Magnetometer-based Detector for Objects in a Pipeline

• US 20100295543A1
• Filed: 05/22/2009
• Published: 11/25/2010
• Est. Priority Date: 05/22/2009
• Status: Active Grant

• Current Assignee: TDW Delaware Incorporated
• Original Assignee: TDW Delaware Incorporated
• Inventors: Logan, Matthew W., Miska, Stephen J., Maltby, Philip M., Register, Mark G., Rankin, William J., Salsman, Lloyd N., Freeman, Eric N.
• Granted Patent: US 8,378,667 B2
• Time in Patent Office: Days
• US Class Current: 324/220
• CPC Class Codes: F16L 55/48 Indicating the position of the pig or mole in the pipe or conduit
• CPC Class Codes: G01N 27/72 by investigating magnetic variables

Abstract

A system and method for detecting the passage of an object in a pipeline includes a non-intrusive detection device that houses one or more shielded magnetometer sensors and a microcontroller with adaptive thresholding detection means. The adaptive thresholding detection means removes outlier data from the magnetic flux data stream and then passes the outlier-free data stream through four low pass filters. A smoothed magnitude of the data stream is compared to detection limits and, if a passage event has occurred, a recent detection is indicated, a counter of a display unit is incremented, a time of passage is recorded, and both statistics are displayed on the display unit. Because a single object may produce multiple magnetic fields, the detector may be locked-out for a predetermined period of time after the passage event to prevent a second detection of the same object as it passes the detection device.

Claims

1. A system for detecting the passage of an object in a pipeline, the system comprising:

a detector arranged about an external surface of a pipeline and including at least one magnetometer sensor;

a shielding surrounding the at least one magnetometer sensor; and

a microcontroller in communication with the at least one magnetometer sensor and having an adaptive thresholding detection means.

2. A system according to claim 1 further comprising a second magnetometer sensor oriented orthogonal to said at least one magnetometer sensor.

3. A system according to claim 1 further comprising a display module in communication with said microcontroller.

4. A system according to claim 1 further comprising said adaptive thresholding detection means including a low pass filter.

5. A system according to claim 4 wherein a transfer function of said low pass filter is

6. A system according to claim 5, the parameter “

f”

is in a range of 1 to 4096.

7. A system according to claim 4 wherein a transfer function of said low pass filter is

8. A system according to claim 7, the parameter “

fn”

is in a range of 1 to 256.

9. A system according to claim 4 wherein a transfer function of said low pass filter is

10. A system according to claim 9, a length of the rectangular window is in a range of 2 to 128.

11. A system according to claim 4 wherein a transfer function of said low pass filter is

12. A system according to claim 1 further comprising means for preventing detection.

13. A system according to claim 12 wherein said preventing means is a reed switch.

14. A system according to claim 12 wherein said preventing means is a Bayesian lockout estimator.

15. A system according to claim 1 further comprising means for adjusting a position of the detector relative to the external surface of the pipeline.

16. A system according to claim 1 further comprising a detachably secured base capable of receiving a portion of said detector.

17. A system according to claim 1 further comprising said shielding being a magnetic permeable shielding.

18. A system according to claim 1 further comprising said shielding being an electrical insulating shielding.

19. A system according to claim 1 further comprising a backup power source, said backup power source configured to break electrical contact prior to exposure to ambient environment.

20. A method for detecting the passage of an object in a pipeline, the method comprising the steps of:

positioning at least one magnetometer sensor near an exterior surface of the pipeline;

collecting a magnetic flux data stream from the at least one magnetometer sensor;

processing the magnetic flux data stream through an adaptive thresholding detection algorithm; and

detecting a passage event.

21. A method according to claim 20, said processing step further comprising the step of passing the magnetic flux data through at least one low pass filter.

22. A method according to claim 20, said processing step further comprising the step of removing outlier data from the magnetic flux data stream to provide an outlier-free magnetic flux data stream.

23. A method according to claim 22, said removing step including the steps of:

removing a baseline value from the magnetic flux data stream; and

limiting the magnetic flux data stream to a value no greater than an outlier limit.

24. A method according to claim 22 further comprising the step of passing the outlier-free magnetic flux data stream through a first low pass filter to estimate a baseline.

25. A method according to claim 24 wherein a transfer function of the low pass filter is:

26. A method according to claim 25 wherein the parameter “

f”

is in a range of 1 to 4096.

27. A method according to claim 22 further comprising the step of passing the outlier-free magnetic flux data stream through a low pass filter to produce a noise estimate.

28. A method according to claim 27 wherein a transfer function of the low pass filter is:

29. A method according to claim 28 wherein the parameter “

fn”

is in a range of 1 to 256.

30. A method according to claim 22 further comprising the step of passing the outlier-free magnetic flux data stream through a low pass filter to produce a smoothed magnitude of the outlier-free magnetic flux data stream.

31. A method according to claim 30 wherein a transfer function of the low pass filter is:

32. A method according to claim 31, wherein the length of the rectangular window is in a range of 2 to 128.

33. A method according to claim 22 further comprising the step of comparing a smoothed magnitude of the outlier-free magnetic flux data stream to a set of detection limits.

34. A method according to claim 33 further comprising the step of passing the smoothed magnitude through at least low pass filter to determine a length of a detection event.

35. A method according to claim 34, wherein a transfer function of the at least one low pass filter is:

36. A method according to claim 20 further comprising the step of incrementing a counter in response to the detection event.

37. A method according to claim 20 further comprising the step of displaying the detection event.

38. A method according to claim 20 further comprising signaling a remote device based upon the passage event.

39. A method according to claim 20, further comprising the step of preventing a detection of a non-passage event.

40. A method according to claim 39 further comprising said preventing step including the sub-step of locking out the at least one magnetometer sensor.

41. A method according to claim 39 further comprising said preventing step including the sub-step of locking out a detector for a predetermined time period after the passage event.

42. A method according to claim 20, said processing step further comprising the sub-step of estimating a noise estimate.

43. A method according to claim 20, said processing step further comprising the sub-step of smoothing a magnitude of the magnetic flux data stream.

44. A method according to claim 20, said processing step further comprising the sub-steps of:

determining an upper and a lower detection threshold value;

comparing a smoothed magnitude of the magnetic flux data stream to at least one of the upper and lower detection thresholds; and

updating a detector value based upon a result of the comparison.

45. A method according to claim 44, each of the detection threshold values is a multiple “

p”

of the noise estimate, “

p”

being in a range of 1 to 10.

46. A method according to claim 20 further comprising said processing step including the sub-step of determining a time length of the detection event.