JP7195099B2 - Gas meter and its control method - Google Patents

Description

The present invention provides a flow rate measurement unit that measures the flow rate of gas flowing through an internal gas flow passage, a temperature measurement unit that measures the temperature of the gas flowing through the gas flow passage, and the gas flow passage. The present invention relates to a gas meter including a pressure measuring unit that measures the pressure in a gas meter, and a control unit that performs control based on the measurement results of the flow rate measuring unit, the temperature measuring unit, and the pressure measuring unit, and a control method thereof.

Conventionally, in the process of installing a gas meter, the presence or absence of gas leakage downstream (indoor) from the gas meter is determined by the leakage determination method disclosed in Patent Document 1 in order to check for gas leakage downstream of the gas meter. . In the leakage determination method, after closing the outdoor gas valve provided at the upstream entrance of the gas meter in the gas flow path, a digital gas sensor having a function such as a pressure gauge is connected to the downstream side of the gas flow path from the gas meter. By connecting a manometer and measuring the pressure change over time in the downstream channel downstream of the gas meter, the presence or absence of gas leakage in the downstream channel is confirmed.

JP 2012-220474 A

In the technique described in Patent Document 1, in the leakage determination, a digital manometer is connected to the connection portion of the downstream flow path, and after the leakage determination is completed, the digital manometer is connected to the connection portion of the downstream flow path. must be removed from In the leakage determination, the airtightness of the connecting portion of the downstream flow path after removing the digital manometer could not be guaranteed, and there was room for improvement.
Furthermore, in the leakage determination method described in Patent Document 1, when performing leakage determination, it is necessary to dispatch an inspector to the site and make determination using a device such as a digital manometer, and a gas meter is installed. There is also the problem that it is necessary to enter the premises, the number of work processes involved in the judgment increases, and the personnel costs associated with the dispatch of inspectors increase. For this reason, for example, there is a situation in which it is difficult to perform periodical leakage determination, etc., and there is room for improvement.

The present invention has been made in view of the above-mentioned problems, and its object is to determine the presence or absence of gas leakage in the downstream flow path while obtaining high economic benefits and simplifying the process of leak determination. The object of the present invention is to provide a gas meter and a method of controlling the gas meter, which can increase the accuracy of .

A gas meter for achieving the above object comprises a flow rate measurement unit for measuring the flow rate of gas flowing through an internal gas flow passage, and a temperature measurement unit for measuring the temperature of the gas flowing through the gas flow passage. , a gas meter comprising: a pressure measuring section for measuring the pressure in the gas flow path; and a control section for performing control based on the measurement results of the flow rate measuring section, the temperature measuring section, and the pressure measuring section. The characteristic configuration is that the control unit is
When the gas flow rate in the gas flow path measured by the flow rate measurement section is less than a predetermined minimum flow rate, the flow rate measurement section measures the gas supply pressure in the pressure measurement section. and blocking the gas passage on the upstream side of the temperature measurement unit and the pressure measurement unit,
When the pressure measured by the pressure measuring unit during a predetermined first predetermined period falls below the pressure drop determination width, there is no gas leakage in the downstream flow path on the downstream side of the blocked portion. It is determined that there is no gas leakage, and gas leakage occurs in the downstream flow path when the pressure measured by the pressure measurement unit during the first predetermined period decreases by a pressure drop determination width or more. While executing the first leakage determination to determine that the state is
Even if it is determined that the gas is leaking in the first leakage determination, if the temperature measured by the temperature measuring unit decreases during the first leakage determination, the first leakage determination executing a second leakage determination for changing the determination from the gas leakage state to the gas non-leakage state when it is determined that the pressure drop is caused by the temperature drop;
When the gas flow rate in the gas flow path measured by the flow rate measuring section is zero, the control section
and blocking the gas flow path on the upstream side of the flow rate measurement section, the temperature measurement section, and the pressure measurement section, and in the blocked state, the flow rate of the downstream side flow path measured by the pressure measurement section. From the first state in which the pressure is atmospheric pressure to the second state in which the pressure measured by the pressure measurement unit becomes the gas supply pressure after releasing the blockage of the gas flow path, the flow rate measurement unit performing channel volume estimation for estimating the channel volume of the downstream channel from the measured integrated flow rate;
Pressure drop determination width adjustment is performed to adjust the pressure drop determination width in the first leakage determination to a smaller value as the flow channel volume of the downstream flow channel estimated in the flow channel volume estimation is larger.
,
The control unit executes the flow path volume estimation when the gas meter is installed,
When the pressure drop determination width adjustment is performed after the flow path volume estimation, the flow path volume estimated at the time of installation is corrected based on the temperature measured by the temperature measurement unit. The point is that pressure drop determination width correction adjustment is performed to adjust the pressure drop determination width based on the flow passage volume .

A method of controlling a gas meter to achieve the above object includes a flow rate measurement unit for measuring the flow rate of gas flowing through an internal gas flow passage, and a temperature sensor for measuring the temperature of the gas flowing through the gas flow passage. A control method for a gas meter comprising a measuring section and a pressure measuring section for measuring pressure in the gas passage, characterized by:
When the gas flow rate in the gas flow path measured by the flow rate measurement section is less than a predetermined minimum flow rate, the flow rate measurement section measures the gas supply pressure in the pressure measurement section. and blocking the gas passage on the upstream side of the temperature measurement unit and the pressure measurement unit,
When the pressure measured by the pressure measuring unit during a predetermined first predetermined period falls below the pressure drop determination width, there is no gas leakage in the downstream flow path on the downstream side of the blocked portion. It is determined that there is no gas leakage, and gas leakage occurs in the downstream flow path when the pressure measured by the pressure measurement unit during the first predetermined period decreases by a pressure drop determination width or more. While performing a first leakage determination step of determining that the state is
Even if it is determined in the first leakage determining step that the gas is leaking, the temperature measured by the temperature measuring unit decreases, and the pressure decrease is the pressure decrease accompanying the temperature decrease. when it is determined that there is a gas leak, executing a second leak determination step of changing the determination from the gas leak state to the gas non-leak state;
When the gas flow rate in the gas flow path measured by the flow rate measurement section is zero, the gas flow path is cut off upstream of the flow rate measurement section, the temperature measurement section, and the pressure measurement section. Then, from the first state in which the pressure in the downstream channel measured by the pressure measuring unit in the blocked state is atmospheric pressure, the blocking of the gas flow channel is released, and the pressure measuring unit performing a channel volume estimation process for estimating the channel volume of the downstream channel from the integrated flow rate measured by the flow rate measuring unit until a second state in which the measured pressure becomes the gas supply pressure;
Perform pressure drop determination width adjustment processing for adjusting the pressure drop determination width in the first leakage determination to a smaller value as the flow passage volume of the downstream flow passage estimated in the flow passage volume estimation processing increases. ,
executing the flow path volume estimation process when the gas meter is installed;
When the pressure drop determination width adjustment process is executed after the flow path volume estimation process, the flow path volume estimated at the time of installation is corrected based on the temperature measured by the temperature measurement unit. The pressure drop determination width correction adjustment process is executed to adjust the pressure drop determination width based on the corrected flow path volume .

According to the above characteristic configuration, since the temperature measurement unit for use in determining gas leakage is provided inside the gas meter, it is not necessary to remove the temperature measurement unit after the first leakage determination is completed. The first leak determination can be completed while maintaining the airtightness of the flow path.
Furthermore, in the present invention, even when it is determined that there is a gas leak in the first leakage determination, when the temperature measured by the temperature measuring unit decreases, the pressure decrease causes the temperature to decrease. When it is determined that there is a pressure drop due to a gas leak, the second leak determination is executed to change the determination from the gas leak state to the gas non-leak state, so even the pressure change due to the gas temperature in the downstream flow path is taken into consideration. The presence or absence of gas leakage can be determined according to the state. As a result, when the pressure drop is accompanied by a temperature drop, it is not judged as a gas leak. Therefore, the gas leak can be judged while eliminating the pressure drop caused by the temperature drop. high gas leakage can be determined. As for the second leak determination, it is not necessary to remove the temperature measurement unit or the like in the downstream flow path after the determination, so the second leak can be detected while maintaining the airtightness in the downstream flow path. Judgment can be completed.
Furthermore, according to the above characteristic configuration, by incorporating a program for periodically performing the first leakage determination and the second leakage determination into the control unit of the gas meter, the first leakage determination can be performed without dispatching an inspector or the like to the site.
Since the leakage judgment and the second leakage judgment can be executed, economic merits can be enjoyed.
As described above, a gas meter and a control method thereof are realized that can increase the accuracy of determining whether or not there is a gas leak in the downstream gas flow path while simplifying the leak determination process while obtaining economic benefits. can.
As in the above characteristic configuration, by estimating the flow channel volume of the downstream flow channel in the flow channel volume estimation, the downstream
It is possible to know the size of the channel volume of the downstream gas channel of the side channel.
Then, according to the above characteristic configuration, when the flow passage volume is large, the pressure drop determination width is small.
Even in this case, the flow rate of the gas leaking to the outside is large, so
By adjusting the pressure stiffening determination width in the first leakage determination to a smaller value as the volume increases,
It is possible to prevent the flow rate of gas leaking to the outside from becoming too large,
1. Safety can be improved by leak determination.
In order to estimate the flow path volume, shut off the shutoff valve of the gas meter to stop the gas supply to the customer.
need to According to the above characteristic configuration, the estimation of the passage volume can be performed when the meter is installed.
Therefore, there is no need to close the shutoff valve of the gas meter each time the pressure drop judgment range is adjusted.
It is possible to improve the convenience of gas use at the customer's site.
Moreover, the setting of the pressure drop determination width is based on the flow passage volume estimated at the time of meter installation.
Therefore, the value corrected by the current gas temperature is used, so the downstream flow path at the time of measurement
The pressure drop judgment range can be adjusted by reflecting the state of the surrounding environment.

A further characteristic configuration of the gas meter is
In the second leakage determination, the control unit determines that the ratio of the amount of decrease in pressure from the start point to the end point with respect to the pressure measured by the pressure measurement unit at the start point of the first predetermined period is , the ratio of the amount of temperature decrease from the start point to the end point with respect to the temperature measured by the temperature measuring unit at the start point, the pressure drop is a pressure drop accompanying the temperature drop. It is at the point where it is determined that there is.

According to the above characteristic configuration, for example, when the ratio of the amount of pressure drop is greater than the ratio of the amount of temperature drop, the temperature drops and the accompanying pressure drop occurs, but the gas leaks. It is determined that the gas is leaking because the pressure drop is also occurring.
That is, according to the above characteristic configuration, only when the pressure drop in the downstream channel is due to a change in state due to a decrease in the temperature of the gas in the downstream channel, the gas leakage is determined in the second leakage determination. It is possible to shift from the state to the gas non-leakage state, and improve the accuracy of determination of the leak state.

By estimating the channel volume of the downstream channel by channel volume estimation as in the above characteristic configuration, it is possible to know the size of the channel volume of the downstream gas channel of the downstream channel.
According to the above characteristic configuration, when the flow channel volume is large, even if the pressure drop determination width is small, the flow rate of the gas leaking to the outside is large, so the estimated flow channel volume By adjusting the pressure hardening determination width in the first leak determination to a smaller value as is larger, it is possible to prevent the flow rate of gas leaking to the outside from becoming too large, and the first leak determination corresponding to the situation of each site It can improve safety.

In order to estimate the flow path volume, it is necessary to shut off the shutoff valve of the gas meter to stop the gas supply to the customer. According to the above characteristic configuration, the estimation of the flow passage volume can be performed when the meter is installed, so there is no need to close the shutoff valve of the gas meter each time the pressure drop determination width is adjusted, and the gas flow can be performed at the customer's site. The convenience of use can be improved.
Moreover, the setting of the pressure drop determination width is based on the flow path volume estimated when the meter is installed, and the value corrected by the current gas temperature is used, so the surrounding environment of the flow path on the downstream side at the time of measurement is also taken into consideration. The pressure drop determination width can be adjusted by reflecting the result.

A further characteristic configuration of the gas meter is
A shutoff valve for shutting off the gas flow path is provided, and the flow rate measurement unit, the temperature measurement unit, and the pressure measurement unit are provided downstream of the shutoff valve in the gas flow path,
The control unit executes the first leakage determination and the second leakage determination in a state in which the gas passage is blocked by the shutoff valve.

According to the above characteristic configuration, the shutoff valve provided inside the gas meter can shut off the upstream end of the downstream flow path, so that the external monitoring center issues a command to the gas meter to perform the first leakage judgment and the second leakage judgment. When the gas meter itself shuts off the shut-off valve, the environment for making the first leak determination and the second leak determination can be set favorably.
As a result, the first leakage determination and the second leakage determination can be performed without the need for a worker to go to the site, the personnel cost can be reduced, and the economic efficiency can be improved.

The gas meters described so far have
Communication capable of receiving an instruction to execute the first leakage determination and the second leakage determination from an external monitoring center, and capable of transmitting determination results of the first leakage determination and the second leakage determination to the monitoring center. is preferably provided.

1 is a schematic configuration diagram of a gas meter according to an embodiment; FIG. It is a flow chart showing a control method of a gas meter concerning an embodiment.

The gas meter 100 and the control method thereof according to the embodiment of the present invention provide high economic benefits, simplify the leak determination process, and increase the accuracy of determination of the presence or absence of gas leakage in the downstream flow path. Regarding what can be raised. The gas meter 100 and its control method will be described below with reference to the drawings.

The gas meter 100 is configured as an ultrasonic flowmeter, and measures the flow rate of gas supplied from a gas pipe to a gas supply location (not shown) such as a residence.
As shown in the partial cross-sectional view of FIG. 1, the gas meter 100 has a gas inlet 11 that communicates with the primary gas pipe and a gas outlet 12 that communicates with the secondary gas pipe. , a gas flow path L is formed to connect the gas inlet 11 and the gas outlet 12 .
A cylindrical member 20 forming a rectifying flow path is disposed in the gas flow path L, and a plurality of rectifying plates 21 extending along the axis of the cylinder are provided inside the cylindrical member 20. there is
Although not shown in detail, the gas meter 100 is provided with a pair of transducers SJ1 and SJ2 for propagating ultrasonic waves to a rectifying flow path formed inside the tubular member 20 .
More specifically, the ultrasonic wave is propagated in a first direction along the flow direction of the gas flowing through the gas passage L and in a second direction opposite to the first direction. a pair of transducers SJ1 and SJ2 for receiving ultrasonic waves that have propagated a predetermined propagation distance in a first direction and ultrasonic waves that have propagated a predetermined propagation distance in a second direction; A first propagation time for the ultrasonic wave to propagate a propagation distance and a second propagation time for the ultrasonic wave to propagate a predetermined propagation distance in the second direction are measured, and the measured first propagation time and the second propagation time and the predetermined propagation a control device C that derives the gas flow rate of the gas flowing through the gas flow path from the distance, and derives the gas flow rate from the gas flow rate and the cross-sectional area of the gas flow path L (rectifying flow path); These function as a flow rate measurement part.
The control device C is mounted as a control board in a central space K formed in the center of the inside of the gas meter 100, and is provided in a state in which a software group and a hardware group such as an arithmetic unit and a storage unit cooperate with each other. there is In the control device C, in the gas meter 100, a control unit C1 that performs gas flow rate calculations, etc., and a communication unit that transmits various signals from the control unit C1 to the monitoring center CS outside the gas meter 100 via a wireless network line N or the like. Functional sites such as C2 are provided. The monitoring center CS is configured to be able to transmit and receive various types of information to and from a plurality of gas meters 100 (M1 to M5) via the communication section CS1.
Further, although not shown, the gas meter 100 is provided with a display section that displays the gas flow rate calculated by the control section C1 in a visible state from the outside.

A shutoff valve 30 is provided on the upstream side of the rectifying flow path formed by the cylindrical member 20 to shut off the gas flow path L from the viewpoint of safety when the gas pressure on the upstream side of the gas meter 100 drops significantly. The shutoff valve 30 is configured such that the valve element 31 is seated on a valve seat portion 32 protruding into the gas flow path L, and closes the opening/closing portion LK of the gas flow path L, thereby The flow path L is closed.

The straightening channel as the gas flow channel L is formed with an opening LR in a direction substantially orthogonal to the channel axis, and is also provided with a communication space SK in a state of communicating with the inside of the straightening channel. . The communication space SK is formed inside the gas meter 100 at a position outside the rectifying flow path so that the flow in the rectifying flow path is not obstructed. Inside the communication space SK, a temperature sensor S1 (an example of a temperature measuring unit) for measuring the temperature of the gas flowing through the gas flow path L and a pressure sensor S2 for measuring the pressure of the gas in the gas flow path L are provided. (an example of a pressure measuring unit) is provided, and the temperature and pressure measured by the temperature sensor S1 and the pressure sensor S2 are received by the control unit C1 of the control device C. FIG.

Now, the control unit C1 is designed to simplify the process of determining leakage, while increasing the accuracy of determining the presence or absence of gas leakage in the downstream flow path La downstream of the shutoff valve 30 in the gas flow path L. , performs the following controls:
The control unit C1 sets the gas flow rate of the gas flow path L measured by the ultrasonic flow meter to a predetermined minimum flow rate (for example, a flow rate of 20 L/h or more and 40 L/h or less, and a flow rate that can be variably set. ), the pressure sensor S2 measures the gas supply pressure (for example, the supply pressure 1.0 to 2.5 kPa described in the supply agreement), and the ultrasonic flowmeter transmits and receives ultrasonic waves The gas flow path L is blocked by the shutoff valve 30 on the upstream side of the wave devices SJ1 and SJ2, the temperature sensor S1, and the pressure sensor S2, and the gas flow rate in the gas flow path L measured by the ultrasonic flow meter is In the state of less than the minimum flow rate, the pressure measured by the pressure sensor S2 in a predetermined first predetermined period (for example, 2 minutes) is a pressure drop determination width (for example, a pressure value less than the gas supply pressure). If the decrease is less than the settable pressure range), it is determined that there is no gas leakage in the downstream flow path La, and the pressure measured by the pressure sensor S2 in the first predetermined period is A first leakage determination is performed to determine that there is a gas leakage in the downstream flow path La when the pressure drops to the pressure drop determination width or more, and it is determined that there is a gas leakage in the first leakage determination. Even in such a case, when the temperature measured by the temperature sensor S1 is lowered and it is determined that the pressure drop is due to the temperature drop, the gas leak state is determined to be the gas non-leak state. is performed to change the second leak determination.
According to this control, the presence or absence of gas leakage can be determined without connecting or removing other equipment such as a digital manometer to or from the connecting portion (not shown) of the downstream flow path La. , the risk of gas leakage from the connecting portion of the downstream flow path La can be eliminated.
Note that the first predetermined period can be set separately for each installation location (each flow channel volume) based on the flow channel volume estimated in the flow channel volume estimation process described later.

More detailed gas leakage control will be described with reference to the control flow in FIG.
In order to appropriately execute the first leakage determination process in accordance with the flow channel volume of the downstream flow channel La, the control unit C1 executes flow channel volume estimation processing for estimating the flow channel volume of the downstream flow channel La ( #01).
The flow path volume estimation process is performed, for example, when the gas meter 100 is attached and the downstream side of the gas meter 100 is near atmospheric pressure. When the gas flow rate of L is zero, the shutoff valve 30 shuts off the gas communication path L, and in the shutoff state, the pressure of the downstream side flow path La measured by the pressure sensor S2 is the atmospheric pressure. The flow rate measured by the ultrasonic flowmeter from state 1 to state 2 in which the shutoff of the gas flow path L by the shutoff valve 30 is released and the pressure measured by the pressure sensor S2 becomes the gas supply pressure. Flow path volume estimation is performed to estimate the flow path volume of the downstream side flow path La from the integrated value of .
The control unit C1 adjusts the pressure drop determination width in the first leakage determination to a smaller value as the flow path volume of the downstream flow path La estimated in the flow path volume estimation increases ( #02). As a result, when the volume of the downstream flow path La is larger than usual and there is leakage, the amount of gas leakage is prevented from becoming too large, thereby improving safety.
The estimated flow path volume and pressure drop determination width are stored in a storage unit (not shown) of the control device C, and used in the following control after the gas meter 100 is installed.

The control unit C1 determines whether or not the flow rate measured by the ultrasonic flowmeter is less than a predetermined minimum flow rate in order to confirm that gas is not used in each house where the gas meter 100 is installed. (#03). If the flow rate is not less than the minimum flow rate, the process of determining whether the flow rate is less than the minimum flow rate is repeated at predetermined time intervals (#04).
When the controller C1 determines that the flow rate is less than the minimum flow rate, it shuts off the shutoff valve 30 while the gas supply pressure is being measured by the pressure sensor S2 (#05).
The control unit C1 controls the gas non-leakage state in which there is no gas leakage in the downstream flow path La when the pressure measured by the pressure sensor S2 during a predetermined first predetermined period of time falls below the pressure drop determination width. In addition, when the pressure measured by the pressure sensor S2 in the first predetermined period falls below the pressure drop determination width set corresponding to the flow channel volume in #02 above, the downstream side A first leakage determination is performed to determine that there is a gas leakage in the flow path La (#06).
However, in the first leakage determination, if the temperature drops during the first leakage determination and the pressure drops along with the temperature drop, the gas leakage state is determined even though the gas is not leaking. There is a possibility that it will be determined that it is.

Therefore, even if it is determined that there is a gas leak in the first leakage determination, the control unit C1 can prevent the first leakage when the temperature measured by the temperature sensor S1 decreases during the first leakage determination. When it is determined that the pressure drop is due to the temperature drop, a second leak determination is executed to change the determination from the gas leak state to the gas non-leak state (#07).
In addition to explaining the second leakage determination, the control unit C1 controls the pressure measured by the pressure sensor S2 at the start of the first predetermined period from the start to the end of the second leak determination. is the ratio of the amount of temperature decrease from the start point to the end point with respect to the temperature measured by the temperature sensor S1 at the start point, the pressure drop is the pressure accompanying the temperature drop Decrease is determined.
By executing the above control #07, for example, when the ratio of the amount of pressure drop is larger than the ratio of the amount of temperature drop, the temperature drops and the pressure drops accordingly. It is determined that there is a gas leak because the pressure drop is also occurring due to the gas leak. Therefore, only when the pressure drop in the downstream flow path La is due to a change in state accompanying a change in the temperature of the gas in the downstream flow path La, in the second leakage determination, the gas leakage state changes from the gas non-leak state. state, and the accuracy of determining the leak state can be improved.

When it is determined that gas is leaking, the control unit C1 flashes the leak lamp R provided in the gas meter 100, and sends a signal to the monitoring center CS via the communication unit C2 to notify that the gas is leaking. A leakage notification process for transmission is executed (#08).

[Another embodiment]
(1) In the above embodiment, the adjustment of the pressure drop determination width, the first leakage determination, and the second leakage determination are performed in a state in which the gas flow path L is shut off by the shutoff valve 30 provided in the gas meter 100. Indicated.
However, the pressure drop determination width adjustment, the first leakage determination, and the second leakage determination are configured to be realized by an on-off valve (not shown) that opens and closes the gas flow path L on the upstream side of the gas meter 100. I don't mind.

(2) In the above-described embodiment, the gas meter 100 is an ultrasonic meter.

(3) In the above embodiment, the temperature sensor S1 may be configured as a relative humidity sensor that measures relative humidity. In this case, the controller C1 executes various controls based on the temperature measured by the relative humidity sensor.
Note that the measurement by the relative humidity sensor is started after the gas meter 100 is restored and the flow rate is equal to or greater than a predetermined flow rate.

(4) In the above embodiment, the flow path volume estimation process and the pressure drop width adjustment process may not be executed.

(5) The channel volume estimated by the channel volume estimation in the above embodiment may be configured to be corrected based on the temperature of the gas meter 100 at the timing of executing the first leakage determination. The correction is performed based on the relationship of the state equation.
Then, the pressure drop determination width adjustment of #02 is replaced with pressure drop determination width correction adjustment for adjusting the pressure drop determination width based on the corrected flow passage volume.

It should be noted that the configurations disclosed in the above embodiments (including other embodiments, the same shall apply hereinafter) can be applied in combination with configurations disclosed in other embodiments as long as there is no contradiction. The embodiments disclosed in this specification are exemplifications, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the object of the present invention.

INDUSTRIAL APPLICABILITY The gas meter and the control method thereof according to the present invention can provide high economic benefits, simplify the leak determination process, and increase the accuracy of determining whether or not there is a gas leak in the downstream flow path. It can be effectively used as a gas meter and its control method.

30: Shutoff valve 100: Gas meter C: Control device C1: Control unit C2: Communication unit CS: Monitoring center L: Gas communication channel La: Downstream channel S1: Temperature sensor S2: Pressure sensor SJ1: Transducer SJ2: transducer

Claims (5)

A flow rate measurement unit for measuring the flow rate of the gas flowing through the internal gas flow passage, a temperature measurement unit for measuring the temperature of the gas flowing through the gas flow passage, and measuring the pressure in the gas flow passage. A gas meter comprising: a pressure measuring unit for measuring; and a control unit for performing control based on the measurement results of the flow rate measuring unit, the temperature measuring unit, and the pressure measuring unit,
The control unit
When the gas flow rate in the gas flow path measured by the flow rate measurement section is less than a predetermined minimum flow rate, the flow rate measurement section measures the gas supply pressure in the pressure measurement section. and blocking the gas passage on the upstream side of the temperature measurement unit and the pressure measurement unit,
When the pressure measured by the pressure measuring unit during a predetermined first predetermined period falls below the pressure drop determination width, there is no gas leakage in the downstream flow path on the downstream side of the blocked portion. It is determined that there is no gas leakage, and gas leakage occurs in the downstream flow path when the pressure measured by the pressure measurement unit during the first predetermined period decreases by a pressure drop determination width or more. While executing the first leakage determination to determine that the state is
Even if it is determined that the gas is leaking in the first leakage determination, if the temperature measured by the temperature measuring unit decreases during the first leakage determination, the first leakage determination executing a second leakage determination for changing the determination from the gas leakage state to the gas non-leakage state when it is determined that the pressure drop is caused by the temperature drop;
When the gas flow rate in the gas flow path measured by the flow rate measuring section is zero, the control section
and blocking the gas flow path on the upstream side of the flow rate measurement section, the temperature measurement section, and the pressure measurement section, and in the blocked state, the flow rate of the downstream side flow path measured by the pressure measurement section. From the first state in which the pressure is atmospheric pressure to the second state in which the pressure measured by the pressure measurement unit becomes the gas supply pressure after releasing the blockage of the gas flow path, the flow rate measurement unit performing channel volume estimation for estimating the channel volume of the downstream channel from the measured integrated flow rate;
Pressure drop determination width adjustment is performed to adjust the pressure drop determination width in the first leakage determination to a smaller value as the flow channel volume of the downstream flow channel estimated in the flow channel volume estimation is larger.
,
The control unit executes the flow path volume estimation when the gas meter is installed,
When the pressure drop determination width adjustment is performed after the flow path volume estimation, the flow path volume estimated at the time of installation is corrected based on the temperature measured by the temperature measurement unit. A gas meter that performs pressure drop determination width correction adjustment for adjusting the pressure drop determination width based on a flow passage volume . In the second leakage determination, the control unit determines that the ratio of the amount of decrease in pressure from the start point to the end point with respect to the pressure measured by the pressure measurement unit at the start point of the first predetermined period is , the ratio of the amount of temperature decrease from the start point to the end point with respect to the temperature measured by the temperature measuring unit at the start point, the pressure drop is the pressure drop accompanying the temperature drop. The gas meter according to claim 1, wherein the gas meter determines that A shutoff valve for shutting off the gas flow path is provided, and the flow rate measurement unit, the temperature measurement unit, and the pressure measurement unit are provided downstream of the shutoff valve in the gas flow path,
The gas meter according to claim 1 or 2 , wherein the control unit executes the first leakage determination and the second leakage determination in a state in which the shutoff valve shuts off the gas passage. Communication capable of receiving an instruction to execute the first leakage determination and the second leakage determination from an external monitoring center, and capable of transmitting determination results of the first leakage determination and the second leakage determination to the monitoring center. The gas meter according to any one of claims 1 to 3 , further comprising a portion. A flow rate measurement unit for measuring the flow rate of the gas flowing through the internal gas flow passage, a temperature measurement unit for measuring the temperature of the gas flowing through the gas flow passage, and measuring the pressure in the gas flow passage. A control method for a gas meter comprising a pressure measuring unit for measuring,
When the gas flow rate in the gas flow path measured by the flow rate measurement section is less than a predetermined minimum flow rate, the flow rate measurement section measures the gas supply pressure in the pressure measurement section. and blocking the gas passage on the upstream side of the temperature measurement unit and the pressure measurement unit,
When the pressure measured by the pressure measuring unit during a predetermined first predetermined period falls below the pressure drop determination width, there is no gas leakage in the downstream flow path on the downstream side of the blocked portion. It is determined that there is no gas leakage, and gas leakage occurs in the downstream flow path when the pressure measured by the pressure measurement unit during the first predetermined period decreases by a pressure drop determination width or more. While performing a first leakage determination step of determining that the state is
Even if it is determined in the first leakage determining step that the gas is leaking, the temperature measured by the temperature measuring unit decreases, and the pressure decrease is the pressure decrease accompanying the temperature decrease. when it is determined that there is a gas leak, executing a second leak determination step of changing the determination from the gas leak state to the gas non-leak state;
When the gas flow rate in the gas flow path measured by the flow rate measurement section is zero, the gas flow path is cut off upstream of the flow rate measurement section, the temperature measurement section, and the pressure measurement section. Then, from the first state in which the pressure in the downstream channel measured by the pressure measuring unit in the blocked state is atmospheric pressure, the blocking of the gas flow channel is released, and the pressure measuring unit performing a channel volume estimation process for estimating the channel volume of the downstream channel from the integrated flow rate measured by the flow rate measuring unit until a second state in which the measured pressure becomes the gas supply pressure;
Perform pressure drop determination width adjustment processing for adjusting the pressure drop determination width in the first leakage determination to a smaller value as the flow passage volume of the downstream flow passage estimated in the flow passage volume estimation processing increases. ,
executing the flow path volume estimation process when the gas meter is installed;
When the pressure drop determination width adjustment process is executed after the flow path volume estimation process, the flow path volume estimated at the time of installation is corrected based on the temperature measured by the temperature measurement unit. A method for controlling a gas meter, comprising: performing pressure drop determination width correction adjustment processing for adjusting the pressure drop determination width based on the corrected flow passage volume .

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