectra values of said first sensor signal, Gaa, and said second sensor signal, Grr, respectively;
(2) calculating the cross spectra values, Gar, of the respective series of time records of said first and second signals, respectively;
(3) summing the auto spectra values and the cross spectra values and determining averages of each, respectively;
(4) calculating the impulse response by determining the inverse Fourier transform of the ratio of the averaged cross spectra to the averaged auto spectra of at least one of said auto spectra;
(5) plotting the resultant values of said inverse Fourier transforms as a function of time to determine a peak value of such resultant values from time=O to determine said time difference; and
(6) determining the location of said event based on said time difference and the acoustic velocity of a stress wave in said conduit.
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Accused Products
Abstract
Fluid leakage from a crack or other leakage point and other vibration-generating events in pipes and conduits may be located and analyzed by sensing axial and torsional vibrations and pressure fluctuations created by such events by placing accelerometers and/or strain gauges and pressure sensors on the conduit at selected points. The location of the event may be determined by comparing the travel time of selected pairs of signals such as axial propagated signals as compared with torsional propagated signals as a result in the difference of the acoustic wave speed of axial versus torsional waves. Cross correlation and deconvolution processes are carried out on the measured signals to determine differential signal arrival times at the sensors and to eliminate pipe response signals. An apparatus having axial and torsional vibration sensing accelerometers thereon includes mechanism for clamping the apparatus to the inside wall of the tubing or pipe and sensing the vibratory output signals of the accelerometers to determine the nature of and location of the vibration inducing event.
87 Citations
18 Claims
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1. A method for determining the occurrence of an event in an elongated conduit comprising the steps of:
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providing first and second sensor means operably connected to said conduit for generating signals related to sensing at least one of axial or torsional vibrations of said conduit in response to said event; recording said signals as a function of time; determining the time difference between arrival of vibrations which generate signals at said first sensor means and said second sensor means, respectively, by (1) subjecting a plurality of multiple point consecutive time records for each signal to fast Fourier transform analysis of the time domain data to produce auto spectra values of said first sensor signal, Gaa, and said second sensor signal, Grr, respectively; (2) calculating the cross spectra values, Gar, of the respective series of time records of said first and second signals, respectively; (3) summing the auto spectra values and the cross spectra values and determining averages of each, respectively; (4) calculating the impulse response by determining the inverse Fourier transform of the ratio of the averaged cross spectra to the averaged auto spectra of at least one of said auto spectra; (5) plotting the resultant values of said inverse Fourier transforms as a function of time to determine a peak value of such resultant values from time=O to determine said time difference; and (6) determining the location of said event based on said time difference and the acoustic velocity of a stress wave in said conduit. - View Dependent Claims (2, 3)
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4. A method for determining the occurrence of an event in an elongated conduit comprising the steps of:
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providing first and second sensor means operably associated with said conduit for sensing vibrations of said conduit and pressure fluctuations of fluid in said conduit in response to said event; comparing signals generated by said first and second sensor means to determine at least one of the location or nature of said event. - View Dependent Claims (5, 6, 7, 8)
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9. A method for determining the occurrence of an event in an elongated fluid conducting conduit comprising the steps of:
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providing means disposed in said conduit at a predetermined position and including axial vibration sensing means, and torsional vibration sensing means for sensing axial and torsional vibrations of said conduit, respectively, and means for sensing changes in fluid pressure in said conduit; and comparing signals generated by said means for sensing changes in said pressure with signals generated by at least one of said means for sensing axial vibrations or torsional vibrations in said conduit for determining at least one of the location or nature of said event. - View Dependent Claims (10, 11)
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12. A method for determining the occurrence of an event in an elongated fluid conducting conduit comprising the steps of:
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providing means disposed in said conduit at a predetermined position and including axial vibration sensing means and torsional vibration sensing means for sensing axial and torsional vibrations of said conduit, respectively, and comparing first signals generated by said axial vibration sensing means and second signals generated by said torsional vibration sensing means, respectively, for determining the location of said event in said conduit by determining the time difference between arrival of vibrations which generate said first and second signals by; (1) subjecting a plurality of multiple point consecutive time records for each signal to fast Fourier transform analysis of the time domain data to produce auto spectra values of said first signal, Gaa, and said second signal, Grr, respectively; (2) calculating the cross spectra values, Gar, of the respective series of time records of said first and second signals, respectively; (3) summing the auto spectra values and the cross spectra values and determining averages of each, respectively; (4) calculating the impulse response by determining the inverse Fourier transform of the ratio of the averaged cross spectra to the averaged auto spectra of at least one of said auto spectra; and (5) plotting the resultant values of said inverse Fourier transforms as a function of time to determine a peak value of such resultant values from time=O to determine said time difference. - View Dependent Claims (13)
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14. An apparatus insertable in an elongated tubular conduit for measuring vibratory movement of said conduit to determine at least one of the location of or nature of the occurrence of an event in said conduit, said apparatus comprising:
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a first body part; first accelerometer means mounted on said first body part for measuring vibrations in an axial direction with respect to said conduit; second accelerometer means mounted on said first body part for measuring torsional vibrations in said conduit; means movable at will for urging said first body part into forcible contact with said conduit; and means on said first body part for engaging a wall surface of said conduit for transmitting said vibrations from said conduit to said apparatus. - View Dependent Claims (15)
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16. An apparatus insertable in an elongated tubular conduit for measuring vibratory movement of said conduit to determine at least one of the location of or nature of the occurrence of an event in said conduit, said apparatus comprising:
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a first body part; first accelerometer means mounted on said first body part for measuring vibrations in an axial direction with respect to said conduit; second accelerometer means mounted on said first body part for measuring torsional vibrations in said conduit; means for urging said first body part into forcible contact with said conduit for transmitting said vibrations from said conduit to said apparatus; and means on said first body part for engaging a wall surface of said conduit at three spaced points on said conduit. - View Dependent Claims (17)
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18. An apparatus insertable in an elongated tubular conduit for measuring vibratory movement of said conduit to determine at least one of the location of or nature of the occurrence of an event in said conduit, said apparatus comprising:
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a first body part; first accelerometer means mounted on said first body part for measuring vibrations in an axial direction with respect to said conduit; second accelerometer means, including at least two accelerometers, mounted on said first body party, said at least two accelerometers being disposed spaced apart from each other radially with respect to said axial direction of said conduit for measuring torsional vibrations in said conduit; and means for urging said first body part into forcible contact with said conduit for transmitting said vibrations from said conduit to said apparatus.
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Specification