JPH0843154A - Gas leak determination method from inner pipe using fluidic gas meter with flow sensor - Google Patents

Abstract

PURPOSE:To judge gas leakage with no error regardless of pressure variation by making a judgement only when the fluctuation in the measurement of a flow sensor is within a predetermined range. CONSTITUTION:A circuit 15 judges fluctuation in the measurement of flow rate received from a flow sensor 6 through a switch circuit 14 within a predetermined time. When the magnitude fluctuation determined based on the maximum and minimum values comes within a preset range, a circuit 16 begins to judge gas leakage. When the magnitude of fluctuation exceeds a set value, such a decision is made that an erroneous judgement is made due to disturbance caused by pressure variation, and the operation is interrupted. When the circuit 16 begins judgement of gas leakage, a circuit 18 determines a measurement period depending on the fluctuation prior to start measurement 20. A circuit 21 averages the measurements within a predetermined time and a circuit 22 judges gas leakage based on the average value (average flow rate signal).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a gas leak from a lamp inner tube (hereinafter referred to as "inner tube") by using a fluidic gas meter with a flow sensor attached to a customer.

[0002]

2. Description of the Related Art In a fluidic gas meter with a flow sensor, a flow sensor measures a flow rate below a certain flow rate, and this flow sensor measures a minute flow rate caused by a minute gas leak. Is possible. Therefore, when a fluidic gas meter with a flow sensor is used as a city gas meter, the fluidic gas meter not only measures the normal flow rate,
A gas leak judgment function is also added.

The conventional concept of gas leak determination using this fluidic gas meter is as shown in FIG. 3, when an integrated flow rate signal is continuously generated for a certain period of time, as shown in FIG. Then, when this value exceeds the threshold value, it is determined that there is a gas leak, and as a specific example thereof, there is one disclosed in JP-A-5-45199.

[0004]

However, according to the above-mentioned conventional idea of gas leak determination, it is determined that there is a gas leak when the integrated flow rate signal is output for a certain period of time. Therefore, for example, fluctuation of gas pressure occurs. In this case, the output of the flow sensor fluctuates greatly, and therefore, if the integration is calculated from the measured values for each time, a certain threshold value may be exceeded, resulting in an erroneous determination. An object of the present invention is to propose a method for determining gas leakage from an inner pipe, which is performed by using a fluidic gas meter with a flow sensor that does not make an erroneous determination even when there is a pressure change.

[0005]

A method for determining gas leakage from an inner pipe, which is performed by using a fluidic gas meter with a flow sensor according to the present invention, is as follows.

1. The magnitude of the variation is determined from the range of the maximum value and the minimum value of the variation of the measurement value output from the flow sensor, and if the magnitude of the variation is within a preset range, measurement according to the variation Determine the cycle to find the average flow rate within a certain period of time, and perform the leak determination from this value.If the magnitude of the variation is outside the preset range, it is determined that the disturbance has an effect. A method for determining gas leakage from an inner pipe using a fluidic gas meter with a flow sensor, characterized in that leakage determination is not performed.

2. A table is prepared in advance for determining the size of the variation and the measurement cycle that are the criteria for determining whether or not to perform the leak determination, and this table can be rewritten and the leak determination is based on this table. A method for judging gas leakage from an inner pipe, which is performed using the fluidic gas meter with a flow sensor according to the above 1.

[0008]

[Operation] The gas leak from the inner tube is checked when all the gas appliances are stopped. The output from the flow sensor is monitored when all the gas appliances are stopped, and if there is no output, there is of course no gas leakage. next,
When the measured value is output from the flow sensor, first, monitor the change in the size of the measured value during this fixed time, and then measure the magnitude of the fluctuation from the range of the maximum and minimum values of the measured value within this fixed time. To judge. If this variation is within a preset range, determine the measurement cycle according to the variation, start leak determination (measurement), and calculate the average flow rate within a certain time to obtain this value. Check for leaks. The size of the variation and the measurement period are determined by providing a table in the determination circuit.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a fluidic gas meter which is subjected to a gas leakage determination method from an inner tube using a fluidic gas meter with a flow sensor, wherein 1 is a meter body, 2 is a gas inlet, 3 is a gas outlet. 4 is a fluidic element, 5 is a nozzle, 6 is a flow sensor incorporated in the nozzle 5 portion, 7 is a gas flow path from the gas inlet to the nozzle 5, 8 is a valve seat, and 9 is a solenoid for opening and closing the shutoff valve 10. , 11 is a reset button, and 12 is a flow rate calculation and gas leak determination circuit built-in unit.

FIG. 2 shows a circuit and a judgment flow for carrying out a method for judging gas leakage from an inner pipe, which is carried out by using the fluidic gas meter with a flow sensor according to the present invention.
When the gas leak determination is performed, the flow sensor 6 is driven by the measurement cycle generation circuit 13 for a fixed period. Flow sensor 6
The flow rate signal output from the switch circuit 14 is input to the variation determination circuit 15 from the switch circuit 14. Variation determination circuit 15
Is the variation of the measured flow rate from the flow sensor 6 that is input within a fixed time, the magnitude of the variation is determined from the maximum value and the minimum value, and if the variation is within a preset range, The leak determination start circuit 16 starts the determination. On the other hand, when the magnitude of the variation is outside the set value, it is determined that there is an erroneous measurement due to the disturbance due to the pressure fluctuation, and the leak determination stopping circuit 17 stops the leak determination.

When the leak determination start circuit 16 starts the leak determination, the measurement period determining circuit 18 determines the measurement period according to the variation, and if the measurement period is changed next, the measurement period changing circuit 19 changes the measurement period. And then the measurement circuit 20
Then, the measurement averaging circuit 21 averages the measured values for a certain period of time.

The leakage determination circuit 22 is a measurement value averaging circuit 2
Whether or not there is a leak is determined based on the average value (average flow rate signal) of the values measured in 1.

Reference numeral 23 is a normal measuring circuit.

Reference numeral 24 is a circuit for determining the measurement cycle based on this variation when the determination is made by the variation determination circuit 15 and the leakage determination is executed.

[0015]

As described above, according to the present invention, the variation of the measured value from the flow sensor is first determined, and the leak determination is performed only when the variation is within a certain range. By changing the averaged number of measurement values within a certain time, it is possible to prevent the threshold value from being exceeded. As a result, it is possible to determine the gas leakage from the inner pipe without erroneous recognition even if there is a pressure change or the like.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a fluidic gas meter with a flow sensor that implements the present invention.

FIG. 2 is an explanatory diagram of a determination circuit and a determination flow for implementing the present invention.

FIG. 3 is an explanatory view of a flow rate change when there is a pressure change.

FIG. 4 is an explanatory diagram of a case where a measurement signal output due to a pressure fluctuation is erroneously integrated to make a leak determination.

[Explanation of symbols]

 1 Fluidic gas meter main body 4 Fluidic element 5 Nozzle 6 Flow sensor 12 Flow rate calculation and gas leak judgment circuit built-in part

Claims (2)

[Claims] 1. The magnitude of the variation is determined from the range of the maximum value and the minimum value of the variation of the measurement value output from the flow sensor. When the magnitude of the variation is within a preset range, Determine the measurement cycle according to the variation and obtain the average flow rate within a certain time, and perform the leak determination from this value.If the magnitude of the variation is outside the preset range, the disturbance will affect A method for determining gas leakage from an inner pipe using a fluidic gas meter with a flow sensor, which is characterized by not determining that there is a leak. 2. A table is prepared in advance for determining the size of the variation and the measurement cycle which are the criteria for determining whether or not to perform the leak determination, and this table can be rewritten and the leak determination can be performed. A method for determining gas leakage from an inner pipe, which is performed based on this table, using the fluidic gas meter with a flow sensor according to claim 1.