JPH09229743A - Estimation method for downstream-side pipe volume of gas meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method in which the downstream-side pipe volume of a gas meter is estimated. SOLUTION: Regarding a plurality of pipes whose volume is different, relationships between the time elapsed and pressures inside the pipes at a time when a gas is supplied under a constant supply condition are found respectively in advance as basic data. Then, a gas supply valve 4 at a gas meter 1 is opened, and the relationship between the time elapsed and a pressure inside a pipe at a time when a gas is supplied to a downstream-side pipe 3 under the same supply condition as in the above is measured. Then, data which is obtained by the measurement is compared with the plurality of basic data. A volume corresponding to the basic data which are indetical to, or approximate to, the measured data is estimated as a volume inside the pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating the downstream (secondary) piping volume of a gas meter.

[0002]

2. Description of the Related Art As one of the next-generation gas meters, a bidirectional valve is used as a gas supply valve to perform not only gas shutoff in an emergency such as an earthquake, but also recovery operation after shutoff. Proposals have been made to make it electrically by remote control. When performing such a gas recovery operation, if damage occurs in the downstream piping of the gas meter and leakage occurs, it may lead to a gas accident after recovery,
At the time of restoration, it is necessary to check for leaks.

The leakage of the downstream pipe of such a gas meter can be confirmed by monitoring the decrease in gas pressure when the valve is opened and gas is supplied into the pipe and then closed. Since the degree also depends on the pipe volume,
In order to accurately determine whether or not there is a leak in the downstream side pipe at the time of restoration, it is necessary to grasp the pipe volume in advance.
Therefore, it is desired to provide a method for knowing the pipe volume.

The present invention has been made in view of the above technical background, and an object of the present invention is to provide a method for estimating the downstream side pipe volume of a gas meter.

[0005]

In order to achieve the above object, the inventor has found that when the gas is supplied to the downstream side pipe under a constant gas supply condition, the degree of increase in the pressure in the pipe which increases with the passage of time is The present invention has been completed by paying attention to the difference according to the pipe volume.

That is, according to the present invention, for a plurality of pipes having different volumes, the relationship between the elapsed time when the gas is supplied under a constant supply condition and the pressure in the pipe is obtained in advance as basic data, and the gas of the gas meter is measured. Open the supply valve,
The relationship between the elapsed time and the pressure inside the pipe when supplying gas to the downstream side pipe under the same supply conditions as above was measured, and the data obtained by this measurement was compared with the plurality of basic data, and the measured data was obtained. The present invention is characterized in that the volume corresponding to the same or approximate basic data is estimated as the internal volume of the pipe, which makes it possible to estimate the volume of the downstream pipe, which has not been realized conventionally.

In this case, if the pressure of the downstream side pipe is measured immediately before the opening of the gas supply valve and the measurement is performed when the pressure is zero or close to this, the obtained pressure data and the previously determined basis are obtained. The correspondence with the data can be easily grasped.

Furthermore, after the downstream side pipe volume is estimated, the pressure drop is measured to estimate the gas leakage, and if the leakage amount is small, the estimation of the pipe volume is made effective. It can be performed reliably and with high accuracy.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic structure of a gas piping system and a gas meter installed therein. In the figure, (1) is a gas meter, (2) is upstream piping,
(3) is a downstream pipe drawn into the customer.

The gas meter is provided with a bidirectional valve (4) and is configured so that it can be closed or opened by electrical control. The bidirectional valve (4) is provided with a main valve for shutting off gas and a small valve for limiting the gas flow rate. When the valve is opened, only the small valve is opened first so that the pressure in the downstream side pipe suddenly rises. By pressing, it is possible to measure the tendency of pressure increase, open the main valve when the pressure difference between the upstream side and the downstream side becomes less than a certain level, and connect the downstream side pipe (3).
It is configured to be able to supply gas to.

In estimating the volume of the downstream side pipe (3), first, for a plurality of pipes having different volumes, the relationship between the time when the gas is supplied under constant conditions and the pressure in the pipe is obtained in advance as basic data. deep. This data can be obtained by calculation or may be actually measured. For the calculation or measurement, the same bidirectional valve (4) as that used in the gas meter (1) is applied, and the same supply condition as in the state in which the small valve is opened to suppress the rapid pressure increase in the downstream space. Set to. When gas supply is started in a state where the pressure in the pipe is zero, the pressure in the pipe increases with the passage of time, but the degree of this pressure increase depends on the pipe volume.

The pressure change in the downstream pipe (3) is given by the following equation.

[0013]

[Equation 1] However, p: Gas pressure in the downstream pipe (differential pressure from atmospheric pressure) p0: Gas supply pressure (differential pressure in atmospheric pressure) V: Volume Pa of the pipe (3) downstream of the bidirectional valve (4) Pa : Atmospheric pressure k1, k2: coefficient t: time. The above formula [1] is derived by the following.

That is, if the atmospheric pressure is Pa and the volume of the gas in the downstream side pipe in terms of atmospheric pressure is v,

[Equation 2] Therefore, v can be calculated by the following equation.

[0015]

(Equation 3) On the other hand, if the gas flow rate into the downstream pipe is Q1 and the gas flow rate out of the pipe is Q2, the volume of the gas in the downstream pipe is v0 (converted to atmospheric pressure) as the initial amount.

(Equation 4) Becomes

First, consider the pressure drop after interruption.

Since the initial value of the pressure in the pipe is equal to p0, the initial value v0 of the gas volume in the downstream pipe is calculated by the following equation.

[0018]

(Equation 5) If there is no valve leakage after shutoff, then Q1 = 0, so the time variation of the gas volume in the pipe at this time is

(Equation 6) Becomes Here, since the volumetric flow rate of the gas passing through the throttle is proportional to the square root of the differential pressure, the gas flow rate Q2 discharged from the pipe is given by the coefficient k2.

(Equation 7) Becomes

Therefore, the following equations are derived from the equations [3], [6] and [7].

[0020]

(Equation 8) If you organize about p,

[Equation 9] here,

(Equation 10) As

[Equation 11] If you put

(Equation 12) Becomes Therefore, the pressure change p can be calculated by the following equation.

[0021]

(Equation 13) Next, let us consider the increase in pressure after valve opening.

In this case, if the flow rate passing through the throttle is considered to be proportional to the square root of the differential pressure, the subsequent calculation becomes complicated.
It is considered that the flow rate is approximately proportional to the differential pressure.

In this case, Q1 and Q2 are calculated by the following equations.

[0024]

[Equation 14] The volume of gas in the pipe at this time is calculated from the formula [4],

(Equation 15) Therefore, from the expressions [3] and [15],

(Equation 16) Here, if the gas pressure in the pipe when the valve is opened is 0, the initial gas volume v0 = V, and the equation [16] is as follows.

[0025]

[Equation 17] If p is arranged, the pressure change can be calculated by the following equation.

[0026]

(Equation 18) Table 1 shows 4 liters, 8 liters, 12 liters, 16 liters under the condition that there is no leak in the downstream pipe, the gas supply pressure is 200 mmH ₂ O, and the initial value of the gas flow rate passing through the valve is 2000 liters / hour. It shows the relationship between the time when gas is supplied to a pipe having each volume of liter and 20 liters and the pressure in the pipe, and is calculated using the above formula [1]. Further, FIG. 2 shows this in a graph. It is assumed that there is no temperature change. As is clear from Table 1 and FIG. 2, it can be seen that the pressure increase characteristic in the downstream side pipe (3) changes depending on the pipe volume.

[0027]

[Table 1] The measurement data indicating the relationship between the pipe volume and the pressure obtained as described above is stored in advance in the basic data storage means (5) provided in the gas meter (1).

Next, regarding the downstream side pipe (3) of the gas meter (1) that has been actually worked, the downstream side pipe (3) is examined for the relationship between the time when the gas is supplied to the pipe and the pressure inside the pipe. The measurement is performed using the pressure sensor (6) installed in the gas meter (1). Such a measurement may be appropriately performed when a gas meter is newly installed or when downstream piping is added. In addition, it is necessary to perform the measurement under the same gas supply conditions as when the basic data was created in order to maintain the correspondence with the basic data.

The measurement is performed according to the following procedure. That is, first, immediately before the opening of the bidirectional valve (4), the pressure in the downstream pipe (3) is measured, and it is confirmed that the pressure is zero or close thereto, and then the valve is opened to supply the gas. In this way, by opening the valve when the pressure in the downstream pipe (3) is zero or close to zero, the correspondence between the obtained measurement data and the basic data can be easily grasped. Of course,
The valve may be opened in a state where the downstream side pipe (3) has an initial pressure, but in this case, a complicated calculation process is required to obtain the correspondence between the measurement data and the basic data.

After the valve is opened, the pressure in the pipe (3) is measured again after a lapse of a fixed time, and the measured value is stored in the measured data storage means (7). This pressure measurement is performed until the main valve opens and the pressure increase in the pipe (3) reaches the saturation limit.

Next, after the main valve is opened and the pressure increase in the downstream side pipe reaches the saturation limit, the main valve is closed and the pressure drop in the pipe (3) is measured. Check for leaks. The presence / absence of leakage also affects the increase characteristic of the pressure in the pipe after gas supply, resulting in lack of reliability of measurement data. However, if the leakage amount is small with respect to the supply conditions such as the gas flow rate, the influence on the pressure increase characteristic in the downstream side pipe (3) is slight, and it can be considered that it is almost the same as the measurement data when there is no leakage. it can. Tables 2 and 3 show the calculation of the relationship between time and pressure when gas is supplied to a pipe having a constant leak under the same gas supply conditions as in Table 1. Table 2 is for a leak of 100 liters / hour, Table 3 is for a leak of 300 liters / hour, and FIG. 3 is a graph showing Table 2 and FIG. 4 is a graph showing Table 3 respectively. Is. As can be seen from the comparison between Table 2, Table 3 and Table 1 and the comparison between FIG. 3, FIG. 4 and FIG. 2, the pressure value at each elapsed time when the leak rate is 100 liters / hour (Table 2). When there is no leakage (Table 1)
The fluctuations are small in the proximity of the pressure value of, and can be regarded as sufficiently reliable as the measured value. Therefore,
When the gas supply pressure is 200 mmH ₂ O and the initial value of the gas flow rate through the valve is 2000 liters / hour, the measured data shall be valid if the gas leakage amount is 100 liters / hour or less. You can

[0032]

[Table 2]

[Table 3] Based on the above, the presence or absence of leakage is checked, and if there is no leakage or if it is below a certain level, the measured data stored in the measured data storage means (7) and the basic data storage means (5) are stored. The basic data for each volume is compared and collated by the comparison and estimation means (8), and the volume corresponding to the same or approximate basic data is estimated as the measured volume of the downstream pipe (3), and this is stored in the volume memory. Store in means (9). The comparison / estimation means (8) may be constituted by a microcomputer incorporated in the gas meter (1).
Further, it is needless to say that the pipe volume can be estimated by comparing the measured data with the basic data without checking the downstream side pipe (3) for leakage, but a more reliable and highly accurate estimated value can be obtained. Therefore, it is preferable to check the presence / absence of leakage as in this embodiment.

If, for example, a downstream side pipe is added later, the pipe volume is estimated by the same procedure as above, and if there is a change in the estimated value, this is stored in the volume storage means (9). It should be newly stored.

Therefore, in the recovery operation after gas shutoff in an emergency such as an earthquake, the estimated value of the pipe volume stored in the volume storage means (9) is used to leak due to damage to the downstream side pipe or the like. It is only necessary to confirm whether or not has occurred.

[0035]

According to the invention described in claim 1, the volume of the downstream side pipe can be estimated relatively easily. Therefore, for example, in the recovery operation of the gas supply valve after gas shutoff in an emergency such as an earthquake, it becomes possible to grasp whether or not there is a leak due to pipe damage or the like, which contributes to the high performance of the gas meter. You can do it.

According to the second aspect of the invention, in addition to the above effects, the pressure in the downstream side pipe is measured immediately before the opening of the gas supply valve, and when the pressure is zero or close to this, Since the supply valve is opened, the correspondence relationship between the obtained pressure data and the basic data obtained in advance can be easily grasped, and the configuration for comparing and collating the pressure data and the basic data can be simplified. There is.

Further, according to the invention described in claim 3, in addition to the above effects, after estimating the downstream side pipe volume, the pressure drop is measured to estimate the gas leakage, and if the leakage amount is small, the pipe is Since the volume estimation is effective, the pipe volume can be estimated more reliably and highly accurately.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a gas meter and a piping system as an example to which the present invention is applied.

FIG. 2 is a graph showing the relationship between the elapsed time of gas supply and the pressure under constant conditions when there is no leakage in the downstream pipe.

FIG. 3 is a graph showing the relationship between the elapsed time of gas supply and the pressure under constant conditions when there is a slight leak in the downstream pipe.

[Fig. 4] When there is a relatively large leak in the downstream piping,
It is a graph which shows the relationship between the elapsed time of gas supply and pressure under fixed conditions.

[Explanation of symbols]

 1 ... Gas meter 3 ... Downstream piping 4 ... Bidirectional valve (gas supply valve)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Eshita 2-10-16 Higashiobashi, Higashinari-ku, Osaka City Kansai Gas Meter Co., Ltd.

Claims (3)

[Claims] 1. With respect to a plurality of pipes having different volumes, a relationship between an elapsed time when gas is supplied under a constant supply condition and a pressure in the pipe is obtained in advance as basic data, and a gas supply valve of a gas meter is opened. Valve, measuring the relationship between the elapsed time and the pressure inside the pipe when supplying gas to the downstream side pipe under the same supply conditions as above, and comparing the data obtained by this measurement with the plurality of basic data, A method for estimating the volume of a pipe on the downstream side of a gas meter, characterized in that the volume corresponding to basic data that is the same as or similar to the measured data is estimated as the internal volume of the pipe. 2. The downstream pipe volume of the gas meter according to claim 1, wherein the pressure of the downstream pipe is measured immediately before the opening of the gas supply valve, and the gas supply valve is opened when the pressure is zero or close to zero. Estimation method. 3. The downstream of the gas meter according to claim 1, wherein after the downstream side pipe volume is estimated, the pressure drop is measured to estimate the gas leakage, and if the leakage amount is small, the estimation of the pipe volume is effective. Side pipe volume estimation method.