JP2007033191A - Gas detecting method, gas detector and gas detecting piping - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably detect a target gas for a long time in an extremely simple manner without frequently adjusting a zero point even if an extremely low concentration of the gas is to be detected. <P>SOLUTION: The electric signal related to a sonic wave when no detecting gas exists in a detection pipe 17 is synchronously locked in a feedback circuit 20 constituting a phase-locked loop. Subsequently, the electric signal related to a sonic wave when a detection gas exists in the detection pipe 17 is introduced into the feedback circuit 20 and the synchronous lock in the feedback circuit 20 is released and the phase change of the electric signal caused by a change in the propagation speed (sound speed) of the sonic wave is taken out as an electric signal to detect the existence of the detecting gas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas detection method and a gas detector that can be suitably used for detection of gas leaks in fields that require gas detection continuously for a long period of time, particularly in mining and manufacturing, petrochemical, and high-pressure gas production facilities. And gas detection piping.

  Conventionally, methods for detecting gases existing in the atmosphere include those using chemical reactions such as galvanic cell type and constant potential electrolysis type, and those using the difference in thermal conductivity of gas. Thus, the target gas can be detected with high sensitivity and high accuracy.

  However, since the conventional gas detection method described above uses chemical reaction or heat conduction, there is a problem that the sensor itself used is basically consumed. For this reason, in the gas detector using the above-described method, the sensor must be periodically replaced, which is not suitable for long-term and continuous use. Moreover, in the detection method using heat conduction, it is necessary to adjust the zero point of the detector as appropriate before and during use, and there is a problem in stability.

  On the other hand, when detecting leak gas from a predetermined device or the like, if the leak gas is released into an unrestricted space such as the atmosphere, the concentration of the leak gas becomes too small and the leak gas is detected with high accuracy. There was a problem that could not. As a result, there has been a problem that it cannot be accurately confirmed whether or not the gas in question is actually leaking from the apparatus or the like.

  An object of the present invention is to detect a target gas in a very simple and stable manner for a long time without frequently performing zero adjustment even when the concentration of a gas to be detected is extremely low.

In order to achieve the above object, the present invention provides:
Preparing a detection tube for circulating a detection gas released from a predetermined environment;
A step of emitting a sound wave toward the detection tube in the absence of the detection gas in the detection tube, and measuring a sound speed at this time as a first sound speed;
In the state where the detection gas is present in the detection tube, emitting the sound wave toward the detection tube, and measuring the sound speed at this time as a second sound speed;
Detecting the presence of the detection gas by obtaining a difference between the first sound speed and the second sound speed;
It is related with the gas detection method characterized by comprising.

  In the gas detection method of the present invention, the target detection gas is introduced into a predetermined detection tube and is caused to flow through the detection tube, so that the detection gas can be prevented from diffusing into the unrestricted space. it can. Therefore, even when the detection gas is very small, for example, a leak gas leaking from the apparatus, the detection gas can be prevented from diffusing into an unrestricted space, so that the leak gas is kept at a high concentration to some extent. become able to.

  Further, the sound wave propagation speed (sound speed) when the detection gas is not present in the detection tube is different from the sound wave propagation speed (sound speed) when the detection gas is present. The presence of the detection gas is detected by detecting the difference in speed. Therefore, the target gas can be detected stably for a long time without exchanging the sensor that has occurred due to the use of chemical reaction or heat conduction.

  In addition, if the zero point adjustment is performed as an initial setting by configuring the generation source for generating the sound wave from a source that can generate a sound wave signal extremely stably, such as a crystal oscillator, the zero point adjustment is performed thereafter. Need not be performed frequently. Therefore, the gas detection operation can be simplified.

  In a preferred aspect of the present invention, a retention tube can be connected to retain the detection gas in the detection tube and increase the concentration of the detection gas to improve detection sensitivity (accuracy). The retention pipe is not particularly limited as long as the detection gas can be retained. For example, when the specific gravity of the detection gas is smaller than air, the outlet of the receiving tube is set downward. When the specific gravity of the detection gas is higher than air, the outlet of the receiving tube is set upward. Or do it.

  In another preferred aspect of the present invention, a difference between the first sound speed and the second sound speed is obtained in a predetermined feedback circuit. In this case, the first sound speed and the second sound speed are converted into an input electric signal such as a pulse train signal, and noise and the like are removed under various controls. Can be obtained easily and with high accuracy. Furthermore, while the detection gas is present, the difference can always be calculated and an electric signal resulting from the difference can be output. Therefore, even the remaining state of the detection gas can be detected.

  In another preferred aspect of the present invention, the feedback circuit constitutes a phase locked loop (PLL). In this case, in the feedback circuit, a predetermined electrical signal is applied in such a manner that the phase is synchronized (locked) with respect to the first input electrical signal related to the first sound velocity in the state where the detection gas is not present. In the presence of the detection gas, the second input electrical signal relating to the second sound velocity is introduced into the feedback circuit, thereby releasing synchronization (lock) in the circuit. Therefore, the presence of the detection gas can be easily detected by detecting the differential electric signal generated in the phase difference at that time.

  In the gas detection method described above, for example, an alarm setter can be driven by the detected differential electric signal, and a voice or a buzzer can be emitted to notify the operator of the presence of the detected gas.

The gas detector of the present invention is for executing the above-described gas detection method,
A sound wave source for generating a predetermined sound wave;
Sound wave emitting means for emitting the sound wave;
A sound wave receiving means for receiving the sound wave;
A detection tube for circulating a detection gas released from a predetermined environment;
The first sound velocity of the sound wave when the predetermined detection gas is not present in the detection tube and the second sound velocity when the detection gas is present in the detection tube are compared and detected, and the difference Measuring means to obtain
It is characterized by comprising.

  In a preferred aspect of the gas detector, the sound wave emitting means, the sound wave receiving means, and the detection tube are unitized together with a terminal box that houses electrical wiring for the sound wave emitting means and the sound wave receiving means. As a result, the number of parts can be reduced and the handling of the gas detector itself can be simplified.

  In another preferred embodiment of the gas detector, for the same reason as the gas detection method described above, the detection gas is retained in the detection tube, and the concentration of the detection gas is increased to detect the detection sensitivity ( In order to improve (accuracy), a residence tube can be connected. As described above, for example, when the specific gravity of the detection gas is smaller than air, the retention pipe is set to have a discharge port of the receiving pipe facing downward, or when the specific gravity of the detection gas is larger than air, This can be done by setting the outlet of the receiving tube upward.

  The measuring means preferably includes a predetermined feedback circuit, and the feedback circuit preferably constitutes a PLL.

  As described above, according to the present invention, even when the concentration of the gas to be detected is extremely low, the target gas can be detected very easily and stably for a long time without frequent zero adjustment. can do.

  Hereinafter, other features and advantages of the present invention will be described based on the best mode for carrying out the invention.

  FIG. 1 is a block diagram showing an example of the gas detector of the present invention, and FIGS. 2 and 3 are diagrams showing in detail the configuration in the vicinity of the detection tube of the gas detector shown in FIG. FIG. 5 is a view for explaining a detection method when the gas detector shown in FIG. 1 is used.

  The gas detector 10 shown in FIG. 1 is arranged as a reference signal generator 11 as a sound wave generation source composed of a crystal oscillator and the like, and a sound wave emission means for emitting sound waves from the generator. The ultrasonic speaker 13 and an ultrasonic microphone 14 as a sound wave receiving means for receiving the sound wave are provided. A detection tube 17 for circulating a predetermined detection gas is provided between the ultrasonic speaker 13 and the ultrasonic microphone 14.

  The detection tube 17 is provided with an opening 17A for emitting and detecting an ultrasonic wave to the detection gas flowing through the detection tube 17. As shown below, the detection gas is detected by the ultrasonic wave. If it is sufficiently detectable, there is no need to provide it.

  A speaker driving amplifier 12 is provided between the reference signal generator 11 and the ultrasonic speaker 13 to drive the speaker 13 and amplify the sound wave. The received sound wave is behind the ultrasonic microphone 14. A preamplifier 15 for amplification and a waveform shaper 16 for shaping the waveform of the received sound wave are provided.

  Behind the waveform shaper 16, a feedback circuit 20 constituting a PLL is provided. In the feedback circuit 20, a phase comparator 21, a low-pass filter 22 and a voltage frequency oscillator 23 are provided. Further, an alarm setting device 31 is provided behind the feedback circuit 20.

As shown in FIGS. 2 and 3, the ultrasonic speaker 13 and the ultrasonic microphone 14 are connected so as to face each other at the opening 17 </ b> A of the detection tube 17, and are provided on the outer peripheral surface of the detection tube 17. The terminal box 18 is supported by the board 19, and these are unitized and configured as an integral unit. The terminal box 18 is configured so that lead wires, connectors, cables, and the like for the ultrasonic speaker 13 and the ultrasonic microphone 14 can be accommodated together.
According to the unitized detection piping configuration as shown in FIGS. 2 and 3, it is possible to detect leak gas from the device only by connecting this unit to a predetermined device via the flange 41. The operability for gas detection can be improved.

  Next, a gas detection method using the gas detector shown in FIG. 1 will be described. A predetermined electrical signal is emitted from the reference signal generator 11, and this electrical signal is amplified through the speaker drive amplifier 12 and then emitted from the ultrasonic speaker 13 toward the detection tube 17 as an ultrasonic wave. Next, the ultrasonic wave is received by the ultrasonic microphone 14, converted into an electric signal, amplified by the preamplifier 15, and then subjected to waveform shaping by the waveform shaper 16. Thereafter, the electrical signal is introduced into the feedback circuit 20.

  Since the feedback circuit 20 constitutes a PLL, in the feedback circuit 20, as shown in FIG. 4, with respect to the received waveform of the input electric signal of the received pulse train when no detection gas is present in the detection tube 17, An electric signal (VCO electric signal) of a predetermined pulse train that is phase-synchronized from the voltage frequency oscillator 23 is applied and locked. That is, the feedback circuit 20 locks the input electric signal when the detection gas is not present. At this time, a pulse train signal at the time of locking is output from the phase comparator 21, and a reference voltage at the time of locking obtained by integrating this pulse signal can be obtained from the low-pass filter 22.

  However, in this example, as shown in FIG. 4, since the output from the phase comparator 21 is zero, the output from the low-pass filter 22 is also zero.

  On the other hand, when the detection gas is present in the detection tube 17, the propagation speed of the ultrasonic wave emitted from the ultrasonic speaker 13 in the space becomes different. Therefore, as shown in FIG. The ultrasonic input electrical signal is out of phase with the input electrical signal in the absence of the detection gas, that is, the VCO electrical signal synchronized with the input electrical signal. As a result, the phase comparator 21 generates a predetermined electrical signal corresponding to the phase difference (difference) between the input electrical signal and the VCO electrical signal, and outputs the electrical signal via the low-pass filter 22.

  The differential electric signal obtained in this way is introduced into the alarm setting device 31, and the presence of a detection gas such as an operator is recognized by a method such as voice or buzzer.

  Further, the phase difference between the input electric signal and the VCO electric signal is always compared by the phase comparator 21 by the feedback mechanism of the feedback circuit 20, and this comparison operation is performed until the phase difference disappears and synchronizes (locks) again. Become so. That is, the comparison operation is automatically performed until no detection gas exists in the space. When the detection gas is present and the phase difference is present, a predetermined differential electric signal is always output, and the alarm setting device It is comprised so that an operator may recognize through 31. Therefore, even the remaining state of the detection gas can be detected.

  FIG. 6 is a configuration diagram illustrating a modification of the piping configuration illustrated in FIGS. 2 and 3. In the example shown in FIG. 6, in the configuration in which the ultrasonic speaker 13, the ultrasonic microphone 14, and the terminal box 18 are integrated with the detection tube 17 as a unit, the detection tube 17 is further connected to the detection tube 17 via the flange 43. The stay pipe 42 is connected. In this example, since the discharge port 42A of the staying tube 42 faces downward, for example, when the detection gas is smaller than the specific gravity of air, the detection gas is retained in the detection tube 17 by the staying tube 42. As a result, the concentration of the detection gas increases.

  Therefore, for example, even a very small amount of detection gas such as leak gas from a predetermined device connected via the flange 41 can be increased in concentration and detected with sufficiently high sensitivity. Become. Therefore, the detection accuracy of the leak gas can be easily increased.

  Although not shown, when the detection gas is larger than the specific gravity of air, if the discharge port 42A is directed upward, the detection gas is retained in the detection tube 17 via the retention tube 42, and the concentration thereof is set. Can be increased. In any case, by using the staying tube 42, the detection gas can be easily retained in the detection tube 17, and the concentration thereof is increased to improve the detection accuracy of a minute concentration detection gas such as a leak gas. be able to.

  As described above, the present invention has been described in detail based on the embodiments of the invention with specific examples. However, the present invention is not limited to the above-described contents, and various modifications are possible without departing from the scope of the present invention. And changes are possible.

  In the above specific example, the ultrasonic speaker 13 and the ultrasonic microphone 14 are arranged so as to face each other, and the detection gas is allowed to flow between them, but the ultrasonic wave emitted from the ultrasonic speaker 13 is not transmitted. As long as it is configured to be introduced into the ultrasonic microphone 14, the specific configuration is not limited. For example, if the ultrasonic wave emitted from the ultrasonic speaker 13 is reflected by a wall surface (not shown) and introduced into the ultrasonic microphone 14 across the detection tube 17, the ultrasonic speaker 13 and the ultrasonic microphone 14. Can also be placed back to back in reverse.

  Further, in the above specific example, the ultrasonic speaker 13 and the ultrasonic microphone 14 are prepared, and the gas is detected using the ultrasonic wave. However, depending on the type of gas to be detected, other arbitrary It is also possible to use sound waves such as sound waves in the audible band.

  Further, in the above specific example, a PLL feedback circuit is used. However, even if such a feedback circuit is not used, it is used as long as a difference in sound wave propagation speed due to the presence or absence of a detection gas, that is, a sound speed difference can be measured. The type of electric circuit is not limited. Further, the sound speed difference may be directly measured without using an electric circuit.

  Further, in the above specific example, a rectangular wave is used as the pulse signal, but a waveform such as a sine wave or a triangular wave may be used.

It is a block diagram which shows an example of the gas detector of this invention. It is a figure which expands and shows the detection piping structure of the detection pipe vicinity of the gas detector shown in FIG. Similarly, it is a figure which expands and shows the detection piping structure of the detection pipe vicinity of the gas detector shown in FIG. It is a figure for demonstrating the detection method at the time of using the gas detector shown in FIG. Similarly, it is a figure for demonstrating the detection method at the time of using the gas detector shown in FIG. It is a block diagram which shows the modification of the detection piping shown to FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Gas detector 11 Reference signal generator 12 Speaker drive amplifier 13 Ultrasonic speaker 14 Ultrasonic microphone 15 Preamplifier 16 Waveform shaper 17 Detector tube 18 Terminal box 19 Support plate 20 Feedback circuit 21 Phase comparator 22 Low-pass filter 23 Voltage Frequency oscillator 31 Alarm setter 41, 43 Flange 42 Retention pipe

Claims (28)

Preparing a detection tube for circulating a detection gas released from a predetermined environment;
A step of emitting a sound wave toward the detection tube in the absence of the detection gas in the detection tube, and measuring a sound speed at this time as a first sound speed;
In the state where the detection gas is present in the detection tube, emitting the sound wave toward the detection tube, and measuring the sound speed at this time as a second sound speed;
Detecting the presence of the detection gas by obtaining a difference between the first sound speed and the second sound speed;
A gas detection method comprising:   The gas detection method according to claim 1, further comprising a step of connecting a retention tube to the detection tube, retaining the detection gas in the detection tube, and increasing a concentration of the detection gas. .   3. The gas according to claim 2, wherein, when the specific gravity of the detection gas is smaller than air, the discharge port of the staying tube is set downward to increase the concentration of the detection gas in the detection tube. Detection method.   3. The gas according to claim 2, wherein when the specific gravity of the detection gas is larger than air, the discharge port of the receiving tube is set upward to increase the concentration of the detection gas in the detection tube. Detection method.   The gas detection method according to claim 1, wherein the first sound speed and the second sound speed are measured as electrical signals.   The gas detection method according to claim 5, wherein the electrical signal is a pulse train signal.   The gas detection method according to claim 1, wherein the difference between the first sound speed and the second sound speed is obtained in a predetermined feedback circuit.   The gas detection method according to claim 7, wherein the feedback circuit constitutes a phase-locked loop.   The gas detection method according to claim 8, wherein the phase locked loop is synchronized with a phase of a first input electric signal related to the first sound velocity.   In the phase-locked loop, the difference between the first sound speed and the second sound speed is the phase of the second input electrical signal related to the second sound speed and the first sound speed related to the first sound speed. The gas detection method according to claim 9, wherein the gas detection method is obtained as a differential electric signal generated according to a difference between the input electric signal and the phase.   The feedback circuit is configured such that the phase of the first input electrical signal related to the first sound speed and the phase of the second input electrical signal related to the second sound speed are the same. The gas detection method according to claim 10, wherein a comparison operation between the phase of the first input electrical signal and the phase of the second input electrical signal is performed.   The gas detection method according to claim 10 or 11, wherein the differential electric signal is output as a detection signal of the detection gas. A sound wave source for generating a predetermined sound wave;
Sound wave emitting means for emitting the sound wave;
A sound wave receiving means for receiving the sound wave;
A detection tube for circulating a detection gas released from a predetermined environment;
The first sound velocity of the sound wave when the predetermined detection gas is not present in the detection tube and the second sound velocity when the detection gas is present in the detection tube are compared and detected, and the difference Measuring means to obtain
A gas detector, comprising:   The gas detector according to claim 13, further comprising a retention tube connected to the detection tube in order to retain the detection gas in the detection tube and increase the concentration of the detection gas.   When the specific gravity of the detection gas is smaller than air, the retention pipe is configured so that the discharge port of the retention pipe is set downward, the detection gas is retained in the detection pipe, and the concentration of the detection gas is increased. The gas detector according to claim 14, wherein the gas detector is a gas detector.   When the specific gravity of the detection gas is larger than that of air, the retention pipe is set so that the discharge port of the retention pipe faces upward, the detection gas is retained in the detection pipe, and the concentration of the detection gas is increased. The gas detector according to claim 14, wherein the gas detector is a gas detector.   The sound wave emitting unit, the sound wave receiving unit, and the detection tube are unitized together with a terminal box that houses electrical wiring for the sound wave emitting unit and the sound wave receiving unit. A gas detector according to claim 1.   The gas detector according to any one of claims 13 to 17, wherein the measuring means includes a predetermined feedback circuit.   The gas detector according to claim 18, wherein the feedback circuit constitutes a phase-locked loop.   A differential electric signal generated according to a difference between a phase of the first input electric signal related to the first sound speed and a phase of the second input electric signal related to the second sound speed is detected by the detection gas. The gas detector according to any one of claims 13 to 19, further comprising output means for outputting as a signal.   The gas detector according to any one of claims 13 to 20, wherein the sound wave generation source is a crystal oscillator.   The gas detector according to any one of claims 13 to 21, wherein the sound wave emitting means is an ultrasonic speaker.   The gas detector according to any one of claims 13 to 22, wherein the sound wave receiving means is an ultrasonic microphone.   The gas detector according to any one of claims 19 to 23, wherein the output means is an alarm setting device. A first sound velocity obtained by emitting a sound wave in an atmosphere in which no detection gas exists, and a second sound velocity obtained by emitting the sound wave in an atmosphere in which a detection gas exists, A detection pipe used for gas detection for detecting the presence of the detection gas by obtaining a difference between the sound speed of 1 and the second sound speed,
The detection pipe includes a sound wave emitting unit for emitting the sound wave, a sound wave receiving unit for receiving the sound wave, a detection tube for circulating a detection gas released from a predetermined environment, and the sound wave emitting unit. A gas detection pipe comprising a terminal box containing electrical wiring for the sound wave receiving means in a unitized state.   The detection pipe includes a retention pipe connected to the detection pipe in order to cause the detection gas to stay in the detection pipe and increase the concentration of the detection gas. Gas detection piping.   When the specific gravity of the detection gas is smaller than air, the retention pipe is configured so that the discharge port of the retention pipe is set downward, the detection gas is retained in the detection pipe, and the concentration of the detection gas is increased. The gas detection pipe according to claim 26, wherein the gas detection pipe is made.   When the specific gravity of the detection gas is larger than that of air, the retention pipe is set so that the discharge port of the retention pipe faces upward, the detection gas is retained in the detection pipe, and the concentration of the detection gas is increased. The gas detector according to claim 26, wherein the gas detector is a gas detector.

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