Method of testing gas analyser performances

FIELD: analytical instrument making.

SUBSTANCE: source of vapours of a substance to be analysed is placed inside a vessel to create the conditions of a linear increase of the substance vapour concentration therein. The gas analyser with an initiator of the flow rate to be tested is connected, by its inlet and outlet, to the said vessel, a time interval between two various gas analyser readouts is measured, and the measured time interval is compared to the preset reference time interval.

EFFECT: no need in determination of the substance vapour concentration in vapour-gas mix passed through the gas analyser, hence, simpler procedure.

7 cl, 2 dwg

 

The invention relates to the field of analytical instrumentation and, in particular, to methods and means for increasing the reliability of gas-analyzing equipment. Well-known methods of performance testing analyzers using the calibration of gas mixtures of known composition, based on a comparison of the readings of the scanned detector with the actual value of the concentration of the measured component in the calibration gas mixture.

The disadvantage of these methods is that they require the use of expensive calibration of gas mixtures of known composition. Because the health check should be carried out regularly, this significantly increases the cost of the verification procedure.

There is also known a method of checking the operability of the detector, which consists in creating in the tank vapor mixture by injection into a closed volume of gas a quantity of the test substance and the subsequent measurement of its concentration (see, for example, Drugov US; Rodin, A. gas Chromatographic analysis of gases, S.-Petersburg, 2001, p.24).

The disadvantage of this method is the need for accurate dispensing a certain amount of the test substance in the container. Manual dosing difficult, and when checking even a small number of analyzers this creates significant non-convenient is TBA. Automation of dispensing substantially increases the cost of the scan.

The objective of the invention was to provide such a method of checking the operability of the detector, which would at its implementation did not require the preparation of vapor-gas mixtures of known composition and would be simple and accessible to the practical implementation.

This task is solved in that a method for checking the operability of the detector using a vapor source of the test substance, which according to the invention, the test substance is placed in the internal volume of the vessel, creating conditions for a linear increase in the concentration of vapor of the substance in time, connected to the vessel inlet and outlet check detector with pump flow rate, measure the time interval between two different readings of the detector, and comparing the measured time period with a predefined reference time.

In a preferred embodiment of the method the test substance is placed in a diffusion cell, and the substance fills it partially.

Another difference is that the vessel is filled by air and by connecting the internal volume with an atmosphere of support equal to the atmospheric pressure.

Another difference is, is that in the internal volume of the vessel produces air circulation.

Among the differences between the way it should be noted that in the internal volume of the vessel to maintain a constant temperature.

Another difference is that the initial vapor concentration of the test substance in the internal volume of the vessel at the beginning of the test detector is generated by blowing the internal volume of the vessel, thread cleaned of impurities of atmospheric air.

Another difference is that the vapor concentration of the test substance in the internal volume of the vessel support a lower concentration of saturated vapor of this substance.

The technical result of the invention is that the health check of the detector is reduced to measuring the rise time of the detector readings.

When using the proposed method validation eliminates the need for dispensing a certain amount of the test substance in the tank must be cleaned after the previous test, because the method is based not on absolute readings of the detector, and the measurement time interval, during which they grow.

To determine the control time, which is actually the nameplate value, you can use a known-good detector (reference), calibrated by the calibration gas mixtures. Pin the Aulnay period of time at constant test conditions (test substance, asked readings of the detector, temperature) is constant.

The invention is illustrated by drawings.

Figure 1 shows a schematic diagram of one possible embodiment of the device for implementing the method.

Figure 2 schematically shows the time dependence of the readings of the reference detector and scanned detector with lower sensitivity.

A device for implementing the proposed method (figure 1) contains the vessel 1, which is placed inside the diffusion cell 2, is made of a transparent material, for example made of quartz glass), partially filled with the test substance 3 (a highly volatile liquid, such as hexane). Cell 2 has a diffusion leak 4 vapor is made in the form of a tube with an inner diameter of 2-10 mm Vessel 1 provided with a cover 5, which is fixed pipe 6, connected with the diffusion cell 2 and is used to populate the test substance. Inside the vessel on the rod 8 has a fan 7, which serves to equalize the vapor concentration of the test substance in the volume of the vessel 1. In the cover 5 has a nozzle 9, is used for messages in the internal volume of the vessel 1 with the atmosphere. The cover 5 is also equipped with two pipes 10 and 11 to which is connected the input and output of detector 12, provided with a FOB is a free air flow (Fig. not shown). The detector is installed photoionization detector, non-destructive test substance. Due to the fact that the steam-air mixture passing through the detector 12, is returned to the vessel 1, the presence detector does not affect the vapor concentration of the test substance in the vessel 1. In the cover 5 also has a pipe 13 is connected to the outlet of the compressor 14, the inlet of which is connected to the device 15 for cleaning atmospheric air (for example adsorber filled with granules of activated carbon).

Before first use of this device to test spend it certification, which consists in determining the control time period during which the readings of the detector increases from one set of values to another. With this purpose, as the detector 12 using known-good detector (reference), calibrated by the calibration gas mixtures.

At the beginning of certification include the detector 12 and a compressor 14 blow the internal volume of the vessel 1 purified from impurities in the fixture 15 by atmospheric air. The concentration of the vapors of the test substance in the vessel 1, as measured by the reference detector 12, is reduced (plot And curve 1, figure 2), and readings fall to a certain value of S0 . The value of S0choose close to the point of equilibrium between the quantity of test substance introduced into the vessel 1 from the diffusion cell 2, and the number of test substances to be removed from vessel 1 through pipe 9.

When the reading of the reference detector 12 is reached values of S0at the moment of time t0shut down the compressor 14. The vapor concentration of the test substance begins to increase with time in a linear fashion, because the vapor pressure of the test substance in the vessel is much less than the saturated vapor pressure (plot curve 1, figure 2). Record the time (t1*)when the reference detector 12 has reached the value indicated on the y-axis of S1. When the reading of the reference detector 12 has reached the value indicated on the y-axis of S2record the time (t2*). The value of t*2-t*1represents the time reference. The value of the control time is constant for a given temperature for the given values of S1and S2.

The values of S2and S1ask so that they were at the beginning of the plot and the value of t*2-t*1made not less than 30 C. this provides increasing evidence is close to linear, and low measurement error value t*2/sub> -t*1. In addition, the value of S2usually choose above the value at which the alarm check gas analyzer that allows you to check the operability of the signaling device. Measured so the time is recorded (written) in the passport of the device indicating the test substance and two values of the readings of the detector (S2and S1).

Health check analyzer of the same type as the reference detector, which was operated for some time, and the sensitivity which could be changed (for example, to decrease due to a dirty window for UV lamp photoionization detector), produce as well as certification. Check the sensor is connected to the branch pipes 10 and 11 of the device and then perform all the above steps. Figure 2 shows the corresponding detector with lower sensitivity curve 2, the plot And which refers to the fall of the vapor concentration of the test substance in the vessel 1 when the compressor 14, and the plot reflects the growing concentration of vapors of the test substance in time. Now the moment of reading to reach the S1corresponds to the time t1and the time readings S2corresponds to the time t2.

The switch is of the compressor 14 is not necessarily occur when reaching the testimony of S 0the compressor can be switched off at any indications of the detector is smaller than S1. Increasing evidence is determined only by the sensitivity of the detector, and for this test analyzer increasing evidence will always occur in a straight line, parallel to the plot In a straight line 2, and hence the time t2-t1will be the same.

Because the sensitivity of the test detector is less than the reference, the slew rate of the readings of the test detector is less than the reference, i.e. the tangent of the slope of the plot of curve 2 is less than the tangent of the slope of the plot of curve 1. The resulting value of t2-t1more than t2-t*1.

Thus, the testing process is reduced to a measurement of the difference t2-t1and comparing this value with the control time interval t*2-t*1.

In the process, there is a constant decrease in the volume of the test substances in the diffusion cell, so you need to periodically add, using the pipe 6.

1. The way to verify that the detectors using a vapor source test substance, wherein the test substance is placed in the internal volume of the vessel, creating conditions for a linear increase of the concentration is the vapor of the substance, connected to the vessel inlet and outlet check detector with pump flow rate, measure the time interval between two different readings of the detector, and comparing the measured time period with a predefined reference time.

2. The method according to claim 1, characterized in that the test substance is placed in a diffusion cell.

3. The method according to claim 1, characterized in that the vessel is filled with air and maintain the pressure therein equal to the atmospheric pressure by connecting the internal volume of the vessel with the atmosphere.

4. The method according to claim 3, characterized in that in the internal volume of the vessel to produce a circulation of air to equalize the vapor concentration of the test substance in the vessel.

5. The method according to claim 4, characterized in that maintain a constant temperature in the air in the internal volume of the vessel.

6. The method according to claim 1 or 2 or 3 or 4 or 5, characterized in that the initial concentration of vapor of the substance in the vessel before the health check of the detector is generated by blowing the internal volume of the vessel, thread cleaned of impurities of atmospheric air.

7. The method according to claim 6, characterized in that the concentration of vapor of the substance in the internal volume of the vessel support a lower concentration of saturated vapor of this substance at a given temperature is ur.



 

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FIELD: instrument engineering.

SUBSTANCE: device for generating flow of vapor-gas mixture with preset concentration of vapor has vessel partially filled with fluid, second vessel provided with branch pipes for supply and removal of gas, and vapors of fluid pipeline-leak. One of vessels is connected with gas discharge forcer; fluid vapors pipeline-leak connects both vessels. Vessel, partially filled with fluid, is mounted inside second vessel. Pipeline-line, connecting both vessels, is totally placed inside second vessel. Device is also provided with additional discharge forcer for adjusting concentration of fluid vapor in second vessel. Granulated filler is introduced into vessel partially filled with fluid. Device is also provided with gas analyzer for providing gas concentration in space of second vessel.

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EFFECT: higher precision of keeping of preset concentration of vapor; improved efficiency of vapor concentration control and adjustment.

FIELD: analytical instrument making.

SUBSTANCE: source of vapours of a substance to be analysed is placed inside a vessel to create the conditions of a linear increase of the substance vapour concentration therein. The gas analyser with an initiator of the flow rate to be tested is connected, by its inlet and outlet, to the said vessel, a time interval between two various gas analyser readouts is measured, and the measured time interval is compared to the preset reference time interval.

EFFECT: no need in determination of the substance vapour concentration in vapour-gas mix passed through the gas analyser, hence, simpler procedure.

7 cl, 2 dwg

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SUBSTANCE: invention relates to methods for separation and analytical gas-chromatographic determination of the amount of an extractant in vegetable material, primarily vegetable oil. A method of determining the amount of an extractant - n-hexane and petroleum ether in vegetable material, primarily oil, includes collecting a sample of vegetable material, separating the remaining extractant therefrom and performing gas-chromatographic analysis; the extractant is separated by preparative distillation, wherein a solvent is first added to the collected sample, said solvent having chromatographically determined intrinsic impurities in the chromatographic output region of n-hexane and components of petroleum ether lower than 1-2 wt %, wherein the solvent is selected from: isooctane, n-butanol, n-butylacetate, toluene, o-xylene, and the ratio of the solvent to the sample ranges from 1:1 to 1:10.

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15 cl, 19 dwg

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