JP5557251B2 - Gas microflow detection method, gas leak inspection method, gas leak inspection apparatus, and ultrasonic flowmeter - Google Patents

Gas microflow detection method, gas leak inspection method, gas leak inspection apparatus, and ultrasonic flowmeter Download PDF

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JP5557251B2
JP5557251B2 JP2010256479A JP2010256479A JP5557251B2 JP 5557251 B2 JP5557251 B2 JP 5557251B2 JP 2010256479 A JP2010256479 A JP 2010256479A JP 2010256479 A JP2010256479 A JP 2010256479A JP 5557251 B2 JP5557251 B2 JP 5557251B2
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豊 田中
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Aichi Tokei Denki Co Ltd
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Description

本発明は、流路管又は容器におけるガスの流れの有無又は流量又はガス漏れを検出するためのガス微流動検出方法、ガス漏れ検査方法、ガス漏れ検査装置及び超音波流量計に関する。   The present invention relates to a gas microflow detection method, a gas leak inspection method, a gas leak inspection apparatus, and an ultrasonic flowmeter for detecting the presence or absence, flow rate, or gas leak of a gas flow in a flow channel tube or container.

従来のこの種のガス流動検出装置として、並列接続された複数の計測管をガス管の途中に接続して、それら各計測管にそれぞれ１対の超音波送受波器を設け、流量の大小に応じてガスを流す計測管の数を増減させることで、通常のガス使用によるガス流動から、ガス漏れのような微少なガス流動まで検出可能としたものが知られている（例えば、特許文献１参照）。   As a conventional gas flow detection device of this type, a plurality of measurement tubes connected in parallel are connected in the middle of the gas tube, and a pair of ultrasonic transducers are provided in each of these measurement tubes. In response to this, by increasing or decreasing the number of measuring tubes through which gas flows, it is possible to detect gas flow from normal gas use to minute gas flow such as gas leakage (for example, Patent Document 1). reference).

特開平１１−２８７６７６号公報（段落［００２８］〜［００３０］、第１図）JP-A-11-287676 (paragraphs [0028] to [0030], FIG. 1)

ところが、上述した従来のガス流動検出装置は、複数の計測管と複数対の超音波送受波器とが必要になるため、構造の大型化及び製品価格の上昇を招くという問題があった。   However, the conventional gas flow detection device described above has a problem in that it requires a plurality of measurement tubes and a plurality of pairs of ultrasonic transducers, resulting in an increase in structure size and an increase in product price.

本発明は、上記事情に鑑みてなされたもので、構造の大型化及び製品価格の上昇を抑えつつ微少なガス流動を検出することが可能なガス微流動検出方法、ガス漏れ検査方法、ガス漏れ検査装置及び超音波流量計の提供を目的とする。   The present invention has been made in view of the above circumstances, and a gas microfluidic detection method, a gas leak inspection method, and a gas leak capable of detecting a minute gas flow while suppressing an increase in structure size and an increase in product price. The purpose is to provide an inspection device and an ultrasonic flowmeter.

上記目的を達成するためになされた請求項１の発明に係るガス微流動検出方法は、第１のガスが滞留した流路管又は容器における内部空間の一部を、１対の超音波送受波器の間で超音波を伝搬させるための超音波伝搬経路とし、第１のガスとは超音波の伝搬速度が異なる第２のガスを流路管又は容器の外部から超音波伝搬経路に注入しかつ滞留させた状態にして、その超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を計測し、その伝搬時間又は伝搬速度の時間経過に伴った推移と、実測又は演算にて求められる第１のガスの流量を０にした場合の第２のガスの自然拡散による伝搬時間又は伝搬速度の時間経過に伴った基準推移との比較に基づいて、第１のガスの流れの有無、流量、或いは、第１のガスの漏れを検出するところに特徴を有する。   In order to achieve the above object, a gas microfluidic detection method according to the invention of claim 1 is characterized in that a part of the internal space in a channel tube or a container in which a first gas is retained is converted into a pair of ultrasonic transmission / reception waves. An ultrasonic propagation path for propagating ultrasonic waves between the vessels is used, and a second gas having a different ultrasonic propagation velocity from the first gas is injected into the ultrasonic propagation path from the outside of the channel tube or container. In addition, the propagation time or propagation speed of the ultrasonic wave propagating through the ultrasonic propagation path is measured in the state of being retained, and the change with the passage of time of the propagation time or propagation speed and the measurement or calculation are obtained. Based on the comparison with the reference transition with the passage of time of propagation time or propagation speed due to natural diffusion of the second gas when the flow rate of the first gas is 0, the presence or absence of the flow of the first gas, the flow rate Or specially where the first gas leak is detected. Having.

ここで、請求項１における「伝搬時間又は伝搬速度の時間経過に伴った推移と、実測又は演算にて求められる第１のガスの流量を０にした場合の第２のガスの自然拡散による伝搬時間又は伝搬速度の時間経過に伴った基準推移との比較」とは、以下の意味を含んでいる。即ち、「第２のガスを滞留させてから所定期間に亘って連続して計測された伝搬時間又は伝搬速度の経過時間に伴う変化を、基準推移の対応する同一所定期間における伝搬時間又は伝搬速度の経過時間に伴う変化と比較すること」や、「第２のガスを滞留させてから所定時間が経過した或る時点で計測された伝搬時間又は伝搬速度を、基準推移の対応する同一時点における伝搬時間又は伝搬速度と比較すること」を含む意味である。   Here, in claim 1, “propagation due to the natural diffusion of the second gas when the flow of the propagation time or propagation speed with the passage of time and the flow rate of the first gas obtained by actual measurement or calculation is zero. The “comparison with the reference transition with the passage of time or propagation speed” includes the following meaning. That is, “change in propagation time or propagation speed measured continuously over a predetermined period after the second gas is retained is equal to the propagation time or propagation speed in the same predetermined period corresponding to the reference transition. ”Or“ the propagation time or propagation speed measured at a certain point in time after the second gas is retained at the same time corresponding to the reference transition ”. It means “compare with propagation time or propagation speed”.

請求項２の発明は、請求項１に記載のガス微流動検出方法において、実測又は演算にて、第１のガス及び第２のガスが一定の温度の下、伝搬時間又は伝搬速度の基準推移を求めておき、第１のガスの流れの有無又は流量又は漏れの検出時の第１のガス及び第２のガスの温度に基づいて、基準推移を補正するところに特徴を有する。   According to a second aspect of the present invention, in the gas microflow detection method according to the first aspect, in the actual measurement or calculation, the first gas and the second gas have a constant transition in propagation time or propagation speed under a constant temperature. And the reference transition is corrected based on the presence or absence of the flow of the first gas, the flow rate or the temperature of the first gas and the second gas at the time of detection of leakage.

請求項３の発明に係るガス漏れ検査方法は、燃料である第１のガスを供給するためのガス管の途中に超音波流量計を接続し、超音波流量計のうち１対の超音波送受波器の間で超音波を伝搬させるための超音波伝搬経路を第１のガスが流動可能な状態にして、その超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度に基づいて第１のガスの流量を計測可能とすると共に、その超音波流量計を用いてガス管からのガス漏れの有無を検査するガス漏れ検査方法において、ガス管のうち超音波流量計を含んだ所定区間の上流側と下流側とを遮断することでガス管内に第１のガスを滞留させた状態にして、第１のガスとは超音波の伝搬速度が異なる第２のガスをガス管の外部から超音波伝搬経路に注入しかつ滞留させた状態にして、その超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を計測し、その伝搬時間又は伝搬速度の時間経過に伴った推移と、実測又は演算にて求められる第１のガスの流量を０にした場合の第２のガスの自然拡散による伝搬時間又は伝搬速度の時間経過に伴った基準推移との比較に基づいて、ガス管からの第１のガスの漏れの有無を検査するところに特徴を有する。   According to a third aspect of the present invention, there is provided a gas leak inspection method comprising: connecting an ultrasonic flow meter in the middle of a gas pipe for supplying a first gas as fuel; and transmitting and receiving a pair of ultrasonic flow meters. The ultrasonic propagation path for propagating the ultrasonic wave between the wavers is made in a state in which the first gas can flow, and the first based on the propagation time or propagation speed of the ultrasonic wave propagating through the ultrasonic propagation path. In the gas leakage inspection method for inspecting the presence or absence of gas leakage from the gas pipe using the ultrasonic flow meter, the gas flow rate of the predetermined section including the ultrasonic flow meter in the gas pipe is measured. By shutting off the upstream side and the downstream side, the first gas is retained in the gas pipe, and the second gas having a different ultrasonic propagation velocity from the first gas is passed from the outside of the gas pipe. Inject and stay in the acoustic wave propagation path, When the propagation time or propagation velocity of the ultrasonic wave propagating through the path is measured, and the transition of the propagation time or propagation velocity with the passage of time and the flow rate of the first gas obtained by actual measurement or calculation are set to zero It is characterized in that the presence or absence of leakage of the first gas from the gas pipe is inspected based on a comparison with a reference transition with the passage of time of propagation time or propagation speed due to natural diffusion of the second gas.

ここで、請求項３における「伝搬時間又は伝搬速度の時間経過に伴った推移と、実測又は演算にて求められる第１のガスの流量を０にした場合の第２のガスの自然拡散による伝搬時間又は伝搬速度の時間経過に伴った基準推移との比較」とは、以下の意味を含んでいる。即ち、「第２のガスを滞留させてから所定期間に亘って連続して計測された伝搬時間又は伝搬速度の経過時間に伴う変化を、基準推移の対応する同一所定期間における伝搬時間又は伝搬速度の経過時間に伴う変化と比較すること」や、「第２のガスを滞留させてから所定時間が経過した或る時点で計測された伝搬時間又は伝搬速度を、基準推移の対応する同一時点における伝搬時間又は伝搬速度と比較すること」を含む意味である。   Here, “propagation due to natural diffusion of the second gas when the flow rate of the first gas obtained by actual measurement or calculation is set to 0, and the transition of the propagation time or the propagation speed with the passage of time in claim 3 The “comparison with the reference transition with the passage of time or propagation speed” includes the following meaning. That is, “change in propagation time or propagation speed measured continuously over a predetermined period after the second gas is retained is equal to the propagation time or propagation speed in the same predetermined period corresponding to the reference transition. ”Or“ the propagation time or propagation speed measured at a certain point in time after the second gas is retained at the same time corresponding to the reference transition ”. It means “compare with propagation time or propagation speed”.

請求項４の発明は、請求項３に記載のガス漏れ検査方法において、第１のガスは、メタンを主成分とした都市ガスであり、第２のガスは、都市ガスに含まれるブタン又はプロパンであるところに特徴を有する。   According to a fourth aspect of the present invention, in the gas leakage inspection method according to the third aspect, the first gas is a city gas mainly composed of methane, and the second gas is butane or propane contained in the city gas. It has the characteristic in that.

請求項５の発明は請求項３に記載のガス漏れ検査方法において、第１のガスは、プロパンガスであり、第２のガスは、メタンであるところに特徴を有する。本発明における「プロパンガス」は、プロパンを主成分とする液化石油ガス（ＬＰガス）を含む意味である。   The invention of claim 5 is characterized in that, in the gas leak inspection method according to claim 3, the first gas is propane gas and the second gas is methane. The “propane gas” in the present invention is meant to include liquefied petroleum gas (LP gas) mainly composed of propane.

請求項６の発明は、請求項３乃至５の何れか１の請求項に記載のガス漏れ検査方法において、実測又は演算にて、第１のガス及び第２のガスが一定の温度の下、伝搬時間又は伝搬速度の基準推移を求めておき、第１のガスの漏れ検査時の第１のガス及び第２のガスの温度に基づいて、基準推移を補正するところに特徴を有する。   According to a sixth aspect of the present invention, in the gas leakage inspection method according to any one of the third to fifth aspects, the first gas and the second gas are measured at a constant temperature by actual measurement or calculation. It is characterized in that a reference transition of propagation time or propagation velocity is obtained, and the reference transition is corrected based on the temperatures of the first gas and the second gas at the time of the first gas leakage inspection.

請求項７の発明に係るガス漏れ検査装置は、第１のガスが滞留した流路管又は容器の内部に連通し、第１のガスで満たされ得る計測管路と、計測管路内を貫通する超音波伝搬経路に沿って超音波を送受波可能な１対の超音波送受波器と、第１のガスとは超音波の伝搬速度が異なる第２のガスを流路管又は容器の外部から計測管路内に注入して滞留させるためのガス注入手段と、超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を、計測管路内に第２のガスを滞留させてからの経過時間に対応させて計測する実測データ取得手段と、第１のガスの流量を０にした状態で超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を基準伝搬時間又は基準伝搬速度として、計測管路内に第２のガスを滞留させてからの経過時間に対応させて記憶した基準データ記憶手段と、経過時間が同じ条件で、実測データ取得手段にて計測された伝搬時間又は伝搬速度と、基準伝搬時間又は基準伝搬速度との差分に基づいて流路管又は容器からの第１のガスの漏れを有無を判別するためのデータ比較手段とを備えたところに特徴を有する。   The gas leak inspection apparatus according to the invention of claim 7 communicates with the inside of the flow path pipe or the container in which the first gas stays and can be filled with the first gas, and penetrates through the measurement pipe A pair of ultrasonic transducers capable of transmitting and receiving ultrasonic waves along an ultrasonic propagation path to be transmitted, and a second gas whose ultrasonic wave propagation speed is different from that of the first gas. The gas injection means for injecting and staying in the measurement pipe from the inside and the propagation time or propagation speed of the ultrasonic wave propagating through the ultrasonic wave propagation path are the same as those after the second gas is held in the measurement pipe. Measured data acquisition means for measuring corresponding to the elapsed time, and the propagation time or propagation speed of the ultrasonic wave propagating through the ultrasonic propagation path with the first gas flow rate set to 0 as the reference propagation time or reference propagation speed , Corresponding to the time elapsed since the second gas was retained in the measurement pipeline Based on the difference between the propagation time or propagation speed measured by the measured data acquisition means and the reference propagation time or reference propagation speed under the same conditions as the stored reference data storage means and the elapsed time, And a data comparison means for determining the presence or absence of leakage of the first gas.

請求項８の発明は、請求項７に記載のガス漏れ検査装置において、第１のガス及び第２のガスの温度を検出するための温度検出手段と、第１のガスの漏れ検査時の第１のガス及び第２のガスの温度に基づいて、基準伝搬時間又は基準伝搬速度を補正するデータ補正手段とを備えたところに特徴を有する。   According to an eighth aspect of the present invention, in the gas leak inspection apparatus according to the seventh aspect, the temperature detection means for detecting the temperatures of the first gas and the second gas, and the first gas leak inspection at the time of the first gas leak inspection It has a feature in that it includes data correction means for correcting the reference propagation time or the reference propagation speed based on the temperature of the first gas and the second gas.

請求項９の発明に係る超音波流量計は、可燃燃料である第１のガスを供給するためのガス管の途中に接続されると共に、ガス管の内部に連通した計測管路と、計測管路内を貫通する超音波伝搬経路に沿って超音波を送受波可能な１対の超音波送受波器と、を有し、通常は、超音波伝搬経路を第１のガスが流動可能な状態で、その超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度に基づいて第１のガスの流量を計測すると共に、超音波伝搬経路に第１のガスを滞留させた状態にしてガス管からのガス漏れの有無を検出可能な超音波流量計において、第１のガスとは超音波の伝搬速度が異なる第２のガスをガス管の外部から計測管路内に注入して滞留させるためのガス注入手段と、超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を、計測管路内に第２のガスを滞留させてからの経過時間に対応させて計測する実測データ取得手段と、第１のガスの流量を０にした状態で超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を基準伝搬時間又は基準伝搬速度として、計測管路内に第２のガスを滞留させてからの経過時間に対応させて記憶した基準データ記憶手段と、経過時間が同じ条件で、実測データ取得手段にて計測された伝搬時間又は伝搬速度と、基準伝搬時間又は基準伝搬速度との差分に基づいてガス管からの第１のガスの漏れを有無を判別するためのデータ比較手段とを備えたところに特徴を有する。 The ultrasonic flowmeter according to the invention of claim 9 is connected to the middle of the gas pipe for supplying the first gas as the combustible fuel, and is connected to the inside of the gas pipe, and the measurement pipe A pair of ultrasonic transducers capable of transmitting and receiving ultrasonic waves along an ultrasonic propagation path penetrating the road, and normally , a state in which the first gas can flow in the ultrasonic propagation path Then, the flow rate of the first gas is measured on the basis of the propagation time or propagation speed of the ultrasonic wave propagating through the ultrasonic wave propagation path, and the first gas is retained in the ultrasonic wave propagation path. In an ultrasonic flowmeter capable of detecting the presence or absence of gas leakage from the first gas, in order to inject and retain a second gas having a different ultrasonic propagation velocity from the first gas into the measurement line from the outside of the gas pipe Gas injection means and the propagation time or propagation speed of the ultrasonic wave propagating through the ultrasonic wave propagation path Measured data acquisition means for measuring in accordance with the elapsed time since the second gas was retained in the measurement pipe, and propagating the ultrasonic wave propagation path with the flow rate of the first gas being zero Reference data storage means storing the ultrasonic wave propagation time or propagation velocity as the reference propagation time or reference propagation velocity and corresponding to the elapsed time since the second gas was retained in the measurement pipeline, and the elapsed time Under the same conditions, for determining whether or not there is leakage of the first gas from the gas pipe based on the difference between the propagation time or propagation speed measured by the actual measurement data acquisition means and the reference propagation time or reference propagation speed And a data comparison means.

請求項１０の発明は、請求項９に記載の超音波流量計において、第１のガス及び第２のガスの温度を検出するための温度検出手段と、第１のガスの漏れ検査時の第１のガス及び第２のガスの温度に基づいて、基準伝搬時間又は基準伝搬速度を補正するデータ補正手段とを備えたところに特徴を有する。   A tenth aspect of the present invention is the ultrasonic flowmeter according to the ninth aspect, wherein the temperature detecting means for detecting the temperatures of the first gas and the second gas, and the first gas leakage test at the time of the first gas leak inspection It has a feature in that it includes data correction means for correcting the reference propagation time or the reference propagation speed based on the temperature of the first gas and the second gas.

請求項１１の発明は、請求項９又は１０に記載の超音波流量計において、データ比較手段は、第２のガスを滞留させてからの経過時間が同じ条件で、実測データ取得手段にて計測された伝搬時間又は伝搬速度と、基準伝搬時間又は基準伝搬速度との差分が予め定められた許容差より大きくなった場合には、ガス漏れ有りと判定するように構成したところに特徴を有する。   The invention according to claim 11 is the ultrasonic flowmeter according to claim 9 or 10, wherein the data comparison means is measured by the actual measurement data acquisition means under the same conditions as the elapsed time after the second gas is retained. The present invention is characterized in that it is determined that there is a gas leak when the difference between the measured propagation time or propagation speed and the reference propagation time or reference propagation speed is greater than a predetermined tolerance.

［請求項１の発明］
請求項１のガス微流動検出方法によれば、第１のガスが滞留した流路管又は容器における超音波伝搬経路に、流路管又は容器の外部から第１のガスとは超音波の伝搬速度が異なる第２のガスを注入しかつ滞留させた状態にして、超音波の伝搬時間又は伝搬速度を計測する。そして、伝搬時間又は伝搬速度の時間経過に伴った推移を、第１のガスの流量を０にした場合の第２のガスの自然拡散による伝搬時間又は伝搬速度の基準推移と比較することで、第１のガスの流れの有無又は流量又は流路管又は容器からの第１のガスの漏れを検出することができる。 [Invention of Claim 1]
According to the gas microfluidic detection method of claim 1, the ultrasonic wave is propagated from the outside of the channel tube or container to the ultrasonic wave propagation path in the channel tube or container in which the first gas stays. A second gas having a different velocity is injected and retained, and the propagation time or propagation velocity of the ultrasonic wave is measured. Then, by comparing the transition of the propagation time or propagation speed with the passage of time with the reference transition of the propagation time or propagation speed by the natural diffusion of the second gas when the flow rate of the first gas is 0, The presence or absence of the flow of the first gas, the flow rate, or the leakage of the first gas from the channel tube or the container can be detected.

例えば、第１のガスが流動していない状態では、流路管又は容器内の気流が穏やかで第２のガスの拡散は比較的ゆっくりと進行するので、第２のガスを滞留させてからの経過時間に伴う超音波の伝搬時間又は伝搬速度の推移と、第１のガスの流量を０にした場合の基準推移との差異が比較的小さくなる。   For example, in the state where the first gas is not flowing, the air flow in the flow path pipe or the container is gentle and the diffusion of the second gas proceeds relatively slowly. The difference between the transition of the propagation time or propagation speed of the ultrasonic wave with the elapsed time and the reference transition when the flow rate of the first gas is 0 is relatively small.

これに対し、第１のガスが流動している状態では、流路管又は容器内の気流によって第２のガスが比較的速く拡散するので、第２のガスを滞留させてからの経過時間に伴なう超音波の伝搬時間又は伝搬速度の推移と、基準推移との差異が比較的大きくなる。従って、経過時間に伴う超音波の伝搬時間又は伝搬速度の推移と基準推移との差異の大小に基づいて、第１のガスの流れの有無等を検出することができる。   On the other hand, in the state where the first gas is flowing, the second gas diffuses relatively quickly due to the airflow in the flow channel tube or the container, so that the elapsed time from the retention of the second gas is reached. The difference between the propagation time or propagation speed of the accompanying ultrasonic wave and the reference transition is relatively large. Therefore, the presence or absence of the first gas flow can be detected based on the difference between the transition of the ultrasonic wave propagation time or propagation speed with the elapsed time and the reference transition.

そして、本発明によれば、従来のように複数の計測管や複数対の超音波送受波器を必要としないので、構造の大型化及び製品価格の上昇を抑えつつ微少なガス流動を検出することが可能になる。   According to the present invention, since a plurality of measuring tubes and a plurality of pairs of ultrasonic transducers are not required as in the prior art, a minute gas flow is detected while suppressing an increase in structure size and an increase in product price. It becomes possible.

［請求項２の発明］
請求項２の発明によれば、ガスの流れの有無等の検出を行ったときの第１のガス及び第２のガスの温度（流路管又は容器の内部温度）に基づいて、経過時間に伴う伝搬時間又は伝搬速度の基準推移を補正するから、第１のガスの流量を０にして実測又は演算により伝搬時間又は伝搬速度の基準推移を求めたときの温度と、実際にガスの流れの有無等の検出を行ったときの温度との相違による誤差分を排除することができる。これにより、ガスの流れの有無等をより正確に検出することが可能になる。 [Invention of claim 2]
According to the invention of claim 2, the elapsed time is determined based on the temperature of the first gas and the second gas (the internal temperature of the flow path tube or the container) when the presence or absence of the gas flow is detected. Since the reference transition of propagation time or propagation velocity is corrected, the flow rate of the first gas is set to 0, the temperature when the reference transition of propagation time or propagation velocity is obtained by actual measurement or calculation, and the actual gas flow An error due to a difference from the temperature when the presence / absence or the like is detected can be eliminated. This makes it possible to more accurately detect the presence or absence of a gas flow.

［請求項３の発明］
請求項３のガス漏れ検査方法によれば、ガス管の途中に接続された超音波流量計の超音波伝搬経路に第１のガスを滞留させると共に、ガス管の外部から第１のガスとは超音波の伝搬速度が異なる第２のガスを超音波伝搬経路に注入しかつ滞留させた状態にして、超音波の伝搬時間又は伝搬速度を計測する。そして、第２のガスを滞留させてからの時間経過に伴った伝搬時間又は伝搬速度の推移を、第１のガスの流量を０にした場合の第２のガスの自然拡散による伝搬時間又は伝搬速度の基準推移と比較することで、ガス管からのガス漏れ（微少なガス流動）の有無を判別することができる。 [Invention of claim 3]
According to the gas leakage inspection method of claim 3, the first gas is retained in the ultrasonic propagation path of the ultrasonic flowmeter connected in the middle of the gas pipe, and the first gas is defined from the outside of the gas pipe. A second gas having a different ultrasonic propagation velocity is injected into the ultrasonic propagation path and stays in a state where the ultrasonic propagation time or propagation velocity is measured. The transition of the propagation time or propagation speed with the passage of time after the second gas is retained is the propagation time or propagation due to the natural diffusion of the second gas when the flow rate of the first gas is zero. By comparing with the reference transition of speed, it is possible to determine the presence or absence of gas leakage from the gas pipe (small gas flow).

例えば、ガス管にガス漏れが無い状態では、ガス管内の気流が穏やかで第２のガスの拡散が比較的ゆっくりと進行するので、経過時間に伴う超音波の伝搬時間又は伝搬速度の推移と、第１のガスの流量を０にした場合の基準推移との差異が比較的小さくなる。   For example, in a state where there is no gas leak in the gas pipe, since the air flow in the gas pipe is gentle and the diffusion of the second gas proceeds relatively slowly, the transition of the ultrasonic wave propagation time or propagation speed with the elapsed time, The difference from the reference transition when the flow rate of the first gas is 0 is relatively small.

これに対し、ガス管にガス漏れがある状態では、ガス管内にガス漏れ箇所へと向かう気流が発生して第２のガスが比較的速く拡散するので、経過時間に伴う超音波の伝搬時間又は伝搬速度の推移と基準推移との間の差異が比較的大きくなる。従って、経過時間に伴う超音波の伝搬時間又は伝搬速度の推移と基準推移との間の差異の大小に基づいて、第１のガスの漏れの有無を判別することができる。   On the other hand, in a state where there is a gas leak in the gas pipe, an air flow toward the gas leak point is generated in the gas pipe and the second gas diffuses relatively quickly. The difference between the propagation speed transition and the reference transition is relatively large. Therefore, the presence or absence of leakage of the first gas can be determined based on the difference between the transition of the propagation time or propagation speed of the ultrasonic wave with the elapsed time and the reference transition.

そして、本発明によれば、従来のように複数の計測管や複数対の超音波送受波器を必要としないので、構造の大型化及び製品価格の上昇を抑えつつ第１のガスの漏れ（微少なガス流動）の有無を検出することが可能になる。   According to the present invention, since a plurality of measurement tubes and a plurality of pairs of ultrasonic transducers are not required as in the prior art, the first gas leakage (without increasing the size of the structure and the product price) It is possible to detect the presence or absence of minute gas flow.

［請求項４の発明］
請求項４の発明によれば、第１のガスが、メタンが主成分の都市ガスである場合に、その都市ガスに含まれるブタン又はプロパンを第２のガスとすれば、ガス漏れ検査のために第２のガスを注入した後でも、そのまま燃料として使用することが可能である。 [Invention of claim 4]
According to the invention of claim 4, when the first gas is a city gas mainly composed of methane, if butane or propane contained in the city gas is used as the second gas, the gas leakage inspection is performed. Even after injecting the second gas, it can be used as fuel as it is.

［請求項５の発明］
請求項５の発明によれば、第１のガスがプロパンガスである場合に、メタンを第２のガスとすれば、ガス漏れ検査のために第２のガスを注入した後でも、そのまま燃料として使用することが可能である。 [Invention of claim 5]
According to the invention of claim 5, when the first gas is propane gas and methane is used as the second gas, even after the second gas is injected for the gas leak inspection, it is used as fuel as it is. It is possible to use.

［請求項６の発明］
請求項６の発明によれば、ガス漏れ検査を行ったときの第１のガス及び第２のガスの温度（ガス管の内部温度）に基づいて、経過時間に伴う伝搬時間又は伝搬速度の基準推移を補正するから、第１のガスの流量を０にして実測又は演算により伝搬時間又は伝搬速度の基準推移を求めたときの温度と、実際のガス漏れ検査時の温度との相違による誤差分を排除することができ、ガス漏れの有無をより正確に判別することが可能になる。 [Invention of claim 6]
According to invention of Claim 6, based on the temperature (internal temperature of a gas pipe) of the 1st gas and 2nd gas when a gas leak test | inspection is performed, the reference | standard of the propagation time or propagation speed accompanying elapsed time Since the transition is corrected, the error due to the difference between the temperature when the standard transition of the propagation time or propagation velocity is obtained by actual measurement or calculation with the flow rate of the first gas set to 0 and the temperature at the actual gas leak inspection This makes it possible to more accurately determine the presence or absence of gas leakage.

［請求項７の発明］
請求項７のガス漏れ検査装置によれば、第１のガスが滞留した流路管又は容器における超音波伝搬経路に、流路管又は容器の外部から第１のガスとは超音波の伝搬速度が異なる第２のガスを注入しかつ滞留させた状態にして、超音波の伝搬時間又は伝搬速度を計測する。そして、時間経過が同じである条件で、ガス漏れ検査時に実測された伝搬時間又は伝搬速度と、第１のガスの流量を０にした状態の基準伝搬時間又は基準伝搬速度との差分に基づいて、流路管又は容器からの第１のガスの漏れ（微少なガス流動）の有無を検出することができる。 [Invention of Claim 7]
According to the gas leak inspection apparatus of the seventh aspect, the ultrasonic gas propagation speed in the ultrasonic wave propagation path in the flow path pipe or container in which the first gas stays is different from the first gas from the outside of the flow path pipe or container. The second propagation gas or the propagation speed of ultrasonic waves is measured while injecting and retaining a second gas different from each other. And based on the difference between the propagation time or propagation velocity actually measured at the time of the gas leak inspection and the reference propagation time or the reference propagation velocity in the state where the flow rate of the first gas is 0 under the condition that the time passage is the same. It is possible to detect the presence or absence of leakage of the first gas from the channel tube or the container (small gas flow).

例えば、流路管又は容器にガス漏れが無い状態では、流路管又は容器内の気流が穏やかで第２のガスの拡散が比較的ゆっくりと進行するので、時間経過が同じという条件で比較すると、ガス漏れ検査時に実測された超音波の伝搬時間又は伝搬速度と、基準伝搬時間又は基準伝搬速度との差分が比較的小さくなる。   For example, in a state where there is no gas leakage in the flow channel tube or container, the air flow in the flow channel tube or container is gentle and the diffusion of the second gas proceeds relatively slowly. The difference between the ultrasonic propagation time or propagation speed actually measured during the gas leak inspection and the reference propagation time or reference propagation speed is relatively small.

これに対し、流路管又は容器にガス漏れがある状態では、流路管又は容器内にガス漏れ箇所へと向かう気流が発生して第２のガスが比較的速く拡散するので、ガス漏れ検査時に実測された超音波の伝搬時間又は伝搬速度と、基準伝搬時間又は基準伝搬速度との差分が比較的大きくなる。従って、経過時間が同じという条件の下で、ガス漏れ検査時に実測された超音波の伝搬時間又は伝搬速度と、基準伝搬時間又は基準伝搬速度との差分の大小に基づいて、第１のガスの漏れ（微少なガス流動）の有無を判別することができる。   On the other hand, in the state where there is a gas leak in the channel pipe or the container, an air flow is generated in the channel pipe or the container and the second gas diffuses relatively quickly. The difference between the ultrasonic propagation time or propagation velocity actually measured and the reference propagation time or reference propagation velocity is relatively large. Therefore, under the condition that the elapsed time is the same, based on the magnitude of the difference between the ultrasonic propagation time or propagation velocity actually measured during the gas leak inspection and the reference propagation time or reference propagation velocity, It is possible to determine the presence or absence of leakage (small gas flow).

そして、本発明によれば、従来のように複数の計測管や複数対の超音波送受波器を必要としないので、構造の大型化及び製品価格の上昇を抑えつつ微少なガス流動（ガス漏れの有無）を検出することが可能になる。   According to the present invention, since a plurality of measuring tubes and a plurality of pairs of ultrasonic transducers are not required as in the prior art, a small gas flow (gas leakage) while suppressing an increase in structure size and an increase in product price. Presence or absence).

［請求項８の発明］
請求項８の発明によれば、ガス漏れ検査時の第１のガス及び第２のガスの実測温度（流路管又は容器の内部温度）に基づいて、基準伝搬時間又は基準伝搬速度を補正するから、第１のガスの流量を０にして基準伝搬時間又は基準伝搬速度を求めたときの温度と、ガス漏れ検査時の実測温度との相違による誤差分を排除することができる。これにより、流路管又は容器からのガス漏れの有無をより正確に判別することが可能になる。 [Invention of Claim 8]
According to the eighth aspect of the present invention, the reference propagation time or the reference propagation speed is corrected based on the actually measured temperatures of the first gas and the second gas at the time of the gas leak inspection (the internal temperature of the channel tube or the container). Thus, an error due to the difference between the temperature when the flow rate of the first gas is set to 0 and the reference propagation time or reference propagation velocity is obtained and the actually measured temperature at the time of the gas leak inspection can be eliminated. As a result, it is possible to more accurately determine the presence or absence of gas leakage from the channel tube or the container.

［請求項９及び１１の発明］
請求項９の超音波流量計によれば、ガス管の途中に接続された計測管路の超音波伝搬経路に第１のガスを滞留させると共に、計測管路の外部から第１のガスとは超音波の伝搬速度が異なる第２のガスを超音波伝搬経路に注入しかつ滞留させた状態にして、超音波の伝搬時間又は伝搬速度を計測する。そして、時間経過が同じである条件で、ガス漏れ検査時に実測された伝搬時間又は伝搬速度と、第１のガスの流量を０にした状態の基準伝搬時間又は基準伝搬速度との差分に基づいて、ガス管からの第１のガスの漏れ（微少なガス流動）の有無を判別することができる。 [Inventions of Claims 9 and 11]
According to the ultrasonic flowmeter of the ninth aspect, the first gas is retained in the ultrasonic propagation path of the measurement pipe connected in the middle of the gas pipe, and the first gas from the outside of the measurement pipe is A second gas having a different ultrasonic propagation velocity is injected into the ultrasonic propagation path and stays in a state where the ultrasonic propagation time or propagation velocity is measured. And based on the difference between the propagation time or propagation velocity actually measured at the time of the gas leak inspection and the reference propagation time or the reference propagation velocity in the state where the flow rate of the first gas is 0 under the condition that the time passage is the same. The presence or absence of leakage of the first gas from the gas pipe (small gas flow) can be determined.

例えば、ガス管にガス漏れが無い状態では、ガス管内の気流が穏やかで第２のガスの拡散が比較的ゆっくりと進行するので、時間経過が同じという条件で比較すると、ガス漏れ検査時に実測された超音波の伝搬時間又は伝搬速度と、基準伝搬時間又は基準伝搬速度との差分が比較的小さくなる。   For example, when there is no gas leak in the gas pipe, the airflow in the gas pipe is gentle and the diffusion of the second gas proceeds relatively slowly. The difference between the propagation time or propagation speed of the ultrasonic wave and the reference propagation time or reference propagation speed is relatively small.

これに対し、ガス管にガス漏れがある状態では、ガス管内にガス漏れ箇所へと向かう気流が発生して第２のガスが比較的速く拡散するので、ガス漏れ検査時に実測された超音波の伝搬時間又は伝搬速度と、基準伝搬時間又は基準伝搬速度との差分が比較的大きくなる。従って、経過時間が同じという条件の下で、ガス漏れ検査時に実測された超音波の伝搬時間又は伝搬速度と、基準伝搬時間又は基準伝搬速度との差分の大小に基づいて、ガス管からの第１のガスの漏れ（微少なガス流動）の有無を判別することができる。   On the other hand, in a state where there is a gas leak in the gas pipe, an air flow toward the gas leak point is generated in the gas pipe and the second gas diffuses relatively quickly. The difference between the propagation time or propagation speed and the reference propagation time or reference propagation speed becomes relatively large. Therefore, under the condition that the elapsed time is the same, the first difference from the gas pipe is determined based on the difference between the propagation time or propagation speed of the ultrasonic wave actually measured at the time of the gas leak inspection and the reference propagation time or the reference propagation speed. It is possible to determine the presence or absence of one gas leak (small gas flow).

そして、本発明によれば、従来のように複数の計測管や複数対の超音波送受波器を必要としないので、構造の大型化及び製品価格の上昇を抑えつつ微少なガス流動（ガス漏れの有無）を検出することが可能になる。   According to the present invention, since a plurality of measuring tubes and a plurality of pairs of ultrasonic transducers are not required as in the prior art, a small gas flow (gas leakage) while suppressing an increase in structure size and an increase in product price. Presence or absence).

ここで、ガス漏れの有無の判別は、データ比較手段による比較結果に基づいて検査員が行うようにしてもよいし、請求項１１の発明のように、データ比較手段がガス漏れの有無の判別まで行うようにしてもよい。   Here, the determination of the presence or absence of gas leakage may be performed by an inspector based on the comparison result by the data comparison means, or the data comparison means may determine whether or not there is a gas leak as in the invention of claim 11. You may make it carry out.

［請求項１０の発明］
請求項１０の発明によれば、ガス漏れ検査時の第１のガス及び第２のガスの実測温度（ガス管の内部温度）に基づいて、基準伝搬時間又は基準伝搬速度を補正するから、第１のガスの流量を０にして基準伝搬時間又は基準伝搬速度を求めたときの温度と、ガス漏れ検査時の温度との相違による誤差分を排除することができる。これにより、ガス管からのガス漏れの有無をより正確に判別することが可能になる。 [Invention of Claim 10]
According to the invention of claim 10, since the reference propagation time or the reference propagation velocity is corrected based on the measured temperatures (internal temperature of the gas pipe) of the first gas and the second gas at the time of the gas leak inspection, It is possible to eliminate an error due to the difference between the temperature when the flow rate of one gas is set to 0 and the reference propagation time or reference propagation velocity is obtained and the temperature at the time of the gas leak inspection. This makes it possible to more accurately determine the presence or absence of gas leakage from the gas pipe.

本発明の一実施形態に係る超音波流量計の側断面図1 is a side sectional view of an ultrasonic flowmeter according to an embodiment of the present invention. 制御処理部のブロック図Block diagram of the control processing unit ガス漏れ検査処理のフローチャートFlow chart of gas leak inspection process 経過時間に伴う超音波の伝搬速度の推移を示すグラフGraph showing the transition of ultrasonic wave propagation speed with time 変形例に係る超音波流量計の側断面図Side sectional view of ultrasonic flowmeter according to modification

以下、本発明の一実施形態を、図１〜図４に基づいて説明する。図１における符号９０は、第１のガス（例えば、都市ガス、ＬＰガス等の可燃性ガス）を供給するためのガス管（本発明の「流路管」に相当する）である。第１のガスは、所定の供給圧力で供給されており、ガス管９０内は外気に対して略一定の加圧状態になっている。このガス管９０の途中に、本発明の「ガス漏れ検査装置」及び「超音波流量計」に相当するガス漏れ検査機能付き超音波流量計１０（以下、単に「超音波流量計１０」という）が設けられている。   Hereinafter, an embodiment of the present invention will be described with reference to FIGS. Reference numeral 90 in FIG. 1 is a gas pipe (corresponding to the “flow pipe” of the present invention) for supplying a first gas (for example, a combustible gas such as city gas or LP gas). The first gas is supplied at a predetermined supply pressure, and the inside of the gas pipe 90 is in a substantially constant pressurized state with respect to the outside air. In the middle of the gas pipe 90, an ultrasonic flowmeter 10 with a gas leakage inspection function (hereinafter simply referred to as "ultrasonic flowmeter 10") corresponding to the "gas leakage inspection device" and "ultrasonic flowmeter" of the present invention. Is provided.

図２に示すように、超音波流量計１０は、検出器１１と変換器１２とから構成されており、検出器１１は、ガス管９０の途中に接続されるフローセル２０を有している。図１に示すように、フローセル２０は両端閉塞の筒形構造をなしており、その内部空間が第１のガスの流路を構成する計測管路２２となっている。また、フローセル２０の両端寄り上面からは、計測管路２２と連通した２つの管接続部２１，２１が長手方向に並んで起立している。これら管接続部２１，２１が、ガス管９０に対して着脱可能となっている。   As shown in FIG. 2, the ultrasonic flowmeter 10 includes a detector 11 and a converter 12, and the detector 11 has a flow cell 20 connected in the middle of a gas pipe 90. As shown in FIG. 1, the flow cell 20 has a cylindrical structure with both ends closed, and the internal space is a measurement pipe line 22 constituting a first gas flow path. Further, from the upper surface near both ends of the flow cell 20, two pipe connection portions 21 and 21 communicating with the measurement pipe line 22 stand up in the longitudinal direction. These pipe connection parts 21 and 21 can be attached to and detached from the gas pipe 90.

フローセル２０のうち、長手方向の両端部壁２３，２３の内面には、１対の超音波送受波器３０，３０が取り付けられている。   In the flow cell 20, a pair of ultrasonic transducers 30, 30 are attached to the inner surfaces of both end walls 23, 23 in the longitudinal direction.

超音波送受波器３０，３０は略円柱構造をなしており、その一方の端面に超音波の送受波面３１が設けられ、他方の端面に接続端子（図示せず）が備えられている。接続端子は、フローセル２０の両端部壁２３，２３を気密状態に貫通して外部に露出しており、この接続端子と変換器１２（図２参照）とが電気接続されている。なお、変換器１２は、フローセル２０の外面に一体に設けてもよいし、フローセル２０から離して設けてもよい。   The ultrasonic transducers 30 and 30 have a substantially cylindrical structure, and an ultrasonic transmission / reception surface 31 is provided on one end face, and a connection terminal (not shown) is provided on the other end face. The connection terminal passes through both end walls 23 and 23 of the flow cell 20 in an airtight state and is exposed to the outside, and the connection terminal and the converter 12 (see FIG. 2) are electrically connected. The converter 12 may be provided integrally on the outer surface of the flow cell 20 or may be provided away from the flow cell 20.

フローセル２０の内部には、計測管路２２を長手方向（図１の左右方向）の中央部で二部屋に隔絶した内部隔壁２４が備えられている。即ち、計測管路２２は上流側の流入部屋２２Ａと下流側の流出部屋２２Ｂとに仕切られており、１対の各超音波送受波器３０，３０が、流入部屋２２Ａと流出部屋２２Ｂとに分けて配置されている。   Inside the flow cell 20, there is provided an internal partition wall 24 in which the measurement pipe line 22 is separated into two rooms at the center in the longitudinal direction (left and right direction in FIG. 1). That is, the measurement pipe line 22 is divided into an upstream inflow chamber 22A and a downstream outflow chamber 22B, and a pair of ultrasonic transducers 30 and 30 are divided into the inflow chamber 22A and the outflow chamber 22B. They are arranged separately.

計測管路２２の長手方向の中間領域には、円筒パイプ状のインナー管２５が配置されている。そのインナー管２５が内部隔壁２４を貫いて計測管路２２（フローセル２０）と平行に延びており、インナー管２５の両端部の開口が流入部屋２２Ａと流出部屋２２Ｂとに配置されている。このインナー管２５を軸方向から挟むようにして１対の超音波送受波器３０，３０が対向配置され、インナー管２５の内部を貫通する超音波伝搬経路Ｒ１に沿って超音波を相互に送受信することが可能となっている。以下、１対の超音波送受波器３０，３０を区別する場合は、「上流側の超音波送受波器３０Ａ」、「下流側の超音波送受波器３０Ｂ」という。   A cylindrical pipe-shaped inner pipe 25 is disposed in the middle region in the longitudinal direction of the measurement pipe line 22. The inner pipe 25 penetrates the inner partition wall 24 and extends in parallel with the measurement pipe line 22 (flow cell 20). Openings at both ends of the inner pipe 25 are disposed in the inflow chamber 22A and the outflow chamber 22B. A pair of ultrasonic transducers 30, 30 are opposed to each other so that the inner tube 25 is sandwiched from the axial direction, and ultrasonic waves are transmitted and received along the ultrasonic wave propagation path R <b> 1 that penetrates the inner tube 25. Is possible. Hereinafter, when a pair of ultrasonic transducers 30 and 30 is distinguished, they are referred to as “upstream ultrasonic transducer 30A” and “downstream ultrasonic transducer 30B”.

両管接続部２１，２１にガス管９０が接続されると、図１の太矢印に示すように、上流側の管接続部２１からフローセル２０の流入部屋２２Ａに第１のガスが流れ込み、インナー管２５を通過し、流出部屋２２Ｂを経て下流側の管接続部２１からフローセル２０の外部に排出される。   When the gas pipes 90 are connected to both the pipe connecting parts 21 and 21, the first gas flows from the upstream pipe connecting part 21 into the inflow chamber 22A of the flow cell 20 as shown by the thick arrows in FIG. It passes through the pipe 25 and is discharged to the outside of the flow cell 20 from the pipe connecting portion 21 on the downstream side through the outflow chamber 22B.

以下、図２を参照しつつ、流量計測時の動作について説明する。変換器１２の制御処理部４０は、送受切替スイッチ４５，４６を制御して、まずは図２に示すように、上流側の超音波送受波器３０Ａを送波回路４２に接続しかつ、下流側の超音波送受波器３０Ｂを受波回路４３に接続した状態にしてから、送波回路４２及びクロックカウンタ４４に送波指令信号Ｘを出力する。すると、送波回路４２が上流側の超音波送受波器３０Ａを駆動し、超音波が上流側の超音波送受波器３０Ａから下流側の超音波送受波器３０Ｂに向けて発信されると同時に、クロックカウンタ４４がクロックパルスに基づいて時間計測を開始する。   Hereinafter, the operation during flow rate measurement will be described with reference to FIG. The control processing unit 40 of the converter 12 controls the transmission / reception change-over switches 45 and 46 to connect the upstream ultrasonic transducer 30A to the transmission circuit 42 as shown in FIG. The ultrasonic wave transmitter / receiver 30 </ b> B is connected to the wave receiving circuit 43, and then the wave transmission command signal X is output to the wave transmitting circuit 42 and the clock counter 44. Then, the transmission circuit 42 drives the upstream ultrasonic transducer 30A, and at the same time, the ultrasonic waves are transmitted from the upstream ultrasonic transducer 30A toward the downstream ultrasonic transducer 30B. The clock counter 44 starts measuring time based on the clock pulse.

上流側の超音波送受波器３０Ａから発信された超音波は、計測管路２２内（超音波伝搬経路Ｒ１上）に存在する第１のガスを媒体として伝搬し、下流側の超音波送受波器３０Ｂにて受信される。受信波は下流側の超音波送受波器３０Ｂに接続された受波回路４３にて検知され、受波回路４３は、受信波を検知すると受信波検知信号Ｙをクロックカウンタ４４に出力する。受信波検知信号Ｙの入力によってクロックカウンタ４４はカウントを停止して、そのカウント値（即ち、超音波の伝搬時間）を制御処理部４０に出力し、０リセットされる。   The ultrasonic wave transmitted from the upstream ultrasonic transducer 30A propagates using the first gas existing in the measurement pipe line 22 (on the ultrasonic propagation path R1) as a medium, and the ultrasonic transmission / reception wave on the downstream side. Is received by the device 30B. The received wave is detected by a wave receiving circuit 43 connected to the ultrasonic transducer 30B on the downstream side, and the wave receiving circuit 43 outputs a received wave detection signal Y to the clock counter 44 when detecting the received wave. When the received wave detection signal Y is input, the clock counter 44 stops counting, outputs the count value (that is, the ultrasonic wave propagation time) to the control processing unit 40, and is reset to zero.

制御処理部４０にカウント値が入力すると、送波回路４２は、上流側の超音波送受波器３０を駆動停止し、次に制御処理部４０から出力される送波指令信号Ｘの待ち状態になる。また、この間に制御処理部４０が送受切替スイッチ４５，４６を駆動し、送波回路４２を下流側の超音波送受波器３０Ｂに接続し、受波回路４３を上流側の超音波送受波器３０Ａに接続する。   When the count value is input to the control processing unit 40, the transmission circuit 42 stops driving the ultrasonic transducer 30 on the upstream side, and then waits for the transmission command signal X output from the control processing unit 40. Become. During this time, the control processing unit 40 drives the transmission / reception change-over switches 45 and 46, connects the transmission circuit 42 to the downstream ultrasonic transducer 30B, and connects the reception circuit 43 to the upstream ultrasonic transducer. Connect to 30A.

次いで、制御処理部４０は、送波回路４２に送波指令信号Ｘを出力する。これにより、今度は、超音波の送信方向を逆向きにして上記した場合と同様の処理が行われる。そして、制御処理部４０は、第１のガスの流れに対する順方向と逆方向の両方向で計測された伝搬時間の逆数差を演算し、これに基づいてインナー管２５を流れる第１のガスの流速を演算する。また、この流速ち、既知であるインナー管２５の管路２５Ａの断面積とから第１のガスの流量を演算する。   Next, the control processing unit 40 outputs a transmission command signal X to the transmission circuit 42. As a result, this time, the same processing as described above is performed with the ultrasonic wave transmission direction reversed. And the control processing part 40 calculates the reciprocal difference of the propagation time measured in both the forward direction and the reverse direction with respect to the flow of the first gas, and based on this, the flow velocity of the first gas flowing through the inner pipe 25 Is calculated. Further, the flow rate of the first gas is calculated from this flow velocity, which is a known cross-sectional area of the pipe 25A of the inner pipe 25.

以上が、流量計測時の動作説明である。ところで、超音波流量計１０による流量計測では、想定されるガス流量の変動範囲に応じて測定レンジの上下限値が設定される。一般的な超音波流量計のレンジアビリティは、１：２００程度であり、例えば、測定レンジの上限値を１００００［Ｌ／時］に設定した場合、測定レンジの下限値は、５０［Ｌ／時］となり、これを下回る微少な流れは０と見なして流量計測が行われる。ガス機器の通常使用中にこのような微少な流れが生じることはないので、ガス使用量を計測する上では、これでも問題は無い。しかしながら、このような測定レンジに設定した場合には、流量の計測結果（表示値）が「０」であっても、実際には、ガス漏れによって測定レンジの下限値を下回る微少なガス流動が生じている可能性が有る。これに対し、本実施形態の超音波流量計１０は、流量計測の測定レンジの下限値を下回る微少なガス流動（ガス漏れ）を検出するためのガス漏れ検査機能を有している。以下、ガス漏れ検査機能に関する構成について説明する。   The above is the description of the operation when measuring the flow rate. By the way, in the flow rate measurement by the ultrasonic flowmeter 10, the upper and lower limit values of the measurement range are set according to the assumed fluctuation range of the gas flow rate. The range ability of a general ultrasonic flowmeter is about 1: 200. For example, when the upper limit value of the measurement range is set to 10000 [L / hour], the lower limit value of the measurement range is 50 [L / hour]. The minute flow below this is regarded as 0 and the flow rate is measured. Since such a minute flow does not occur during normal use of the gas equipment, there is no problem in measuring the amount of gas used. However, when such a measurement range is set, even if the measurement result (display value) of the flow rate is “0”, in reality, a slight gas flow that falls below the lower limit value of the measurement range is caused by gas leakage. It may have occurred. On the other hand, the ultrasonic flowmeter 10 of this embodiment has a gas leak inspection function for detecting a minute gas flow (gas leak) below the lower limit value of the measurement range of the flow rate measurement. Hereinafter, the configuration related to the gas leak inspection function will be described.

図１に示すように、フローセル２０には、第１のガスとは超音波の伝搬速度が異なる第２のガスをフローセル２０の外部から計測管路２２内に注入するためのガス注入部５０が設けられている。ガス注入部５０は、例えば、流入部屋２２Ａと連通しており、開閉弁５１を介して第２のガスを封入したガスボンベ５２が接続可能となっている。ガスボンベ５２の内圧は、ガス管９０（フローセル２０）の内圧より高くなっており、開閉弁５１が開放すると圧力差によって第２のガスが計測管路２２内に注入されるようになっている。また、第２のガスの注入量の調節は、内圧差やガス注入部５０の口径等に応じて開閉弁５１の開放時間を調節することで行う。ガスボンベ５２は、市販のガスボンベを流用してもよいし、本実施形態の超音波流量計１０のために設計された専用のガスボンベでもよい。ガス注入部５０及び開閉弁５１が本発明の「ガス注入手段」に相当する。   As shown in FIG. 1, the flow cell 20 has a gas injection unit 50 for injecting a second gas having a different ultrasonic propagation velocity from the first gas into the measurement pipe line 22 from the outside of the flow cell 20. Is provided. For example, the gas injection part 50 communicates with the inflow chamber 22 </ b> A, and a gas cylinder 52 filled with a second gas can be connected via the on-off valve 51. The internal pressure of the gas cylinder 52 is higher than the internal pressure of the gas pipe 90 (flow cell 20). When the on-off valve 51 is opened, the second gas is injected into the measurement pipe line 22 due to the pressure difference. Further, the adjustment of the injection amount of the second gas is performed by adjusting the opening time of the on-off valve 51 according to the internal pressure difference, the diameter of the gas injection part 50, or the like. The gas cylinder 52 may be a commercially available gas cylinder or a dedicated gas cylinder designed for the ultrasonic flowmeter 10 of the present embodiment. The gas injection part 50 and the on-off valve 51 correspond to the “gas injection unit” of the present invention.

超音波流量計１０は、通常は、上述の如く第１のガスの流量計測を行っており、定期的に流量計測を中断して以下に説明するガス漏れ検査を行う。ガス漏れ検査時の動作を図３のフローチャートに基づいて説明する。   The ultrasonic flowmeter 10 normally measures the flow rate of the first gas as described above, periodically interrupts the flow rate measurement, and performs a gas leak test described below. The operation during the gas leak inspection will be described based on the flowchart of FIG.

ガス漏れ検査時には、第１のガスが通常の流動中（ガス管９０に接続されたガス機器が使用中）ではないことを確認するため、超音波の伝搬時間に基づいて計測された流量の計測結果が「０」か否かを判定する（Ｓ１０）。流量の計測結果が「０」ではない（Ｓ１０でＮｏ）場合には、ガス機器が使用中であることが推定されるから、ガス漏れ検査を中止する。一方、流量の計測結果が「０」である場合（Ｓ１０でＹｅｓ）には、全てのガス機器が使用されていないことが推定されるから、ガス漏れ検査を続行する。即ち、開閉弁５１を開放して、ガス注入部５０からフローセル２０内に一定量の第２のガスを注入する（Ｓ１１）。これにより、フローセル２０内には、互いに超音波の伝搬速度が異なる第１と第２のガスが滞留した状態になる。第２のガスの注入量は、第１のガスの種類や、フローセル２０の容積等に応じて適宜設定すればよい。   At the time of a gas leak test, in order to confirm that the first gas is not in a normal flow (the gas device connected to the gas pipe 90 is in use), the flow rate measured based on the ultrasonic propagation time is measured. It is determined whether or not the result is “0” (S10). If the measurement result of the flow rate is not “0” (No in S10), it is estimated that the gas device is in use, and thus the gas leak inspection is stopped. On the other hand, when the measurement result of the flow rate is “0” (Yes in S10), it is estimated that not all gas devices are used, and thus the gas leak inspection is continued. That is, the on-off valve 51 is opened, and a certain amount of the second gas is injected into the flow cell 20 from the gas injection unit 50 (S11). Thereby, in the flow cell 20, the 1st and 2nd gas from which the propagation velocity of an ultrasonic wave mutually differs will be in the state which stayed. The injection amount of the second gas may be appropriately set according to the type of the first gas, the volume of the flow cell 20, and the like.

次に、第２のガスを計測管路２２内に滞留させてから予め定めた待機時間（例えば、数秒程度）が経過したか否かを判定する（Ｓ１２）。この待機時間は、第２のガスの注入時に計測管路２２内に発生した気流が落ち着くのを待つために設けられている。待機時間が経過したら（Ｓ１２でＹｅｓ）、流量計測時と同様に、１対の超音波送受波器３０，３０間で超音波の送受信を行って、その伝搬時間及び伝搬速度を計測する（Ｓ１３）。即ち、一方の超音波送受波器３０から他方の超音波送受波器３０へと超音波を送信してその伝搬時間を計測する。次に送信方向を逆向きにして（他方の超音波送受波器３０から一方の超音波送受波器３０へと）超音波を送信してその伝搬時間を計測する。   Next, it is determined whether or not a predetermined standby time (for example, about several seconds) has elapsed since the second gas was retained in the measurement pipeline 22 (S12). This waiting time is provided to wait for the airflow generated in the measurement pipe line 22 to settle when the second gas is injected. When the standby time elapses (Yes in S12), ultrasonic waves are transmitted / received between the pair of ultrasonic transducers 30 and 30 and the propagation time and propagation velocity are measured (S13). ). That is, an ultrasonic wave is transmitted from one ultrasonic transducer 30 to the other ultrasonic transducer 30 and its propagation time is measured. Next, the transmission direction is reversed (from the other ultrasonic transducer 30 to one ultrasonic transducer 30), and an ultrasonic wave is transmitted and its propagation time is measured.

この超音波の伝搬速度は、正逆両方向で送音波を送受信したときの伝搬時間の和又は逆数和により演算することができる。即ち、第２のガスを滞留させてから或る時間が経過した時点（第１と第２のガスが或る体積比になった時点）の超音波の伝搬速度をＣとし、計測管路２２内を流動するガスの流速をｖとし、正逆両方向で送音波を送受信したときの伝搬時間をそれぞれｔ１，ｔ２とし、超音波送受波器３０，３０間の距離をＬとした場合に、
ｔ１＝Ｌ／（Ｃ＋ｖ）
ｔ２＝Ｌ／（Ｃ−ｖ）
ｔ１＋ｔ２≒２Ｌ／Ｃ
（１／ｔ１）＋（１／ｔ２）＝２Ｃ／Ｌ
上記関係式が成立する。この関係式にｔ１，ｔ２及びＬの値を代入することで、第２のガスを滞留させてから或る時間が経過した時点（第１と第２のガスが或る体積比になった時点）での超音波の伝搬速度Ｃを演算することができる。 The propagation speed of this ultrasonic wave can be calculated by the sum of the propagation times or the reciprocal sum when the sound waves are transmitted and received in both forward and reverse directions. That is, the ultrasonic wave propagation velocity at the time when a certain time has elapsed since the second gas was retained (the time when the first and second gases reached a certain volume ratio) is C, and the measurement line 22 When the flow velocity of the gas flowing inside is v, the propagation times when transmitting and receiving sound waves in both forward and reverse directions are t 1 and t 2 , respectively, and the distance between the ultrasonic transducers 30 and 30 is L ,
t 1 = L / (C + v)
t 2 = L / (C−v)
t 1 + t 2 ≒ 2L / C
(1 / t 1 ) + (1 / t 2 ) = 2 C / L
The above relation is established. By substituting the values of t 1 , t 2, and L into this relational expression, a certain amount of time has elapsed since the second gas was retained (the first and second gases have a certain volume ratio). Can be calculated.

そして、予め定めたモニター期間（例えば、５分間）に亘って、上記した正逆両方向で超音波の送受信を繰り返し行い、伝搬速度Ｃと、フローセル２０内に第２のガスを滞留させてからの経過時間とを対応させた実測推移データを、制御処理部４０の実測データ記憶部４７に一時記憶する。なお、この処理が本発明の「実測データ取得手段」に相当する。   Then, over a predetermined monitoring period (for example, 5 minutes), the ultrasonic waves are repeatedly transmitted and received in both the forward and reverse directions, and the propagation velocity C and the second gas are retained in the flow cell 20. The actual measurement transition data corresponding to the elapsed time is temporarily stored in the actual measurement data storage unit 47 of the control processing unit 40. This process corresponds to “actual measurement data acquisition means” of the present invention.

ここで、計測管路２２内の第２のガスは、第２のガスを滞留させてからの経過時間に伴って計測管路２２の外部（ガス管９０）へと徐々に拡散するので、計測管路２２内の第１と第２のガスの体積比（濃度比）は、経過時間に伴って徐々に変化する。換言すれば、計測管路２２内の第２のガスは、第１のガスによって時間経過と共に徐々に希釈される。そして、図４に示すグラフのように、計測管路２２内の第１と第２のガスの体積比（濃度比）の変化、即ち、経過時間に伴って超音波の伝搬速度が徐々に変化する。   Here, the second gas in the measurement pipe 22 gradually diffuses to the outside of the measurement pipe 22 (the gas pipe 90) with the elapsed time from the retention of the second gas. The volume ratio (concentration ratio) of the first and second gases in the pipe line 22 gradually changes with the elapsed time. In other words, the second gas in the measurement pipeline 22 is gradually diluted with the passage of time by the first gas. Then, as shown in the graph of FIG. 4, the change in volume ratio (concentration ratio) of the first and second gases in the measurement pipe line 22, that is, the propagation speed of the ultrasonic wave gradually changes with the elapsed time. To do.

モニター期間が終了したら（Ｓ１４でＹｅｓ）、超音波の送受信を停止する。そして、制御処理部４０の基準データ記憶部４８（本発明の「基準データ記憶手段」に相当する）から、予め求めておいた基準推移データ（図４の破線で示したグラフ）を読み出して、これら基準推移データと実測推移データとをデータ比較部４９（本発明の「データ比較手段」に相当する）にて比較する（Ｓ１５）。   When the monitoring period ends (Yes in S14), transmission / reception of ultrasonic waves is stopped. Then, from the reference data storage unit 48 (corresponding to the “reference data storage unit” of the present invention) of the control processing unit 40, the reference transition data (a graph indicated by a broken line in FIG. 4) obtained in advance is read out. These reference transition data and measured transition data are compared by the data comparison unit 49 (corresponding to “data comparison means” of the present invention) (S15).

基準推移データは、例えば、第１のガスと第２のガスを一定の温度にして実測により求められたものであって、第１のガスの流量を０（真値）にして計測管路２２内に第２のガスを自然拡散させた場合の超音波の伝搬速度（基準伝搬速度）と、第２のガスを計測管路２２内に滞留させてからの経過時間とを対応させて記憶したデータである（例えば、図４の破線グラフ）。なお、基準推移データは、第１のガスと第２のガスを一定の温度にして演算により求めてもよい。   The reference transition data is obtained, for example, by actual measurement with the first gas and the second gas at a constant temperature. The flow rate of the first gas is set to 0 (true value), and the measurement pipeline 22 is used. The ultrasonic wave propagation speed (reference propagation speed) when the second gas is naturally diffused therein and the elapsed time after the second gas was retained in the measurement pipe line 22 were stored in association with each other. Data (for example, a broken line graph in FIG. 4). The reference transition data may be obtained by calculation with the first gas and the second gas at a constant temperature.

ガス管９０にガス漏れ箇所が有る場合と無い場合とでは、第２のガスを滞留させてからの経過時間に伴う超音波の伝搬速度Ｃの推移に、以下のような違いが生じる。即ち、ガス管９０にガス漏れが無い場合、計測管路２２内の気流は比較的穏やかなので、第２のガスは比較的ゆっくりと計測管路２２の外部（ガス管９０）へと自然拡散する。従って、計測管路２２内における第２のガスの濃度変化（濃度低下）が比較的緩慢で、第２のガスを滞留させてからの経過時間に伴う伝搬速度Ｃの推移（単位時間当たりの変化量）が比較的緩やかになる（例えば、図４の破線で示したグラフを参照）。   The following difference occurs in the transition of the ultrasonic wave propagation speed C with the elapsed time after the second gas is retained depending on whether or not the gas pipe 90 has a gas leak point. That is, when there is no gas leak in the gas pipe 90, the air flow in the measurement pipe line 22 is relatively gentle, so the second gas naturally diffuses to the outside (gas pipe 90) of the measurement pipe line 22 relatively slowly. . Therefore, the concentration change (concentration decrease) of the second gas in the measurement pipeline 22 is relatively slow, and the transition of the propagation velocity C (change per unit time) with the elapsed time after the second gas is retained. (Amount) becomes relatively moderate (see, for example, the graph shown by the broken line in FIG. 4).

これに対し、ガス管９０にガス漏れがある場合には、計測管路２２内にガス漏れ箇所へと向かうガスの流れが生じるので、第２のガスが比較的速やかに計測管路２２の外部（ガス管９０）へと拡散する。従って、計測管路２２内における第２のガスの濃度変化（濃度低下）が比較的速く、第２のガスを滞留させてからの経過時間に伴う伝搬速度Ｃの推移（単位時間当たりの変化量）が比較的大きくなる（例えば、図４の実線で示したグラフを参照）。   On the other hand, when there is a gas leak in the gas pipe 90, a gas flow toward the gas leak point is generated in the measurement pipe line 22, so that the second gas flows out of the measurement pipe line 22 relatively quickly. It diffuses into (gas pipe 90). Therefore, the concentration change (concentration decrease) of the second gas in the measurement pipeline 22 is relatively fast, and the transition of the propagation velocity C (the amount of change per unit time) with the elapsed time since the second gas was retained. ) Becomes relatively large (for example, see the graph shown by the solid line in FIG. 4).

そして、データ比較部４９は、第２のガスを滞留させてから（第２のガス注入後から）の経過時間が同じ条件で基準推移データと実測推移データとを比較し、その差分（図４における「ΔＣ１」）が予め定められた許容差より大きくなった場合、或いは、単位時間当たりの伝搬速度の変化量（図４における「ΔＣ２／Δｔ」）が、予め定められた許容変化量より大きくなった場合には、ガス漏れ有りと判定する。ガス漏れ有りと判定した場合には、超音波流量計１０又は超音波流量計１０とは別に設けた警告器１３を作動させたり、緊急遮断弁１４を閉じて第１のガスの供給を遮断する等の対処動作を行うようにしてもよい。   Then, the data comparison unit 49 compares the reference transition data with the actual measurement transition data under the same conditions as the elapsed time after the second gas is retained (after the second gas injection), and the difference (FIG. 4). Or “ΔC1” in FIG. 4 is larger than a predetermined allowable change amount or “ΔC1” in FIG. 4 is larger than a predetermined allowable difference. If it becomes, it is determined that there is a gas leak. When it is determined that there is a gas leak, the ultrasonic flow meter 10 or the alarm device 13 provided separately from the ultrasonic flow meter 10 is operated, or the emergency shut-off valve 14 is closed to cut off the supply of the first gas. Such coping operations may be performed.

ここで、ガス漏れ検査時の計測管路２２内に滞留した第１及び第２のガスの温度を図示しない温度センサ（本発明の「温度検出手段」に相当する）にて計測し、そのガス漏れ検査時の実測温度に基づいて、基準推移データを補正するようにしてもよい。これにより、ガス漏れ検査時の計測管路２２内（第１と第２のガス）の温度と、第１のガスの流量を０（真値）にして実測又は演算により基準推移データを求めたときの設定温度との相違による誤差分を排除することができ、ガス漏れの有無をより正確に判別することができる。なお、このような構成とした場合、制御処理部４０は本発明の「データ補正手段」に相当する。   Here, the temperature of the first and second gases staying in the measurement pipeline 22 at the time of the gas leak inspection is measured by a temperature sensor (corresponding to “temperature detection means” of the present invention), and the gas The reference transition data may be corrected based on the actually measured temperature at the time of leak inspection. Thereby, the reference transition data was obtained by actual measurement or calculation with the temperature in the measurement pipe line 22 (first and second gas) at the time of gas leak inspection and the flow rate of the first gas set to 0 (true value). The error due to the difference from the set temperature at the time can be eliminated, and the presence or absence of gas leakage can be more accurately determined. In the case of such a configuration, the control processing unit 40 corresponds to the “data correction unit” of the present invention.

第１のガスがメタンを主成分とする都市ガスである場合には、第２のガスとして都市ガスに含まれているブタン又はプロパン（又はＬＰガス）を用いることが好ましい。その理由は、ガス漏れ検査のためにガス管９０内に第２のガスを注入した場合でも、そのまま燃料として使用することが可能であるからである。また、第２のガスをブタンとする場合には、ガスボンベ５２として、市販の家庭用カセットボンベを流用することが可能になる。なお、第２のガスは、超音波の伝搬速度が第１のガスとは異なるものであればよく、第１のガスが都市ガスの場合に、第２のガスとして、例えば、空気、窒素、酸素、不活性ガスを使用しても、同様にガス漏れ検査を行うことができる。   When the first gas is a city gas mainly composed of methane, it is preferable to use butane or propane (or LP gas) contained in the city gas as the second gas. The reason is that even when the second gas is injected into the gas pipe 90 for the gas leak inspection, it can be used as fuel as it is. When the second gas is butane, a commercially available household cassette cylinder can be used as the gas cylinder 52. Note that the second gas only needs to have an ultrasonic wave propagation velocity different from that of the first gas. When the first gas is city gas, examples of the second gas include air, nitrogen, Even when oxygen or an inert gas is used, a gas leak test can be performed in the same manner.

計測管路２２内の第１のガスと第２のガスの濃度比と、超音波の伝搬速度Ｃとの関係を具体例を挙げて説明する。例えば、第１のガスとしての「メタン」が滞留している容積５００［ｍｌ］の計測管路２２内に、第２のガスとしての「ブタン」を１００［ｍｌ］注入したと仮定すると、注入直後の計測管路２２内のメタン濃度は８０％、ブタン濃度は２０％になる。ガス中の超音波の伝搬速度Ｃは、ガスを理想気体と仮定すると公知な下記関係式から演算することができる。メタン濃度８０％、ブタン濃度２０％、摂氏２３度（２９６［Ｋ］）とした場合の超音波の伝搬速度Ｃは、下記関係式から３５６．４４８ｍ／ｓとなる。これを、１対の超音波送受波器３０，３０間の距離を０．１［ｍ］と仮定して伝搬時間に換算すると２８０５４６［ｎｓ］となる。   A relationship between the concentration ratio of the first gas and the second gas in the measurement pipe line 22 and the ultrasonic wave propagation speed C will be described with a specific example. For example, if it is assumed that 100 [ml] of “butane” as the second gas is injected into the measurement pipe 22 having a volume of 500 [ml] in which “methane” as the first gas is retained. Immediately after, the methane concentration in the measurement pipeline 22 is 80% and the butane concentration is 20%. The ultrasonic wave propagation velocity C in the gas can be calculated from the following well-known relational expression assuming that the gas is an ideal gas. The ultrasonic wave propagation velocity C when the methane concentration is 80%, the butane concentration is 20%, and the temperature is 23 degrees Celsius (296 [K]) is 356.448 m / s from the following relational expression. When this is converted into a propagation time assuming that the distance between the pair of ultrasonic transducers 30 and 30 is 0.1 [m], 280546 [ns] is obtained.

Ｃ［ｍ／ｓ］＝｛（γ・Ｒ・Ｔ／Ｍ）・１０３｝１／２
γ：比熱比（メタン１．３、ブタン１．１１）
Ｒ：気体定数（＝８．３１４４７２）
Ｔ：絶対温度
Ｍ：平均分子量 C [m / s] = {(γ · R · T / M) · 10 3 } 1/2
γ: specific heat ratio (methane 1.3, butane 1.11)
R: Gas constant (= 8.3314472)
T: Absolute temperature
M: average molecular weight

ガス管９０にガス漏れが無いと仮定すると、メタンより比重が重く拡散し難いブタンは、気流の穏やかな計測管路２２内でゆっくりと自然拡散することになるので、計測管路２２内におけるブタンの濃度低下は非常に緩慢である。   If it is assumed that there is no gas leakage in the gas pipe 90, butane, which has a higher specific gravity than methane and is difficult to diffuse, slowly diffuses naturally in the measurement pipe 22 where the airflow is gentle. The concentration drop is very slow.

これに対し、ガス管９０にガス漏れ箇所が有ったとすると、計測管路２２内にガス漏れ箇所へと向かう気流が発生して、その気流の影響でブタンの拡散が促進されるので、計測管路２２内のブタン濃度は、ガス漏れ箇所が無い場合に比べて速く減少する。例えば、ガス管９０に０．０８［Ｌ／分］（約５［Ｌ／時］）のガス漏れ箇所が有ったとすると、計測管路２２内に滞留したメタンとブタンの混合ガスが、０．０８［Ｌ／分］の割合でフローセル２０から流出するのに対し、メタンが０．０８［Ｌ／分］の割合で計測管路２２に流入することになり、時間経過に伴ってメタン濃度が上昇し、ブタン濃度が低下する。より具体的には、当初２０％であったブタン濃度は、注入後、１分経過すると約１６．８％、２分経過すると約１４．１％、３分経過すると約１１．９％、４分経過すると約９．９６％になる。そして、上記関係式からも明らかなように、計測管路２２内のブタン濃度の低下及びメタン濃度の上昇に伴い、平均分子量Ｍが小さくなるので、超音波の伝搬速度Ｃが速くなり、例えば、注入から約４分経過後（ブタン濃度が１０％まで低下した状態）では３９４．６７３［ｍ／ｓ］になる。これを、超音波送受波器３０，３０間の距離を０．１［ｍ］と仮定して伝搬時間に換算すると、２５３３７４［ｎｓ］になる。つまり、ブタン濃度が１０％（１０００００ｐｐｍ）低下することで、伝搬速度に換算して約３８［ｍ／ｓ］の差が生じると共に、伝搬時間に換算して約２７０００［ｎｓ］の差異が生じる。   On the other hand, if there is a gas leak point in the gas pipe 90, an air flow is generated in the measurement pipe line 22 toward the gas leak point, and diffusion of butane is promoted by the influence of the air flow. The butane concentration in the pipe line 22 decreases more quickly than when there is no gas leak point. For example, if there is a gas leak point of 0.08 [L / min] (about 5 [L / hr]) in the gas pipe 90, the mixed gas of methane and butane staying in the measurement pipe line 22 is 0. 0.08 [L / min] flows out of the flow cell 20 whereas methane flows into the measuring line 22 at a rate of 0.08 [L / min]. Increases and the butane concentration decreases. More specifically, the butane concentration, which was initially 20%, was about 16.8% after 1 minute after injection, about 14.1% after 2 minutes, about 11.9% after 3 minutes, 4% When minutes pass, it becomes about 9.96%. As apparent from the above relational expression, the average molecular weight M decreases as the butane concentration in the measurement line 22 decreases and the methane concentration increases, so that the ultrasonic wave propagation speed C increases, for example, After about 4 minutes from the injection (the state in which the butane concentration has been reduced to 10%), it becomes 394.673 [m / s]. When this is converted into a propagation time assuming that the distance between the ultrasonic transducers 30 and 30 is 0.1 [m], it becomes 253374 [ns]. That is, when the butane concentration is reduced by 10% (100,000 ppm), a difference of about 38 [m / s] is generated in terms of propagation velocity, and a difference of about 27000 [ns] in terms of propagation time is produced.

このように、本実施形態の超音波流量計１０は、ガス管９０の途中に超音波流量計１０のフローセル２０が接続され、その内部空間である計測管路２２に第１のガスを滞留させると共に、計測管路２２の外部から第１のガスとは超音波の伝搬速度が異なる第２のガスを注入しかつ滞留させた状態にして、第２のガスを滞留させてからの時間経過に対応させて超音波の伝搬速度を計測する。次いで、時間経過に伴った伝搬速度の推移（実測推移データ）と、第１のガスの流量を０にして第２のガスを自然拡散させた場合の伝搬速度の推移（基準推移データ）とを比較する。そして、経過時間が同じであるという条件で、基準推移データと実測推移データとの差分「ΔＣ１」が予め定められた許容差より大きくなった場合、或いは、単位時間当たりの伝搬速度の変化量「ΔＣ２／Δｔ」が、予め定められた許容変化量より大きくなった場合に、ガス管９０からの第１のガスの漏れ有りと判定する。本実施形態によれば、従来のように複数の計測管や複数対の超音波送受波器を必要としないので、構造の大型化及び製品価格の上昇を抑えつつ、流量の測定レンジを下回る微少なガス流動（ガス漏れ）の有無を検出することが可能になる。   As described above, in the ultrasonic flow meter 10 of the present embodiment, the flow cell 20 of the ultrasonic flow meter 10 is connected in the middle of the gas pipe 90, and the first gas is retained in the measurement pipe line 22 that is the internal space. At the same time, the second gas having a different ultrasonic propagation speed from the first gas is injected from the outside of the measurement pipe line 22 and retained, and the time elapsed since the second gas was retained. Correspondingly, the ultrasonic wave propagation velocity is measured. Next, the transition of propagation velocity with time (measurement transition data) and the transition of propagation velocity when the second gas is naturally diffused with the first gas flow rate set to 0 (reference transition data) Compare. When the difference “ΔC1” between the reference transition data and the measured transition data becomes larger than a predetermined tolerance under the condition that the elapsed times are the same, or the amount of change in the propagation speed per unit time “ When “ΔC2 / Δt” becomes larger than a predetermined allowable change amount, it is determined that the first gas leaks from the gas pipe 90. According to the present embodiment, since a plurality of measurement tubes and a plurality of pairs of ultrasonic transducers are not required as in the prior art, the size of the flow rate is slightly smaller than the measurement range while suppressing an increase in structure size and an increase in product price. It is possible to detect the presence or absence of a gas flow (gas leak).

また、既存の超音波流量計の設置スペースに、ガス注入手段（ガス注入部５０及び開閉弁５１）及びガスボンベ５２の配置スペースが有れば、ガス管９０を変更することなく、本実施形態の超音波流量計１０に交換することができる。   Further, if there is an arrangement space for the gas injection means (the gas injection unit 50 and the on-off valve 51) and the gas cylinder 52 in the installation space of the existing ultrasonic flowmeter, the gas pipe 90 is not changed, and the present embodiment can be used. The ultrasonic flow meter 10 can be replaced.

［他の実施形態］
本発明は、前記実施形態に限定されるものではなく、例えば、以下に説明するような実施形態も本発明の技術的範囲に含まれ、さらに、下記以外にも要旨を逸脱しない範囲内で種々変更して実施することができる。 [Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

（１）上記実施形態では、ガス漏れの検査対象物としてガス管９０（流路管）を例示したが、検査対象物は、気密性を要する「容器」でもよい。   (1) In the above embodiment, the gas pipe 90 (flow channel pipe) is exemplified as the inspection object for gas leakage, but the inspection object may be a “container” that requires airtightness.

（２）上記実施形態では、第２のガスを滞留させてからの経過時間に伴う超音波の伝搬速度の推移に基づいて、「ガス漏れの有無」を判別する構成であったが、流路管や容器内における「ガスの流れの有無」を判別したり、「流量」を検出する構成にしてもよい。   (2) In the above embodiment, the configuration is such that “the presence or absence of gas leakage” is determined based on the transition of the ultrasonic wave propagation speed with the elapsed time since the second gas was retained. A configuration may be adopted in which “the presence or absence of gas flow” in the pipe or the container is determined, or “flow rate” is detected.

（３）上記実施形態では、第２のガスを滞留させてからの経過時間に伴う超音波の「伝搬速度」の推移に基づいてガス漏れの有無を判別していたが、「伝搬時間」の推移に基づいてガス漏れの有無やガスの流れの有無を判別したり、流量を検出するようにしてもよい。   (3) In the above embodiment, the presence or absence of gas leakage is determined based on the transition of the “propagation speed” of the ultrasonic wave with the elapsed time since the second gas was retained. Based on the transition, the presence or absence of gas leakage or the presence or absence of gas flow may be determined, or the flow rate may be detected.

（４）上記実施形態では、第２のガスを計測管路２２のうちインナー管２５の外側に注入していたが、超音波伝搬経路Ｒ１が貫通したインナー管２５の内側に直接注入するようにしてもよい。   (4) In the above embodiment, the second gas is injected into the outer side of the inner pipe 25 in the measurement pipe line 22, but is directly injected into the inner side of the inner pipe 25 through which the ultrasonic wave propagation path R1 passes. May be.

（５）上記実施形態では、１対の超音波送受波器３０，３０を利用して流量計測とガス漏れ検査とを行っていたが、ガス漏れ検査だけを行うようにしてもよい。   (5) In the above embodiment, the flow rate measurement and the gas leak test are performed using the pair of ultrasonic transducers 30 and 30. However, only the gas leak test may be performed.

（６）上記実施形態では、１対の超音波送受波器３０，３０を計測管路２２の軸方向で対向配置していたが、ガスの流れ方向（計測管路２２の軸方向）に対して斜めに交差する方向で対向配置してもよい。また、超音波が流路管や容器の内面で１回又は複数回反射して送受信されるように１対の超音波送受波器を配置してもよい。   (6) In the above embodiment, the pair of ultrasonic transducers 30, 30 are arranged opposite to each other in the axial direction of the measurement pipeline 22, but with respect to the gas flow direction (axial direction of the measurement pipeline 22). Alternatively, they may be arranged to face each other in an obliquely intersecting direction. Further, a pair of ultrasonic transducers may be arranged so that the ultrasonic waves are reflected and transmitted / received once or a plurality of times on the inner surface of the flow channel tube or the container.

（７）上記実施形態では、１対の超音波送受波器３０，３０が、フローセル２０の内側（計測管路２２内）に配置されていたが、フローセル２０の外側に配置してもよい。   (7) In the above embodiment, the pair of ultrasonic transducers 30, 30 are arranged inside the flow cell 20 (inside the measurement pipeline 22), but may be arranged outside the flow cell 20.

（８）上記実施形態では、計測管路２２を内部隔壁２４で二部屋に仕切ってそれらの間をインナー管２５で連通していたが、内部隔壁２４及びインナー管２５を設ける替わりに、計測管路２２の中間部の断面積を絞ってもよい。   (8) In the above embodiment, the measurement pipeline 22 is divided into two chambers by the internal partition wall 24 and communicated between them by the inner tube 25. Instead of providing the internal partition wall 24 and the inner tube 25, the measurement tube 22 The cross-sectional area of the middle part of the path 22 may be reduced.

（９）上記実施形態では、第２のガスが流入部屋２２Ａから注入される構成となっていたが、流出部屋２２Ｂから注入される構成としてもよい。また、流入部屋２２Ａと流出部屋２２Ｂの両方から注入可能な構成としてもよい。   (9) In the above embodiment, the second gas is injected from the inflow chamber 22A. However, the second gas may be injected from the outflow chamber 22B. Moreover, it is good also as a structure which can be inject | poured from both inflow room 22A and outflow room 22B.

（１０）上記実施形態では、超音波流量計１０のデータ比較部４９が、基準推移データと実測推移データとの比較結果に基づいてガス漏れの有無を判定するように構成されていたが、データ比較部４９では、基準推移データと実測推移データとを比較するだけにしておき、ガス漏れの有無の判定は、データ比較部４９による比較結果に基づいて検査員が行ってもよい。   (10) In the above embodiment, the data comparison unit 49 of the ultrasonic flowmeter 10 is configured to determine the presence or absence of gas leakage based on the comparison result between the reference transition data and the actual measurement transition data. The comparison unit 49 may simply compare the reference transition data and the measured transition data, and the inspector may determine whether or not there is a gas leak based on the comparison result by the data comparison unit 49.

（１１）上記実施形態では、ガス漏れ検査時のフローセル２０内（第１及び第２のガス）の温度に基づいて基準推移データを補正していたが、ガス漏れ検査時の実測推移データを、実測又は演算により基準推移データを求めたときの温度に基づいて補正してもよい。   (11) In the above embodiment, the reference transition data is corrected based on the temperature in the flow cell 20 (first and second gases) at the time of the gas leak inspection. You may correct | amend based on the temperature when reference | standard transition data are calculated | required by measurement or calculation.

（１２）上記実施形態において、需要家のガス使用パターンに基づいてガスが使用される可能性が低い時間帯を割り出しておき、その時間帯にガス漏れ検査を実行するように構成することが好ましい。また、検査の実行周期は、半日、１日、１週間、１ヶ月その他、適宜設定すればよい。   (12) In the above-described embodiment, it is preferable to determine a time zone in which there is a low possibility that gas will be used based on the gas usage pattern of the consumer, and to perform a gas leak test in that time zone. . Further, the inspection execution cycle may be set as appropriate, such as half a day, one day, one week, one month, or the like.

（１３）上記実施形態において、第２のガスを滞留させてからの経過時間が同じ条件で、基準推移データと実測推移データとの差分が、予め定められた許容差に比べて極端に大きくなった場合或いは、単位時間当たりの伝搬速度の変化量が、予め定められた許容変化量に比べて極端に大きくなった場合には、通常のガス使用が開始されたことが推定されるから、ガス漏れ検査を中止して流量計測を再開するようにしてもよい。   (13) In the above embodiment, the difference between the reference transition data and the actual measurement transition data is extremely larger than a predetermined tolerance under the same condition as the elapsed time after the second gas is retained. Or if the amount of change in propagation velocity per unit time is extremely large compared to a predetermined allowable change, it is estimated that normal gas use has started. Leakage inspection may be stopped and flow measurement may be resumed.

（１４）上記実施形態では、第１のガスとして都市ガス、第２のガスとしてブタン及びプロパンを例示したが、超音波の伝搬速度が互いに異なる組み合わせであれば、これ以外でもよい。例えば、第１のガスがプロパンガス（ＬＰガスを含む）である場合に、第２のガスとしてメタンを用いてもよい。   (14) In the above embodiment, city gas is exemplified as the first gas and butane and propane are exemplified as the second gas. However, other combinations may be used as long as the ultrasonic wave propagation speeds are different from each other. For example, when the first gas is propane gas (including LP gas), methane may be used as the second gas.

（１５）上記実施形態では、第２のガスを滞留させてから所定のモニター期間に亘って連続して超音波の伝搬時間及び伝搬速度を計測する構成であったが、第２のガスを滞留させてから所定時間が経過した或る一時点だけで伝搬時間又は伝搬速度を計測し、その「或る一時点で計測された伝搬時間又は伝搬速度」を、基準推移データのうちで対応する同一時点における伝搬時間又は伝搬速度と比較して、ガスの微流動（ガス漏れ）の有無を検出するようにしてもよい。或いは、第２のガスを滞留させた後の不連続な複数の時点で伝搬時間又は伝搬速度を計測し、その「不連続な複数の時点で計測された伝搬時間又は伝搬速度」を、基準推移データのうちで対応する同一複数の時点における伝搬時間又は伝搬速度とそれぞれ比較して、ガスの微流動（ガス漏れ）の有無を検出するようにしてもよい。   (15) In the above embodiment, the configuration is such that the ultrasonic propagation time and propagation velocity are continuously measured over a predetermined monitoring period after the second gas is retained, but the second gas is retained. The propagation time or propagation speed is measured only at a certain temporary point after a predetermined time has elapsed, and the "propagation time or propagation speed measured at a certain temporary point" is the same in the reference transition data. The presence / absence of fine gas flow (gas leakage) may be detected by comparison with the propagation time or propagation speed at the time. Alternatively, the propagation time or propagation velocity is measured at a plurality of discontinuous points after the second gas is retained, and the "propagation time or propagation velocity measured at a plurality of discontinuous points" is changed as a reference. The presence / absence of a microfluidic gas (gas leakage) may be detected by comparing with the propagation time or propagation velocity at the same plurality of corresponding time points in the data.

１０ 超音波流量計
２０ フローセル
２２ 計測管路
３０ 超音波送受波器
４０ 制御処理部
４７ 実測データ記憶部
４８ 基準データ記憶部（基準データ記憶手段）
４９ データ比較部（データ比較手段）
５０ ガス注入部（ガス注入手段）
５１ 開閉弁（ガス注入手段）
５２ ガスボンベ
９０ ガス管（流路管）
Ｒ１ 超音波伝搬経路 DESCRIPTION OF SYMBOLS 10 Ultrasonic flow meter 20 Flow cell 22 Measuring pipe line 30 Ultrasonic transducer 40 Control processing part 47 Actual measurement data storage part 48 Reference data storage part (reference data storage means)
49 Data comparison part (data comparison means)
50 Gas injection part (gas injection means)
51 On-off valve (gas injection means)
52 Gas cylinder 90 Gas pipe (channel pipe)
R1 Ultrasonic propagation path

Claims (11)

第１のガスが滞留した流路管又は容器における内部空間の一部を、１対の超音波送受波器の間で超音波を伝搬させるための超音波伝搬経路とし、
前記第１のガスとは超音波の伝搬速度が異なる第２のガスを前記流路管又は前記容器の外部から前記超音波伝搬経路に注入しかつ滞留させた状態にして、その超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を計測し、
その伝搬時間又は伝搬速度の時間経過に伴った推移と、実測又は演算にて求められる前記第１のガスの流量を０にした場合の前記第２のガスの自然拡散による前記伝搬時間又は伝搬速度の時間経過に伴った基準推移との比較に基づいて、前記第１のガスの流れの有無、流量、或いは、前記第１のガスの漏れを検出することを特徴とするガス微流動検出方法。 A part of the internal space in the channel tube or container in which the first gas stays is used as an ultrasonic propagation path for propagating ultrasonic waves between a pair of ultrasonic transducers,
A second gas having an ultrasonic propagation speed different from that of the first gas is injected into the ultrasonic propagation path from the outside of the flow channel tube or the container and stays there, and the ultrasonic propagation path. Measure the propagation time or propagation speed of the ultrasonic wave propagating through
The propagation time or propagation speed due to the natural diffusion of the second gas when the propagation time or propagation speed of the first gas flow rate is zero, and the transition of the propagation time or propagation speed over time. A micro gas flow detection method, comprising: detecting presence / absence of a flow of the first gas, a flow rate, or leakage of the first gas, based on a comparison with a reference transition with time. 実測又は演算にて、前記第１のガス及び前記第２のガスが一定の温度の下、前記伝搬時間又は伝搬速度の前記基準推移を求めておき、
前記第１のガスの流れの有無又は流量又は漏れの検出時の前記第１のガス及び前記第２のガスの温度に基づいて、前記基準推移を補正することを特徴とする請求項１に記載のガス微流動検出方法。 In the actual measurement or calculation, the reference transition of the propagation time or propagation velocity is obtained under a constant temperature of the first gas and the second gas,
The reference transition is corrected based on the presence or absence of the flow of the first gas, the flow rate, or the temperature of the first gas and the second gas at the time of detection of a leak. Gas microfluidic detection method. 燃料である第１のガスを供給するためのガス管の途中に超音波流量計を接続し、前記超音波流量計のうち１対の超音波送受波器の間で超音波を伝搬させるための超音波伝搬経路を前記第１のガスが流動可能な状態にして、その超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度に基づいて前記第１のガスの流量を計測可能とすると共に、その超音波流量計を用いて前記ガス管からのガス漏れの有無を検査するガス漏れ検査方法において、
前記ガス管のうち前記超音波流量計を含んだ所定区間の上流側と下流側とを遮断することで前記ガス管内に前記第１のガスを滞留させた状態にして、前記第１のガスとは超音波の伝搬速度が異なる第２のガスを前記ガス管の外部から前記超音波伝搬経路に注入しかつ滞留させた状態にして、その超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を計測し、
その伝搬時間又は伝搬速度の時間経過に伴った推移と、実測又は演算にて求められる前記第１のガスの流量を０にした場合の前記第２のガスの自然拡散による前記伝搬時間又は伝搬速度の時間経過に伴った基準推移との比較に基づいて、前記ガス管からの前記第１のガスの漏れの有無を検査することを特徴とするガス漏れ検査方法。 An ultrasonic flow meter is connected in the middle of a gas pipe for supplying a first gas as fuel, and ultrasonic waves are propagated between a pair of ultrasonic transducers of the ultrasonic flow meter. The flow of the first gas can be measured based on the propagation time or propagation speed of the ultrasonic wave propagating through the ultrasonic propagation path by making the first gas flowable in the ultrasonic propagation path. In the gas leakage inspection method for inspecting the presence or absence of gas leakage from the gas pipe using the ultrasonic flowmeter,
The first gas is retained in the gas pipe by blocking the upstream side and the downstream side of the predetermined section including the ultrasonic flowmeter in the gas pipe. Is a state in which a second gas having a different ultrasonic propagation velocity is injected into the ultrasonic propagation path from the outside of the gas pipe and stays there, and the propagation time or propagation of the ultrasonic wave propagating through the ultrasonic propagation path. Measure speed,
The propagation time or propagation speed due to the natural diffusion of the second gas when the propagation time or propagation speed of the first gas flow rate is zero, and the transition of the propagation time or propagation speed over time. A gas leakage inspection method, wherein the presence or absence of leakage of the first gas from the gas pipe is inspected based on a comparison with a reference transition with the passage of time. 前記第１のガスは、メタンを主成分とした都市ガスであり、
前記第２のガスは、前記都市ガスに含まれるブタン又はプロパンであることを特徴とする請求項３に記載のガス漏れ検査方法。 The first gas is a city gas mainly composed of methane,
The gas leakage inspection method according to claim 3, wherein the second gas is butane or propane contained in the city gas. 前記第１のガスは、プロパンガスであり、
前記第２のガスは、メタンであることを特徴とする請求項３に記載のガス漏れ検査方法。 The first gas is propane gas;
The gas leakage inspection method according to claim 3, wherein the second gas is methane. 実測又は演算にて、前記第１のガス及び前記第２のガスが一定の温度の下、前記伝搬時間又は伝搬速度の前記基準推移を求めておき、
前記第１のガスの漏れ検査時の前記第１のガス及び前記第２のガスの温度に基づいて、前記基準推移を補正することを特徴とする請求項３乃至５の何れか１の請求項に記載のガス漏れ検査方法。 In the actual measurement or calculation, the reference transition of the propagation time or propagation velocity is obtained under a constant temperature of the first gas and the second gas,
6. The reference transition according to claim 3, wherein the reference transition is corrected based on temperatures of the first gas and the second gas at the time of the leak inspection of the first gas. The gas leak test method described in 1. 第１のガスが滞留した流路管又は容器の内部に連通し、前記第１のガスで満たされ得る計測管路と、
前記計測管路内を貫通する超音波伝搬経路に沿って超音波を送受波可能な１対の超音波送受波器と、
前記第１のガスとは超音波の伝搬速度が異なる第２のガスを前記流路管又は前記容器の外部から前記計測管路内に注入して滞留させるためのガス注入手段と、
前記超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を、前記計測管路内に前記第２のガスを滞留させてからの経過時間に対応させて計測する実測データ取得手段と、
前記第１のガスの流量を０にした状態で前記超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を基準伝搬時間又は基準伝搬速度として、前記計測管路内に前記第２のガスを滞留させてからの経過時間に対応させて記憶した基準データ記憶手段と、
前記経過時間が同じ条件で、前記実測データ取得手段にて計測された前記伝搬時間又は前記伝搬速度と、前記基準伝搬時間又は前記基準伝搬速度との差分に基づいて前記流路管又は前記容器からの前記第１のガスの漏れを有無を判別するためのデータ比較手段とを備えたことを特徴とするガス漏れ検査装置。 A measurement conduit that communicates with the interior of the channel tube or container in which the first gas stays and can be filled with the first gas;
A pair of ultrasonic transducers capable of transmitting and receiving ultrasonic waves along an ultrasonic wave propagation path penetrating through the measurement pipe;
A gas injection means for injecting and retaining a second gas having a different ultrasonic propagation speed from the first gas into the measurement pipe from the outside of the flow pipe or the container;
Measured data acquisition means for measuring the propagation time or propagation speed of the ultrasonic wave propagating through the ultrasonic wave propagation path in accordance with the elapsed time after the second gas is retained in the measurement pipeline;
The second gas is introduced into the measurement pipeline with the propagation time or propagation speed of the ultrasonic wave propagating through the ultrasonic propagation path in the state where the flow rate of the first gas is 0 as the reference propagation time or reference propagation speed. Reference data storage means stored corresponding to the elapsed time since the
Based on the difference between the propagation time or the propagation velocity measured by the actual measurement data acquisition means and the reference propagation time or the reference propagation velocity under the same condition as the elapsed time, from the channel tube or the container And a data comparison means for determining whether or not there is a leakage of the first gas. 前記第１のガス及び前記第２のガスの温度を検出するための温度検出手段と、
前記第１のガスの漏れ検査時の前記第１のガス及び前記第２のガスの温度に基づいて、前記基準伝搬時間又は前記基準伝搬速度を補正するデータ補正手段とを備えたことを特徴とする請求項７に記載のガス漏れ検査装置。 Temperature detecting means for detecting temperatures of the first gas and the second gas;
Data correction means for correcting the reference propagation time or the reference propagation speed based on the temperature of the first gas and the second gas at the time of the first gas leakage inspection, The gas leak inspection apparatus according to claim 7. 可燃燃料である第１のガスを供給するためのガス管の途中に接続されると共に、前記ガス管の内部に連通した計測管路と、
前記計測管路内を貫通する超音波伝搬経路に沿って超音波を送受波可能な１対の超音波送受波器と、を有し、
通常は、前記超音波伝搬経路を前記第１のガスが流動可能な状態で、その超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度に基づいて前記第１のガスの流量を計測すると共に、前記超音波伝搬経路に前記第１のガスを滞留させた状態にして前記ガス管からのガス漏れの有無を検出可能な超音波流量計において、
前記第１のガスとは超音波の伝搬速度が異なる第２のガスを前記ガス管の外部から前記計測管路内に注入して滞留させるためのガス注入手段と、
前記超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を、前記計測管路内に前記第２のガスを滞留させてからの経過時間に対応させて計測する実測データ取得手段と、
前記第１のガスの流量を０にした状態で前記超音波伝搬経路を伝搬する超音波の伝搬時間又は伝搬速度を基準伝搬時間又は基準伝搬速度として、前記計測管路内に前記第２のガスを滞留させてからの経過時間に対応させて記憶した基準データ記憶手段と、
前記経過時間が同じ条件で、前記実測データ取得手段にて計測された前記伝搬時間又は前記伝搬速度と、前記基準伝搬時間又は前記基準伝搬速度との差分に基づいて前記ガス管からの前記第１のガスの漏れを有無を判別するためのデータ比較手段とを備えたことを特徴とする超音波流量計。 A measuring line connected to the inside of the gas pipe and connected to the middle of the gas pipe for supplying the first gas as the combustible fuel ;
A pair of ultrasonic transducers capable of transmitting and receiving ultrasonic waves along an ultrasonic wave propagation path penetrating through the measurement pipe line ,
Usually , the flow rate of the first gas is measured based on the propagation time or velocity of the ultrasonic wave propagating through the ultrasonic propagation path in a state where the first gas can flow through the ultrasonic propagation path. In addition, in the ultrasonic flowmeter capable of detecting the presence or absence of gas leakage from the gas pipe in a state where the first gas is retained in the ultrasonic propagation path,
A gas injection means for injecting and retaining a second gas having a different ultrasonic propagation velocity from the first gas into the measurement pipe from the outside of the gas pipe;
Measured data acquisition means for measuring the propagation time or propagation speed of the ultrasonic wave propagating through the ultrasonic wave propagation path in accordance with the elapsed time after the second gas is retained in the measurement pipeline;
The second gas is introduced into the measurement pipeline with the propagation time or propagation speed of the ultrasonic wave propagating through the ultrasonic propagation path in the state where the flow rate of the first gas is 0 as the reference propagation time or reference propagation speed. Reference data storage means stored corresponding to the elapsed time since the
The first time from the gas pipe based on the difference between the propagation time or the propagation speed measured by the actual measurement data acquisition means and the reference propagation time or the reference propagation speed under the same condition as the elapsed time. An ultrasonic flowmeter comprising data comparison means for determining whether or not there is a gas leak. 前記第１のガス及び前記第２のガスの温度を検出するための温度検出手段と、
前記第１のガスの漏れ検査時の前記第１のガス及び前記第２のガスの温度に基づいて、前記基準伝搬時間又は前記基準伝搬速度を補正するデータ補正手段とを備えたことを特徴とする請求項９に記載の超音波流量計。 Temperature detecting means for detecting temperatures of the first gas and the second gas;
Data correction means for correcting the reference propagation time or the reference propagation speed based on the temperature of the first gas and the second gas at the time of the first gas leakage inspection, The ultrasonic flowmeter according to claim 9. 前記データ比較手段は、前記第２のガスを滞留させてからの経過時間が同じ条件で、実測データ取得手段にて計測された前記伝搬時間又は前記伝搬速度と、前記基準伝搬時間又は前記基準伝搬速度との差分が予め定められた許容差より大きくなった場合には、ガス漏れ有りと判定するように構成したことを特徴とする請求項９又は１０に記載の超音波流量計。   The data comparison means includes the propagation time or the propagation speed measured by the actual measurement data acquisition means, the reference propagation time or the reference propagation under the same conditions as the elapsed time since the second gas was retained. The ultrasonic flowmeter according to claim 9 or 10, wherein when the difference from the speed becomes larger than a predetermined tolerance, it is determined that there is a gas leak.
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