JPH0843246A - Method for judging gas leakage from inner tube using fluidic gas meter with flow sensor - Google Patents

Abstract

PURPOSE:To judge the presence of gas leakage without error even when the pressure of a gas fluctuates by judging the fluctuation of measured values from a flow speed sensor and performing leakage judgement only when the dispersion of the measured values falls within a specific range. CONSTITUTION:A dispersion judging means 101 inputs the flow rate of a gas measured by means of a flow speed sensor 6 which is periodically operated by means of a measuring cycle generating means 100 and judges the magnitude of the fluctuation of the flow rates. When the dispersion exceeds a preset range, leakage judgement is interrupted 102 and, when the dispersion falls within the range, leakage judgement is started 103. A deciding means 104 which decides the number of measuring times decides the number of leakage judging times to a larger (smaller) value when the dispersion is larger (smaller) even when the dispersion falls within the range of judgement starting condition. Then, the leakage is measured 105 by the number of measuring times and a measured value averaging means 106 averages the measured values. When the mean value is larger than a preset value, a leakage judging means 107 judges the presence of leakage and, when the means value is smaller than the preset value, judges the absence of leakage.

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 a specific example thereof is disclosed in Japanese Patent Application Laid-Open No. 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 judging gas leakage from an inner pipe by using a fluidic gas meter with a flow sensor which does not make an erroneous judgment even if there is a pressure fluctuation.

[0006]

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 when the magnitude of the variation is within a preset range, the number of measurements according to the variation is determined. The leak judgment is started based on this average flow rate value.If the magnitude of the variation is outside the preset range, it is judged that the disturbance is affecting and the leak judgment is made. A method for determining gas leakage from an inner pipe using a fluidic gas meter with a flow sensor, characterized in that

2. A table is prepared in advance for determining the size of the variation and the number of measurements 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.

[0009]

[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 there is an output of the measured value from the flow sensor, first, the change in the size of the measured value during this fixed time is monitored, and the variation in the maximum and minimum values of the measured value within this fixed time is varied. Determine the size of. If this variation is within a preset range, the number of measurements according to the variation is determined and leak determination (measurement) is started, and after a certain number of measurements, all measured values are averaged. Then, the average flow rate is calculated, and the leak is judged from this value. The size of the variation and the number of times of measurement are determined by providing a table in the determination circuit.

[0010]

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 part, 7 is a gas flow path from the gas inlet 2 to the nozzle 5, 8 is a valve seat, and 9 is a shutoff valve 10. A solenoid, 11 is a reset button, and 12 is a flow rate calculation and gas leak determination circuit built-in unit.

FIG. 2 is a determination flow of a method for determining gas leakage from an inner pipe using the fluidic gas meter with a flow sensor according to the present invention. When performing gas leakage determination, the flow sensor (flow velocity sensor) 6 is , Is driven at a constant cycle (interval) by the measurement cycle generating means (step 1
00). Next, the measured flow rate from the flow sensor 6 is input to the variation determining means, and the magnitude of the variation is determined here (step 101). If the magnitude of the variation is outside the predetermined range, the leak determination is stopped (step 102), and if it is within the range, the leak determination is started (step 103). The number of leak determinations is determined by the number-of-measuring determination means to determine a large number of measurements when the variation is within the range of the determination start condition, and to determine a small number of measurements when the variation is small. (Step 10
4). The measurement is performed for the number of times of measurement (step 105), then all of the measured values are averaged by the measured value averaging means (step 106), and if the average value is larger than the preset value, the leak determination means It is determined that there is a leak, and if it is small, it is determined that there is no leak (step 107).

[0012]

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 flow according to 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, and when the magnitude of the variation is within a preset range, the variation is determined. Determine the number of measurements and start the leak determination, and perform the leak determination based on this average flow rate 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 leak determination is not performed. 2. A table for determining the magnitude of variation and the number of times of measurement, which is a reference for determining whether or not to perform the leak determination, is prepared in advance, 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.