Gas shutoff device

Abstract

To provide a gas cutoff device capable of preventing erroneous determination as a leakage due to fluctuations in instantaneous flow rate due to pulsation or breathing phenomena.SOLUTION: The gas cutoff device is configured so as to accumulate at predetermined intervals the flow rate values calculated by a flow rate calculation unit 3 from the instantaneous flow rate measured by a flow rate measurement unit 2, and a flow rate existence / absence determination section 6 determines whether the flow rate exists / absent based on the result of a first determination unit 4 that determines whether the integrated flow rate value is equal to or higher than a predetermined flow rate and the result of a second determining unit 5, which determines whether the continuous time in which the integrated flow rate value of the first determining unit 4 is less than the predetermined flow rate is longer than the unit integration period.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a gas shutoff device that detects the presence or absence of leakage. [Background technology]

[0002] Conventionally, gas shutoff devices have the function of detecting gas leaks and issuing an alarm or shutting off the gas. The typical operation of leak detection is to, for example, monitor the flow rate in the gas pipe, determine whether there is a gas flow rate according to predetermined conditions, clear a leak determination timer when it determines that there is no flow rate, and count the leak determination timer when it determines that there is a flow rate, and when the leak determination timer has reached a predetermined period (e.g., 30 days), determine that there is a leak and issue an alarm or shut off the system. Therefore, when determining whether there is a leak, it is necessary to accurately determine whether there is a flow rate or not.

[0003] Furthermore, with city gas, fluctuations in gas supply pressure and pressure fluctuations (hereafter referred to as pulsation) caused by the use of gas appliances such as gas engines, heat pumps and air conditioners, as well as pressure fluctuations in gas pipes due to temperature changes (rises and falls) during the day, can cause long-term gas flow (hereafter referred to as breathing). Therefore, studies are being conducted to determine whether or not there is a flow rate that takes these factors into account, and to determine whether or not there is a leak.

[0004] For example, in Patent Document 1, a moving average flow rate within a specified interval (e.g., 20 minutes) is calculated from the interval average flow rate (e.g., average flow rate over a 2-minute period), and if the difference between the maximum and minimum moving average flow rate within the specified interval is within a specified range (e.g., 0.5 L / h), the interval average flow rate is within a specified range (e.g., ±11 L / h), the difference between the maximum and minimum instantaneous flow rates from which the interval average flow rate is calculated is within a specified range (e.g., 50 L / h), and the cumulative average flow rate obtained by accumulating and averaging M interval average flow rates (e.g., 30) included in the moving average flow rate is less than an average judgment flow rate (e.g., 1.1 L / h), it is determined that there is no flow. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-50906 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Document 1, even if there is no gas leak in the gas piping and the gas is not being used, if large variations occur due to fluctuations in instantaneous flow rate caused by pulsation, the difference between the maximum and minimum instantaneous flow rate used to calculate the section average flow rate may fall outside the specified range, or the difference between the maximum moving average flow rate and the minimum moving average flow rate may fall outside the specified range.If either of these falls outside the specified range, the condition for determining that there is no flow rate cannot be met, and it will be erroneously determined that there is flow rate, which could result in a false leak alarm or erroneous leakage shutdown.

[0007] The present invention has been made to solve such problems, and has an object to provide a gas shutoff device that can suppress erroneous determinations in leakage detection. [Means for solving the problem]

[0008] The gas shutoff device of the present invention comprises a flow rate measuring unit that is connected to a gas supply pipe and measures the instantaneous flow rate of a gas flow at predetermined intervals; a flow rate calculation unit that calculates a flow rate value from the instantaneous flow rate measured by the flow rate measuring unit; a first judgment unit that integrates the flow rate values ​​of the flow rate calculation unit at predetermined intervals and determines whether the integrated flow rate value is equal to or greater than a predetermined flow rate; a second judgment unit that determines whether a period during which the integrated flow rate value of the first judgment unit is less than the predetermined flow rate is equal to or greater than a predetermined period; a flow rate presence / absence judgment unit that determines whether a flow rate is present based on the judgment results of the first judgment unit and the second judgment unit; and a leak judgment unit that determines whether a leak is present based on the judgment result of the flow rate presence / absence judgment unit, wherein the flow rate presence / absence judgment unit counts the number of times that the second judgment unit has determined that the period during which the integrated flow rate value of the first judgment unit is less than the predetermined flow rate is equal to or greater than the predetermined period, and judges that there is no flow rate if the count value is equal to or greater than a predetermined value, and judges that there is a flow rate otherwise.

[0009] As a result, even if no gas is actually being used, pressure fluctuations caused by pulsation cause gas in the piping to move upstream or downstream and return, resulting in positive or negative variations in the instantaneous flow rate measured by the flow rate measuring unit at predetermined time intervals.However, by converting the instantaneous flow rate (L / h) measured by the flow rate measuring unit into a flow rate value (L) in the flow rate calculation unit and integrating this flow rate value in the integration buffer in the first determination unit, it becomes possible to grasp the volume of gas that has actually moved through the piping and more accurately determine that there is no flow rate.The presence or absence of a leak is then determined based on the result of this no flow rate determination, making it possible to prevent false leak alarms or false shutoffs. [Effects of the Invention]

[0010] By using the gas shutoff device of the present invention, even if gas in the pipe moves upstream or downstream and then returns due to pressure fluctuations caused by pulsation despite the fact that no gas is actually being used, it is possible to grasp the volume of gas that has actually moved in the pipe, and it is possible to more accurately determine that there is no flow rate.Furthermore, since the presence or absence of a leak is determined based on the result of the determination that there is no flow rate, it is possible to prevent false alarms or false shutoffs of leaks. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram of a gas meter according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a diagram showing an operation procedure for determining whether or not there is a flow rate in the first embodiment of the present invention. [Figure 3] FIG. 10 is a block diagram of a gas meter according to a second embodiment of the present invention. [Figure 4] FIG. 10 is a diagram showing an operation procedure for determining whether or not there is a flow rate in the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The first invention comprises a flow rate measuring unit that is connected to a gas supply pipe and measures the instantaneous flow rate of gas at predetermined intervals; a flow rate calculation unit that calculates a flow rate value from the instantaneous flow rate measured by the flow rate measuring unit; a first judgment unit that integrates the flow rate values ​​of the flow rate calculation unit at predetermined intervals and determines whether the integrated flow rate value is an abnormality at a predetermined flow rate; a second judgment unit that determines whether the period during which the integrated flow rate value of the first judgment unit is less than the predetermined flow rate is equal to or longer than a predetermined period; a flow rate presence / absence judgment unit that determines whether there is a flow rate based on the judgment results of the first judgment unit and the second judgment unit; and a leak judgment unit that determines whether there is a leak based on the judgment result of the flow rate presence / absence judgment unit, wherein the flow rate presence / absence judgment unit counts the number of times the second judgment unit has determined that the period during which the integrated flow rate value of the first judgment unit is less than the predetermined flow rate is equal to or longer than the predetermined period, and judges that there is no flow rate if the count value is equal to or greater than a predetermined value, and judges that there is a flow rate otherwise.

[0013] As a result, even if there is no actual flow rate, pressure fluctuations due to pulsation cause gas in the piping to move upstream or downstream and return, resulting in positive or negative variations in the instantaneous flow rate measured by the flow rate measuring unit at predetermined time intervals.By converting the instantaneous flow rate (L / h) measured by the flow rate measuring unit into a flow rate value (L) in the flow rate calculation unit and integrating this flow rate value in the integration buffer in the first determination unit, it becomes possible to grasp the volume of gas that has actually moved in the piping and more accurately determine that there is no flow rate.And, because the presence or absence of a leak is determined based on the result of this no flow rate determination, it becomes possible to prevent false leak alarms or false shutoffs.

[0014] The second invention is the first invention, which has, separate from the flow rate presence / absence determination unit, at least one flow rate presence / absence determination unit that determines the presence or absence of a flow rate using a determination method different from that of the flow rate presence / absence determination unit, and the leak determination unit determines the presence or absence of a leak using one or more determination results determined by the multiple flow rate presence / absence determination units, and by making a determination using the determination results of the multiple flow rate presence / absence determination units, the leak determination can be optimized according to the installation situation.

[0015] The third invention is the second invention, wherein the leakage determination unit is provided with a determination method selection unit that switches the execution of determination by the multiple flow rate determination units under predetermined conditions or sets the units to perform the determination in parallel. This makes it possible to switch the multiple flow rate determination units under predetermined conditions or set them to process in parallel, making it possible to select a determination method that suits the environment and situation on the market.

[0016] Hereinafter, embodiments will be described in detail with reference to the drawings. However, some detailed descriptions may be omitted. For example, detailed descriptions of well-known matters or redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art.

[0017] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0018] (Embodiment 1) FIG. 1 shows a block diagram of a gas meter according to a first embodiment of the present invention. 1, gas meter 1 is installed on gas supply pipe a, and one or more gas appliances installed in each user's home are connected to the downstream piping (not shown). Gas meter 1 is also composed of a flow rate measurement unit 2, a flow rate calculation unit 3, a first determination unit 4, a second determination unit 5, a flow rate presence / absence determination unit 6, a leak determination unit 7, a control unit 8, and an external communication unit 9.

[0019] The flow rate measuring unit 2 is installed in the gas supply pipe a, and uses ultrasonic signals to determine the propagation time difference caused by the gas flow rate in the gas supply pipe a, thereby detecting the instantaneous gas flow rate. The flow rate calculation unit 3 calculates the gas flow rate based on the instantaneous flow rate detected at regular time intervals by the flow rate measurement unit 2. The flow rate measurement unit 2 and the flow rate calculation unit 3 realize the flow rate measurement function.

[0020] The first determination unit 4 accumulates the flow rate value calculated by the flow rate calculation unit 3 in an accumulation buffer, and determines whether the accumulation buffer is larger or smaller than a predetermined accumulation determination value. The second determination unit 5 determines whether the continuous time during which the integrated flow rate value in the integration buffer of the first determination unit 4 was less than a predetermined integration determination value is larger than a predetermined period (hereinafter referred to as a unit integration period).

[0021] The flow presence / absence determination unit 6 counts as one occurrence when the integrated flow rate value of the integration buffer of the second determination unit 5 is less than a predetermined integration determination value and the continuous time is equal to or longer than the unit integration period, and determines whether the count is greater than or equal to the predetermined number of times to determine whether a flow rate is present or absent.

[0022] The leakage determination unit 7 restarts the leakage determination timer (not shown) when the flow rate presence / absence determination unit 6 determines that there is no flow rate, and when the flow rate presence determination unit 6 determines that there is a flow rate, it times the duration, and confirms the leakage determination when it determines that there is a flow rate for a predetermined period of time.

[0023] The control unit 8 controls the operation of each part within the gas meter 1, as well as performs safety processing such as issuing warnings and shutting off gas based on the flow rate determination result by the flow rate determination unit 6 and the confirmation of the leak determination by the leak determination unit 7.

[0024] The external communication unit 9 not only changes the setting of the predetermined cumulative judgment value of the first judgment unit 4, the unit cumulative period of the second judgment unit 5, and the predetermined number of times of the flow rate presence / absence judgment unit 6, but also notifies the outside world of warnings and shutdown information when the leak judgment by the leak judgment unit 7 is confirmed.

[0025] 2 is a schematic flowchart of the flow rate presence / absence determination performed by the gas meter 1 in embodiment 1. The flow rate presence / absence determination operation performed by the gas meter 1 will be described below with reference to FIGS. 1 and 2, the measurement interval of the instantaneous flow rate of the flow rate measurement unit 2 is, for example, 2 seconds. In the following explanation, the counts of the clock timer T1 and the leakage determination timer T2 refer to the counts of this measurement interval.

[0026] First, the flow rate measuring unit 2 measures the instantaneous flow rate of gas flowing through the gas supply pipe a (step S1). Next, the flow rate calculation unit 3 calculates a flow rate value from the instantaneous flow rate measured by the flow rate measurement unit 2 (step S2).

[0027] Next, the first judgment unit 4 has an accumulation buffer (not shown) for accumulating flow rate values ​​over a predetermined unit accumulation period (e.g., 60 minutes), accumulates the flow rate values ​​from the flow rate calculation unit 3 in the accumulation buffer (step S3), and determines whether the accumulated value in the accumulation buffer is larger or smaller than a predetermined accumulation judgment value (e.g., 1.1 L) (step S4).

[0028] When the integrated flow rate value of the integration buffer becomes equal to or greater than the predetermined integration judgment value (step S4: Yes), the integration buffer is cleared to zero (step S41), and the clock timer T1 for the unit integration period is restarted (step S42).

[0029] Next, if the accumulated flow rate value of the accumulation buffer is less than the predetermined accumulation judgment value (step S4: No), the second judgment unit counts the clock timer T1 for the unit accumulation period (step S43) and judges whether the clock timer T1 for the unit accumulation period has elapsed the unit accumulation period (step S5).

[0030] If the unit integration period count timer T1 has elapsed (step S5: Yes), the integration buffer is cleared to zero (step S51), and the unit integration period count timer T1 is restarted (step S52).

[0031] Next, if the first judgment unit 4 judges that the accumulated flow rate value of the accumulation buffer is less than the predetermined accumulation judgment value (step S4: No) and the second judgment unit judges that the unit accumulation period has elapsed (step S5: Yes), the flow rate presence / absence judgment unit 6 counts this as one occurrence (step S53), and compares this count value with a predetermined number of times judgment value (e.g., 2 times) to determine which is larger (step S6).

[0032] If the count value reaches the predetermined number of times judgment value (step S6: Yes), it is judged that there is no flow rate, the count value is cleared to zero (step S61), and the leakage judgment timer T2 of the leakage judgment unit 7 is restarted (step S9).

[0033] Then, if the first judgment unit 4 judges that the accumulated flow rate value of the accumulation buffer is equal to or greater than the predetermined accumulation judgment value (step S4: Yes), i.e., if gas is clearly flowing and it is judged that there is a flow rate, or if the second judgment unit 5 judges that it is less than the unit accumulation period (step S5: No), i.e., if the unit accumulation period has not been reached and it is not possible to judge whether there is a flow rate or not, or if the flow rate presence / absence judgment unit 6 judges that the count value is less than a predetermined number of times judgment value (step S6: No), i.e., it is not possible to judge that there is no flow rate, the leak judgment unit 7 counts the leak judgment timer T2 (step S62) and judges whether the leak judgment timer T2 has elapsed a predetermined time (e.g., 30 days) (step S7).

[0034] The leak determination timer T2 is a timer that measures the period during which it cannot be determined that there is clearly no flow, and when the leak determination timer T2 has elapsed a predetermined time (step S7: Yes), that is, when the flow presence / absence determining unit 6 has not been able to determine that there is no flow for a predetermined time, it confirms the determination that there is a leak (step S8). If the predetermined period has not elapsed (step S7: No), the process returns to flow measurement (step S1).

[0035] Here, the unit integration period of the first judgment unit 4 and the predetermined number of times of the second judgment unit 5 may be set to optimal values, or may be set externally via the external communication unit 9.

[0036] As described above, in this first embodiment, even if there is no actual flow rate, pressure fluctuations due to pulsation cause gas in the piping to move upstream or downstream and return, resulting in positive or negative variations in the instantaneous flow rate measured by the flow rate measuring unit at predetermined time intervals.However, by converting the instantaneous flow rate (L / h) measured by the flow rate measuring unit into a flow rate value (L) in the flow rate calculation unit and integrating this flow rate value in the integration buffer in the first determination unit, it becomes possible to grasp the volume of gas that actually moved in the piping and more accurately determine that there is no flow rate.The presence or absence of a leak is then determined based on the result of this no flow rate determination, making it possible to prevent false leak alarms or false shutoffs.

[0037] (Embodiment 2) FIG. 3 shows a block diagram of a gas meter according to the second embodiment of the present invention. 3, the gas meter 1 includes a first flow rate presence / absence determining unit 10, a second flow rate presence / absence determining unit 11, and a determination method selecting unit 12 in addition to the components shown in FIG.

[0038] In addition, the first flow rate presence / absence determination unit 10 is composed of a first determination unit 4, a second determination unit 5, and a flow rate presence / absence determination unit 6, and performs the operations described in Figures 1 and 2 of embodiment 1. On the other hand, the second flow rate presence / absence determination unit 11 determines the presence or absence of a flow rate using a method different from that of the first flow rate presence / absence determination unit 10, and is composed of, for example, an interval calculation means, a moving average flow rate calculation means, a flow rate determination means, a first determination means, a second determination means, and a flow rate presence / absence determination means (none of which are shown), as described in Patent Document 1. Both the first flow rate presence / absence determining unit 10 and the second flow rate presence / absence determining unit 11 are configured to transmit the determination result of the presence / absence of a flow rate to the leakage determining unit 7.

[0039] The determination method selection unit 12 switches between the first flow rate presence / absence determination unit 10 and the second flow rate presence / absence determination unit 11 to use for processing, or sets whether to use the first flow rate presence / absence determination unit 10 and the second flow rate presence / absence determination unit 11 in parallel for processing, based on predetermined conditions set from outside by the external communication unit 9.

[0040] The second flow rate presence / absence determining unit 11 of this embodiment will be described below with reference to FIG. In Figure 3, the second flow presence / absence determination unit 11 first accumulates the instantaneous flow rates measured by the flow rate measurement unit 2 for a first predetermined interval using the interval calculation means to calculate the interval average flow rate, and then uses the moving average flow rate calculation means to calculate a moving average from N consecutive interval average flow rates and hold it for a second predetermined interval. Next, the relevant flow rate determination means determines whether the difference between the maximum and minimum values ​​of the moving average flow rate in the second predetermined section is less than a threshold value, and holds the section average flow rate determined to be less than the threshold value.

[0041] Next, a first judgment means judges whether the section average flow rate held in the corresponding flow rate judgment means is within a first predetermined range, a second judgment means judges whether the difference between the maximum and minimum instantaneous flow rates obtained as flow rate values ​​used to calculate the section average flow rate is within a second predetermined range, the section average flow rates judged to be within the first predetermined range by the first judgment means and to be within the second predetermined range by the second judgment means are accumulated, and when M section average flow rates have been accumulated, the flow rate presence / absence judgment means calculates an accumulated average flow rate from the accumulated section average flow rates, and if this accumulated average flow rate is less than the average judgment flow rate, it is judged that there is no flow rate, and if it is equal to or greater than the average judgment flow rate, it is judged that there is a flow rate.

[0042] 4 is a schematic flowchart of flow rate presence / absence determination performed by the gas meter 1 in embodiment 2. The flow rate presence / absence determination operation performed by the gas meter 1 will be described below with reference to FIGS.

[0043] First, based on predetermined conditions set externally by the external communication unit 9, the judgment method selection unit 12 judges whether or not to perform processing by the first flow rate presence / absence judgment unit 10 (step S10), and if processing by the first flow rate presence / absence judgment unit 10 is to be performed (step S10: Yes), the first flow rate presence / absence judgment unit 10 judges whether or not the first flow rate is present (step S11).

[0044] Next, the result of the processing of the first flow rate presence / absence determination unit is determined (step S12), and if it is determined that there is no flow rate (step S12: Yes), the leak determination timer T2 of the leak determination unit 7 is restarted (step S13), and the determination method selection unit 12 determines whether or not to perform processing of the second flow rate presence / absence determination unit 11 (step S14).

[0045] When processing the second flow rate presence / absence determination unit 11 (step S14: Yes), the second flow rate presence / absence determination unit 11 determines whether or not there is a second flow rate (step S15), determines whether or not there is a flow rate (step S16), and if it is determined that there is no flow rate (step S16: Yes), restarts the leakage determination timer T2 of the leakage determination unit 7 (step S17).

[0046] Then, it is determined whether the leakage determination timer of the leakage determination unit 7 has elapsed (step S18), and if a predetermined time (for example, 30 days) has elapsed, the determination that there is a leak is confirmed (step S19). Note that if the answer is YES in step S10 and NO in step S14, the presence or absence of a flow rate is determined only by the first flow rate presence or absence determination unit 10, if the answer is NO in step S10 and YES in step S14, the presence or absence of a flow rate is determined only by the second flow rate presence or absence determination unit 11, and if the answer is YES in both step S10 and step S14, the presence or absence of a flow rate is determined using both the first flow rate presence or absence determination unit 10 and the second flow rate presence or absence determination unit 11.

[0047] As described above, in the second embodiment, two flow rate presence / absence determination units are provided, the first flow rate presence / absence determination unit 10 and the second flow rate presence / absence determination unit 11, and these two flow rate presence / absence determination methods are switched under predetermined conditions or processed in parallel, and if either one determines that there is no flow rate, the leak determination timer T2 of the leak determination unit 7 is restarted, and as a result of both the first flow rate presence / absence determination unit 10 and the second flow rate presence / absence determination unit 11 determining that there is a flow rate, the leak determination timer T2 of the leak determination unit 7 continues counting, and when the predetermined time has elapsed on the leak determination timer T2, leaks can be detected more accurately and false alarms and shutoffs can be prevented. Furthermore, since the determination methods can be switched or set in parallel, it is possible to select a determination method suited to the environment and situation on the market.

[0048] For example, in an environment where pulsation is likely to occur, large variations in instantaneous flow rate occur, and therefore the difference between the maximum and minimum instantaneous flow rate is likely to fall outside the specified range in the processing of the second flow rate presence / absence determination unit 11, which may result in a false determination that there is a flow rate rather than a determination that there is no flow rate.Therefore, by setting the determination method selection unit 12 to process the first flow rate presence / absence determination unit 10, it becomes possible to convert the variations in positive and negative instantaneous flow rates into flow rate values ​​and accumulate them, and by accumulating them, it becomes possible to cancel out the positive and negative variations, making it possible to more accurately determine that there is no flow rate and prevent false alarms or false shutoffs of leaks.

[0049] Furthermore, in respiratory phenomena where gas flow occurs over a long period of time, processing by the second flow rate presence / absence determination unit 11, which can monitor a stable flow rate for a long period of time, is more advantageous, and therefore, by selecting the second flow rate presence / absence determination unit 11, it is possible to more accurately determine whether or not a flow rate is present.

[0050] Furthermore, when the first flow rate presence / absence determination unit 10 and the second flow rate presence / absence determination unit 11 are executed in parallel, even if one of them erroneously determines that there is a flow rate, the other will determine that there is no flow rate, restarting the leak determination timer and enabling more accurate leak detection and preventing false leak alarms and shutoffs.

[0051] In this embodiment, two flow rate presence / absence determination units, the first flow rate presence / absence determination unit 10 and the second flow rate presence / absence determination unit 11, have been described. However, it is also possible to add another flow rate presence / absence determination unit that uses a different determination method from these two, and configure the determination method selection unit 12 to select or combine these multiple flow rate presence / absence determination units. [Industrial Applicability]

[0052] As described above, the gas shutoff device of the present invention can determine leakage even in an environment where pulsation or breathing occurs, and therefore the subject matter of the present invention is not limited to this, but also includes other flammable gases, non-flammable gases, etc., and can also be applied to methods for detecting water or gas leaks. [Explanation of symbols]

[0053] 1 Gas meter 2 Flow measurement section 3 Flow rate calculation section 4 First Judgment Department 5 Second judgment section 6 Flow rate determination section 7 Leakage detection section 8 Control Unit 9. External Communications Department 10 First flow rate determination section 11 Second flow rate determination section 12 Judgment method selection section

Claims

1. a flow rate measuring unit connected to the gas supply pipe and configured to measure an instantaneous flow rate of the gas at predetermined intervals; a flow rate calculation unit that calculates a flow rate value from the instantaneous flow rate measured by the flow rate measurement unit; a first determination unit that integrates the flow rate value of the flow rate calculation unit at predetermined intervals and determines whether the integrated flow rate value is equal to or greater than a predetermined flow rate; a second determination unit that determines whether a period during which the integrated flow rate value of the first determination unit is less than a predetermined flow rate continues for a predetermined period or longer; a flow rate presence / absence determination unit including a first flow rate presence / absence determination unit that determines the presence or absence of a flow rate based on the determination results of the first determination unit and the second determination unit, and a second flow rate presence / absence determination unit that determines the presence or absence of a flow rate using a determination method different from that used by the first flow rate presence / absence determination unit; a leakage determination unit that determines whether or not there is a leakage based on the determination result of the flow rate determination unit; Equipped with the first flow rate presence / absence determination unit counts the number of times that the second determination unit determines that the time during which the integrated flow rate value of the first determination unit is less than the predetermined flow rate continues is equal to or longer than the predetermined period, and determines that there is no flow rate when the count value is equal to or greater than a predetermined value; The leakage determination unit a determination method selection unit that selects one of use of the first flow rate presence / absence determination unit, use of the second flow rate presence / absence determination unit, and use of both the first flow rate presence / absence determination unit and the second flow rate presence / absence determination unit, a gas shutoff device characterized in that, when the flow rate presence / absence determination unit set to be used by the determination method selection unit does not determine that there is no flow rate, a leak determination timer is counted, and when the count value of the leak determination timer has passed a predetermined time that is longer than the predetermined period, it is determined that there is a leak.

2. When the determination method selection unit is set to use both the first flow rate presence / absence determination unit and the second flow rate presence / absence determination unit, the leakage determination unit restarts the leakage determination timer when it is determined that there is no flow rate in at least one of the first flow rate presence / absence determination unit and the second flow rate presence / absence determination unit. The gas shutoff device according to claim 1 .

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