System and method for acoustically imaging an underground tank

• US 5,563,845 A
• Filed: 11/07/1995
• Issued: 10/08/1996
• Est. Priority Date: 11/07/1995
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Walsh, Kenneth M.
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US08/556,301
• Time in Patent Office: 336 Days
• Field of Search: 367/7, 367/908, 367/99, 181/124, 340/621, 73/290 V
• US Class Current: 367/7
• CPC Class Codes: G01F 23/2965 Measuring attenuation of transmitted waves
• CPC Class Codes: G01F 23/2966 making use of acoustical resonance or standing waves
• CPC Class Codes: G01M 3/24 using infrasonic, sonic, or ultrasonic vibrations
• CPC Class Codes: G01S 15/88 Sonar systems specially adapted for specific applications seismic or acoustic prospecting or detecting G01V1/00
• CPC Class Codes: Y10S 367/908 Material level detection, e.g. liquid level

Abstract

A vertical acoustic array system and method for acoustically imaging the tents of a partially or completely buried tank which can contain radioactive solids and may not be entirely filled. The transducer array is placed proximate a side of a tank in a vessel such as a tube filled with water. Dirt or other filler material located between the tube and the tank is saturated with water, allowing the acoustic signal to propagate through the side of the tank and into the tank. The vertical array consists of one or more transmitting units and receiving units set in a vertical array including dipole receiving elements which allow horizontal directionality. The signals are analyzed by a field unit which includes a portable self-powered trailer providing signal transmitting and analysis devices. The field unit can transmit signals to a second unit which provides further signal analysis.

Claims

1. A system for imaging contents of a tank comprising:

at least one transducer unit including;

at least one acoustic signal transmitting member, for producing at least one acoustic signal; and

at least one acoustic signal receiving member, disposed proximate to said at least one acoustic signal transmitting member, said acoustic signal receiving member receiving a reflected said at least one acoustic signal;

a liquid saturated filler material proximate at least a first side of said tank whose contents are being imaged and disposed in acoustic contact with said at least one transducer unit, said liquid saturated filler material allowing said at least one acoustic signal to reach and penetrate said tank whose contents are being imaged; and

a transducer unit controller electrically coupled to said at least one transducer unit for controlling said produced at least one acoustic signal and for analyzing said reflected at least one acoustic signal received by said acoustic signal receiving member.

2. The system of claim 1 wherein said at least one transducer unit further comprises a second acoustic signal transmitting member disposed proximate to said at least one acoustic receiving member, said second acoustic transmitting member producing a second acoustic signal, and said at least one acoustic receiving member receives reflected acoustic signals produced by reflection of said at least one acoustic signal and said second acoustic signal.

3. The system of claim 1 further including a plurality of transducer units disposed in a transducer array.

4. The system of claim 1 wherein at least a second transducer unit is disposed generally vertically below said at least one transducer unit.

5. The system of claim 1 wherein said at least one acoustic receiving member comprises at least two acoustic elements joined together to form a dipole.

6. The system of claim 5 further including a plurality of transducer units disposed in a transducer array.

7. The system of claim 6 wherein said at least one acoustic receiving member comprises at least four acoustic elements joined together to form two dipoles to determine the directionality of received acoustic signals.

8. The system of claim 1 wherein said at least one transducer unit comprises ceramic transducers.

9. The system of claim 3 further comprising a fluid filled tube disposed vertically next to said tank, said transducer array being disposed inside said tube and being covered by said fluid.

10. The system of claim 1 wherein said liquid saturated filler material includes dirt saturated with water.

11. The system of claim 1 further comprising a trailer having said transducer array controller positioned thereon.

12. The system of claim 1 further comprising a power supply joined to said transducer array controller.

13. The system of claim 12 wherein said power supply includes batteries.

14. The system of claim 1 wherein said at least one acoustic signal includes Gaussian-enveloped frequency modulated slide pulses.

15. The system of claim 1 wherein said at least one acoustic signal includes low frequency long pulses.

16. A method of acoustically imaging contents of an underground tank including the steps of:

disposing a transducer array proximate at least a first side of said tank whose contents are to be acoustically imaged;

saturating a material generally disposed between the said transducer array and said underground tank whose contents are being acoustically imaged, with water;

producing an acoustic signal from said transducer array;

receiving a reflected acoustic signal at said transducer array said acoustic signal being reflected by contents of said tank; and

analyzing said received reflected acoustic signal.

17. The method of claim 16 further comprising the step of providing a fluid filled tube disposed vertically proximate an exterior region of said tank, said transducer array being disposed within said tube.