Measuring and testing – Sampler – sample handling – etc. – Withdrawing through conduit or receptacle wall
Reexamination Certificate
1999-09-22
2001-05-15
Williams, Hezron (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Withdrawing through conduit or receptacle wall
C073S863810, C422S086000
Reexamination Certificate
active
06230573
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a device for sampling gas for gas analysis by means of detector tubes.
BACKGROUND OF THE INVENTION
In a glass tube, detector tubes contain a chemical preparation that reacts with the substance to be detected while undergoing a change in color, while the conversion of the substance is quantitatively displayed in the form of a color length display. For sampling, the gas tube is first opened by breaking off the tips of the detector tube on both sides. The detector tube is then placed into a sampling pump in order to draw a predetermined volume of the test gas through the detector tube. A sampling pump, with which a gas sample can be delivered through a detector tube stroke by stroke, has been known from DE 38 22 001.
However, the prior-art device for sampling gas cannot be used if very small amounts of substances that are also present in the ambient air atmosphere are to be detected. For example, a detector tube that is highly sensitive to water vapor must be used to detect water vapor in natural gas. If the tips of the detector tube are broken off only before the beginning of the measurement and the detector tube is placed into the sampling pump, the substance to be detected, which is present in the detector tube, is preloaded by the water vapor entering from the ambient atmosphere via the open tips of the detector tube such that measurement is no longer possible.
SUMMARY AND OBJECTS OF THE INVENTION
The primary object of the present invention is to improve a device of the above-described type such that gas analysis is possible without the influence of gas components from the ambient atmosphere.
According to the invention a device for gas sampling for gas analysis using detector tubes is provided including a test gas container with a gas inlet pipe, a gas outlet pipe, a mounting opening for the detector tube and with a break-off device for a detector tube tip located in the mounting opening. Nonreturn valves are provided on the gas inlet pipe and the gas outlet pipe. The closing bodies of the nonreturn valves are pressed by springs against corresponding valve seats and are held in a closed position, and are arranged in relation to one another such that a sample gas flow can be established from the gas inlet pipe to the gas outlet pipe.
The advantage of the present invention is essentially that by arranging the detector tube on a test gas container, through which sample gas flows, and by breaking off the tip of the detector tube under the atmosphere of the sample gas, effects of the ambient air on the substance to be detected are completely prevented from occurring. The gas sampling takes place such that the gas inlet pipe is connected to the gas source to be analyzed and the gas outlet pipe is connected to a gas delivery pump. The nonreturn valves located in the pipes open due to the vacuum applied by the gas delivery pump and the gas sample flows through the test gas container. The detector tube is then placed into the mounting opening located on the test gas container. The tip of the detector tube located within the mounting opening is removed by pressing the break-off device. The other end of the detector tube is then connected to a sampling pump, and the second tip of the detector tube is then opened, e.g., with another break-off device located on the sampling pump. The sample volume corresponding to the detector tube can now be drawn through the detector tube.
The gas sampling may be performed either with or without flow through the test gas container, and a site-independent measurement is also possible in the case of a test gas container with flow through, because the nonreturn valves close after interruption of the suction process or after the test gas container has been uncoupled from the sampling source and the gas delivery pump, so that no gas can penetrate into the interior space of the test gas container from the outside.
The spring force acting on the closing body of the nonreturn valve at the gas inlet pipe is advantageously selected to be such that it is stronger than the maximum suction force that can be applied by the sampling pump. It is achieved as a result that no foreign gas can be drawn into the test gas container from the environment by means of the sampling pump in the case of a site-independent measurement. A sampling pump with a detector tube has been known from U.S. Pat. No. 4,947,696 which is hereby incorporated by reference.
With a test gas container of a specifically defined volume, e.g., 100 mL, the sample volume can be limited to less than 100 mL. In the case of measurement at the test gas container with the valves closed, sample is taken only until the vacuums in the test gas container and in the sampling pump become equal. As a result, it is possible to use even smaller sample volumes for the measurement of very high pollutant concentrations.
One exemplary embodiment of the present invention is shown in the figure and will be explained in greater detail below.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawing and descriptive matter in which a preferred embodiment of the invention is illustrated.
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Sensidyne, Inc., (registered), Universal Tube Holder System for Constant Low Flow & Constant-Pressure (Multi-Flow) Operation Instruction Manual, Doc. No. F-PRO-1218, Rev. B, Nov. 1996.
Evers Wolfgang
Schulten Armin
Drager Sicherheitstechnik GmbH
Garber C D
McGlew and Tuttle , P.C.
Williams Hezron
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