JPH01314939A - Method and apparatus for detecting leakage of gas - Google Patents

Abstract

PURPOSE:To detect the leakage of a very small amount of gas at an early stage by holding leaked gas in a leaked gas sampling part and subsequently transferring a carrier gas through said sampling part. CONSTITUTION:An opening and closing solenoid valve 11 is opened by the order from a controller 12 and a definite flow rate of a carrier gas is supplied to an infrared type gas detector by a pressure regulator 9 and a needle valve 10 through a leaked gas sampling part 2. At this time, the supply of the carrier gas is performed by a pump or compressor 8. Next, the solenoid valve 11 is closed to stop the flow of the carrier gas. Subsequently, the solenoid valve 11 is opened to start the supply of the carrier gas. When there is the leakage of gas, the leaked gas mass is held in the sampling part 2 and guided to a detection cell 14 by starting the supply of the carrier gas. Herein, a pulse like change is generated in the concn. of the gas to be detected in the cell 14 and the pulse like output electrically converted by an infrared ray detector 16 is processed by a band-pass filter circuit 17 and a peak holding circuit 18 to detect the leaked gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for detecting gas leaks.

[Conventional technology]

An example of a gas leak detection device currently used for boat fishing is shown in FIG. This device includes a leak gas sampling section 2, a conduit 3
and a gas detection device R4, and a leak gas sampling section 2 is provided so as to surround but not seal the location where gas leakage is expected (leak detection location 1), and between this sampling section 2 and leak detection location 1. Atmospheric gas is sucked through the gap by a pump built in the gas detection device 4, and the leaked gas is guided along with the sucked atmospheric gas to the gas detection device 4 through the conduit 3, and the concentration of the component gas to be detected is detected. This is used to detect gas leaks.

[Problem to be solved by the invention]

In this type of device, the time required to replace the gas in the conduit from the leaked gas sampling section to the gas detection device results in a detection delay. For the purpose of detecting gas leaks, it is desirable that this detection delay be small. Therefore, in order to reduce this detection delay, a measure is generally used to increase the suction flow rate.

However, in the conventional technology, the leaking gas is diluted by constantly sucking the atmospheric gas, and by increasing the suction flow rate, the concentration of the detected component gas guided to the gas detection device can be further increased by m
It will be. Here, the maximum suction flow rate that can be taken is determined by the lowest concentration that can be detected by the equipped gas detection device. That is, the suction flow rate at which the target minimum leakage amount to be detected is diluted with the atmospheric gas and reaches the minimum concentration is the maximum. Therefore, in order to further reduce the detection delay, a higher performance device is required, and such a device is expensive and impractical.

Conversely, in order to increase the concentration of the component gas to be detected that is guided to the gas detection device, it is necessary to reduce the suction flow rate, and as a result, the detection delay increases.

Additionally, gas detection devices generally detect changes in concentration from a certain standard concentration, and if the atmospheric gas contains a gas component to be detected, that amount is the true component to be detected. This is an error due to the gas concentration.

The present invention provides a new method and device that can increase the concentration of the component gas to be detected led to the gas detection device, reduce the detection delay, and quantify leaked gas.

[Means to solve the problem]

The present invention provides a gas leak detection method that provides a leak gas sampling section at a location where a gas leak is expected, communicates the leak gas sampling section with a gas detection means, introduces the leaked gas into the gas detection means, and detects a gas leak. In this method, after the leaked gas is accumulated in the leaked gas sampling section, the carrier gas is transferred from the carrier gas source to the gas detection means via the leaked gas sampling section, and the air mass of the accumulated leaked gas is transferred to the gas detection means. a method for detecting gas leakage, and a method used in this method, comprising a device for transferring carrier gas and a control device for controlling transfer and stop of carrier gas to a leak gas sampling section. This is a characteristic gas leak detection device.

In order to achieve the above object, in the device of the present invention, the gap between the leak gas sampling section and the leak detection location is made airtight or has a nearly airtight structure. This leak gas sampling section has a space in which leak gas is retained. Further, a separate inlet is provided in the leakage gas sampling section, and carrier gas is continuously transferred from the carrier gas source through this inlet to the gas detection device via the leakage gas sampling section. During this transfer, the flow of the carrier gas into the leak gas sampling section is temporarily stopped by closing the valve attached to the transfer path, or by bypassing the valve to the gas detection device. If there is a leak, the leaked gas remains in the leaked gas sampling section during this stoppage and forms an air mass. Transfer of the carrier gas into the leakage gas sampling section is started again, and the air mass of the leakage gas staying within the leakage gas sampling section is guided to the gas detection device. In this way, by temporarily stopping the flow of carrier gas into the leak gas sampling section and allowing the leaked gas to stay within the leak gas sampling section, the leaked gas can be diffused into the leak gas sampling section and diluted only to the extent that it is diluted. It is merely diluted, and when carrier gas transfer is next initiated, the carrier gas can be introduced into the gas detection device at a much higher concentration than in the prior art without substantially diluting the leaking gas mass. Therefore, it is possible to make the transfer flow rate considerably larger than the suction flow rate of the prior art, and as a result, the detection delay can be reduced.

Regarding the stopping time, in the prior art, the time required for the leaked gas to reach the lowest concentration detectable by the equipped gas detection device in the leaked gas sampling section while being diluted with atmospheric gas, and in the present invention, the leaked gas is diluted with atmospheric gas. ,
In the leaked gas sampling section with the same internal volume as mentioned above, an air mass of leaked gas will form during the stoppage until the concentration of the detected component gas reaches the above minimum concentration when the carrier gas is mixed instantaneously after restarting the carrier gas transfer. The time required is longer in the prior art due to the amount of gas of the component to be detected that is sucked into the conduit while being diluted before reaching the above-mentioned minimum concentration.

By carrier gas transfer, the leakage gas sampling section and/or the gas detection device, and if a gas transfer path is provided between the leakage gas sampling section and the gas detection device, this gas may be transferred. Preferably, the transfer path is replaced with the carrier gas. The object of the present invention is achieved by replacing at least one or both of the air mass immediately before and after the leaking gas with the carrier gas.

The method of the present invention consists of the above-mentioned cycle, and by fixing the leakage gas sampling section at a location where gas leakage is expected and repeating this cycle at predetermined time intervals, gas leakage can be detected. can be continuously monitored and detected early.

In both the prior art and the present invention, it is preferable that the internal volume of the leaked gas sampling section be small.

Referring to FIG. 2, the relationship between the detection delay and the concentration of the detected component gas that has passed through the detection section of the gas detection device will be explained.

In the conventional technology, if the suction flow rate is reduced and the degree of dilution of the leaked gas by the atmospheric gas is kept low, the concentration of the detected component gas can be made sufficiently high as shown in A.
The detection delay is large. When the suction flow rate is increased, the detection delay becomes smaller as shown in B, but the degree of dilution of the leaked gas by the atmospheric gas is increased, and therefore the concentration of the component gas to be detected is lowered.

In the present invention, even if the flow rate of the carrier gas is increased, the concentration of the detected component gas is high as in C, and the detection delay is small.

In addition, during one cycle of carrier gas transfer, that is, carrier gas transfer - stop - retransfer, there is a pulse-like change in the concentration of the detected component gas in the detection section of the gas detection device as the leaked gas air mass passes. arise. Therefore, by transporting the carrier gas at a constant flow rate and determining the peak height or time rate of change of the pulse-like change in the concentration of the component gas to be detected, it becomes possible to quantify the leaked gas.

In the present invention, it is preferable that the carrier gas does not contain the component gas to be detected.
The carrier gas may contain the component gas to be detected. When the carrier gas contains the gas to be detected, the concentration of the gas to be detected in the air mass of the leaked gas passing through the detection section of the gas detection device is equal to the concentration of the gas to be detected when the carrier gas does not contain the gas to be detected. becomes higher. That is, when the carrier gas contains the gas to be detected, the baseline of the pulse-like change in the concentration of the gas to be detected in the detection section is higher than when the gas does not contain the gas to be detected. Conventional technology that sucks atmospheric gas detects changes in the concentration of the detected component gas from a reference concentration, and if there is a change in the concentration of the detected component gas contained in the atmospheric gas, quantification is impossible. It is. However, in the present invention, the concentration change of the detected component gas in the air mass of the leaked gas in one cycle with respect to the baseline is detected, and the peak height of such a short-time pulse-like change in the concentration of the detected component gas is detected. By determining the rate of change over time, it is possible to detect only the leaked bone without being affected by the concentration of the gas component to be detected in the carrier gas. Furthermore, there is no need for a zero point adjustment function or work, and there is no zero drift in principle, so long-term use is possible.

〔Example〕

Embodiments of the present invention will be described based on FIGS. 3 to 5.

Figures 3 and 4 are examples of the leak gas sampling section, and
The figure shows the leak gas sampling unit 2 attached to a flange 6 provided in a flow path 5 through which LPG flows, and FIG. represent

FIG. 5 shows the gas leak detection device of the present invention.

First, the solenoid valve 11 opens and closes according to a command from the controller 12.
is open, pressure regulator 9 and needle valve 10
The carrier gas adjusted to a constant flow rate begins to be fed to the infrared gas detection device via the leak gas sampling section 2. At this time, the carrier gas is fed by a pump or compressor 8, and a smoothing chamber may be provided to average the detected component gas in the carrier gas. Next, the on-off solenoid valve 11 is closed by a command from the controller 12, and the flow of the carrier gas is stopped.

Next, the solenoid valve 1 is opened and closed by a command from the controller 12.
1 is opened and the supply of carrier gas is started. If there is a gas leak, an air mass of the leaked gas remains in the leaked gas sampling section while the flow of the carrier gas is stopped, and is guided to the detection cell 14 of the infrared gas detection device when the carrier gas starts being fed. Here, a pulse-like change occurs in the gas concentration of the component to be detected within the detection cell. The peak height of this short and sudden pulse-like change is determined by electrically processing the pulse-like output signal electrically converted by the infrared detector 16 by the bandpass filter circuit 17 and the peak hold circuit 18. is obtained in response to concentration changes. Furthermore, the time rate of change of the pulse-like change can be adjusted in response to the concentration change by electrically processing the pulse-like output signal electrically converted by the infrared detector 16 using a differentiation circuit and a peak hold circuit 18. can get. Furthermore, the same function as described above can be achieved in a combination of a differential infrared detector and a peak hold circuit.

In the above, a case has been described in which the carrier gas is supplied from a gas source (not shown), but it goes without saying that the carrier gas may also be transferred by suction at the rear of the device. . In the case where the carrier gas is transferred by suction as described above, and when the ambient atmosphere gas is used as the carrier gas, the leaked gas sampling section does not need to be sealed or in a state close to that.

Although illustrations and explanations are omitted, an indicator or an alarm device may be provided. In addition, it is often used in conventional infrared gas detection devices to obtain output based on the peak height or time rate of change of the pulse-like change in the concentration of the component gas to be detected in the detection cell, which is intentionally created. In this embodiment, a chopper for modulation as a means for extracting the output and a comparison cell for zero correction are unnecessary, and gas leakage can be reliably detected using an infrared gas detection device with a very simple structure.

Also, in other gas detection devices, the output signal obtained in response to the peak height or time rate of change of the pulse-like change in the gas component to be detected in the detection section can be electrically processed in the same manner as described above. , a similar effect can be obtained. Other optical detection devices, such as an ultraviolet gas detection device or an optical interferometer gas detection device with a function of electrically extracting the amount of movement of interference fringes, are also effective. The ultraviolet gas detection device, like the external beam gas detection device, does not require a modulation device or a comparison cell for zero correction, and has a simple structure. The effect of zero drift can also be eliminated in an optical interferometer type gas detection device.

Further, a hot wire type gas detection device, for example, a catalytic combustion type gas detection device, a semiconductor type gas detection device, or a thermal conductivity type gas detection device is also effective. In these cases, no further compensation element for zero correction is required.

Further, an electrochemical gas detection device, such as a constant potential electrolytic gas detection device or a galvanic cell type gas detection device, is also effective.

〔Effect of the invention〕

The present invention is configured as described above, and produces effects as described below.

By retaining the leak gas in the leak gas sampling section and then transferring the carrier gas, dilution of the leak gas can be minimized and the air mass of the leak gas can be quickly guided to the gas detection device. In other words, it is possible to detect a small amount of gas leakage at an early stage, and there is no need for expensive, complicated, and high-performance equipment for this purpose.

Furthermore, since there is no zero drift in the gas detection device, stable detection is possible over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a conventional gas leak detection device, Fig. 2 is a diagram showing the relationship between detection delay and the concentration of the detected component gas in the detection section, and Figs. 3 and 4 are leakage gas sampling according to the present invention. FIG. 5 is a diagram showing an embodiment of the device of the present invention. 1... Leak detection point, 2... Leak gas sampling part, 3... Conduit, 4...
Gas detection device, Flow path, 6... Flange, 7... Inlet/outlet valve, 8... Pump or compressor, 9... Pressure regulator, 10... Needle pulp, 11... Open/close Solenoid valve, 12... Controller, 13... Light source, 1
4...Detection cell, 15...Optical filter, 1
6...Infrared detector, 17...Band pass filter circuit, 18...Peak hold circuit. Figure 1 Figure 2

Claims (1)

[Claims] 1. A leakage gas sampling section is provided at a location where gas leakage is expected, the leakage gas sampling section and gas detection means are communicated, and the leakage gas is introduced into the gas detection means to detect gas leakage. This is a gas leak detection method in which the leaked gas is accumulated in the leaked gas sampling section, and then the carrier gas is transferred from the carrier gas source to the gas detection means via the leaked gas sampling section to remove the air mass of the accumulated leaked gas. A gas leak detection method characterized by detecting a gas leak by guiding the gas to a gas detection means. 2. A gas leak detection device that provides a leak gas sampling section at a location where a gas leak is expected, communicates the leak gas sampling section with a gas detection means, introduces the leaked gas into the gas detection means, and detects a gas leak. A gas leak detection device comprising a device for transferring a carrier gas and a control device for controlling transfer of the carrier gas to a leak gas sampling section and stop.