JP4250095B2 - Return safety confirmation method and gas meter - Google Patents

Description

  The present invention relates to a return safety confirmation method after gas shutoff and a gas meter that implements the return safety confirmation method.

  In recent years, in addition to the function of measuring the passing flow rate that passes through the gas flow rate, the gas meter has exceeded a predetermined total flow rate value (preset by summing the consumption flow rates of the connected combustors). If the combustor is used continuously for a predetermined period or longer, it detects a flow rate abnormality such as gas leakage in the gas flow path or forgetting to turn off the combustor, and closes the gas shut-off valve to An increasing number have a safety shut-off function that shuts off the gas supply through the road.

  Now, when opening the gas shut-off valve closed by the safety shut-off function and returning it, open the gas shut-off valve once and confirm safety for gas leakage, only when it is safe It is necessary to return the gas shut-off valve. Therefore, it is stipulated by law that the gas shut-off valve is returned only when the passage flow rate is less than 21 L / h.

  By the way, the membrane type gas meter using the movement of the diaphragm outputs one pulse every 0.35 L, for example, and when one pulse is output per minute, the passage flow becomes 21 L / h. Therefore, in the case of this membrane gas meter, at least one minute is required to confirm the return safety because of its performance.

  On the other hand, since the gas meter provided with the flow rate sensors such as the ultrasonic type and the thermal type disclosed in Patent Literature 1 and Patent Literature 2 can measure the instantaneous gas flow velocity in the gas flow path, In other words, safety confirmation can be performed based on a single flow rate measured immediately after the return operation. However, although there are such merits, the conditions under which the environment in the gas flow path immediately stabilizes immediately after the return operation is performed and the gas cutoff valve is opened are limited.

  For example, if the gas shutoff valve is closed by the safety shutoff function and the gas supply from the upstream side of the gas shutoff valve is shut off, the combustor consumes the gas in the gas flow path between the gas shutoff valve and the combustor. Therefore, the pressure in the gas flow path is almost equal to the atmospheric pressure. After that, if the gas shut-off valve is closed at the timing when the return operation is performed, gas is supplied to the gas flow path between the gas shut-off valve and the combustor filled with the atmosphere. Even without forgetting to turn it off, a gas having a certain flow rate flows immediately after the return operation, and then the flow rate is stabilized.

  For this reason, as described above, based on the single flow rate measured immediately after the return operation, if the safety is confirmed, it is erroneously determined to be abnormal although it is safe, and the gas shut-off valve cannot be returned. There is a risk of this happening. Therefore, it is conceivable that the safety check is not performed immediately after the return operation, and the safety check is performed after a certain time has elapsed until the gas flow rate is stabilized.

However, the time until the flow rate in the gas flow path after the return operation is stabilized varies depending on the volume on the downstream side of the gas cutoff valve, as shown in FIG. For this reason, as described above, simply waiting for a certain period of time makes it possible to confirm safety despite the fact that the flow rate is not stable, or does not confirm safety despite the fact that the flow rate is stable. As a result, there was a problem that not only the safe return check could not be performed accurately but also the gas shut-off valve could not be returned quickly.
Japanese Patent Publication No.7-119638 Japanese Patent Publication No. 6-43906

  Therefore, the present invention pays attention to the above-mentioned problems and provides a safety return confirmation method capable of quickly returning the gas shut-off valve while accurately confirming safety and a gas meter implementing the safety return confirmation method. The issue is to provide.

The invention according to claim 1, which has been made in order to solve the above problems, includes a flow rate measuring unit that intermittently measures the flow rate of the gas in the gas flow path, and a flow rate measuring unit that obtains the gas flow rate based on the measured flow rate. A gas shut-off valve that shuts off gas supply through the gas flow path, an abnormality detection means that detects a flow rate abnormality by monitoring a gas flow rate measured by the flow rate measurement means, and the detection according to the detection of the flow rate abnormality A safety check method by the safety check means of the gas meter, comprising: a shut-off means for closing the gas shut-off valve; and a safety check means for confirming safety when the gas shut-off valve closed by the return operation is closed. a is, the safety check means, and valve opening of the gas shut-off valve in response to the return operation, the safety check means is smaller than a first predetermined value by the flow rate measuring means after the return operation When the scan rate is determined continuously first predetermined time or more, the gas shut-off valve to terminate the return safety checks while the valve opening, the safety check means, the return operation the first predetermined time wherein when the gas flow rate determined by the flow rate measuring means or larger than the second predetermined value said first predetermined value after waiting for the elapse of the longer second predetermined time, the return safety to the gas shut-off valve to the closed valve The present invention resides in a return safety confirmation method characterized by terminating confirmation.

According to the first aspect of the present invention, when the safety confirmation means continuously obtains the gas flow rate smaller than the first predetermined value by the flow rate measurement means after the return operation for the first predetermined time or more, the gas cutoff valve is turned on. The return safety check is terminated with the valve open. Safety check means, when the return operation gas flow rate obtained by the flow rate measuring means after waiting for the elapse of a long second predetermined time than the first predetermined time is equal to or more than the second predetermined value larger than the first predetermined value, the gas shut-off Close the valve and complete the return safety check.

  Therefore, by waiting for the gas flow rate to stabilize after the second predetermined time has elapsed since the return operation, a state in which the gas flow rate is not stable is not erroneously determined as an abnormal flow rate and blocked. Moreover, by setting the second predetermined value to a value larger than the first predetermined value, even if the gas flow rate is not stable after the second predetermined time has elapsed, this state is erroneously determined as a flow rate abnormality. Without blocking, leakage exceeding the second predetermined value can be accurately blocked. In addition, by making the first predetermined time shorter than the second predetermined time, if the flow rate of the first predetermined value or less continues to flow after the return operation, there is no need to wait for the second predetermined time to elapse. The return safety check can be completed while the gas shut-off valve is opened.

The invention according to claim 2 is the return safety confirmation method according to claim 1, wherein the safety confirmation means averages the gas flow rate obtained a plurality of times by the flow rate measurement means after the second predetermined time has elapsed since the return operation. Is equal to or greater than the second predetermined value, the gas flow rate obtained by the flow rate measuring means is greater than or equal to the second predetermined value , the gas shut-off valve is closed, and the return safety check is terminated. It exists in the return safety confirmation method.

According to the invention of claim 2, wherein, when the average gas flow rate was determined several times by the flow rate measuring means is equal to or more than the second predetermined value, as the gas flow rate determined by the flow rate measuring means is equal to or more than the second predetermined value, the gas Close the shut-off valve and finish the return safety check. Therefore , even if the gas flow rate is not stable even after the second predetermined time has elapsed and the gas flow rate equal to or higher than the second predetermined value flows for a moment, the gas flow rate is not interrupted.

The invention according to claim 3 is the return safety confirmation method according to claim 1 or 2, wherein the safety confirmation means performs the first predetermined by the flow rate measurement means after the second predetermined time has elapsed since the return operation. When the gas flow rate smaller than the value is not continuously determined for the first predetermined time or more and the gas flow rate smaller than the second predetermined value is continuously determined by the flow rate measuring means for the third predetermined time, the flow rate is determined. if multiple average of the obtained gas flow rate is less than or equal to the first predetermined value by the measuring means, the gas shut-off valve to end the Shitama or pre Symbol return safety check in the valve opening, is larger than the first predetermined value It lies in the return safety confirmation method characterized by terminating the confirmation before Symbol return safe closed valve pre SL gas shut-off valve.

According to the invention of claim 3, the safety confirmation means cannot continuously obtain a gas flow rate smaller than the first predetermined value by the flow rate measurement means after the second predetermined time has elapsed since the return operation, for a first predetermined time or more , In addition, if the gas flow rate smaller than the second predetermined value is continuously determined for the third predetermined time by the flow rate measuring unit and the average of the gas flow rates obtained several times by the flow rate measuring unit is equal to or less than the first predetermined value, the gas the shut-off valve to end the Shitama or return safety check in valve opening, the end to the return safety confirmation closed greater if the valve of the gas shut-off valve than the first predetermined value

  Therefore, after the return operation, if the gas flow rate continues to be unstable even after the second predetermined time and further the third predetermined time, the gas flow rate is not stabilized by checking the safety based on the average gas flow rate. Thus, the return safety check will not end indefinitely, and the state where the flow rate is not stable will not be erroneously determined as a flow rate abnormality and blocked.

The invention according to claim 4 is the return safety confirmation method according to claim 3, wherein the safety confirmation means obtains the gas obtained by the flow rate measurement means until the second predetermined time elapses after the return operation. When the flow rate is greater than or equal to a third predetermined value that is greater than the second predetermined value , the return safety confirmation method is characterized in that the gas shut-off valve is closed and the return safety confirmation is terminated.

According to the fourth aspect of the present invention, when the gas flow rate obtained by the flow rate measuring means is greater than or equal to the third predetermined value greater than the second predetermined value until the second predetermined time elapses after the return operation , the gas cutoff valve The valve is closed and the return safety check is completed. Therefore, if the gas is larger than the third predetermined value, that is, larger than the second predetermined value, that is, if a large amount of gas is leaked, it can be blocked by the side material after the return operation.

According to a fifth aspect of the present invention, there is provided a flow rate measuring means for intermittently measuring a gas flow rate in a gas flow path, a flow rate measuring means for obtaining a gas flow rate based on the measured flow speed, and a gas passing through the gas flow path. A gas shut-off valve for shutting off the supply; an abnormality detecting means for detecting a flow rate abnormality by monitoring the gas flow rate measured by the flow rate measuring means; and a shut-off for closing the gas shut-off valve in response to the detection of the flow rate abnormality. And a safety confirmation means for confirming safety when the gas shut-off valve closed by the return operation is opened, wherein the safety check means is configured to shut off the gas in response to the return operation. and valve opening the valve, the safety check means, when the smaller flow rate than the first predetermined value is determined to continue the first predetermined time or more by the flow rate measuring means after the return operation, the gas shut-off valve valve Nishitama or Quit before Symbol return safety check, the safety check means, a gas flow rate of the determined by the flow rate measuring means after waiting from the return operation to elapse long second predetermined time than the first predetermined time when is the first predetermined value or more larger than the second predetermined value, it resides in a gas meter, characterized in that to end the safety check before Symbol return to the gas shut-off valve in the closed valve.

According to the invention of claim 5, the flow velocity measuring means intermittently measures the flow velocity of the gas in the gas flow path. The flow rate measuring means obtains the gas flow rate based on the measured flow velocity. A gas shut-off valve shuts off the gas supply through the gas flow path. The abnormality detection unit detects a flow rate abnormality by monitoring the gas flow rate measured by the flow rate measurement unit. The shut-off means closes the gas shut-off valve in response to detection of an abnormal flow rate. Safety check means, when the smaller flow rate than the first predetermined value is determined to continue the first predetermined time or more by the flow rate measuring means after returning operation, the Shitama or return safety check the gas shut-off valve in the valve opening finish. When the safety confirmation means waits for a second predetermined time longer than the first predetermined time from the return operation, and the gas flow rate obtained by the flow rate measuring means is equal to or greater than a second predetermined value greater than the first predetermined value, the gas is shut off Close the valve and complete the return safety check.

  Therefore, by waiting for the gas flow rate to stabilize after the second predetermined time has elapsed since the return operation, a state in which the gas flow rate is not stable is not erroneously determined as an abnormal flow rate and blocked. Moreover, by setting the second predetermined value to a value larger than the first predetermined value, even if the gas flow rate is not stable after the second predetermined time has elapsed, this state is erroneously determined as a flow rate abnormality. Without blocking, leakage exceeding the second predetermined value can be accurately blocked. In addition, by making the first predetermined time shorter than the second predetermined time, if the flow rate of the first predetermined value or less continues to flow after the return operation, there is no need to wait for the second predetermined time to elapse. The return safety check can be completed while the gas shut-off valve is opened.

  As described above, according to the first and fifth aspects of the present invention, when the gas flow rate is stabilized after the second predetermined time has elapsed since the return operation, the gas flow rate is not stabilized. It is not erroneously judged and blocked. Moreover, by setting the second predetermined value to a value larger than the first predetermined value, even if the gas flow rate is not stable after the second predetermined time has elapsed, this state is erroneously determined as a flow rate abnormality. Without blocking, leakage exceeding the second predetermined value can be accurately blocked. In addition, by making the first predetermined time shorter than the second predetermined time, if the passing flow rate below the first predetermined value is continuously flowing after the return operation, it is not necessary to wait for the second predetermined time to elapse. Since the return safety check can be completed with the gas shut-off valve open, it is possible to obtain a return safety check method and gas meter that can quickly return the gas shut-off valve while accurately checking the safety. it can.

  According to the second aspect of the present invention, the gas flow rate is determined even if the second predetermined time has elapsed by determining whether the gas flow rate equal to or greater than the second predetermined value is flowing based on the average of the gas flow rates obtained a plurality of times. However, even if a gas flow rate equal to or greater than the second predetermined value flows for a moment, the state of being unstable is not interrupted, so that it is possible to obtain a return safety confirmation method capable of accurately confirming safety. .

  According to the third aspect of the present invention, if the gas flow rate is not stable after the second predetermined time and further the third predetermined time after the return operation, the safety check is performed by the average of the gas flow rate. As a result, the gas flow rate does not stabilize and the return safety check does not end indefinitely, and the state where the flow rate is not stable will not be erroneously judged as a flow rate error and will not be shut off. It is possible to obtain a return safety check method capable of quickly returning the gas cutoff valve while performing safety check.

  According to the fourth aspect of the present invention, if the gas is leaked in a large amount, which is larger than the second predetermined value, that is larger than the second predetermined value, it can be shut off immediately after the return operation, so that it can be safely returned. A return safety confirmation method that can be confirmed can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an electronic gas meter that implements the return safety confirmation method of the present invention. The electronic gas meter shown in the figure is configured as an ultrasonic type, and is disposed 2 opposite to each other so as to be separated from the gas flow path by a distance L and to form an angle θ with respect to the gas flow direction Y. There are two acoustic transducers TD1 and TD2.

  The two acoustic transducers TD1 and TD2 are composed of, for example, piezoelectric vibrators that operate at an ultrasonic frequency. The gas flow path is provided with a gas shut-off valve 10 that shuts off the gas flow path by closing the valve upstream of the two acoustic transducers TD1 and TD2.

  Each transducer TD1 and TD2 is connected to a transmission circuit 12 and a reception circuit 13 via transducer interface (I / F) circuits 11a and 11b, respectively. The transmission circuit 12 transmits a signal for generating an ultrasonic signal by driving one of the transducers TD1 and TD2 in the form of a pulse burst under the control of the microcomputer (μCOM) 14, and an oscillation circuit (see FIG. (Not shown).

  As shown in FIG. 2, the μCOM 14 described above includes a central processing unit (CPU) 14a that performs various processes according to a program, a ROM 14b that is a read-only memory that stores a program for processing performed by the CPU 14a, and the like. A RAM 14c, which is a readable / writable memory having a work area used in the processing process, a data storage area for storing various data, and the like are built in, and these are connected to each other by a bus line 14d.

  Next, the operation of the electronic gas meter having the above-described configuration will be described. The above-described CPU 14a functions as a flow rate measuring unit and a flow rate measuring unit, measures the gas flow rate at each sampling time using the two transducers TD1 and TD2, and instantaneously multiplies the measured gas flow rate by the cross-sectional area of the gas flow path. Performs an instantaneous flow rate measurement process to measure the flow rate. Details of the instantaneous flow rate measurement process will be described below.

  First, the CPU 14a outputs a trigger signal to the transmission circuit 12 to generate a pulse burst signal, supplies the pulse burst signal to one of the transducers TD1 and TD2, and causes this one transducer to generate an ultrasonic signal. In addition, the receiving circuit 13 receives the signal from the other transducer that receives the ultrasonic signal transmitted from one transducer, and takes in the signal generated by the receiving circuit 13 in response thereto.

  Thereafter, the CPU 14a performs control to turn back the same operation again by reversing the transducer for generating the ultrasonic signal and the transducer for receiving the ultrasonic signal. Then, the CPU 14a uses the propagation time timer formed in the RAM 14c to output a trigger signal to the transmission circuit 12 to generate an ultrasonic signal of one transducer, and then receives the ultrasonic signal of the other transducer. Propagation times T1 and T2 until a signal generated by the signal is taken in via the receiving circuit 13 are measured.

Assuming that the sound velocity is c and the gas flow velocity is v, the propagation speed of the ultrasonic signal from the transducer TD1 to the transducer TD2 is (c + v cos θ), and the propagation speed of the ultrasonic signal from the transducer TD2 to the transducer TD1 is (c− vcos θ). Accordingly, if the distance between the transducers TD1 and TD2 is L, the time T1 when the ultrasonic signal from the transducer TD1 travels in the same direction Y as the gas flow and reaches the transducer TD2, and the ultrasonic signal from the transducer TD2 is the gas flow. The time T2 that travels in the opposite direction to reach the transducer TD2 is
T1 = L / (c + vcos θ) (1)
T2 = L / (c−v cos θ) (2)
It becomes.

From equations (1) and (2), v = (L / 2 cos θ) · (1 / T1-1 / T2)
= (L / 2cos θ) · {(T2−T1) / (T2 · T1)} (3)
Thus, when L is known, the flow velocity v can be obtained by measuring T1 and T2.

By the way, T2 · T1 = L ² / {(c + v cos θ) · (c−v cos θ)}.
= L ² / (c ² −v ² cos ² θ)
Since the flow velocity v is an extremely small numerical value compared to the sound velocity c, v ^{2 in} the equation can be negligibly small compared to c ² cos ² θ, and T2 · T1 = L ² / c ² can be obtained. . And the above equation (3) finally becomes
v = {(T2-T1) · c ² } / 2L cos θ
= (T2-T1) · (c ² ) · (1 / 2L cos θ)
Can be rewritten. Here, when Td = (T2−T1),
v = Td · k (4)
Where k = c ² / 2L cos θ
It becomes. That is, the gas flow velocity v is obtained by multiplying the difference Td in the propagation time of the ultrasonic signal by the constant k. The instantaneous flow rate can be obtained by multiplying the gas flow velocity v by the cross-sectional area of the gas flow path. The CPU 14a further multiplies the obtained instantaneous flow rate by the sampling time to obtain a flow rate measurement process for obtaining the gas passage flow rate, an integration process for integrating the obtained passage flow rate, and a display for displaying the accumulated passage flow rate on the display 15. Process.

  Further, the CPU 14a functions as an abnormality detection unit, performs an abnormality detection process for detecting a flow rate abnormality by monitoring the flow rate obtained by the above-described flow rate measurement process, functions as a blocking unit, and detects gas flow according to the detection of the flow rate abnormality. A shut-off process for closing the shut-off valve 10 is performed. Further, the CPU 14a performs a safety confirmation process for confirming safety when the gas cutoff valve 10 that has been closed by the cutoff process by the return operation is opened.

  Next, details of the above-described safety confirmation process will be described with reference to a flowchart showing a processing procedure of the CPU 14a in FIGS. As shown in the figure, after the shut-off process, when a return operation is performed by operating a magnet switch or the like, safety confirmation processes 1 and 2 are started in parallel. First, the safety confirmation process 1 will be described.

  First, the CPU 14a outputs a valve opening signal to the gas cutoff valve 10 (step S10). By the output of this valve opening signal, the gas shut-off valve 10 that has been closed by the shut-off process is opened. Thereafter, the CPU 14a performs the instantaneous flow rate measurement process described above to measure the instantaneous flow rate Rn (step S11).

If the measured instantaneous flow rate Rn is, for example, 8.3 L / h (= first predetermined value) or more (N in step S12), the CPU 14a returns to step S11 again. On the other hand, if the measured instantaneous flow rate Rn is smaller than 8.3 L / h (Y in step S12), the continuation counter C1 is incremented (step S13).

  Thereafter, the CPU 14a determines whether or not the continuation counter C1 exceeds a predetermined number of times M1 (step S14). If the predetermined number of times M1 is exceeded (Y in step S14), the gas flow rate is continuously less than 8.5 L / h for the first predetermined time t1 or more, and it is determined that the flow rate abnormality does not occur and is safe. Then, after outputting the safety confirmation signal (step S15), the process ends. The safety confirmation process 2 described later is forcibly terminated by the output of the safety confirmation signal.

  Next, the safety confirmation process 2 performed in parallel with the safety confirmation process 1 described above will be described. First, the CPU 14a starts an invalid timer T2 and counts the elapsed time from the return operation (step S21). Thereafter, the instantaneous flow rate measurement process described above is performed to measure the instantaneous flow rate Rn (step S22). Next, the CPU 14a determines whether or not the measured instantaneous flow rate Rn has exceeded 1000 L / h (= third predetermined value) (step S23).

  If it exceeds 1000 L / h (Y in Step S23), after incrementing the abnormal number counter C2 (Step S24), it is determined whether or not the abnormal number counter C2 exceeds a predetermined number M2 (Step S24). S25). On the other hand, if it does not exceed 1000 L / h (N in step S23), after resetting the abnormal number counter C2 (step S34), the process proceeds to step S25.

  If the predetermined number of times M2 has been exceeded (Y in step S25), the CPU 14a determines that a large flow rate exceeding 1000 L / h continues to flow, and outputs a cutoff signal to the gas cutoff valve 10. After (step S35), the safety confirmation process 2 is terminated. Due to the output of this shut-off signal, the gas shut-off valve 10 is closed, the supply of gas is shut off, and the safety confirmation process 1 described above is also forcibly terminated.

  On the other hand, if the predetermined number of times M2 has not been exceeded (N in step S25), the CPU 14a determines whether or not the invalid timer T2 has exceeded the second predetermined time t2 (> first predetermined time t1) (step S26). If T2 ≦ t2 (N in step S26), the CPU 14a returns to step S22 again. In contrast, if T2> t2 (Y in step S26) and the second predetermined time t2 has elapsed since the return operation, the CPU 14a counts the elapsed time after the second predetermined time t2 has elapsed. Timer T3 is started (step S27).

  Next, the CPU 14a performs an instantaneous flow rate measurement process intermittently n times (step S28). Thereafter, an average calculation process for calculating an average flow rate Rave that is an average of the n instantaneous flow rates Rn obtained by the n instantaneous flow rate measurement processes is performed (step S29). The CPU 14a determines whether or not the average flow rate Rave is equal to or greater than 21 L / h, which is a second predetermined value (step S30).

  If it is 21 L / h or more (Y in step S30), the flow rate of 21 L / h or more flows, and it is determined that a flow rate abnormality such as leakage has occurred, and the CPU 14a proceeds to step S35 described above. On the other hand, if it is smaller than 21 L / h (N in step S30), it is next determined whether or not the return safety completion timer T3 has exceeded the third predetermined time t3 (step S31).

  If T3 ≦ t3 (N in step S31), the CPU 14a returns to step S28 again. On the other hand, if T3> t3 (Y in step S31), after the second predetermined time t2, the CPU 14a continues to flow for the first predetermined time t1 or more and does not become less than 8.3 L / h. It is determined that the state where the average flow rate Rave does not exceed 21 L / h continues for the third predetermined time t3 or more, and then it is determined whether the average flow rate Rave is 8.3 L / h or more (step S32). .

  If it is 8.3 L / h or more (Y in step S32), the CPU 14a determines that a flow rate abnormality has occurred, and proceeds to step S35 described above. On the other hand, if it is smaller than 8.3 L / h (N in step S32), the CPU 14a does not continue at 8.3 L / h or less because the flow rate is not stable, and no flow rate abnormality has occurred. After judging and outputting a safety confirmation signal (Y in step S33), the return safety processing 2 is terminated. The output of the safety confirmation signal forcibly terminates the safety confirmation process 1 described later.

  As described above, in the safety recovery process 2, by waiting for the gas flow rate to stabilize after the second predetermined time t2 has elapsed from the return operation, the state where the gas flow rate is not stable is erroneously determined as a flow rate abnormality. There is no blocking. Moreover, in the safety confirmation process 2, when the average flow rate Rave exceeds 21 L / h, which is looser than 8.3 L / h, the gas flow rate is not stable after the second predetermined time t2 has elapsed by outputting a shut-off signal. Even if the state continues, this state is not erroneously determined as a flow rate abnormality and is blocked, and leakage of 21 L / h or more can be accurately blocked. Further, by making the first predetermined time t1 shorter than the second predetermined time t2, if the gas flow rate of 8.3 L / h or less continues for the first predetermined time t1 or more after the return operation, the second predetermined time t2 The return safety confirmation can be ended without waiting for the elapse.

  Further, in step S30 of the safety confirmation process 2, it is determined whether the gas flow rate of 21 L / h or more is flowing based on the average flow rate Rave that is the average of the instantaneous flow rates Rn obtained n times. Even if t2 elapses, the state where the gas flow rate is not stable continues, and even if a gas flow rate of 21 L / h or more flows for a moment, the gas flow is not interrupted, so safety can be confirmed accurately.

  In addition, after the return operation, the gas flow rate does not stabilize even after the second predetermined time t2, and the flow rate less than 8.3 L / h does not continue for the first predetermined time t1 or more, and the flow rate is 21 L / h or more. If the non-flowing state continues for the third predetermined time t3 (Y in step S31), it is determined whether or not a flow rate smaller than 8.3 L / h is flowing based on the average flow rate Rave. As a result, the gas flow rate does not become stable and the return safety check does not end indefinitely, and the state where the flow rate is not stable is not erroneously determined as an abnormal flow rate and blocked.

  Furthermore, the gas shut-off valve 10 is closed again when it can be considered that a passing flow rate greater than 1000 L / h continuously flows until the second predetermined time t2 elapses after the return operation. Thereby, when it is larger than 1000 L / h, that is, when a large amount of gas has leaked, it can be shut off immediately after the return operation.

It is a block diagram which shows one Embodiment of the electronic gas meter which implemented the return safety confirmation method of this invention. It is a block diagram which shows the detailed structure of (micro | micron | mu) 14 which comprises the electronic gas meter of FIG. It is a flowchart which shows the process sequence of CPU14a in the safety confirmation process 1. FIG. It is a flowchart which shows the process sequence of CPU14a in the safety confirmation process 2. FIG. It is a graph which shows the relationship between the gas flow rate after reset operation, and time.

Explanation of symbols

14a CPU (flow velocity measuring means, flow rate measuring means, abnormality detecting means, blocking means, safety confirmation means)
10 Gas shut-off valve

Claims (5)

A flow rate measuring means for intermittently measuring a gas flow rate in the gas flow path, a flow rate measuring means for obtaining a gas flow rate based on the measured flow speed, and a gas shut-off valve for shutting off the gas supply through the gas flow path; An abnormality detecting means for detecting an abnormality in the flow rate by monitoring the gas flow rate measured by the flow rate measuring means, a shutoff means for closing the gas shutoff valve in response to the detection of the abnormal flow rate, and closing the valve by a return operation. A safety confirmation means for confirming safety when closing the gas shut-off valve, and a return safety confirmation method by the safety confirmation means of the gas meter,
The safety confirmation means opens the gas shut-off valve in response to the return operation,
When the gas flow rate smaller than the first predetermined value is continuously obtained for the first predetermined time or more by the flow rate measuring unit after the return operation, the safety check unit returns the gas shut-off valve with the valve shut open. Finish the safety check,
After the safety confirmation means waits for a second predetermined time longer than the first predetermined time from the return operation, the gas flow rate obtained by the flow rate measuring means is not less than a second predetermined value greater than the first predetermined value. At this time , the return safety check method is characterized in that the return safety check is ended by closing the gas shut-off valve. A return safety confirmation method according to claim 1,
When the average of the gas flow rate obtained by the flow rate measurement unit a plurality of times after the second predetermined time has elapsed from the return operation is equal to or greater than the second predetermined value, the gas flow rate obtained by the flow rate measurement unit is A return safety confirmation method characterized by closing the gas shut-off valve and ending the return safety confirmation, assuming that it is equal to or greater than a second predetermined value . The return safety confirmation method according to claim 1 or 2,
The safety check means, without being prompted to continue the return operation from the second predetermined time elapsed the flow rate measuring means by a small gas flow rate than the first predetermined value is the first predetermined time or more after, and the flow rate When the gas flow rate smaller than the second predetermined value is continuously determined by the measuring unit for a third predetermined time and the average of the gas flow rates obtained by the flow rate measuring unit a plurality of times is not more than the first predetermined value, the gas shut-off valve to end the Shitama or pre Symbol return safety check in valve open, characterized in that to end the safety check before Symbol return to closed valve pre SL gas shut-off valve is greater than the first predetermined value Return safety confirmation method. The return safety confirmation method according to claim 3,
When the gas flow rate obtained by the flow rate measuring means is greater than or equal to a third predetermined value that is greater than the second predetermined value until the second predetermined time elapses after the return operation , the gas cutoff is performed. A return safety confirmation method characterized by closing the valve and closing the return safety confirmation. A flow rate measuring means for intermittently measuring a gas flow rate in the gas flow path, a flow rate measuring means for obtaining a gas flow rate based on the measured flow speed, and a gas shut-off valve for shutting off the gas supply through the gas flow path; An abnormality detection means for detecting a flow rate abnormality by monitoring the gas flow rate measured by the flow rate measurement means; a shutoff means for closing the gas shutoff valve in response to the detection of the flow rate abnormality; and the valve by a return operation A gas meter equipped with safety confirmation means for confirming safety when opening the closed gas shut-off valve,
The safety confirmation means opens the gas shut-off valve in response to the return operation,
The safety check means, when the smaller flow rate than the first predetermined value is determined to continue the first predetermined time or more by the flow rate measuring means after the restoring operation, Shitama or the gas shut-off valve in the valve opening Exit before Symbol return safety check,
After the safety confirmation means waits for a second predetermined time longer than the first predetermined time from the return operation, the gas flow rate obtained by the flow rate measuring means is not less than a second predetermined value greater than the first predetermined value. when, gas meter, characterized in that to end the pre-Symbol return safety check by the gas shut-off valve in the closed valve.

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