Fuel storage tank leak prevention and detection system and method

• US 6,834,534 B2
• Filed: 03/17/2003
• Issued: 12/28/2004
• Est. Priority Date: 03/17/2003
• Status: Expired due to Term

• Current Assignee: Veeder-Root Co (Vontier Corp.)
• Original Assignee: Veeder-Root Co (Vontier Corp.)
• Inventors: Lucas, Richard, Dolson, Richard, Reid, Kent, Hutchinson, Ray, Halla, Don, Hart, Robert P.
• Primary Examiner(s): LARKIN, DANIEL SEAN
• Application Number:
  US10/390,346
• Publication Number:
  US 20040182136A1
• Time in Patent Office: 652 Days
• Field of Search: 73/492, 73/493, 220/560.03, 220/567.1, 220/567.2, 340/605, 405/52, 405/53, 405/54
• US Class Current: 73/49.2
• CPC Class Codes: B65D 90/503 under pressure or vacuum
• 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

Abstract

A storage tank leak detection and prevention system that detects a breach or leak in the interstitial space of a double-walled fuel storage tank in a service station environment. The interstitial space is placed under a vacuum using a submersible turbine pump that is also used to pump fuel to the fuel dispensers in the service station and therefore a separate vacuum generating source is not required. A sensing unit and/or tank monitor monitors the vacuum level in the interstitial space over time. If a significant vacuum level change occurs in the interstitial space after the interstitial space is placed under a vacuum level, a catastrophic leak detection alarm is generated. If a minor vacuum level change occurs in the interstitial space after the interstitial space is placed under a vacuum, a precision leak detection alarm is generated. Functional tests also ensure that the leak detection system is functioning properly.

Claims

1. A system for detecting a leak in a double-walled fuel storage tank having an interstitial space in a service station environment, comprising:

a sensing unit, comprising;

a vacuum tubing that is coupled to the interstitial space of the fuel storage tank;

a pressure sensor that is coupled to said vacuum tubing to detect the vacuum level in the interstitial space of the fuel storage tank; and

a sensing unit controller that is coupled to said pressure sensor to determine the

vacuum level in the interstitial space of the fuel storage tank; and

a submersible turbine pump that is fluidly coupled to the fuel in the fuel storage tank to draw the fuel out of the fuel storage tank, wherein said submersible turbine pump is also coupled to said vacuum tubing;

said submersible turbine pump creates a vacuum level in said vacuum tubing to create a vacuum level in the interstitial space of the fuel storage tank wherein said sensing unit controller monitors the vacuum level in the interstitial space of the fuel storage tank.

2. The system of claim 1, further comprising a tank monitor that is electrically coupled to said submersible turbine pump wherein said submersible turbine pump creates a defined initial threshold vacuum level in the interstitial space after receiving a test initiation signal from said tank monitor.

3. The system of claim 2, further comprising a differential pressure indicator that is coupled to said vacuum tubing between said submersible turbine pump and said sensing unit, and is communicatively coupled to said tank monitor wherein said monitor determines if said submersible turbine pump is drawing a sufficient vacuum level in said vacuum tubing.

4. The system of claim 3, wherein said tank monitor generates an alarm if said differential pressure indicator indicates that said submersible turbine pump is not drawing a sufficient vacuum level in said vacuum tubing.

5. The system of claim 2, wherein said tank monitor generates a catastrophic leak detection alarm if said submersible turbine pump cannot create said defined initial threshold vacuum level in the interstitial space.

6. The system of claim 5, wherein said tank monitor communicates said catastrophic leak detection alarm to a system comprised from the group consisting of a site controller and a remote system.

7. The system of claim 2, wherein said tank monitor is electrically coupled to said sensing unit controller to receive the vacuum level in the interstitial space of the fuel storage tank.

8. The system of claim 7, wherein said tank monitor determines if the vacuum level in the interstitial space has decayed to a catastrophic threshold vacuum level from said defined initial threshold vacuum level.

9. The system of claim 8, wherein said tank monitor activates said submersible turbine pump to attempt to lower the vacuum level in the interstitial space back down to said defined initial threshold vacuum level if the vacuum level in the interstitial space decays to said catastrophic threshold vacuum level.

10. The system of claim 9, wherein said tank monitor determines if the vacuum level in the interstitial space lowers to said defined initial threshold vacuum level within a defined amount of time.

11. The system of claim 10, wherein said tank monitor generates a catastrophic leak detection alarm if the vacuum level in the interstitial space does not lower to said defined initial threshold vacuum level with said defined amount of time.

12. The system of claim 7, wherein the electrical coupling between said tank monitor and said sensing unit uses intrinsically safe wiring.

13. The system of claim 7, wherein said tank monitor determines if a leak exists in the fuel storage tank by determining if the vacuum level in the interstitial space decays to a threshold vacuum level in a predetermined amount of time.

14. The system of claim 13, wherein said threshold vacuum level is a precision threshold vacuum level.

15. The system of claim 7, further comprising an isolation valve located in said vacuum tubing between said sensing unit and the interstitial space wherein closing said isolation valve isolates the interstitial space from the sensing unit to allow verification of a leak in the fuel storage tank without relieving the vacuum in the interstitial space.

16. The system of claim 7, further comprising a drain valve within said vacuum tubing to drain any leaked fuel out of said vacuum tubing wherein said tank monitor indicates a pass condition to a vacuum leak test when said drain valve is manually opened and said tank monitor determines that the vacuum level in the interstitial space falls below a vacuum level threshold level in a predetermined amount of time.

17. The system of claim 16, wherein said drain valve is located at the lowest point of said vacuum tubing.

18. The system of claim 7, further comprising a liquid detection sensor that is coupled to the interstitial space, wherein said liquid detection sensor is coupled to said sensing unit controller and wherein said liquid detection sensor detects if liquid is present in the interstitial space.

19. The system of claim 18, wherein said sensing unit controller communicates a liquid detection by said liquid detection sensor to said tank monitor.

20. The system of claim 19, wherein said tank monitor generates a leak detection alarm when said liquid detection is communicated from said sensing unit controller.

21. The system of claim 20, wherein said tank monitor communicates said leak detection alarm to a system comprised from the group consisting of a site controller and a remote system.

22. The system of claim 18, wherein said tank monitor disables said submersible turbine pump when said liquid detection is communicated from said sensing unit controller.

23. The system of claim 18, wherein said liquid detection sensor comprises a float.

24. The system of claim 18, wherein said tank monitor indicates a pass condition to a functional liquid leak detection test when liquid is placed on said liquid detection sensor and said liquid detection sensor detects liquid.

25. The system of claim 1, further comprising a vacuum control valve that is coupled inline to said vacuum tubing between said submersible turbine pump and said pressure sensor wherein said vacuum control valve is electrically coupled under control of said sensing unit controller.

26. The system of claim 25, wherein said sensing unit controller closes said vacuum control valve before monitoring the vacuum level in the interstitial space of the fuel storage tank to determine if a leak exists in the fuel storage tank so that said submersible turbine pump is isolated from the interstitial space.

27. The system of claim 1, further comprising a check valve located in said vacuum tubing between said submersible turbine pump and said sensing unit to prevent ingress from the interstitial space to said submersible turbine pump.

28. A system for conducting a functional vacuum leak detection test for a fuel storage tank having an interstitial space in a service station environment, comprising:

a sensing unit, comprising;

a vacuum tubing that is coupled to the interstitial space of the fuel storage tank;

a pressure sensor that is coupled to said vacuum tubing to detect the vacuum level in the interstitial space of the fuel storage tank; and

a sensing unit controller that is coupled to said pressure sensor to determine the

vacuum level in the interstitial space of the fuel storage tank;

a drain valve located in said vacuum tubing to drain any leaked fuel out of said vacuum tubing;

a controller coupled to said sensing unit; and

a submersible turbine pump that is electrically coupled and under control of a tank monitor, wherein said submersible turbine pump is fluidly coupled to the fuel in the fuel storage tank to draw the fuel out of the fuel storage tank; and

wherein said submersible turbine pump is coupled to said vacuum tubing, wherein said tank monitor causes said submersible turbine pump to generate a vacuum level in the interstitial space when said drain valve is opened wherein said sensing unit controller monitors the vacuum level in the interstitial space and said tank monitor indicates that the vacuum leak test passed if a leak is detected by said sensing unit.

29. The system of claim 28, wherein said tank monitor communicates said indication of the functional vacuum leak detection test to a system comprised from the group consisting of a site controller and a remote system.

30. A system for conducting a liquid leak detection test for a fuel storage tank having an interstitial space in a service station environment, comprising:

a sensing unit, comprising;

a vacuum tubing that is coupled to the interstitial space of the fuel storage tank;

a pressure sensor that is coupled to said vacuum tubing to detect the vacuum level in the interstitial space of the fuel storage tank;

a sensing unit controller that is coupled to said pressure sensor to determine the vacuum level in the interstitial space of the fuel storage tank; and

a liquid detection sensor located in the interstitial space, wherein said liquid detection sensor detects if liquid is present in the interstitial space;

a submersible turbine pump that is fluidly coupled to the fuel in the fuel storage tank to draw the fuel out of the fuel storage tank wherein said submersible turbine pump is also coupled to said vacuum tubing, wherein said submersible turbine pump creates a vacuum level in said vacuum tubing to create a vacuum level in the interstitial space of the fuel storage tank wherein said sensing unit controller monitors the vacuum level in the interstitial space of the fuel storage tank; and

a controller coupled to said sensing unit wherein said controller indicates that the functional liquid leak detection test passed if said sensing unit detects liquid present in said liquid trap when said liquid detection sensor is placed in contact with liquid.

31. The system of claim 30, further comprising a drain valve coupled to the interstitial space to drain any leaked fuel out of the interstitial space.

32. The system of claim 30, wherein said controller communicates said indication of the functional liquid leak detection test to a system comprised from the group consisting of a site controller and a remote system.

33. A method for detecting a leak in a double-walled fuel storage tank having an interstitial space in a service station environment, comprising the steps of:

creating a defined initial threshold vacuum level in a vacuum tubing fluidly coupled to the interstitial space using a submersible turbine pump that is also fluidly coupled to the fuel in the fuel storage tank to draw the fuel out of the fuel storage tank;

sensing the vacuum level in the interstitial space using a pressure sensor;

communicating the vacuum level in the interstitial space to a tank monitor; and

monitoring the vacuum level in the interstitial space to determine if a leak exists in the fuel storage tank.

34. The method of claim 33, further comprising the step of sending a test initiation signal to said submersible turbine pump before performing said step of creating a vacuum level.

35. The method of claim 34, wherein said step of monitoring further comprises determining if a leak exists in the fuel storage tank by determining if the vacuum level in the interstitial space decays to a threshold vacuum level in a predetermined amount of time.

36. The method of claim 35, wherein said threshold vacuum level is a precision threshold vacuum level.

37. The method of claim 34, wherein said step of monitoring further comprising determining if the vacuum level in the interstitial space has decayed to a catastrophic threshold vacuum level from said defined initial threshold vacuum level.

38. The method of claim 37, wherein said step of monitoring further comprises activating said submersible turbine pump to attempt to lower the vacuum level in the interstitial space back down to said defined initial threshold vacuum level if the vacuum level in the interstitial space decays to said catastrophic threshold vacuum level.

39. The method of claim 38, wherein said step of monitoring further comprises determining if the vacuum level in the interstitial space lowers to said defined initial threshold vacuum level within a defined amount of time.

40. The method of claim 39, wherein said step of monitoring further comprises generating a catastrophic leak detection alarm if the vacuum level in the interstitial space does not lower to said defined initial threshold vacuum level with said defined amount of time.

41. The method of claim 40, further comprising communicating said catastrophic leak detection alarm to a system comprised from the group consisting of a site controller and a remote system.

42. The method of claim 33, further comprising the step of sensing whether fluid is present in the interstitial space using a liquid detection sensor.

43. The method of claim 42, further comprising generating a liquid leak detection alarm if said liquid detection sensor senses liquid in the interstitial space.

44. The method of claim 43, further comprising communicating said liquid leak detection alarm to a system comprised from the group consisting of a site controller and a remote system.

45. The method of claim 42, further comprising disabling said submersible turbine pump if said liquid detection sensor senses liquid in the interstitial space.

46. The method of claim 33, further comprising closing a vacuum control valve to isolate said submersible turbine pump from the interstitial space before performing said step of monitoring the vacuum level in the interstitial space.

47. The method of claim 33, further comprising verifying a leak in the interstitial space by closing an isolation valve in said vacuum tubing that isolates the interstitial space from said submersible turbine pump.

48. The method of claim 33, further comprising preventing ingress from the interstitial space to said submersible turbine pump.

49. The method of claim 33, further comprising determining if said submersible turbine pump is drawing a sufficient vacuum level in the interstitial space.

50. The system of claim 49, further comprising generating an alarm if said submersible turbine pump is not drawing a sufficient vacuum level in the interstitial space.

51. A method for conducting a functional vacuum leak test for a fuel storage tank having an interstitial space in a service station environment, comprising:

opening a drain valve located in a vacuum tubing fluidly coupled to the interstitial space;

creating a vacuum level in said vacuum tubing using a submersible turbine pump that is also fluidly coupled to the fuel in the fuel storage tank to draw the fuel out of the fuel storage tank;

sensing the vacuum level in the interstitial space using a pressure sensor;

communicating the vacuum level in the interstitial space to a tank monitor; and

indicating a vacuum leak test pass condition if the vacuum level in the interstitial space falls below a threshold vacuum level.

52. The method claim of 51, wherein said step of indicating further comprises indicating a vacuum leak test pass condition if the vacuum level in the interstitial space falls below a threshold vacuum level within a defined amount of time.