Leak and pipe detection method and system

• US 6,650,125 B1
• Filed: 12/06/2001
• Issued: 11/18/2003
• Est. Priority Date: 12/06/2001
• Status: Expired due to Fees

• Current Assignee: US Government As Represented By The Director National Security Agency
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Youngquist, Robert C.
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): He, Amy
• Application Number:
  US10/007,487
• Time in Patent Office: 712 Days
• Field of Search: 324/559, 324/678, 324/66, 324/686, 324/444, 324/447, 324/519, 324/522, 324/710, 324/713, 324/718, 324/658, 324/664, 324/689, 73/40, 735/92, 340/605
• US Class Current: 324/658
• CPC Class Codes: G01M 3/18 for pipes, cables or tubes; for pipe joints or seals; for valves; for welds; for containers, e.g. radiators
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat

Abstract

A method and system for locating leaks of conductive fluids from non-conductive pipes and other structures or for locating non-conductive pipes or structures having conductive fluid contained therein, employ a charge generator to apply a time varying charge to the conductive fluid, and a capacitive type detector that can detect the variable charge that is induced in the fluid. The capacitive detector, which preferably includes a handheld housing, employs a large conductive pickup plate that is used to locate the pipe or leak by scanning the plate over the ground and detecting the induced charge that is generated when the plate comes in close proximity to the pipe or leak. If a leak is encountered, the resulting signal will appear over an area larger than expected for a buried pipe, assuming the leak provides an electrically conductive path between the flow and the wet surrounding ground. The detector uses any suitable type of indicator device, such as a pair of headphones that enable an operator to hear the detected signal as a chirping sound, for example.

Claims

1. A method for detecting location of a conductive fluid comprising the steps of:

a) applying a time varying charge to a conductive fluid disposed in a non-conductive structure;

b) providing a charge detector including a capacitive conductive pickup plate for receiving an induced charge that is generated by a charged material in close proximity to, but not contacting said pickup plate, said detector including an indicator device that is responsive to charge that is induced on said pickup plate; and

c) scanning said detector over an area without contacting said conductive fluid to determine whether said conductive fluid is located in close proximity to said area, based on an output generated by said indicator device in response to detection of said time varying charge in said conductive fluid.

2. The method of claim 1, wherein said step of applying a time varying charge comprises providing a function generator and applying a time varying voltage signal generated by said function generator to said conductive fluid.

3. The method of claim 1, wherein said conductive fluid is contained in a non-conductive pipe and said step of scanning further comprises determining the location of said pipe from the location of said conductive fluid.

4. The method of claim 1, wherein said conductive fluid is contained in a non-conductive pipe and said step of scanning further comprises determining the location of a leak in said pipe from the location of said conductive fluid by determining whether said fluid is detected in a location external to said pipe.

5. The method of claim 1, wherein the step of providing a charge detector further comprises providing a charge detector including a current-to-voltage converter connected to said pickup plate for receiving current there from and generating a voltage, and a conditioning circuit for receiving said voltage and generating a signal for driving said indicator device.

6. The method of claim 5, wherein said charge indicator device comprises a pair of audio headphones and said conditioning circuit generates an audio signal for driving said headphones.

7. The method of claim 6, wherein said step of applying a time varying charge comprises providing a function generator that generates a chirped audio frequency voltage signal and applying said chirped voltage signal to said conductive fluid so that when said pickup plate in said charge detector is scanned in close proximity to said conductive fluid, said conditioning circuit will generate a chirped audio signal for driving said headphones.

8. A system for detecting a location of a conductive fluid in a non-conductive structure comprising:

a) a charge generator for generating a time varying electrical charge, said charge generator having an output to be connected to an accessible portion of a conductive fluid to be located for applying a time varying charge to said conductive fluid; and

b) a charge detector including a capacitive conductive pickup plate for receiving an induced charge that is generated by a charged material in close proximity, to but not contacting said pickup plate, said detector including an indicator device that is responsive to charge that is induced on said capacitive pickup plate,

whereby, when said detector is scanned over an area to determine whether said conductive fluid is present, said indicator device will generate an indication when said pickup plate is in close proximity to, but not contacting said conductive fluid.

9. The system of claim 8, wherein said charge generator comprises a function generator that generates a time varying voltage output.

10. The system of claim 9, wherein said function generator generates a chirped audio frequency signal output.

11. The system of claim 8 wherein said charge detector further comprises a current-to-voltage converter connected to said pickup plate for receiving current there from and generating a voltage, and a conditioning circuit for receiving said voltage and generating a signal for driving said indicator device.

12. The system of claim 11, wherein said charge indicator device comprises a pair of audio headphones.

13. The system of claim 12, wherein said charge detector further includes a ground plane plate connected to said current-to-voltage converter and disposed parallel to said pickup plate for shielding said pickup plate from extraneous charge that is generated by sources other than the conductive fluid to be detected.

14. The system of claim 8, wherein said charge detector includes a portable handheld housing in which said pickup plate is disposed.

15. The system of claim 8, wherein said charge generator and said charge detector are connected to one another to facilitate communication between said charge generator and said charge detector.

16. The system of claim 8, wherein said pickup plate is a flat, rectangular plate.

17. A system for detecting location of a conductive fluid in a non-conductive structure comprising:

a) a function generator for generating a time varying voltage output, said function generator having an output to be connected to an accessible portion of a conductive fluid to be located for applying a time varying charge to said conductive fluid; and

b) a charge detector including;

1) a portable handheld housing;

2) a flat capacitive conductive pickup plate in said housing for receiving an induced charge that is generated by a charged material in close proximity to, but not contacting said pickup plate;

3) a current-to-voltage converter connected to said pickup plate for receiving current there from and generating a voltage;

4) a conditioning circuit for receiving said voltage from said current-to-voltage converter and generating an output signal; and

5) an indicator device for receiving said output signal and generating an output indication when a time varying charge is induced on said capacitive pickup plate,

whereby, when said detector is scanned over an area without contacting said conductive fluid to determine whether said conductive fluid is present, said indicator device will generate an indication when said pickup plate is in close proximity to, but not contacting said conductive fluid.

18. The system of claim 17, wherein said function generator generates a chirped audio frequency signal output.

19. The system of claim 17, wherein said charge indicator device comprises a pair of audio headphones.

20. The system of claim 17, wherein said charge detector further includes a flat ground plane plate connected to said current-to-voltage converter and disposed in said housing parallel to said pickup plate for shielding said pickup plate from extraneous charge that is generated by sources other than the conductive fluid to be detected.