Electricity: measuring and testing – Of geophysical surface or subsurface in situ – For small object detection or location
Reexamination Certificate
2001-03-16
2004-05-11
Barlow, John (Department: 2863)
Electricity: measuring and testing
Of geophysical surface or subsurface in situ
For small object detection or location
C324S693000
Reexamination Certificate
active
06734674
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for locating and inspecting underground or other nonvisible non-electrically conductive pipes, such as underground plastic pipes used for residential and commercial plumbing, and particularly for locating the pipes and for detecting leaks therein.
It is sometimes necessary to inspect damaged underground or other nonvisible pipes for leaks, or to determine the location of an undamaged pipe to prevent damage to the pipe by, e.g., excavation in the area of the pipe. A well known method for inspecting a buried pipe introduces a camera into and through the pipe at one end of a probe, the camera sending video to an operator operating the camera remotely at the other end of the probe. The method is often effective but still relatively expensive. Microphones may also be used to listen to the sound of fluid escaping through a damaged section of pipe, however, this method requires that the leak be large enough to make a discernible sound above the level of background noise, which can be considerable.
To locate or chart a length of buried or otherwise non-observable pipe that is either damaged or undamaged, a typical, standard method relies on the electrical conductivity of the pipe to carry an electrical signal that produces an electromagnetic field. A portable receiving device detects the resulting field and indicates its strength, which indicates proximity to the pipe and assists to locate it.
However, pipes used in plumbing such as water and sewer lines are often formed of an electrically nonconductive material such as PVC or ABS plastic. The standard method for locating these pipes does not work without providing, along the length of the pipe, an electrically conductive wire, or feeding an electrically conductive snake through the pipe and using the snake as the conductor. Though wires are often laid with plastic pipe, there are many existing plastic pipes for which this has not been done Moreover, to employ the electrically conductive snake generally requires cutting into the pipe in order to provide a point of entry for the snake, damaging the pipe. Snakes are also limited in reach, and the pipe may have to be unearthed down the line and cut again in order to reinstall the snake and continue inspecting or locating.
It may also be noted that the standard method is of no assistance in detecting leaks in the pipe, unless the damage to the pipe is so catastrophic that the pipe is separated into two spaced apart pieces, breaking the electrical connection.
Accordingly, there is a need for a method for locating and inspecting underground or other nonvisible non-electrically conductive pipes that provides for employing the standard method for locating such pipes, along the length of which electrically conductive materials have not been laid, at less cost and difficulty than provided by the prior art, and that may also be employed for leak detection.
SUMMARY OF THE INVENTION
The method for locating and inspecting underground or other nonvisible non-electrically conductive pipes solves the aforementioned problems and meets the aforementioned needs by introducing an electrically conductive fluid into the pipe, applying a time varying electrical signal to the fluid and employing the standard method for determining proximity to the pipe by assessing the strength of the electromagnetic field produced thereby.
The method also provides for detecting leaks by introducing the electrically conductive fluid at a sufficiently slow rate that a pool of the electrically conductive liquid accumulates outside the pipe adjacent the leak, and employing the standard method for determining proximity to the leak by assessing the strength of the electromagnetic field produced thereby.
Therefore, it is a principal object of the present invention to provide a novel and improved method for locating and inspecting underground or other nonvisible non-electrically conductive pipes.
It is another object of the present invention to provide a method for locating and inspecting underground or other nonvisible non-electrically conductive pipes that provides for employing the standard method for locating the pipes.
It is still another object of the present invention to provide a method for locating and inspecting underground or other nonvisible non-electrically conductive pipes that provides for employing the standard method at lower cost and with less difficulty.
It is yet another object of the present invention to provide a method for locating and inspecting underground or other nonvisible non-electrically conductive pipes that provides for leak detection by employing the standard method for locating underground or other nonvisible pipes.
The foregoing and other objects, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the following drawings.
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International Search Report, PCT/US02/07684, filed Mar. 15, 2002, entitled Method For Locating and Inspecting Underground or Other Non-Visible Non-Electrically Conductive Pipes, Jared Struse, et al., Inventors.
Struse Daniel P.
Struse Jared H.
Barlow John
Birdwell & Janke, LLP
Le Toan M.
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