GB2349695A

GB2349695A - Gas sampling device

Info

Publication number: GB2349695A
Application number: GB9921604A
Authority: GB
Inventors: Armin Schulten; Wolfgang Evers
Original assignee: Draeger Sicherheitstechnik GmbH
Current assignee: Draeger Safety AG and Co KGaA
Priority date: 1999-05-07
Filing date: 1999-09-13
Publication date: 2000-11-08
Anticipated expiration: 2019-09-13
Also published as: GB9921604D0; GB2349695B

Abstract

Device comprises a test gas container 1 with a gas inlet pipe 2, a gas outlet pipe 3, a receiving aperture 4 for a testing tube 5 and a breaking-off device 6 for the tube tip 7. The tube 5 is connected to a sampling pump 9. Connecting pipes 2, 3 have non-return valves 11, 12 whose closure members 13, 14 are pressed by springs 15, 16 against the associated valve seats 17, 18. The non-return valves 11, 12 are fitted inside the connecting pipes 2, 3 so that only one sample gas flow is possible from the gas inlet 2 to the gas outlet 3. The gas inlet 2 is connected to a sampling source 19 outlet connecting pipe 3 is connected to a gas feed pump 20 to produce gas flow from the inlet 2 to the outlet 3.

Description

Device for gas sampling The invention relates to a device for gas sampling for gas analysis by means of test tubes.

In a known method of gas analysis, test tubes contain in a glass tube a chemical preparation which reacts with the material to be identified and produces a colour change, the material reaction being quantitively represented in the form of a colour length, or extension, indication. For sampling, the glass tube is first of all opened by the test tube tips being broken off at both ends. The test tube is then inserted into a sampling pump in order to draw a specific test gas volume through the test tube. A sampling pump, with which a gas sample can be conveyed stroke-wise through a test tube, is known from DE 38 22 001.

However, the known device for gas sampling cannot be used when extremely small amounts of substances, which are also present in the ambient air atmosphere, have to be identified. For instance, to detect water vapour in natural gas a test tube which is highly sensitive with respect to water vapour has to be used. If the test tube tips are broken off momentarily before the measurement begins, and the test tube is inserted into the sampling pump, then the identifying substance, which is in the test tube, is pre-influenced to such an extent by the water vapour emerging from the ambient atmosphere via the opened test tube tips, that measurement is no longer possible.

Embodiments of the invention aim to improve a device of the above type in such a way that gas analysis is not unduly influenced by gas components from the ambient atmosphere.

According to the present invention there is provided a device for gas sampling for gas analysis by means of test tubes, the device comprising: a test gas container having a gas inlet connecting pipe, a gas outlet connecting pipe, a receiving aperture for the test tube and a breaking-off device for a test tube tip located in the receiving aperture, and non-return valves on the gas inlet connecting pipe and gas outlet connecting pipe, the closure members of which are biased by resilient means against associated valve seats and held in the closed position, and which are arranged in such a way with respect to each other that a sample measurement gas flow can be produced from the gas inlet connecting pipe to the gas outlet connecting pipe.

Further preferred features may be found in the attached dependent claims.

Embodiments of the invention enjoy the advantage that by mounting the test tube on a test gas container which has sample gas flowing through it, and by breaking-off the tip of the test tube under the atmosphere of the sample gas, influences of the ambient air on the substance to be identified are completely eliminated.

Gas sampling occurs in such a way that the gas intake connecting pipe is connected to the gas source to be tested, and the gas outlet connecting pipe is connected to a gas feed pump. By means of the vacuum applied by the gas feed pump the non-return valves located in the connecting pipes are opened, and the gas sample flows through the test gas container. After that the test tube is inserted into the receiving aperture located on the test gas container. The test tube tip inside the receiving aperture is removed by pressing on the breaking-off device. The other end of the test tube is then connected to a sampling pump, and then the second test tube tip is opened, for instance with a further breaking-off device located on the sampling pump. The sample volume of the test tube can now be drawn out through the test tube.

Gas sampling can be effected both with gas flowing through the test gas container and with no gas flowing through it and, when there is no gas flowing through the test gas container, remote measurement is also possible. After the suction process has been interrupted, or after the test gas container has been uncoupled from the sampling source and the gas feed pump, the non-return valves close so that no gas can penetrate from outside into the inner chamber of the test gas container.

The spring force acting on the closure member of the non-return valve on the gas inlet connecting pipe is preferably determined to be greater than the maximum suction force that can be applied by the sampling pump.

This means that in the case of remote measurement, no foreign gas can be drawn into the test gas container from the environment by means of the sampling pump.

With a test gas container of a quite specific volume, for instance 100 ml, the sample volume can be restricted to less than 100 ml. In the case of a measurement on the test gas container with closed valves, only so much sample is removed until the partial vacuum in the test gas container and in the sampling pump is equal. This means that it is also possible to use smaller sample volumes to measure high concentrations of harmful substances.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawing, in which Figure 1 shows schematically a test gas container 1 with a gas inlet connecting pipe 2, a gas outlet connecting pipe 3, a receiving aperture 4 for a test tube 5 and a breaking-off device 6 for the test tube tip 7.

The other end of the test tube 5 is connected by means of a tube 8 to a sampling pump 9, whose grip plates 10 can be pressed together for the gas sampling.

In the connecting pipes 2,3 there are non-return valves 11,12 whose closure members 13,14 are pressed by resilient biasing means, such as springs 15,16 against the associated valve seats 17,18. The nonreturn valves 11,12 are fitted inside the connecting pipes 2,3 in such a way that only one sample gas flow is possible from the gas inlet 2 to the gas outlet 3.

The gas inlet 2 is connected to a sampling source 19, for instance a natural gas source, whilst the gas outlet connecting pipe 3 is connected to a gas feed pump 20.

Devices in accordance with the invention should be capable of detecting water vapour in natural gas, for instance during gas sampling on a bore platform.

Measurement is effected in such a way that first of all the gas feed pump 20 is switched on and natural gas is drawn out of the sampling source 19. After sufficient rinsing of the test container 1, the unopened test tube 5 is inserted with one side into the receiving aperture 4, whilst the other side is connected by means of the tube 8 to the sampling pump 10. The tips of the test tubes are then removed by means of the breakingoff device 6 and by pressure on the tube 8. The gas sampling can now be carried out by pressure on the grip plates 10 according to the measurement instruction of the test tube 5.

In the case of remote gas analysis, the sampling source 19 and the gas feed pump 20 are separated from the test gas container 1, the non-return valves 11,12 then closing automatically. The remote measurement may be necessary when gas sampling is possible only under difficult conditions when no test tube 5 can be used for gas analysis on site.

Claims

Claims 1. A device for gas sampling for gas analysis by means of test tubes, the device comprising: a test gas container having a gas inlet connecting pipe, a gas outlet connecting pipe, a receiving aperture for the test tube and a breaking-off device for a test tube tip located in the receiving aperture, and non-return valves on the gas inlet connecting pipe and gas outlet connecting pipe, the closure members of which are biased by resilient means against associated valve seats and held in the closed position, and which are arranged in such a way with respect to each other that a sample measurement gas flow can be produced from the gas inlet connecting pipe to the gas outlet connecting pipe.
2. A device according to claim 1, wherein the biasing force acting on the closure member of the gas inlet connecting pipe is determined in such a way that it is greater than the suction force of a sampling pump connected to the test tube.
3. A device according to claim 1, wherein the nonreturn valves are designed as spherical seat valves.
4. A device according to any of claims 1 to 3, wherein the gas inlet connecting pipe is designed to be connectable to a sampling source, and the gas outlet connecting pipe has means for connection to a gas feed pump.
5. A device for gas sampling the device being substantially as herein described with reference to the accompanying drawing.

5. A device for gas sampling the device being substantially as herein described with reference to the accompanying drawing.

Amendments to the claims have been filed as follows Claims 1. A device for gas sampling for gas analysis by means of test tubes, the device comprising: a test gas container having a gas inlet connecting pipe, a gas outlet connecting pipe, a receiving aperture for the test tube and a breaking-off device for removing the test tube tip inside the test gas container, and non-return valves on the gas inlet connecting pipe and gas outlet connecting pipe, the closure members of which are biased by resilient means against associated valve seats and held in the closed position, and which are arranged in such a way with respect to each other that a sample measurement gas flow can be produced from the gas inlet connecting pipe to the gas outlet connecting pipe.

2. A device according to claim 1, wherein the biasing force acting on the closure member of the gas inlet connecting pipe is determined in such a way that it is greater than the suction force of a sampling pump connected to the test tube.

3. A device according to claim 1, wherein the nonreturn valves are designed as spherical seat valves.

4. A device according to any of claims 1 to 3, wherein the gas inlet connecting pipe is designed to be connectable to a sampling source, and the gas outlet connecting pipe has means for connection to a gas feed pump.