Electric leakage detector for underground storage tank systems

• US 5,202,667 A
• Filed: 10/19/1990
• Issued: 04/13/1993
• Est. Priority Date: 10/19/1990
• Status: Expired due to Fees

• Current Assignee: Monitoring Systems, Inc.
• Original Assignee: Monitoring Systems, Inc.
• Inventors: Alvin, David W.
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): Jackson, Jill
• Application Number:
  US07/600,538
• Time in Patent Office: 907 Days
• Field of Search: 340/604, 340/605, 340/539, 73/49.2 T, 73/304 C, 361/284
• US Class Current: 340/605
• CPC Class Codes: B67D 7/04 for transferring fuels, lubricants or mixed fuels and lubricants
• CPC Class Codes: B67D 7/3209 relating to spillage or leakage, e.g. spill containments, leak detection leak detectors for underground fuel dispensing systems G01M3/2892
• CPC Class Codes: G01F 23/265 for discrete levels
• CPC Class Codes: G01F 23/266 measuring circuits therefor
• CPC Class Codes: G01F 23/268 mounting arrangements of probes
• CPC Class Codes: G01M 3/16 using electric detection means G01M3/045, G01M3/06, G01M3/12, G01M3/20, G01M3/24, G01M3/26 take precedence
• CPC Class Codes: G01M 3/186 for containers, e.g. radiators
• CPC Class Codes: G01N 27/221 by investigating the dielectric properties using microwaves G01N22/00; measuring loss factors or dielectric constants per se G01R27/26
• CPC Class Codes: G08B 21/20 responsive to moisture

Abstract

A fluid detection system by which the presence or absence and identity of fluids may be detected within confined areas, such as those existing within underground storage tank systems and in which fluids may accumulate. The fluid detection system includes a probe assembly having circuitry which determines the presence of fluids by the capacitance developed across a variable capacitor. The output signal provided by the capacitor is converted to frequency values, is filtered by a receiver included with the system, and transmitted to a remote location for display. The system is suitable for deployment within and monitoring of one or a multiple of tank systems.

Claims

1. A fluid detection system for identifying the presence or absence and the identity of fluids within confined areas within an underground storage tank system, said confined areas including accumulation areas on which fluids unintentionally or accidentally entering the confined area can generally accumulate, said fluid detection system comprising:

a probe assembly sized and shaped for deployment within said confined areas and adjacent to one of said accumulation areas, said probe assembly including a sensor for detecting the presence or absence and identity of said fluids collecting on said one of said accumulation areas;

said sensor including capacitor means that develops a capacitance characteristic of air or said fluids that contact said capacitor means;

said probe assembly including a converter responsive to the capacitance of said capacitor means for generating a variable frequency output signal;

an analyzer unit including circuitry by which said variable frequency signal is edited to provide selected frequencies as an edited output signal; and

a transmitter for digitalizing and transmitting said edited output signal to a display, said display for indicating the presence or absence and the identity of said fluids within said one of said confined areas or a multiple of said confined areas, whereby said fluids unintentionally or accidentally entering said tank system are identified and displayed.

2. The system according to claim 1, wherein said capacitor means include wire traces arranged flat and forming a sensing face across which said air or said fluids are contacted.

3. The system according to claim 1, further including a housing in which said sensor is contained, said housing having a face on which said probe assembly can rest on said one of said accumulation areas and inward from which said capacitor means is recessed such that said capacitor means is positionable approximate to but separate from said one of said accumulation areas.

4. The system according to claim 1, wherein said capacitor means operate using a low-voltage, low-current source, whereby said probe assembly is made intrinsically safe.

5. The system according to claim 3, wherein said housing is cylindrically shaped and includes an outer wall whose diameter is less than the inner diameter of a monitoring pipe within said tank system, whereby said sensor is of a suitable diameter for deployment within said monitoring pipe.

6. The system according to claim 2, further including a housing surrounding said sensor such that said sensor can be deployed within said confined areas.

7. The system according to claim 6, wherein said housing includes a face on which said housing can rest on one of said accumulation areas and inward from which said sensing face is recessed, whereby said sensing face is positionable adjacent to but separate from said one of said accumulation areas.

8. System for detecting the presence of fluids or gases unintentionally or accidentally entering confined areas within a plurality of underground storage tank systems, each of said confined areas including accumulation areas on which said fluids and adjacent to which gases can collect, said apparatus comprising:

a plurality of probe assemblies sized and shaped for positioning within said confined areas, each of said plurality of probe assemblies including a sensor that responds to contact with said fluids or said gases by developing a capacitance generally characteristic of said fluids or said gases;

said each of said plurality of probe assemblies including conversion means by which said voltages are received and are converted to frequencies, said frequencies provided as a converted output signal;

said each of said plurality of probe assemblies further including means by which said converted output signal is filtered to remove noise and frequencies of non-selected fluids, said filtering means providing a filtered output signal;

a transmitter by which said filtered output signal from said converting means is digitalized and transmitted to a display; and

said display for indicating the presence or absence of said fluids or said gases unintentionally or accidentally entering or developing in or around one or more of said accumulation areas, whereby leakage in said plurality of said underground storage tank system is detachable.

9. The detectable system according to claim 8, wherein said each of said probe assemblies includes a housing in which said sensor is contained and by which said sensor is positionable adjacent to one of said accumulation areas.

10. The detection system according to claim 9, wherein said housing includes a face inward from which said sensor is recessed such that said sensor can rest adjacent to but separated from said one of said accumulation areas.

11. The detection system according to claim 8, wherein said sensor includes insulated wire traces forming thereby a sensing face by which said air or said fluids can be contacted.

12. The detection system according to claim 11, wherein said each of said probe assemblies includes a housing in which said sensor is contained and by which said sensor can be positioned adjacent to said one of said accumulation areas.

13. The detection system according to claim 12, wherein said housing includes a face on which said housing can rest on said one of said accumulation areas.

14. The detection system according to claim 13, wherein said sensing face is recessed inward from said face of said housing, whereby said sensing face is positionable adjacent to but not in direct contact with said one of said accumulation areas.

15. The detection system according to claim 8, wherein said each of said probe assemblies includes connection means by which said each of aid probe assemblies can be positioned into said confined areas.

16. The detection system according to claim 8, wherein each said of capacitors operates using a low-voltage, low-amperage power source, whereby said system is made safer.

17. The detection system according to claim 15, wherein said each of said probe assemblies positioned within said confined areas includes a cap positioned at or approximate to ground level and which indicates the presence or the absence of said fluids or said gases within said confined areas.

18. Method of monitoring an underground storage tank system for presence of fluids o gases unintentionally or accidentally entering confined areas within the system, said system including a storage tank buried at least partially below the surface of surrounding ground, said confined areas including accumulation areas on which the fluids or adjacent to which the gases can accumulate or develop, said method comprising the steps of:

positioning one or more probe assemblies into each of one or more of the confined areas such that a sensor of each of said probe assemblies is approximate to, but separate from the accumulation areas;

each of said probes defining a flat variable capacitor, the capacitance of said capacitor directly varying according to the presence or absence and type of the fluids or the gases that contact said capacitor;

developing a signal having a frequency dependent on the capacity of said capacitor;

transmitting said frequency signal as an output signal;

processing said signal to remove non-selected frequencies caused by noise or by ambient conditions, said processing step producing an edited signal;

digitizing said edited signal;

transmitting said digitized edited signal to a display; and

indicating on said display the presence or absence of the fluids or the gases that have accidentally or unintentionally contacted said capacitor.

19. The method of claim 18, further including the step of initiating an audible alarm remote from said sensor when the fluids or the gases are detected by said probe assembly.

20. The method of claim 18, wherein said displaying step includes the step of differentially identifying on said display the fluids or the gases that contact said capacitor.

21. A system for reliably monitoring for fluids or gases accidentally or unintentionally collecting on or adjacent to accumulation areas within an underground storage tank system, said system comprising:

a plurality of probe assemblies, each of said probe assemblies sized and shaped to be deployed within said tank system and on said accumulation areas;

said each of said probe assemblies including a sensor that develops a capacitance characteristic of said fluids or said gases that contact said sensor, said sensor sized and shaped to be positioned adjacent to but separate from said one of said accumulation areas whereby at a minimum a thin layer of said fluids or said gases that collects on or adjacent to said accumulation areas can contact said sensor;

said each of said probe assemblies including a converter for producing an output signal having a capacitance characteristic frequency dependent on said capacitance characteristic;

said each of said probe assemblies including a frequency counter by which frequencies caused by noise or ambient conditions can be edited from said output signal to form an edited signal;

said each of said probe assemblies including means to form a digitized signal; and

means by which said digitized signal is transmitted to a remote display on which the presence of said fluids or said gases detected by one or more of said plurality of probe assemblies an be reliably indicated.

22. The system according to claim 21, wherein said sensor is insulated with a substance whose effect on said capacitance developed by said sensor upon contact by said fluids or gases is known, said sensor as insulated providing a sensing face.

23. The apparatus according to claim 21, wherein said sensor includes wire traces arranged flat whereby said thin layer of said fluids or said gases are contact uniformly.

24. The apparatus according to claim 23, wherein said wire traces are insulated by a substance whose effect on the capacitance developed by said sensor upon contact by said fluids or gases is known, said wire traces as insulated forming a sensing face.

25. The apparatus according to claim 22, wherein said probe includes a housing in which said sensor is contained, said housing including a face on which said housing rests on said accumulation area and recessed from which said sensing face is positioned adjacent to but separate from said accumulation area.

26. The apparatus according to claim 24, wherein said probe assembly includes a housing in which said sensor is contained, said housing including a face on which said housing rests on said accumulation area and recessed from which said sensing face is positioned adjacent to but separate from said accumulation area.

27. The apparatus according to claim 26, wherein each of said plurality of said probe assemblies includes a receiving circuit by which digitalized signals from said plurality of probe assemblies can be received by one of said probe assemblies and retransmitted to other of said plurality of probe assemblies or said display.

28. The apparatus according to claim 27, wherein said apparatus operates using a low voltage, low current power source.

29. The apparatus according to claim 21, further including a cap positioned at or approximate to one of said probe assemblies and on which the presence of said fluids or said gases detected by said one of said probe assemblies is indicated.