Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
2000-09-18
2002-03-12
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S046000, C073S049100
Reexamination Certificate
active
06354140
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to fluid conducting systems, and more particularly to an improved leak detection system for use with various types of fluid conducting systems operating in vacuum environments, such as space.
BACKGROUND OF THE INVENTION
With respect to current space vehicles, such as the Space Shuttle, there has been increased interest in ensuring that any leaks in the vehicle's fluid conducting systems are immediately-identified and quickly eliminated in order to prevent any catastrophic accidents or mission interruptions. For example, a leak of the vehicle's fuel system could jeopardize the safety of the crew or cause the shortening of the mission duration.
All fluid conducting systems, whether ground- or space-based, generally consist of a combination of pipes or conduits, joints, valves, fittings, and various other plumbing devices. Any one of these components can become a leak source during routine operation of the fluid conducting system. There are many commercially available leak detectors for ground-based operations, but effective detectors for space/vacuum use are not readily available because fluid behaves vastly differently in vacuum. Because the usage of space vehicles, such as the Space Shuttle, as well as satellites, rockets, and space stations, has recently increased to a substantial degree, the need for a reliable leak detector in a vacuum environment, such as that found in space, has increased as well.
The majority of existing leak detectors require direct contact with the leaking substance in the form of a vapor or liquid, and typically relies on a chemical reaction. Most of the readily available leak detectors and indicators utilize chemically reactive substances. For example, a sample of air or vapor is collected and introduced to a chemically sensitive substance (e.g., a reagent). The chemical reaction (e.g., electrical conductivity, pH balance, heat release, etc.) is measured and then used to quantify the particular leak.
However, this methodology can not work in the high vacuum conditions of space because fluid freezes instantly (i.e., flash freezes) as it is introduced into the vacuum environment and does not produce vapor. A leak detector which uses chemical sensing and is located even next to the source cannot detect a leak in vacuum. Thus, leak detectors designed for ground-based operation are completely useless for space-based operations.
Therefore there exists a need for a reliable, inexpensive, and easy to manufacture leak detection system that is capable of detecting fluid leaks in vacuum environments, such as those encountered during space-based operations.
BACKGROUND ART
The following U.S. Patents contain information relating generally to the background of the present invention, the entire disclosures of all of which are incorporated herein by reference:
U.S. Pat. No. 5,637,789 discloses a downstream leak detection system for use with pipeline systems, especially those of residential type. The system makes use of a single thermistor, or other sensing element, to detect extraneous fluid flow via thermal transport. The leakage rate may be set over a wide range, and an alarm is activated when the desired leak flow rate is detected over a predetermined time interval.
U.S. Pat. No. 5,378,995 discloses a low molecular weight organic liquid detection sensor which is a wire body formed by coating a core material with a conductive layer made of a substantially non-crosslinked material having a Shore A hardness not more than 70 which is mainly composed of thermoplastic elastomer and conductive carbon, the conductive layer varying in its electric resistance upon contact with a low molecular weight organic liquid. The sensor of the invention permits secured mechanical strength, its easy installation in a narrow conduit or over a wide area, and highly sensitive sensing of a low molecular weight organic liquid in the longitudinal direction. The detector of the invention comprises a sensor having the above structure, preferably a porous body which houses and protects the sensor, a means which is connected to this sensor and detects electric resistance variation, and a means for transmitting this electric resistance variation as an alarm signal, and the detector can be used in the presence of underground water, which in turn permits use of existing liquid-leakage detection holes and installation at low costs.
U.S. Pat. No. 5,203,202 discloses a leak detection assembly that employs a layer of pliable conductive construction between a fluid conduit or tube and a tape containing signal carrying elements disposed along the length of the tape. The signal carrying element can be a series of parallel electrical conductors disposed longitudinally.
U.S. Pat. No. 4,5334,662 discloses a device used for detecting leakages of steam contained in hollow bodies, particularly in pipes. It is intended for tending high temperature steam conduits. The hollow body is surrounded by a thermal insulation containing a measuring chamber. A temperature sensor and a steam detector are disposed within that measuring chamber. Signaling apparatus announces the simultaneous presence of steam and temperature drop. When the pressurized steam contained in the hollow body or in the conduit happens to leak, it expands thereby producing a temperature drop. The sensing of both effects, i.e. the temperature drop and the presence of vapor avoids erroneous warnings.
U.S. Pat. No. 4,500,865 discloses a fluid leakage detecting element comprising a heat generating resistive member and a temperature compensating resistive member disposed on a substrate. Each of the resistive members is prepared in the form of a paste of a metal which has a high temperature coefficient and a high thermal conductivity and whose melting point is higher than the baking temperature of the substrate. These resistive members are printed in thick film form on the substrate which is sufficiently electrical insulating and has a high thermal conductivity.
U.S. Pat. No. 4,206,632 discloses a liquid leak detecting device comprising at least two electrical conductors arranged in parallel and separated from each other by a material comprised of continuously porous polytetrafluoroethylene containing an electroconductive material within its pores.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore a principal object of this invention to provide a new and improved leak detection system.
It is another object of this invention to provide a new and improved leak detection system for use with fluid conducting systems.
It is another object of this invention to provide a new and improved leak detection system for use with fluid conducting systems that operate in vacuum environments.
It is another object of this invention to provide a new and improved leak detection system that takes advantage of the phenomenon of flash freezing of fluids in vacuum environments.
It is another object of this invention to provide a new and improved leak detection system for use with fluid conducting systems that operate in space-based environments.
In accordance with one embodiment of the present invention, a leak detection system for use with a fluid conducting system in a vacuum environment is provided, comprising:
a member adjacent to the fluid conducting system; and
at least one sensor disposed within the member;
wherein the at least one sensor is capable of detecting a decrease in temperature of the member when a leak condition causes the fluid of the fluid conducting system to freeze when exposed to the vacuum environment.
In accordance with another embodiment of the present invention, a leak detection system for use with a fluid conducting system in a vacuum environment is provided, comprising:
a member substantially disposed about the fluid conducting system; and
at least one sensor disposed within the member;
wherein the at least one sensor is capable of detecting a decrease in temperature of the member when a leak condition causes the fluid of the fluid conducting system to freeze when exposed to the vac
Farkas Tibor
Kim Brian Byungkyu
Nguyen Bich Ngoc
Garber C D.
Harness & Dickey & Pierce P.L.C.
The Boeing Company
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