JP5946673B2 - Gas shut-off device - Google Patents

Description

  The present invention relates to a gas cutoff device that performs leakage determination.

  Conventionally, as this type of gas shut-off device, there has been a gas shut-off device that reliably detects leakage of the inner pipe even in an environment in which pulsation occurs (see, for example, Patent Document 1).

  FIG. 4 shows a block diagram of such a gas shut-off device, which comprises a control means 31, a flow rate measurement means 32, a section calculation means 34, and a flow rate presence / absence determination means 35.

  The flow rate presence / absence determination means 35 is such that the difference between the maximum flow rate and the minimum flow rate calculated by the interval calculation means 34 at a predetermined time is less than the determination allowable range, and the interval average flow rate is within the determination allowable range and the determination allowable range shift amount. The average flow rate (section average flow rate) for a given time is accumulated, and when the number of determinations is accumulated, the average flow rate is calculated by averaging the section average flow rate for the number of determination times. When the flow rate is within the determination flow rate, there is no flow rate, and an inner pipe leakage determination timer (not shown) is initialized.

  The inner pipe leakage determination timer is a timer for determining that leakage has occurred when a predetermined period is counted, and determining that there is no flow rate by determining the average flow rate calculated periodically as described above. In such a configuration, initialization (reset) is performed, and time measurement is continued unless it is determined that there is no flow rate. Therefore, it can be determined that there is an inner pipe leak when the time measurement is continued without being reset for a predetermined period.

JP 2010-216724 A

  However, the actual flow rate may swell for a long time due to gas piping conditions and pulsations, and the entire flow rate may shift to the negative side during short-time measurement. For this reason, in the conventional configuration, even if the average flow rate exceeds the threshold value for determining leakage, the flow rate is measured by shifting to the negative side, so that this threshold value is not reached. In some cases, there was no flow rate.

  Accordingly, when it is determined that there is no flow rate, the inner pipe leakage determination timer is reset, and there is a possibility that it is determined that there is no inner pipe leakage and is not accurate.

  The present invention solves the above-mentioned conventional problem. When it is detected that the actual flow rate is shifted to the negative side, the inner pipe leakage determination timer is not reset, so that there is no leakage. An object of the present invention is to provide a gas cutoff device that can prevent inaccurate determination.

  In order to solve the above-described conventional problems, a gas shutoff device according to the present invention includes a flow rate measuring unit for measuring a gas flow rate, a time measuring unit for measuring a predetermined period, and a flow rate measured by the flow rate measuring unit. A flow rate non-determining unit that determines the presence or absence of a flow rate every predetermined time, and resets the time value of the timing unit when it is determined that there is no flow rate, and a leak determination unit that determines that there is a leak when a predetermined period of time is counted by the timing unit And a flow rate shift determining unit that determines whether or not the flow rate is shifted to the negative side by the flow rate measuring unit, wherein the leak determination unit is configured such that the flow rate measured by the flow rate shift determining unit is negative. When it is determined that there is a shift, the time value of the time measuring means is not reset by the flow rate non-determining means, and it is determined that the flow rate is shifted to the negative side. If there is no possibility that the flow rate is not determined and the timer that performs the leak determination is not reset, the flow rate threshold may not actually be exceeded, but it is not accurate. It is possible to prevent the determination.

  Note that if this state continues by not resetting the leak determination timer, it is determined that there is a leak after the timer counts up, but this is a safe determination and does not reduce the safety.

  When it is determined that the flow rate has shifted to the negative side, the gas shutoff device of the present invention avoids resetting the time measured value by the flow rate non-determining means, so that there is no leakage despite the flow rate. This makes it possible to prevent inaccurate determinations and improves security.

The block diagram of the gas cutoff device in Embodiment 1 of this invention Schematic configuration diagram of the flow rate measuring means in Embodiment 1 of the present invention The figure explaining operation | movement of the time measuring means in Embodiment 1 of this invention. Block diagram of a conventional gas shut-off device

  According to a first aspect of the present invention, a flow rate measuring unit for measuring a flow rate of gas, a time measuring unit for measuring a predetermined period, and determining the presence / absence of a flow rate for each first predetermined time from the flow rate measured by the flow rate measuring unit, When it is determined that there is no flow rate, the flow rate non-determining unit that resets the time value of the time measuring unit, the leak determination unit that determines that there is a leak when a predetermined period of time is measured by the time measuring unit, and the flow rate measuring unit makes the flow rate negative. A flow rate shift determining means for determining whether or not a shift has occurred, and the leakage determination means determines that the flow rate is not determined when it is determined that the flow rate measured by the flow rate shift determination means is shifted to the minus side. The time value of the time measuring means is not reset by the means. Thereby, when it is detected that the flowing flow rate is shifted to the minus side, the time value of the time measuring means for performing the leakage determination is not reset, so that the inaccurate determination in the inner pipe leakage determination is performed. This can be prevented and the security is improved.

  According to a second aspect, in the first aspect, the flow rate shift determining unit obtains an average flow rate every second predetermined time from the flow rate measured by the flow rate measuring unit, and the average flow rate is a third predetermined time. When the value falls below a predetermined number of times, it is determined that the flow rate has shifted to the minus side. As a result, an abnormal gas flow rate due to gas piping or pulsation can be detected, and measurement at an inaccurate flow rate can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 shows a block diagram of a gas shut-off device according to a first embodiment of the present invention. In the figure, a flow rate measuring means 1 obtains a flow rate at a predetermined sampling interval (for example, every 2 seconds), and in this embodiment, a gas in a gas supply pipe (not shown) is used using an ultrasonic signal. The system detects the difference in propagation time caused by the flow and detects the instantaneous flow rate of gas.

  FIG. 2 shows a flow rate measuring method in the flow rate measuring means 1, and as shown in the figure, it has a measurement flow path 21 connected to a gas supply pipe (not shown), A pair of ultrasonic transceivers 22 and 23 are arranged on the upper and lower sides of the road side surface. These ultrasonic transceivers 22 and 23 are set so that the ultrasonic propagation path A obliquely crosses the gas flow B flowing through the measurement flow channel 21, and by alternately transmitting and receiving ultrasonic waves, The ultrasonic wave propagates in the forward and reverse directions.

  At this time, the distance between the ultrasonic transceivers 22 and 23, that is, the measurement distance is L, the angle of the ultrasonic propagation path with respect to the gas flow is φ, and the ultrasonic propagation time from the upstream to the downstream of the ultrasonic transceivers 22 and 23 is If t1, the ultrasonic wave propagation time from the downstream to the upstream is t2, and the sound velocity is C, the flow velocity V is obtained by the following equation.

V = L / 2COSφ ((1 / t1-1 / t2))
The instantaneous flow rate of the gas flow is calculated from the flow velocity V and the cross-sectional area of the measurement channel 21.

  In addition, although the ultrasonic-type measuring means is used regarding the flow-rate measuring means of this invention, as a measuring system, what is necessary is just to be able to measure instantaneous flow volume continuously also by other flow-rate measuring systems.

  The flow rate non-determining unit 2 determines the presence or absence of a flow rate from the flow rate measured by the flow rate measuring unit 1, and a specific operation will be described later.

  The flow rate shift determining unit 3 obtains an average flow rate every second predetermined time from the flow rate measured by the flow rate measuring unit 1, and when the average flow rate falls below the predetermined flow rate a predetermined number of times within the third predetermined time. It is determined that the actual flow rate has shifted to the minus side.

In the present application, the second predetermined time is set to 120 seconds, the third predetermined time is set to 30 days, the predetermined flow rate is set to -3.5 L / h , and the predetermined number of times is set to 10 times.

  FIG. 3 is a diagram for explaining the operation of the time measuring means in the present embodiment, and the time measuring means 4 measures the fourth predetermined time as shown in the figure. Here, the flow rate non-determining means 2 is based on the flow rate measured by the flow rate measuring means 1 and the difference between the maximum flow rate and the minimum flow rate is less than the determination allowable width at every predetermined time and the average flow rate (hereinafter, section average flow rate). If it is less than the average determination flow rate, it is determined that there is no flow rate, the time value of the time measuring means 4 is reset, and time measurement is started again (a in FIG. 3).

In the present application, the fourth predetermined time is set to 30 days, the predetermined time is set to 120 seconds, the determination allowable range is set to 10 L / h , and the average flow rate determination is set to 1.5 L / h .

  Further, the leak determination means 5 determines that there is a leak when the clock means 4 completes the time measurement for a predetermined period (b in FIG. 3).

  The operation and action of the gas shut-off device configured as described above will be described below.

  First, the flow rate shift determining means 3 obtains an average flow rate every second predetermined time, and when the average flow rate falls below a predetermined value a predetermined number of times within the third predetermined time, it is measured by the flow rate measuring means 1. Is determined to have shifted to the negative side.

  And when it is determined that the flow rate is shifted to the minus side, the flow rate non-determining means 2 does not perform the flow rate non-determination process. The time value of the means 4 is not reset.

  Therefore, if the state in which the flow rate is shifted to the minus side continues in this way, the timing by the timing means 4 is continued until the predetermined period has elapsed, and when the timing of the predetermined period is completed, the leakage determination means 5 determines that there is a leak. Is done.

  The flow rate shift determining means 3 obtains the average flow rate every second predetermined time, and if this average flow rate does not fall below the predetermined value within the third predetermined time, the flow rate measuring means 1 It is determined that the measured flow rate is not shifted to the minus side with respect to the actual flow rate, and the flow rate non-determination unit 2 resumes the non-flow rate determination.

  The gas shut-off device shown above can be easily realized by a program in a computer.

  As described above, the gas shutoff device according to the present invention is inaccurate to prevent leakage even when the flow rate measured in a situation where pulsation occurs shifts to the negative side. Since determination can be prevented, the present invention can be applied not only to gas but also to a method for detecting gas leakage.

DESCRIPTION OF SYMBOLS 1 Flow measurement means 2 No flow determination means 3 Flow shift determination means 4 Timing means 5 Leakage determination means

Claims (2)

A flow rate measuring means for measuring the flow rate of the gas;
A time measuring means for measuring a predetermined period;
Whether or not the flow rate measured by the flow rate measuring means is within a predetermined flow range, the presence or absence of the flow rate is determined.
Leakage determination means for determining that there is a leak when a predetermined period of time is counted by the timing means;
A flow rate shift determining means for determining whether or not the flow rate measured by the flow rate measuring means is shifted to the negative side,
The flow rate shift determining unit obtains an average flow rate every second predetermined time from the flow rate measured by the flow rate measuring unit, and the average flow rate is set to be more negative than the flow rate range within the third predetermined time. When the predetermined flow rate is less than the predetermined number of times, it is determined that the flow rate has shifted to the negative side,
The leak determining means does not reset the time value of the time measuring means by the non-flow rate determining means when it is determined that the flow rate measured by the flow rate shift determining means is shifted to the minus side. Gas shut-off device. A program that causes a computer to function as all or part of the gas cutoff device according to claim 1 .

Images