LEAK DETECTOR

• US 20120007744A1
• Filed: 09/19/2011
• Published: 01/12/2012
• Est. Priority Date: 08/19/2009
• Status: Active Grant

• Current Assignee: Severn Trent Water Limited (Severn Trent PLC)
• Original Assignee: Severn Trent Water Limited (Severn Trent PLC)
• Inventors: Pal, Maninder, Dixon, Neil, Flint, James
• Granted Patent: US 8,717,183 B2
• Time in Patent Office: Days
• US Class Current: 340/605
• CPC Class Codes: G01M 3/243 for pipes

Abstract

A leak detector for detecting and locating leaks in a water supply pipe of plastics, the leak detector comprising a first sensor at a first position arranged to detect a leak signal travelling along a pipe, a second sensor arranged to detect a leak signal travelling along the pipe at a second position spaced from the first position, and a processing device adapted to receive the signals from the first sensor and the second sensor. The processing device may be adapted to determine the velocity of the signals from characteristics of the leak signals. The processing device is adapted to use the velocity and distance between the first sensor and the second sensor to determine the location of a leak. The characteristics may be the relationship between the phase and frequency of the leak signals.

Claims

1. A leak detector for detecting and locating leaks in a water supply pipe of plastics, the leak detector comprising a first sensor at a first position arranged to detect a leak signal travelling along a pipe, a second sensor arranged to detect a leak signal travelling along the pipe at a second position spaced from the first position, and a processing device adapted to receive the signals from the first sensor and the second sensor, the processing device adapted to determine the velocity of the signals from measurement of characteristics of the leak signals and, using the velocity and distance between the first sensor and the second sensor, determine the location of a leak.

2. A leak detector according to claim 1, in which the characteristics are the phase and frequency of the leak signals.

3. A leak detector according to claim 1, in which the processing device is adapted to determine the velocity of the leak signals using a linear relationship between the phase and frequency of the leak signals.

4. A leak detector according to claim 1, in which the first and second sensors each include a signal conditioning element arranged to filter the signals received by the respective sensors and a transmitting element adapted to transmit the filtered signals to the processing device.

5. A leak detector according to claim 4, in which the signal conditioning elements include low-pass filters wherein the pass-band is substantially below 760 Hz.

6. A leak detector according to claim 4, in which the leak detector includes a transmitting element and a receiving element arranged such that the first sensor and the second sensor with their associated signal conditioning elements can operate wirelessly with respect to the remainder of the leak detector and wherein the transmitting element is adapted to preserve the phase of the leak signal detected by the first sensor and to preserve the phase of the leak signal detected by the second sensor.

7. A leak detector according to claim 1, in which the processing device is adapted to digitize and store the signals received from the first sensor and the second sensor.

8. A leak detector according to claim 1, in which the processing device includes a fine filtering element adapted to filter the digitised leak signals, the fine filtering element comprising a Bessel Finite Impulse Response (FIR) filter.

9. A leak detector according to claim 8, in which the fine filtering element comprises a ninth order Bessel low pass filter and an eighth order Bessel high pass filter.

10. A leak detector according to claim 1, in which the processing device includes a windowing element adapted to apply a Hanning window to the signals obtained from the first sensor to obtain a plurality of windowed signals and to the signals obtained from the second sensor to obtain a plurality of windowed signals.

11. A leak detector according to claim 10, in which the processing device includes a transform element adapted to apply a Fast Fourier Transform to the windowed signals.

12. A leak detector according to claim 10, in which the processing device includes an averaging element, the averaging element adapted to calculate the root mean square average of the plurality of windowed signals from the first sensor following the application of the Fourier transform to each of the windowed signals and the root mean square average of the plurality of windowed signals from the second sensor following the application of the Fourier transform to each of the windowed signals.

13. A leak detector according to claim 1, in which the processing device includes a velocity determination element arranged to determine the velocity of the leak signals from the characteristics of the leak signals and the distance between the first sensor and the second sensor, wherein the velocity is obtained by the following equation;

14. A leak detector according to claim 13, in which the processing device includes a leak location element adapted to receive the velocity calculated by the velocity determination element, the leak location element is also adapted to perform cross-correlation of the signal from the first sensor with the signal from the second sensor and using the results of the cross-correlation and the velocity, calculate the location of the leak with respect to either the first sensor position or second sensor position.

15. A method of detecting the position of a leak in pipes of plastics comprising the steps of;

listening for a leak signal at a first position along a pipe;

listening for a leak signal at a second position along a pipe spaced from the first position;

determining a sensor spacing distance between the first position and the second position;

determining the velocity of the leak signals from characteristics of the signals; and

identifying the location of a leak using the sensor spacing distance and the velocity.

16. A method according to claim 15, in which identifying the location of a leak also comprises determining the time delay between the leak signals received at the first sensor and the second sensor positions using a correlation function;

and

identifying the location of a leak using the sensor spacing distance, the velocity and the time delay.

17. A method according to claim 15, in which the steps of listening for a signal indicative of a leak are performed over a predetermined measurement period.

18. A method according to claim 15, in which the method includes the step of performing cross-correlation with the signal obtained at the first position and the signal received at the second position.

19. A method according to claim 15, in which the method includes the step of confirming a leak is detected in the correlation function by determining if a distinctive peak is obtained.

20. A method according to claim 18, in which cross-correlation is performed over a frequency range of the leak signal between 0 Hz and 350 Hz.