JP7828218B2 - Gas shutoff device - Google Patents

Description

The present invention relates to a gas shutoff device that detects the presence or absence of a leak.

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 piping, 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 counted for a predetermined period (e.g., 30 days), determine that there is a leak and issue an alarm or shut off the equipment. Therefore, when determining whether there is a leak, it is necessary to accurately determine whether there is a flow rate or not.

In addition, with city gas, fluctuations in gas supply pressure and pressure fluctuations (hereinafter 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 factors such as temperature changes (rises and falls) during the day, can cause long-term gas flow (hereinafter 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, thereby determining whether or not there is a leak.

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 rates 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 was calculated is within a specified range (e.g., 50 L/h), and the accumulated 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 determination flow rate (e.g., 1.1 L/h), it is determined that there is no flow.

JP 2016-50906 A

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 rates used to calculate the section average flow rate may fall outside the specified range, or the difference between the maximum and minimum moving average flow rates 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.

The present invention was made to solve these problems, and aims to provide a gas shutoff device that can reduce erroneous leak detection.

The gas shutoff device of the present invention comprises a flow rate measurement unit connected to a gas supply pipe and measuring the instantaneous gas flow rate 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 values from 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 the period during which the integrated flow rate value of the first determination unit is less than the predetermined flow rate is equal to or greater than a predetermined period; a flow rate presence/absence determination unit that determines whether there is a flow rate based on the determination results of the first determination unit and the second determination unit; and a leak determination unit that determines whether there is a leak based on the determination result of the flow rate presence/absence determination unit. The flow rate presence/absence determination unit counts the number of times the second determination unit determines that the period during which the integrated flow rate value of the first determination unit is less than the predetermined flow rate is equal to or greater than the predetermined period, and determines that there is no flow rate if the count value is equal to or greater than a predetermined value, and determines that there is a flow rate otherwise.

As a result, even if no gas is actually being used, pressure fluctuations caused by pulsation can cause gas in the pipe to move upstream or downstream and return, resulting in positive or negative variations in the instantaneous flow rate measured by the flow rate measurement unit at specified time intervals. By converting the instantaneous flow rate (L/h) measured by the flow rate measurement 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 determine the actual volume of gas that has moved through the pipe, enabling a more accurate determination of no flow rate. Furthermore, because the presence or absence of a leak is determined based on the result of this no flow rate determination, it is possible to prevent false leak alarms or false shutoffs.

By using the gas shutoff device of the present invention, even if no gas is actually being used, pressure fluctuations caused by pulsation cause gas in the pipe to move upstream or downstream and then return, it is possible to determine the actual volume of gas that has moved through the pipe, making it possible to more accurately determine whether there is no flow. Furthermore, because the presence or absence of a leak is determined based on this no-flow determination result, it is possible to prevent false leak alarms or false shutoffs.

1 is a block diagram of a gas meter according to a first embodiment of the present invention. 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. FIG. 10 is a block diagram of a gas meter according to a second embodiment of the present invention. 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.

The first invention comprises a flow rate measurement unit connected to a gas supply pipe and measuring the instantaneous gas flow rate 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 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 determination unit that determines whether the period during which the integrated flow rate value of the first determination unit is less than the predetermined flow rate is equal to or longer than a predetermined period; a 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 leak determination unit that determines the presence or absence of a leak based on the determination result of the flow rate presence/absence determination unit. The flow rate presence/absence determination unit counts the number of times the second determination unit determines that the period during which the integrated flow rate value of the first determination unit is less than the predetermined flow rate is equal to or longer than the predetermined period, and determines that there is no flow rate if the count value is equal to or greater than a predetermined value, and determines that there is a flow rate otherwise.

As a result, even if there is no actual flow rate, pressure fluctuations caused by pulsation can cause gas in the pipe to move upstream or downstream and return, resulting in positive or negative variations in the instantaneous flow rate measured by the flow rate measurement unit at specified time intervals. By converting the instantaneous flow rate (L/h) measured by the flow rate measurement 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 determine the actual volume of gas that has moved through the pipe, making it possible to more accurately determine whether there is no flow rate. Furthermore, because the presence or absence of a leak is determined based on the result of this no-flow determination, it is possible to prevent false leak alarms or false shutoffs.

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

A third invention is the second invention, wherein the leak determination unit includes a determination method selection unit that switches the determination execution of the multiple flow rate determination units under predetermined conditions or sets them to perform processing in parallel.This allows the multiple flow rate determination units to switch under predetermined conditions or to be set to process in parallel, making it possible to select a determination method that suits the environment and situation on the market.

Embodiments will be described in detail below with reference to the drawings. However, some detailed descriptions may be omitted. For example, detailed descriptions of matters that are already well known or duplicate descriptions of substantially identical configurations may be omitted. This is to avoid making the following description unnecessarily redundant and to make it easier for those skilled in the art to understand.

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.

(Embodiment 1)
FIG. 1 shows a block diagram of a gas meter according to a first embodiment of the present invention.
1, a gas meter 1 is installed on a gas supply pipe a, and one or more gas appliances installed in each user's home are connected to the downstream pipe (not shown). The 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.

The flow rate measuring unit 2 is installed in the gas supply pipe a, and uses ultrasonic signals to determine the difference in propagation time 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 implement the flow rate measurement function.

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 accumulated value in the accumulation buffer is larger than a predetermined accumulation determination value.
The second judgment unit 5 judges whether the continuous time during which the integrated flow rate value in the integration buffer of the first judgment unit 4 was less than a predetermined integration judgment value is greater than a predetermined period (hereinafter referred to as the unit integration period).

The flow presence/absence determination unit 6 counts as one occurrence an instance where the integrated flow value in 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 greater than the unit integration period, and determines whether or not a flow is present by determining whether this count is greater than the predetermined number of times.

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

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 in response to the flow rate determination results from the flow rate determination unit 6 and the confirmation of a leak determination from the leak determination unit 7.

The external communication unit 9 notifies the outside world 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 settings of the flow rate judgment unit 6, as well as warnings and shutdown information when the leak judgment by the leak judgment unit 7 is confirmed.

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 description, the counts of the clock timer T1 and the leakage determination timer T2 refer to the counts of this measurement interval.

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).

Next, the first determination 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 determination value (e.g., 1.1 L) (step S4).

If the integrated flow rate value in the integration buffer is equal to or greater than the predetermined integration judgment value (Step S4: Yes), the integration buffer is cleared to zero (Step S41), and the timer T1 for the unit integration period is restarted (Step S42).

Next, if the integrated flow rate value of the integration buffer is less than the predetermined integration determination value (step S4: No), the second determination unit counts the unit integration period clock timer T1 (step S43) and determines whether the unit integration period clock timer T1 has elapsed (step S5).

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).

Next, if the first determination unit 4 determines that the integrated flow rate value of the integration buffer is less than the predetermined integration determination value (step S4: No) and the second determination unit determines that the unit integration period has elapsed (step S5: Yes), the flow rate determination unit 6 counts this as one occurrence (step S53), and compares this count value with a predetermined number of occurrences determination value (e.g., 2 times) to determine which is larger (step S6).

If the count value reaches the predetermined number of times judgment value (Step S6: Yes), it is determined that there is no flow, the count value is cleared to zero (Step S61), and the leak judgment timer T2 of the leak judgment unit 7 is restarted (Step S9).

Then, if the first determination unit 4 determines that the integrated flow rate value of the integration buffer is equal to or greater than the predetermined integration determination value (Step S4: Yes), i.e., if gas is clearly flowing and it is determined that there is a flow rate, or if the second determination unit 5 determines that the unit integration period is less than the unit integration period (Step S5: No), i.e., if the unit integration period has not been reached and it is not possible to determine whether there is a flow rate, or if the flow rate presence/absence determination unit 6 determines that the count value is less than the predetermined number of times determination value (Step S6: No), i.e., it is not possible to determine that there is no flow rate, the leak determination unit 7 counts the leak determination timer T2 (Step S62) and determines whether the leak determination timer T2 has counted a predetermined time (e.g., 30 days) (Step S7).

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

Note that 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.

As described above, in this first embodiment, even if there is no actual flow rate, pressure fluctuations caused by pulsation can cause gas in the pipe to move upstream or downstream and return, resulting in positive or negative variations in the instantaneous flow rate measured by the flow rate measurement unit at predetermined time intervals. However, by converting the instantaneous flow rate (L/h) measured by the flow rate measurement 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 determine the actual volume of gas that has moved through the pipe, enabling a more accurate determination of no flow rate. Furthermore, 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.

(Embodiment 2)
FIG. 3 shows a block diagram of a gas meter according to a 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.

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 in a manner 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 .

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 the first flow rate presence/absence determination unit 10 and the second flow rate presence/absence determination unit 11 should be used in parallel for processing, based on predetermined conditions set externally by the external communication unit 9.

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 rate 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 corresponding flow rate determining 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 stores the section average flow rate determined to be less than the threshold value.

Next, the first determination means determines whether the section average flow rate held by the corresponding flow rate determination means is within a first predetermined range, the second determination means determines 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 determined by the first determination means to be within the first predetermined range and by the second determination means to be within the second predetermined range are accumulated, and the flow rate presence/absence determination means calculates an accumulated average flow rate from the accumulated section average flow rates when M section average flow rates have been accumulated, and determines that there is no flow if this accumulated average flow rate is less than the average determination flow rate, and determines that there is a flow if it is equal to or greater than the average determination flow rate.

Figure 4 is a schematic flowchart of the flow rate presence/absence determination performed by gas meter 1 in embodiment 2. Below, the flow rate presence/absence determination operation performed by gas meter 1 will be explained using Figures 3 and 4.

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

Next, the presence or absence of flow rate determined by the processing of the first flow rate determination unit is determined (step S12). 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 determination unit 11 (step S14).

When processing by the second flow rate presence/absence determination unit 11 is performed (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 determines that there is no flow rate (step S16: Yes), restarts the leak determination timer T2 of the leak determination unit 7 (step S17).

Then, the leak determination unit 7 determines whether the leak determination timer has elapsed (step S18), and if a predetermined time (e.g., 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 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 determination unit 11; and if the answers are YES in both step S10 and step S14, the presence or absence of a flow rate is determined using both the first flow rate determination unit 10 and the second flow rate determination unit 11.

As described above, in this second embodiment, two flow rate determination units, the first flow rate determination unit 10 and the second flow rate determination unit 11, are provided. These two flow rate determination methods are switched under specified conditions or processed in parallel. If either one determines that there is no flow, the leak determination timer T2 of the leak determination unit 7 is restarted. If both the first flow rate determination unit 10 and the second flow rate determination unit 11 determine that there is a flow, the leak determination timer T2 of the leak determination unit 7 continues counting. When the leak determination timer T2 reaches a specified time, leaks can be detected more accurately, preventing false leak alarms and shutoffs. Furthermore, because the determination methods can be switched or set in parallel, the market can select a determination method that suits the environment and situation.

For example, in environments where pulsation is likely to occur, large variations in instantaneous flow rate occur, and the difference between the maximum and minimum instantaneous flow rate is likely to fall outside the specified range when processed by the second flow rate presence/absence determination unit 11, which may result in a false determination that there is flow rather than a determination that there is no flow. 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 and integrate the variations in positive and negative instantaneous flow rate into flow rate values. By integrating, it becomes possible to offset the positive and negative variations, making it possible to more accurately determine that there is no flow rate and prevent false leak alarms or false shutoffs.

Furthermore, in respiratory phenomena where gas flow occurs over a long period of time, processing by the second flow rate determination unit 11, which can monitor a stable flow rate for a long period of time, is more effective. Therefore, by selecting the second flow rate determination unit 11, it is possible to more accurately determine whether or not a flow rate is present.

Furthermore, when the first flow rate determination unit 10 and the second flow rate determination unit 11 are run 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.

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, other flow rate presence/absence determination units that use different determination methods from these two may also be added, and the determination method selection unit 12 may be configured to select or combine these multiple flow rate presence/absence determination units.

As described above, the gas shutoff device of the present invention can detect leaks even in environments where pulsation or breathing is occurring. Therefore, the scope of the present invention is not limited to this, but can also be applied to methods for detecting leaks of other flammable gases, non-flammable gases, etc., as well as water and gas leaks.

REFERENCE SIGNS LIST 1 Gas meter 2 Flow rate measurement unit 3 Flow rate calculation unit 4 First determination unit 5 Second determination unit 6 Flow rate presence/absence determination unit 7 Leak determination unit 8 Control unit 9 External communication unit 10 First flow rate presence/absence determination unit 11 Second flow rate presence/absence determination unit 12 Determination method selection unit

Claims (2)

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 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. 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 at least one of the first flow rate presence/absence determination unit and the second flow rate presence/absence determination unit determines that there is no flow rate.
The gas shutoff device according to claim 1 .