JP2008039440A - Safety valve device and gas sampling container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a safety valve device capable of preventing inverse diffusion when a safety valve is operated, and a gas sampling container capable of preventing the contamination of the sample gas in a gas sampling container even if the gas pressure in the gas sampling container is raised by any cause and the safety valve is operated. <P>SOLUTION: The safety valve device is equipped with the safety valve 17 which is mounted on the container (gas sampling container 11) and opened when the pressure in the container exceeds set pressure and the check valve 18 connected to the secondary side of the safety valve to permit only the flowing of a fluid from a safety valve and the set pressure for opening the check valve is set to the set pressure of the safety valve or below. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a safety valve device and a gas sampling container, and more particularly to a safety valve device provided in a gas container filled with high-pressure gas, and particularly suitable for a gas sampling container for sampling a trace air component for analysis. The present invention relates to a safety valve device and a gas sampling container equipped with the safety valve device.

  In the analysis of a high purity gas, a gas sampling container from which a sample gas is collected is transported to a place where analytical equipment is provided, and the purity of the sample gas and the impurity concentration in the sample gas are measured. The gas sampling container used for this purpose can be obtained even if the analyzer is highly reliable if the gas in the gas sampling container is contaminated for some reason between collection of the sample gas and analysis. Therefore, maintaining the cleanliness of the sample gas in the gas sampling container is an important factor (see, for example, Patent Document 1).

In order to prevent the gas pressure inside the gas container (including the inside of the path connected to the gas container, the same shall apply hereinafter) from exceeding a certain value, there is a possibility that the gas pressure in the gas container may increase. A safety valve is attached (see, for example, Patent Document 2).
JP 2000-171362 A JP 2001-304498 A

  A general safety valve that operates with a pressure difference between the inside and outside of a gas container keeps the valve closed by urging the valve body toward the container with an urging means such as a coil spring, and the gas pressure inside the container exceeds a certain pressure. And the valve body is pushed in the valve opening direction by the gas pressure, and immediately after the safety valve is activated (opened), a large amount of gas in the gas container is exhausted to the outside. The gas flow velocity passing through is high. However, when the gas pressure in the gas container gradually decreases and approaches a constant pressure, the gas flow rate passing through the safety valve decreases, so the atmospheric gas outside the gas container, usually air, passes through the safety valve in the reverse direction to gas. A phenomenon of diffusion into the container, that is, reverse diffusion occurs.

  The amount of air that diffuses into the gas container by back diffusion is very small, and it is not a problem for gas containers filled with commonly used gas. In the case of the gas sampling container, analysis in the gas sampling container When a gas of the same type as the target gas component is mixed into the sample gas in the gas sampling container by back diffusion, the sample gas is contaminated and greatly affects the analysis result. In particular, when the analysis target gas is a trace air component of several ppm or less, it should be absolutely avoided that air is mixed into the sample gas in the gas sampling container by back diffusion.

  Therefore, the present invention provides a safety valve device that can prevent back diffusion when the safety valve is activated, and the gas pressure in the gas sampling container rises for some reason and the sample gas in the gas sampling container is activated even if the safety valve is activated. An object of the present invention is to provide a gas sampling container that can prevent contamination of the gas.

  In order to achieve the above object, the safety valve device and the gas sampling container of the present invention are safety valve devices that are opened when the gas pressure in the container exceeds the set pressure and keep the pressure in the container at or below the set pressure. A safety valve that is attached to the container and opens when the inside of the container exceeds the set pressure, and a check valve that is connected to the secondary side of the safety valve and allows only fluid to flow from the safety valve side The set pressure at which the check valve opens is set to be less than the set pressure of the safety valve, preferably 20% or more and less than the set pressure with respect to the set pressure of the safety valve.

  Further, the gas sampling container of the present invention is characterized by including the safety valve device having the above-described configuration, and in particular, the gas to be sampled is an analysis gas, and the analysis target component is a trace air component. Yes.

  In the safety valve device of the present invention, when the pressure in the container rises above the set pressure of the safety valve, first, the safety valve is opened by the gas pressure in the container, and the gas in the container flows out to the secondary side of the safety valve. The gas that has flowed out to the secondary side of the safety valve temporarily stays in the space between the secondary side of the safety valve and the primary side of the check valve, and the pressure of this retained gas exceeds the set pressure of the check valve And the check valve opens. As a result, the gas in the container whose pressure has exceeded the set pressure is released from the safety valve to the outside of the container through the check valve.

  The gas in the space between the safety valve and the check valve is related to the amount of gas passing through the safety valve and the amount of gas passing through the check valve due to the pressure in the container decreasing and the flow rate of gas passing through the safety valve decreasing. When the pressure is equal to or lower than the set pressure of the check valve, the check valve is intermittently opened and closed while the safety valve is open, and the gas in the container is continuously released.

  Therefore, when the safety valve device is activated due to an increase in the pressure inside the container, the gas pressure in the container becomes lower than the set pressure of the safety valve by opening the safety valve, and between the secondary side of the safety valve and the primary side of the check valve. The gas pressure in the space is equal to or slightly lower than the set pressure of the check valve.

  Even when a small amount of outside air (air) is diffused back to the primary side of the check valve when the check valve is opened, the safety valve device is mixed into the space between the safety valve and the check valve. Since the amount of air is very small, even if the gas in this space passes back through the safety valve into the container, the amount of air mixed into the container becomes extremely small.

  That is, when the sample is a gas sampling container, and the sample gas whose analysis object is a minute amount of air components (nitrogen, oxygen, argon, etc.) is sampled in the gas sampling container, the safety valve device is provided in the gas sampling container. By providing it, the gas pressure in the gas sampling container can be kept below a certain pressure, and even if the gas pressure in the gas sampling container rises and the safety valve is activated, air components are mixed in the gas sampling container. There is almost no analysis, and analysis with high accuracy and reliability can be performed.

  FIG. 1 is an explanatory view showing one embodiment of a gas sampling container equipped with the safety valve device of the present invention.

  This gas sampling container 11 is a so-called flow-through sampler that has been used in the past. Sample gas paths 14 and 14 having valves 13 and 13 are provided at both ends of a container part 12 having a predetermined diameter and length. Each is provided. Further, the vessel portion 12 is provided with a pressure gauge 15 and a safety valve device 16.

  The safety valve device 16 includes a safety valve 17 attached to the container portion 12 and a check valve 18 that allows only fluid flow from the safety valve 17 side connected to the secondary side (gas release side) of the safety valve 17. The safety valve 17 is opened when the gas pressure in the gas sampling container 11 exceeds the set pressure of the safety valve 17 and the gas in the gas sampling container 11 is moved to the secondary side of the safety valve 17. The check valve 18 opens and opens when the pressure of the gas released to the secondary side of the safety valve 17 exceeds the set pressure of the check valve 18. The gas temporarily staying in the space between the primary side of the valve 18 is formed to be discharged to the secondary side of the check valve 18, that is, to the outside.

  The set pressure (safety valve set pressure) of the safety valve 17 is set in advance according to the pressure resistance performance of the gas sampling container 11 and the valve 13. On the other hand, the set pressure of the check valve 18 (check valve set pressure) is set to be less than the safety valve set pressure. That is, if the check valve set pressure is set to be equal to or higher than the safety valve set pressure, the check valve 18 may not open even if the safety valve 17 is activated and opened. It becomes impossible to keep below a certain pressure. The lower limit of the check valve set pressure varies depending on the diameter of the safety valve 17 and the check valve 18 and the value of the safety valve set pressure. If the check valve 18 is opened with a slight pressure difference, the outside air is not checked when the valve is opened. Since the possibility of back diffusion from the secondary side to the primary side of the valve 18 increases, it may be set to 0.1 MPa (gauge pressure, the same applies hereinafter), preferably 0.2 MPa or more, and the relationship with the safety valve set pressure. From the above, it is desirable to set the check valve set pressure to a value of 20% or more with respect to the safety valve set pressure, and if it is less than 20%, no significant effect is seen, but if it is 20% or more, The amount of leakage due to despreading can be suppressed to less than half.

  Thus, in the safety valve device 16 in which the check valve 18 having a set pressure lower than the set pressure of the safety valve 17 is connected to the secondary side of the safety valve 17, the pressure in the gas sampling container 11 exceeds the set pressure of the safety valve. Then, the safety valve 17 is opened by the gas pressure in the gas sampling container 11, and the gas in the gas sampling container 11 flows out to the secondary side of the safety valve 17. The gas that has flowed out to the secondary side of the safety valve 17 temporarily stays in a space portion such as a joint for connecting the secondary side of the safety valve 11 and the primary side of the check valve 18, and enters the space portion. When the pressure of the accumulated gas exceeds the check valve set pressure, the check valve 18 is opened. As a result, when the internal pressure of the gas sampling container 11 rises exceeding a preset pressure in the gas sampling container 11, the gas in the gas sampling container 11 is released from the safety valve 17 through the check valve 18 to the outside.

  The pressure in the gas sampling container 11 decreases, the flow rate of the gas passing through the safety valve 17 decreases, and the gas pressure in the space portion is related to the amount of gas passing through the safety valve 17 and the amount of gas passing through the check valve 18. Becomes lower than the check valve set pressure, the check valve 18 is intermittently opened and closed while the safety valve 17 is open, and the gas sampling container 11 continues to release the gas. Is kept below a certain pressure.

  Accordingly, when the safety valve device 16 is activated due to an increase in the gas pressure in the gas sampling container 11, the safety valve 17 is opened, so that the gas pressure in the gas sampling container 11 becomes lower than the safety valve set pressure, and the secondary side of the safety valve 17. And the primary side of the check valve 18 have a gas pressure equal to or slightly lower than the check valve set pressure.

  Even when a small amount of air is reversely diffused to the primary side of the check valve 18 when the check valve 18 is opened when the safety valve device 16 is operated, the space portion between the safety valve 17 and the check valve 18 is used. Since the amount of air mixed in is very small, the amount of air mixed into the sample gas in the gas sampling container 11 is not limited even if the gas in this space portion is reversely diffused into the gas sampling container 11 through the safety valve 17. It becomes a very small amount. That is, in the gas sampling container 11 provided with such a safety valve device 16, even if the gas pressure in the gas sampling container 11 rises for some reason, the gas pressure in the gas sampling container 11 is activated by operating the safety valve device 16. Gas sampling even when the safety valve device 16 of the gas sampling container 11 that samples a sample gas that is a trace amount of air component (nitrogen, oxygen, argon, etc.) of several ppm or less is operated. Since the sample gas is hardly contaminated by the air component mixed into the container 11, the micro analysis of the air component can be performed with high accuracy, and the reliability of the analysis result can be improved.

  In the structure shown in FIG. 1, only a safety valve 17 (manufactured by Chiyoda Seiki Co., Ltd.) having a set pressure of 0.7 MPa is provided in a gas sampling container 11 having an internal volume of the container 12 of 6 liters, and 0.9 MPa in the gas sampling container 11. High-purity oxygen gas (nitrogen concentration of less than 1 ppm) was introduced from one sample gas path 14.

  Since the introduction pressure of the high purity oxygen gas is higher than the set pressure of the safety valve 17, the safety valve 17 is activated when the pressure exceeds 0.7 MPa, and the oxygen gas in the gas sampling container 11 is released into the atmosphere to release the gas sampling container. When the inside of 11 decreased to 0.7 MPa, the safety valve 17 was closed and the release of oxygen gas was completed. The nitrogen concentration in the gas sampling container 11 at this time was analyzed with a gas chromatograph analyzer.

  As a result of repeating this experiment four times, the nitrogen concentrations were 4 ppm, 3 ppm, 6 ppm, and 3 ppm (average 4 ppm), respectively, and the nitrogen in the atmosphere was converted into the sample gas (high) in the gas sampling container 11 by back diffusion from the safety valve 17. It was found that the sample gas was contaminated with the pure oxygen gas).

  Next, a check valve 18 (CPA type manufactured by Swagelok Co., Ltd.) is connected to the rear stage of the safety valve 17 via a joint, and the set pressure of the check valve 18 is set to 0 to 0.6 MPa, as described above. The experiment was conducted. A pressure gauge was also provided at the joint between the safety valve 17 and the check valve 18, and the gas pressure in the space between the secondary side of the safety valve 17 and the primary side of the check valve 18 was measured.

  When high-purity oxygen gas of 0.9 MPa is introduced into the gas sampling container 11, the safety valve 17 is activated when the measured value of the pressure gauge 15 exceeds 0.7 MPa, and the high-purity oxygen gas in the gas sampling container 11 is The check valve 18 was released when it was discharged from the safety valve 17 and accumulated in the joint portion between the safety valve 17 and the check valve 18, and the gas pressure in the joint portion exceeded the set pressure of the check valve 18.

  As a result, the high-purity oxygen gas in the gas sampling container 11 was released from the safety valve 17 through the joint portion and through the check valve 18 into the atmosphere. The safety valve 17 closes when the gas pressure in the gas sampling container 11 drops to 0.7 MPa, which is the set pressure of the safety valve 17, and reverses when the gas pressure at the joint becomes the set pressure of the check valve 18. The stop valve 18 was also closed.

  The experiment was performed five times at each set pressure while changing the set pressure of the check valve 18, and the nitrogen concentration contained in the high purity oxygen gas in the gas sampling vessel 11 was analyzed. The average value of the analysis results at each set pressure is shown in FIG.

  As is clear from FIG. 2, when the set pressure of the check valve 18 is 0 MPa, which is actually slightly higher than 0 MPa, but the function as the check valve is hardly exhibited, the reverse diffusion is sufficiently performed. It cannot be prevented that the effect of providing the check valve 18 is hardly obtained. That is, to the extent that a valve that opens with a slight pressure difference (less than 0.1 MPa), for example, a valve for preventing dust or the like from entering the safety valve 17 is provided on the secondary side of the safety valve 17. It can be seen that despreading cannot be sufficiently prevented.

  When the set pressure of the check valve 18 is set to 0.1 MPa, an effect of preventing back diffusion appears. When the set pressure becomes 0.2 MPa, the effect of preventing back diffusion becomes clear, and when the set pressure is set to 0.3 MPa or more, It can be seen that the reverse diffusion is prevented and the high-purity oxygen gas in the gas sampling container 11 is not contaminated with nitrogen in the atmosphere.

  From this result, if the set pressure of the check valve 18 is 0.1 MPa or more, a reverse diffusion prevention effect can be obtained, and further, if the set pressure is 0.2 MPa or more, a sufficient back diffusion prevention effect can be obtained, In particular, it can be seen that the reverse diffusion can be reliably prevented by setting the set pressure to 0.3 MPa or more.

It is explanatory drawing which shows one example of a gas sampling container equipped with the safety valve apparatus of this invention. It is a figure which shows the relationship between the setting pressure of a non-return valve in Example 1, and a nitrogen concentration analysis value.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Gas sampling container, 12 ... Container part, 13 ... Valve, 14 ... Sample gas path, 15 ... Pressure gauge, 16 ... Safety valve apparatus, 17 ... Safety valve, 18 ... Check valve

Claims (4)

  A safety valve device that opens when the gas pressure in the container exceeds the set pressure and keeps the pressure in the container at or below the set pressure, and is attached to the container and the inside of the container exceeds the set pressure. A safety valve that is sometimes opened, and a check valve that is connected to the secondary side of the safety valve and allows only fluid flow from the safety valve side, and the safety valve has a set pressure that opens the check valve. A safety valve device that is set to a pressure lower than the set pressure.   The safety valve device according to claim 1, wherein a set pressure at which the check valve opens is set to 20% or more with respect to a set pressure of the safety valve.   A gas sampling container comprising the safety valve device according to claim 1.   The gas sampling container according to claim 3, wherein the gas to be sampled is an analysis gas, and the analysis target component is a trace air component.

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