JP2020106343A - Calculation method and calculation device of gas sound speed - Google Patents

Abstract

To accurately calculate a gas sound speed even when the ultrasonic wave propagating through gas must be transmitted or received via a steel material.SOLUTION: In an ultrasonic wave measurement method, a guide wave is excited though a steel material by transmitting an ultrasonic wave to the steel material from a transmission unit, a part of the guide wave leaks into gas and propagates as a longitudinal wave, a longitudinal leak wave having arrived at a separate place of the steel material generates the phenomenon in which the leak wave is converted into a guide wave propagating again through the steel material, and the guide wave after the conversion is received by a receiving unit. In this method, using the propagation time from the transmission of the ultrasonic wave by the transmission unit to the reception of the guide wave by the receiving unit, the sound speed of the guide wave propagating through the steel material, the distance between the transmission unit and the receiving unit that are projected in the direction parallel with a guide wave travel direction through the steel material, and the propagation distance of the longitudinal leak wave through the gas that is projected in the direction perpendicular to the guide wave travel direction through the steel material, a longitudinal wave sound speed propagating through the gas is calculated.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method and a device for calculating a sound velocity of a gas surrounded by steel materials, and in particular, a method of measuring an ultrasonic wave propagating in a gas through a pipe steel material or a container steel material and calculating the sound speed thereof. And involved in the equipment.

When a gas pipe or a storage container for supplying city gas or LP gas is damaged by a disaster, it is necessary to repair it, remove unnecessary pipes, and redraw new pipes as soon as possible. When the inside of the pipe or container is flammable gas, if the pipe or container is cut for repair or removal, sparks generated at the time of cutting may become an ignition source and explode. In such a case, it is necessary to select a repair or removal method that does not involve cutting, or apply a cutting method that does not generate sparks. On the other hand, if it is known that flammable gas has already leaked from pipes and containers and replaced with air in the event of a disaster, you can immediately cut the pipes, etc. by normal methods, and repair or remove them. Can be done quickly. In order to determine which method to select, it is necessary to identify the type of internal gas before cutting the pipe or the like.

As one of the methods for identifying the type of gas, it is possible to measure the sound velocity of gas. Since the sound velocity of methane gas, which is the main component of city gas, is about 442 m/s and the sound velocity of air is about 340 m/s, there is a possibility that city gas and air can be distinguished if the sound velocity can be measured. Further, LP gas such as propane gas (sound speed of about 262 m/s), butane gas (sound speed of 212 m/s), and air may also be identified if the sound speed can be measured. However, in order to identify the type of gas surrounded by steel such as piping, ultrasonic waves are propagated in the gas via the steel and the ultrasonic waves propagated in the gas are received via the steel. As a conventional technique for identifying the type of gas by calculating the sound velocity of gas by measuring the ultrasonic waves propagated in the gas through the steel material, there is, for example, Patent Document 1.

JP, 2005-179027, A

In the above-mentioned conventional technology, oblique-angle ultrasonic waves are injected into the steel material from the ultrasonic sensor for transmission mounted on the surface of the pipe steel material, and the ultrasonic waves propagated in the steel material are transmitted into the gas while refracting at the interface between the steel material and the gas. Then, the transmitted wave propagating in the gas is reflected by the inner surface of the steel material on the opposite side of the pipe and returns to the pipe transmission/reception side, and the oblique ultrasonic wave that is transmitted through the steel material while refracting at the interface between the gas and the steel material It is assumed to be received by the sensor (Fig. 14). In such an assumption,
(Equation 1)
Sound velocity V=(pipe) inner diameter φ/time difference (from transmission timing to reception of transmitted propagating wave) ΔT Equation (1)
The sound velocity of gas is calculated by the following equation (1). Originally, when accurately determining the sound velocity of gas,
(Equation 2)
Sound velocity of gas = ultrasonic wave propagation distance in gas / ultrasonic wave propagation time in gas Equation (2)
Should be asked for.

However, in the above-mentioned conventional technique, the gas sound velocity is calculated using the entire propagation time from the transmission timing to the reception of the transmitted propagating wave, that is, the time obtained by adding the propagation time in the steel material and the propagation time in the gas. In addition, since the transmitted wave propagating in the gas has a refraction angle and propagates obliquely with respect to the axial direction of the pipe, it is also considered that the ultrasonic wave propagation distance in the gas is larger than the pipe inner diameter. Absent. Therefore, in the above-mentioned conventional technique, the approximate value of the gas sound velocity can be calculated, but the gas sound velocity cannot be calculated accurately.

An object of the present invention is to provide a gas sonic velocity calculation method capable of accurately calculating the gas sonic velocity even when ultrasonic waves propagating in a gas must be transmitted and received via a steel material.

For the above purpose in the present invention, the ultrasonic wave is transmitted from the ultrasonic wave transmitting section to the steel material to excite the guide wave in the steel material, and a part of the guide wave leaks into the gas and propagates as a longitudinal wave, In the ultrasonic measurement method in which a longitudinal wave leaking wave that reaches another location of the steel material is converted into a guided wave that propagates through the steel material again, and the converted guided wave is received by the ultrasonic receiver Propagation time from the transmission of ultrasonic waves at the receiving part until receiving the guide wave, the speed of sound of the guide wave propagating in the steel material, and the transmission part projected in the direction parallel to the guide wave traveling direction in the steel material. Characteristic of calculating the longitudinal wave sound velocity propagating in the gas by using the distance of the receiving part and the propagation distance of the longitudinal wave leakage wave in the gas projected in the direction perpendicular to the guide wave traveling direction in the steel material. To do.

According to the present invention, even when ultrasonic waves propagating in a gas have to be transmitted and received via a steel material, it is possible to accurately calculate the sound velocity of gas. Therefore, it is possible to accurately identify the type of internal gas before cutting the steel pipe or the steel container.

FIG. 3 is an explanatory diagram showing a configuration of an ultrasonic measurement device according to the first embodiment. It is a figure for explaining a subject. It is explanatory drawing which shows the 1st example of an ultrasonic wave propagation path. It is explanatory drawing which shows the 2nd example of an ultrasonic wave propagation path. It is explanatory drawing which shows the 3rd example of an ultrasonic wave propagation path. FIG. 5 is an explanatory diagram for explaining a plate thickness measurement of a pipe steel material in Example 1. 5 is a graph showing an example of plate thickness measurement results in Example 1. FIG. 5 is an explanatory diagram for explaining the guided wave measurement of the pipe steel material in the first embodiment. 6 is a graph showing an example of a guided wave result in Example 1. FIG. 5 is an explanatory diagram showing an example of an input screen for calculating a gas sound velocity in the first embodiment. 7 is an explanatory diagram showing a propagation path of ultrasonic waves in Example 2. FIG. FIG. 8 is a development view for explaining a propagation path of ultrasonic waves in the second embodiment. FIG. 7 is an explanatory diagram showing a propagation path of ultrasonic waves in the third embodiment.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram for explaining the problem, and FIGS. 3 to 5 are explanatory diagrams showing first to third examples of the ultrasonic wave propagation path. As shown in FIG. 2, in order to measure the sound velocity of the gas 2 inside the steel pipe 1, ultrasonic waves are transmitted to the steel pipe from the ultrasonic transmission unit 3 that is a combination of a transmission sensor 3a and a shoe 3b. It is assumed that the ultrasonic wave propagating in the order of the steel material is received by the ultrasonic wave receiving unit 5 in which the shoe 5b and the receiving sensor 5a are combined. Even if the inner diameter P _in is known from the specifications of the steel pipe and the distance L _p between the transmitter and the receiver projected in a direction parallel to the ultrasonic wave traveling direction in the steel pipe can be measured, the gas in the steel pipe In a situation where a plurality of candidates for ultrasonic waves propagating in the inside are considered, such as 15, 16, and 17, the ultrasonic wave propagation distance cannot be determined, so that the sound velocity of gas cannot be accurately calculated.

FIG. 3 shows a first example of the propagation path of ultrasonic waves. The ultrasonic wave transmitting unit 3 including the receiving sensor 3a and the shoe 3b is installed on the outer surface of the steel pipe 1, and the guide wave 11 is excited in the steel pipe. A longitudinal wave leaking wave 12 leaks into the gas from the guided wave propagating in the steel pipe. The angle of refraction of this leaky wave is φ. The leak wave propagates to the steel material on the side opposite the steel material pipe and is converted into the guide wave 13 that propagates in the steel material pipe. Therefore, in order to receive this guide wave 13, the ultrasonic wave receiving portion 5 including the shoe 5b and the receiving sensor 5a is used. Install.

When the guide wave sound velocity in the steel pipe is V _s , the longitudinal wave sound velocity in the gas is V _g , and the refraction angle when propagating from the steel pipe to the gas is φ, the following formula (3) is obtained according to Snell's law. To establish.

The propagation distance of the guide wave 11 on the transmission side is L _s1 , the propagation distance of the leaky wave 12 in the gas is L _g , and the propagation distance of the guide wave 13 on the reception side is L _{s2. In the} steel pipe of the transmission side, in the gas, and the reception side. When the total propagation time in the steel pipe is T _s1 , T _g , T _s2 , and Tall, the following equation (4) is obtained.

Propagation of a longitudinal wave leakage wave in a gas projected in a direction perpendicular to the guide wave traveling direction in the steel pipe, L _p , the distance between the transmitting part and the receiving part projected in a direction parallel to the guide wave traveling direction in the steel pipe Substituting the equation (1) into the equation (2), where L _v (in FIG. 3, L _v =inside diameter P _{in of the} pipe), the following equation (5) is obtained, and the refraction angle φ and the gas sound velocity V are obtained. _g can be calculated by the following equations (6) and (7).

Further, as shown in FIG. 4, when the leaky wave 12b leaks from a place where the propagation distance of the guide wave 11b is short, or when the leaky wave 12c leaks from a place where the propagation distance of the guide wave 11c is long as shown in FIG. Also, the total guide wave propagation distance in the steel material, which is obtained by adding the transmitting side guide wave (11, 11b, 11c) and the receiving side guide wave (13, 13b, 13c), is the same in any case, and In any case, the leaky waves (12, 12b, 12c) are parallel and have the same propagation distance. Therefore, also in the cases of FIGS. 4 and 5, the equations (6) and (7) are established similarly to the case of FIG.

As described above, the sound velocity V _{s of the} guided wave propagating in the steel pipe, the distance L _p between the transmitter and the receiver projected in the direction parallel to the guided wave travel direction in the steel pipe, the guided wave travel direction in the steel pipe If the propagation distance of the longitudinal wave leaking wave in the gas projected in the direction perpendicular to is known, L _v , the propagation time Tall from the transmission of the ultrasonic wave by the transmission sensor to the reception of the guide wave by the reception sensor Tall By measuring, the sound velocity V _g of the gas in the pipe can be accurately calculated from the equations (6) and (7).

Example 1 will be described with reference to FIGS. 1 and 6 to 10.

The first embodiment is an example in which the transmitting unit and the receiving unit are installed on the facing surfaces of the steel pipe, and the sound velocity of gas in the steel pipe is measured and calculated. FIG. 1 shows a schematic configuration when ultrasonically measuring the gas in the steel pipe and calculating the sound velocity. The pulsar 21 incorporated in the ultrasonic flaw detector 20 excites the ultrasonic wave transmitter 3 including the reception sensor 3a and the shoe 3b to transmit the guide wave 11. A longitudinal wave leaking wave 12 leaks into the gas from the guided wave propagating in the steel pipe. The angle of refraction of this leaky wave is φ. The leak wave propagates to the steel material on the opposite side of the steel material pipe and is converted into the guide wave 13 to propagate in the steel material piping. Therefore, the ultrasonic wave receiving portion 5 in which the shoe 5b and the receiving sensor 5a are combined with the guide wave 13 is used. To receive. The signal of the receiving unit 5 is received by the receiver 22 incorporated in the ultrasonic flaw detector 20, the ultrasonic waveform is displayed on the display unit 23, and the analog signal is output to the PC 30. The A/D converter 31 incorporated in the PC 30 converts the analog output into a digital signal, performs arithmetic processing, and displays the result on the display 32.

Although only a part of the steel material pipe 1 is shown in FIG. 1, since the steel material pipe to be measured is long, it is necessary to select a place where the transmission/reception sensor is installed in the steel material pipe. Considering that the guide wave is propagated in the steel pipe in the present invention, it is desirable to select a place where the plate thickness of the steel pipe is constant, and a place where the plate thickness of the steel product is uneven due to internal corrosion is Not desirable. Therefore, prior to the measurement as shown in FIG. 1, first, as shown in FIG. 6, the variation of the plate thickness of the steel pipe is measured from the propagation time when the ultrasonic wave is vertically incident on the steel by the ultrasonic sensor 7. To do. As shown in FIG. 7(A), when the variation in the measurement results is small, the plate thickness of the steel pipe is uniform and the guided wave easily propagates, as shown in FIG. 7(B). In addition, when the measurement results have a large variation, as shown in FIG. 6B, the plate thickness of the steel pipe is not uniform and the guided wave is hard to propagate. As a place where the transmitting unit 3 and the receiving unit 5 are installed, a place where the variation in the plate thickness measurement result is small is selected.

Further, in the measurement of FIG. 1, it is assumed that the guide wave propagates in the steel pipe, so it is desirable to select a place where the guide wave can be transmitted and received and a place where the guide wave propagates at a constant speed. As shown in FIG. 8, the transmitter 3 and the receiver 5 are arranged on the same side of the pipe, and it is confirmed whether or not the ultrasonic waves can be stably received even when the distance between the transmitter 3 and the receiver 5 is changed. If the ultrasonic waves cannot be received with the arrangement as shown in FIG. 8 or the ultrasonic waves can be transmitted/received only at a specific transmission/reception distance, it is necessary to reexamine the specifications of the sensor and the shoe because the guided wave cannot be excited. There is.

FIG. 9 shows a graph of the relationship between the transmission/reception distance and the propagation time when ultrasonic waves can be stably received regardless of the transmission/reception distance. Since the inclination of the approximate straight line of the measurement point represents the sound velocity of the guide wave, the sound velocity of the guide wave propagating in the steel material can be measured by this method. Further, since the Y-intercept of the approximate straight line corresponds to the time delay in the measurement system (the ultrasonic wave propagation time of the shoes 3b, 5b, etc.), the time delay in the measurement system can be measured and evaluated by this method.

As shown in FIG. 9(A), when the variation of the measurement points with respect to the approximate straight line is small, as shown in FIG. 8(A), the plate thickness of the steel pipe is uniform and the guide wave is propagating at a constant velocity. As shown in FIG. 9B, when there is a large variation in measurement points with respect to the approximate straight line, the propagation velocity of the guided wave is not constant because the plate thickness of the steel pipe is uneven as shown in FIG. 8B. It is in a state. As a place where the transmitter 3 and the receiver 5 are installed, a place where the guided wave velocity is constant is selected.

A procedure for calculating the gas sound velocity when the sensor is installed at the selected location and ultrasonic measurement is performed with the configuration shown in FIG. 1 will be described. FIG. 10 is an example of a display screen of the display 32 of the PC 30. The received ultrasonic waveform 41 is displayed in the upper half of the screen. The lower half of the screen displays the input of the numerical values required to calculate the sound velocity of gas and the calculation result. The operator of the device uses a keyboard and a mouse (not shown) to project the sound velocity V _s of the guide wave propagating in the steel pipe on the frame 43 in a direction parallel to the traveling direction of the guide wave in the steel pipe. and the frame 44 a distance Lp of the receiving unit, when the propagation distance L _{v (example} 1 of the longitudinal wave leakage waves in the gas which is projected onto the guided wave traveling direction perpendicular to the direction in the steel pipe, L _v = Enter the inner diameter P _{in of the} pipe in the frame 45. When the delay time in the measurement system is input in the frame 46 and the ultrasonic peak propagated along the path assumed in FIG. 1 in the ultrasonic waveform 41 is designated by the cursor 42, the ultrasonic wave is transmitted by the transmission sensor and then the reception sensor The PC 30 calculates the propagation time Tall until the guided wave is received and displays it in the frame 47. From these numerical values, the PC 30 calculates the longitudinal wave sound velocity V _g propagating in the gas based on the equations (6) and (7), and displays it in the frame 48.

According to the present embodiment, even when ultrasonic waves propagating in a gas have to be transmitted and received via the steel material, it is possible to accurately calculate the sound velocity of the gas. Therefore, it is possible to accurately identify the type of internal gas before cutting the steel pipe.

Example 2 will be described with reference to FIGS. 11 and 12.

The second embodiment is an example in which the transmitting unit and the receiving unit are installed on the same surface of the pipe, and the sound velocity of gas in the pipe is measured and calculated. FIG. 11 shows an ultrasonic wave propagation path in this embodiment. A transmitter 3 including a receiving sensor 3a and a shoe 3b is installed on the outer surface of the steel pipe 1 to excite a guide wave 51 propagating in the steel pipe. A longitudinal wave leaking wave 52a leaks into the gas from the guide wave propagating in the steel material. The angle of refraction of this leaky wave is φ. The leakage wave is reflected by the inner surface of the steel material on the pipe-opposing side (52b), and when it propagates to the steel material on the transmitting/receiving side, it is converted into a guide wave 53 propagating in the steel material. It is received by the receiving unit 5 consisting of. As shown in the development view of FIG. 12, the route consisting of the transmission sensor, the guided wave propagating in the steel material, the longitudinal wave leaking in the gas, the guided wave propagating in the steel material, and the receiving sensor is L _v = The same as Example 1 except that it is 2×P _in . Therefore, even when the transmitting unit and the receiving unit are installed on the same surface of the steel pipe, it is possible to calculate the gas sound velocity based on the equations (6) and (7).

According to the present embodiment, in addition to the effects of the first embodiment, it is possible to calculate the gas sonic velocity even when the ultrasonic transmitter and the receiver are installed on the same surface of the steel pipe.

Example 3 will be described with reference to FIG.

The third embodiment is an example in which a transmitting unit and a receiving unit are installed on a flat surface of a steel container having a structure that can be used as an ultrasonic reflector inside, and the sound velocity of gas in the container is measured and calculated. FIG. 13 shows an ultrasonic wave propagation path in this embodiment. The transmitter 3 including the reception sensor 3a and the shoe 3b is installed on the flat surface of the steel container 61 to excite the guide wave 51 propagating in the steel material. A longitudinal wave leaking wave 52 a leaks into the gas 62 from the guided wave propagating in the steel material. The angle of refraction of this leaky wave is φ. The leakage wave is reflected by the structure 63 in the container (52b), and when it propagates to the flat portion of the container, it is converted into a guide wave 53 that propagates in the steel material. Therefore, the guide wave 53 is transmitted from the shoe 5b and the reception sensor 5a. It is received by the receiving unit 5. The route including the transmitting portion, the guided wave propagating in the steel material, the longitudinal wave leaking in the gas, the guided wave propagating in the steel material, and the receiving portion is the same as that of the second embodiment. If the distance L _gap from the inner wall of the flat surface of the container 61 in which the transmission/reception sensor is installed to the structure 63 is known in the design drawing or the like, Lv=2×L _gap , and based on the equations (6) and (7). Thus, it becomes possible to calculate the gas sound velocity.

According to the present embodiment, even when ultrasonic waves propagating in a gas have to be transmitted and received via the steel material, it is possible to accurately calculate the sound velocity of the gas. Therefore, it is possible to accurately identify the type of internal gas before cutting the steel container.

Each of the embodiments described above can be applied to measure and calculate the sound velocity of gas surrounded by steel materials of pipes and containers, and identify the type of gas before cutting the steel materials. Further, the present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail for the purpose of explaining the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of a certain embodiment. Further, with respect to a part of the configuration of each embodiment, other configurations can be added/deleted/replaced.

1: Steel pipe 2, 62: Gas 3a: Transmission sensor 3b: Shoe 3: Ultrasonic wave transmission unit 5a: Reception sensor 5b: Shoe 5: Ultrasonic wave reception unit 11, 13, 51, 53: Guide wave,
12, 52a, 52b: longitudinal wave leakage wave 20: ultrasonic flaw detector,
21: Pulsar 22: Receiver 23: Display 30: PC
31: A/D converter 32: Display 61: Container 63: Structure

Claims (8)

An ultrasonic wave is transmitted from the transmitting part to the steel material to excite the guided wave into the steel material, and part of the guided wave leaks into the gas and propagates as a longitudinal wave, which then reaches another location of the steel material. In the ultrasonic measurement method of generating a phenomenon in which the wave is converted into a guided wave propagating in the steel material again, and receiving the converted guided wave in the receiving unit,
Propagation time from the transmission of ultrasonic waves at the transmission unit to the reception of guided waves at the reception unit, the speed of sound of the guided waves propagating in the steel material, and the transmission projected in a direction parallel to the traveling direction of the guided waves in the steel material. It is possible to calculate the sound velocity of a longitudinal wave propagating in a gas by using the distance between the receiving part and the receiving part and the propagation distance of the longitudinal wave leaking wave in the gas projected in a direction perpendicular to the traveling direction of the guided wave in the steel material. A method of calculating the characteristic sound velocity of gas. The method of calculating the sound velocity of gas according to claim 1,
The propagation time from the transmission of the ultrasonic wave by the transmitting unit to the reception of the guide wave by the receiving unit is Tall, the sound velocity of the guide wave propagating in the steel material is V _s , and the direction of travel of the guide wave in the steel material is parallel. The distance between the transmitting part and the receiving part projected in any direction is L _p , the propagation distance of the longitudinal wave leakage wave in the gas projected in the direction perpendicular to the traveling direction of the guided wave in the steel material is L _v , the longitudinal direction in the gas When the angle of refraction of the leaking wave is φ,

A method of calculating the sound velocity of gas, characterized in that the sound velocity of longitudinal waves propagating in the gas is calculated using the following equation. The method for calculating a gas sound velocity according to claim 1,
In a plurality of candidates for the location of transmitting and receiving ultrasonic waves to the steel material, the variation in the plate thickness of the steel material is measured, and the location with the small variation in the plate thickness is selected as the location for transmitting and receiving the ultrasonic waves. Calculation method of gas sound velocity. The method for calculating a gas sound velocity according to claim 1,
In a plurality of candidates for the location of transmitting and receiving ultrasonic waves to the steel material, it is confirmed whether or not the guided wave propagating through the steel material can be measured, and in the location where the guided wave can be measured, the sound velocity of the guided wave and its variation are measured. A method of calculating the sound velocity of gas, characterized in that a place where the guided wave can be measured and the variation of the sound velocity of the guided wave is small is selected as a place for transmitting and receiving ultrasonic waves. A transmitter for exciting a guided wave in steel,
A receiver for receiving a guided wave propagating in the steel material,
Measuring means for measuring the distance between the transmitter and the receiver projected in a direction parallel to the guided wave traveling direction in the steel material,
A pulsar for exciting the transmitter,
A receiver for receiving the signal of the receiver,
Waveform display means for displaying the received waveform,
Propagation time from transmitting the ultrasonic wave at the transmitting unit to receiving the guide wave at the receiving unit, sound velocity of the guided wave propagating in the steel material, and transmission projected in a direction parallel to the traveling direction of the guided wave in the steel material Means for calculating the longitudinal sound velocity propagating in the gas when the distance between the receiving part and the receiving part and the propagation distance of the longitudinal wave leaking wave in the gas projected in the direction perpendicular to the traveling direction of the guided wave in the steel are input. ,
A device for calculating a sound velocity of gas, comprising: The gas sonic velocity calculation device according to claim 5,
The distance L _p between the transmitter and the receiver projected in a direction parallel to the guided wave traveling direction in the steel material, the propagation time Tall from the transmission of the ultrasonic wave by the transmitter to the reception of the guided wave by the receiver, and the steel material. The sound velocity V _{s of the} guided wave propagating through it, the distance L _p between the transmitter and the receiver projected in a direction parallel to the traveling direction of the guided wave in the steel, and the gas projected in a direction perpendicular to the traveling direction of the guided wave in the steel. Means for storing the propagation distance L _v of the longitudinal leaky wave and the mathematical expression,
Means for displaying the longitudinal wave velocity of sound propagating in the gas;
A device for calculating a sound velocity of gas, comprising: The gas sonic velocity calculation device according to claim 5,
A vertical ultrasonic sensor,
An ultrasonic flaw detector that gives a signal to the vertical ultrasonic sensor,
A means for calculating the plate thickness by measuring the propagation time of the ultrasonic wave,
A device for calculating a sound velocity of gas, comprising: The gas sound velocity calculation device according to claim 7,
Means for displaying the measurement result of the guided wave,
A device for calculating a sound velocity of gas, comprising:

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