Fluid leak detection via thermal sensing

Details Fluid leak detection via thermal sensing Fluid leak detection via thermal sensing

2001-06-13

2003-06-03

Williams, Hezron (Department: 2856)

Measuring and testing

With fluid pressure

Leakage

C073S04050R, C073S025030, C073S061460

Reexamination Certificate

active

06571607

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to fluid leak detection, and more specifically to such detection by thermal sensing. A thermally sensitive detector senses a difference in temperature when a fluid leak occurs, where the detector is isolated from the leaking fluid. The thermally sensitive detector may be a thermally sensitive resistor, the resistance of which changes with differences in temperature.
BACKGROUND OF THE INVENTION
Semiconductor manufacture, as well as other processes and applications, rely on the use of fluids, many of which are flammable. The fluids are typically stored in tanks, such as reserving tanks, and are moved from one location to another through piping lines. The detection of leaks of these fluids is usually important in such critically precise processes as semiconductor manufacture.
FIG. 1
shows one existing manner by which fluid leaks can be detected. The tank
102
stores liquid. The tank
102
is connected to a leak detector
104
at piping points
106
and
108
. When there is no leak in the tank
102
, the pressure of the fluid is the same at both points
106
and
108
, such that the detector
104
senses a differential pressure of zero across the points
106
and
108
. However, when there is a leak in the tank
102
, the pressure of the fluid is slightly more at one of the points
106
and
108
. This non-zero differential pressure is sensed by the detector
104
, which provides notification that a leak has been detected.
The differential pressure approach to leak detection of
FIG. 1
has several disadvantages, however. The volume of fluid stored in the tank
102
must be sufficiently great for the minute differences in pressure across the points
106
and
108
to be detected by the leak detector
104
. Thus, the differential pressure manner of leak detection may not be appropriate for non-tank applications, such as piping lines. Leak detection is also point specific. That is, if the leak is too close to the piping points
106
and
108
, the differential pressure across them may remain zero even though a leak has occurred, preventing its detection by the detector
104
. Finally, since detection occurs as a result of fluid leak dispersion, there can be a significant time lag between when the leak first occurs, and when the leak is detected by the detector
104
.
FIG. 2
shows another existing manner by which fluid leaks can be detected. Fluid flows through the piping line
202
. The piping line
202
is connected to a leak detector
204
by conductors
206
and
208
. Alternatively, the conductors may be integrated within the detector
204
itself. The piping line
202
is normally non-conductive, or has a measurable resistance, between the conductors
206
and
208
. As a result, the detector
204
normally does not detect a short between the conductors
206
and
208
when there is no fluid leak and the detector
204
is passing a small amount of current between the conductors
206
and
208
. However, when a fluid leak occurs, the zero-resistance nature of the fluid cases a short between the conductors
206
and
208
, which is detected by the detector
204
. The detector then provides notification that a leak has been detected. This type of leak detection is also applicable to tanks, and not just piping lines as shown in FIG.
2
.
The short circuit approach to leak detection of
FIG. 2
also has several disadvantages, however. There is no electrical isolation between the conductors
206
and
208
and the fluid during a leak. Therefore, this manner of leak detection is not appropriate for leaks of flammable fluid, which may explode as a result of the current passed between the conductors
206
and
208
by the detector
204
. Furthermore, the conductors
206
and
208
typically cannot be fixed to the piping line
202
. This means that the detector
204
does not precisely contact the surface of the piping line
202
.
Therefore, there is a need to overcome these and other disadvantages of the prior art. Specifically, there is a need for fluid leak detection where large volumes of fluid are not present. Furthermore, there is a need for fluid leak detection that is not point specific. There is also a need for fluid leak detection without a significant time lag between when the leak first occurs and when it is detected. Furthermore, there is a need for fluid leak detection of flammable fluid. Finally, there is a need for fluid leak detection that allows fixing of the leak detector to the piping line, tank, or other source of potential leaks. For these and other reasons, there is a need for the present invention.
SUMMARY OF THE INVENTION
The invention relates to fluid leak detection through thermal sensing. A sensor most generally includes one or more flexible, thermally conductive, fluid isolating layers, and a thermally sensitive detector situated within the flexible, thermally conductive isolating layers. The detector is responsive to a temperature change resulting from leaking fluid coming in contact with the sensor. The sensor may also include an affixing mechanism, such as glue, on the isolating layers, to affix the sensor to a potential fluid leak source, such as a tank or a piping line. Furthermore, the sensor may include electrical connectors located at its ends. At least one of the connectors is receptive to electrical coupling, such as to circuitry to at least indirectly measure the temperature change resulting from the leaking fluid coming in contact with the sensor.
The invention provides for advantages not found within the prior art. Fluid leak detection can be accomplished by the inventive sensor even where large volumes of fluid are not present, because the thermally sensitive detector may be able to detect even minute changes in temperature, and thus minute amounts of leakage. Furthermore, there is no significant time lag between when the leak first occurs and when it is detected, on account of the thermal sensing manner of the invention. The presence of the, fluid isolating layers prevents fluid contact with the thermally sensitive detector, so the inventive sensor can be used for fluid leak detection of flammable fluid, too. The inventive sensor, on account of the flexible nature of the, fluid isolating layers and the affixing mechanism, allows it to be placed nearly anywhere a potential leak may occur, directly fixed on the piping line, tank, or other source of potential leaks.
In one embodiment, the thermally sensitive detector is a thermally sensitive resistor, such that the temperature change resulting from the leaking fluid coming in contact with the sensor causes a measurable change in electrical resistance of the sensor. When the measurable change in resistance in one embodiment is five percent, this indicates the presence of the leaking fluid. The thermally sensitive resistor can be platinum or nickel, whereas the flexible isolating layers can be capton. A system for fluid leak detection may include one or more fluid leak detection sensors as have been described, in a serial, parallel, or combination thereof configuration. Circuitry is electrically coupled to the sensors, and responsive to the measurable change in resistance to detect leaking fluid. Still other embodiments, aspects, and advantages of the invention will become apparent by reading the detailed description that follows, and by referencing the attached drawings.


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patent: 5546790 (1996-08-01), Kudo et al.
patent: 5553482 (1996-09-01), Mathews et al.

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