JPH049633A - Gas leakage detector - Google Patents

Abstract

PURPOSE:To surely detect gas leakage and to previously prevent the generation of a serious accident by comparing a pressure signal outputted from a pressure signal oscillator connected to a pressure sensor arranged on the upstream side of a shut-off valve with a flow rate signal outputted from a flow rate signal oscillator connected to a downstream flow rate sensor to detect a gas leakage state. CONSTITUTION:A microcomputer 14 compares the pressure signal received from the pressure signal oscillator 13 connected to the pressure sensor 11 connected to the upstream side of the cut-off valve 10 with a flow rate signal received from the flow rate signal oscillator 15 connected to the downstream gas meter 12, detects the gas leakage state and displays the detected result on a display part 16. Namely when the flow rate signal is inputted to at the time of inputting a pressure variation signal, the generation of gas leakage on the upstream or downstream side of the flow rate sensor 12 is decided, and when no input of the flow rate signal, the generation of a leakage signal on the upstream side of the sensor 12 is decided.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a gas leak detection device for detecting gas leak from a gas flow path.

<Background Art> In recent years, gas explosion accidents caused by gas leaks from gas piping have been occurring frequently. In particular, when there is a long distance from a gas storage facility to a gas usage facility, such as in a hospital or school, and the distance is connected by a gas pipe buried underground, corrosion of the buried pipe and uneven ground subsidence may occur. There is a risk of cracks forming in the buried pipes and gas leakage.

Conventionally, in order to detect gas leakage from such a gas flow path, a pressure sensor is placed inside the gas flow path, and inspection is carried out at a predetermined period, for example, once a year or once every two years. , Close both ends of the gas flow path to be inspected and reduce the pressure inside the gas flow path to 850 mmH.
Gas leakage is detected by increasing the pressure to about zO and inspecting for the presence or absence of pressure drop due to leakage.

There is also a method of detecting gas leakage by disposing a flow rate sensor in the gas flow path and constantly monitoring the gas flow rate to monitor for abnormalities in the gas flow rate that would not occur during normal gas use.

The gas cutoff device 1 linked to the pressure sensor shown in FIG.
This is an example.

This gas cutoff device 1 includes a gas flow path 3 equipped with a cutoff valve 2, a pressure sensor 4 that detects a pressure drop in the gas flow path 3, and a pressure sensor 4 that detects the flow of gas in the gas flow path 3 and transmits a flow rate signal. a pressure signal transmitter 5 that transmits a pressure signal when the pressure sensor 4 detects a pressure drop in the gas flow path 3; After the input pressure signal is stored, the decreasing gas pressure increases and the flow rate transmitter 5
A cutoff signal device 7 is provided which sends a signal to cut off the cutoff valve 2 when a flow rate signal sent from the cutoff valve 2 is input.

With this gas cutoff device 1, when the gas appliance is in use, when replacing the LP cylinder (container) or for some other reason,
If you forget to turn off the gas appliance even though the gas pressure has dropped and the flame has gone out, if the gas pressure rises again,
Gas flow path 3 is shut off to prevent gas leakage.

<Problems to be solved by the invention> However, the method of detecting gas leaks through periodic inspections
Leakage that occurs immediately after an inspection is overlooked until the next inspection, making early detection impossible. In other words, if there is no leakage during periodic inspections, or if the leakage is not detected because it is a very small amount, leakage over a long period of time may cause the accumulated gas to reach a dangerous amount, or the buried pipe may corrode over time. As the gas progresses, the amount of leakage increases, creating the risk of a gas explosion.

In addition, with the method of detecting gas leaks by constantly monitoring the gas flow rate with a flow sensor, if a leak occurs upstream of the flow sensor, the flow sensor will not function, so leaks downstream of the flow sensor will be detected. Even if possible, leaks on the upstream side cannot be detected.

As explained earlier, in facilities such as hospitals and schools,
The distance between gas storage facilities and gas usage facilities is long, and these are often connected by gas pipes buried underground. In such cases, the flow rate sensor is usually built into a gas meter of the gas-using facility or fixed to the wall of the gas-using facility.

Therefore, even if a leak occurs in the buried pipe, the flow rate sensor does not function and the gas leak cannot be detected.

<Means for Solving the Problems> The present invention has been proposed in view of the above, and is provided in a gas passage provided with a shutoff valve on the downstream side of the shutoff valve to control the flow rate of gas flowing into the gas passage. a flow rate sensor for detecting a gas flow; a flow rate signal transmitter for transmitting a flow rate signal when the flow rate sensor detects a gas flow; and a pressure sensor provided on the upstream side of the shutoff valve for detecting gas pressure in a gas flow path; A pressure signal transmitter that transmits a pressure fluctuation signal when the pressure sensor detects a change in gas pressure is electrically connected to the flow rate signal transmitter and the pressure signal transmitter, and the signals from both transmitters are compared and calculated. It is characterized by comprising a calculation means that detects a gas leakage state by doing so and generates a leakage signal.

<Function> The flow rate sensor monitors the gas flow rate in the gas flow path, and when the flow rate sensor detects the gas flow, the flow rate signal transmitter emits a flow rate signal.

The pressure sensor monitors pressure fluctuations in the gas flow path, and when the pressure sensor detects a fluctuation in gas pressure, the pressure signal transmitter transmits a pressure fluctuation signal.

The calculation means compares and calculates the flow rate signal from the flow signal transmitter and the pressure fluctuation signal from the pressure signal transmitter.

If a pressure fluctuation signal is input even though the gas appliance, etc. is not in use, and a flow rate signal is input, it indicates that a gas leak has occurred on the upstream or downstream side of the flow sensor. As a result, a leakage signal is transmitted. Also,
If a pressure fluctuation signal is input but a flow rate signal is not input, it is assumed that a gas leak has occurred on the upstream side of the flow rate sensor, and a leak signal is transmitted.

Embodiments The present invention will be described below based on embodiments shown in the drawings.

FIG. 1 is a schematic block diagram of one embodiment of the present invention.

This gas leak detection device 8 includes a cutoff valve 10 provided in the middle of a gas flow path 9 , a pressure sensor 11 for detecting gas pressure in the gas flow path 9 on the upstream side of the cutoff valve 10 , and a pressure sensor 11 on the downstream side of the cutoff valve 10 . A gas meter 12 which is a flow rate sensor for detecting the flow rate of gas flowing through the gas flow path 9 is provided. Then, the pressure sensor 11 is electrically connected to a microcomputer 14 which is a calculation means via a pressure signal transmitter 13, and
Gas meter 12 is electrically connected to microcomputer 14 via flow rate signal transmitter 15 . In addition, the microcomputer 14 is electrically connected to a display section 16 that displays an abnormality display, etc., and a shutoff valve 10, and a battery 17.
Provides more driving power. The shutoff valve 10 includes a shutoff valve 10
Connect the return safety device 18 for returning the .

Further, on the upstream side of the gas flow path 9, a pressure regulator 19 is provided for adjusting the gas pressure flowing into the gas flow path 9 to a constant value.

The pressure signal transmitter 13 described above amplifies the signal from the pressure sensor 11, extracts only effective signal components using a filter, shapes the waveform using a waveform shaper, and transmits a pressure fluctuation signal that is a pulse signal.

Further, the flow rate signal transmitter 15 converts the mechanical movement of the gas meter 12 into an electrical signal every time the gas meter 12 rotates once. To explain the case where this flow rate signal transmitter 15 is installed in an abdominal type gas meter, the flow rate signal transmitter 15 is as follows.
It consists of a membrane that is driven by the flow of gas, a magnet that rotates in conjunction with the movement of the membrane, and a reed switch that detects the movement of the magnet and repeatedly turns on and off. and,
When the magnet rotates in response to the gas flow, the magnet approaches or moves away from the reed switch, turning the reed switch on and off, and each time the membrane moves back and forth, that is, each time the magnet rotates, one pulse is generated. Sends a flow signal.

The pressure regulator 19 is a device for adjusting the gas pressure flowing into the gas flow path 9 to a constant value. For example, in the case of LP gas, the cylinder pressure is 0.7 to 15.6 Kg/cm"
In order to normally burn the combustion equipment, it is necessary to reduce the gas pressure to 200 to 330 mm HwO and supply it. Therefore, a pressure regulator 19 is attached to the cylinder outlet to adjust the gas pressure flowing into the gas flow path 9.

FIG. 3 shows an example of the pressure regulator 19.

This pressure regulator 19 is a single-stage pressure regulator, and the inside of the main body 20 is divided into upper and lower parts by a diaphragm 21.
The upper part is an air chamber 22, and the lower part is a decompression chamber 23. A nozzle 25 is provided on the side of the gas inlet 24 of the decompression chamber 23, and a valve rod 2 is provided with a closing valve 27 at the injection port 26 of the nozzle 25.
8, and the valve stem 28 is connected via a lever 29 to an actuator 30 attached to the diaphragm 21. Further, the diaphragm 21 is pushed down toward the decompression chamber 23 by a spring 31 provided within the air chamber 22.

Therefore, when high-pressure gas flows in from the gas inlet 24, the gas passes through the nozzle 25 and enters the decompression chamber 23. If the gas continues to flow here, the pressure inside the decompression chamber 23 increases,
The diaphragm 21 is pushed up toward the air chamber 22 against the bias of the spring 31. Therefore, the actuator 30 attached to the diaphragm 21 also rises, the lever 29 connected to the actuator 30 rotates about the fulcrum 32, and the valve stem 28
moves to the gas inlet 24 side, and the closing valve 27 throttles the amount of gas injected from the nozzle 25, or closes the injection port 26 if the pressure is high. On the other hand, when the gas in the decompression chamber 23 flows out from the gas outlet 33, the pressure in the decompression chamber 23 decreases, and the diaphragm 21 descends toward the decompression chamber 23 due to the bias of the spring 31. Therefore, the lever 29 connected to the actuator 30 rotates about the fulcrum 32, and the valve stem 29 rotates about the fulcrum 32.
8 moves to the gas outlet 33 side, the closing valve 27 separates from the injection 026 of the nozzle 25, and the inflow amount of high pressure gas increases again.

In this way, the diaphragm 21 moves up and down as the pressure inside the decompression chamber 23 rises and falls, adjusting the inflow from the nozzle 25 and the gas flowing into the gas passage 9.
). In this case, the waste flow path 9 I;
: Oil, inflow t:i Gas pressure will pulsate.

In addition, in this embodiment, j k5 is used for the single-stage pressure regulator.
11 (-I explained the mechanism 7 of the power control beach, but this can be explained in other ways.
:Earth force A adjuster, θ11o, is changed to automatic switching pressure regulator, change j, lL! It's so hot! I am also 1illj (there is).

1” g+ffl, l, f:3.v;,, ”,' +
2, j Wang Rikyo 1 Seiki 19 is used Itegas i:f':, f
l! : "11! IV・Niro Ii、Insertion Buj I?、When adjusting the pressure, the monthly fluctuation of the pressure is important).This pressure fluctuation is婬、1 pox・：I
) When using 1, the gas flow path! 'li, T,'
, ! ', 1', , '· shows a different pattern from the case where an l+ crack or the like occurs and a minute gas leak occurs. 1, that is, the pressure fluctuation pattern 1' in the case of a minute leakage of pressure f, the fluctuation i''A, · time n, F''·< Ei seconds - several tens of seconds, 1 Hayabusa has a burning・(J・!”!
Compared to the pressure fluctuation pattern in the case of 'l I, ° (1, to 1..] <',)L'r I.

Figures 4 and 5 show the pressure fluctuations in the case of small gas leaks. , '1th11J force A adjustment j
With the convex fluctuating butter, the four patterns are small. In addition, FIG. 1-1) shows a pattern 1 using the automatic switching pressure regulator 19. This pressure fluctuation bata 12.

The time interval between death and birth is not constant, and leakage −i;: J
j)・Become a soldier. In addition, the pattern is also 8
1. Although it varies depending on the component equipment of the thread, if the flow path system is specified and there is a change in the leakage amount by 4, then L4 is almost constant.
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Ishi East 1) Bar 1N-・4 Elementary 1-, f-fl 7U
Ayu 2 action pattern 2/ka starting point!・１１、”i ['!i
between 1 and 2) is a 1) 1)
Uzor 20 minutes, in the case of 1 seishan style 1 oka regulator (:i
approx.]-IO') i deto) and.

Top: 1iFl gas leak (1 to the center) Device 8
1. Determining gas leakage, explaining the principles 1.2. The presence or absence of the flow rate signal and the pressure fluctuation signal depending on the size of the
``Judge carefully.

Added t7t-i 1.11-no, the support where the pressure of 1 gegureki haiku was detected (j zo 1 1'ri ゛).

Gas Mego IS, if the current signal is detected! A gas leak occurred on the upstream side of the JT (JT downstream side).

If the assembly variation A No. 6 is 4' out, is the flow rate signal cedar d? ,ff, it is determined that a gas leak has occurred on the upstream side of the gas meter 12.

) - is detected but is not detected, but if a flow rate signal is detected (), it is determined that the j-soil sensor 11 is abnormal.

If the pressure deformation signal is not detected and no flow rate signal is detected, it is determined that there is no gas leakage.

According to the flowchart of No. 7 and 1, it is possible to determine whether there is a gas leak! II
A first embodiment of the concept will be explained. In this embodiment, when a gas leak is detected (1), the location where the gas leak occurs is also shown on the display section 16.

Judgment processing! ! From the beginning, if the flow rate signal Q is not detected, iJ determines the presence or absence of the pressure fluctuation signal P.

Here, the pressure fluctuation signal P is detected f:lJ, L. If there is no dregs leakage, the display section 10 displays that there is no leakage, and the process ends. −) Uh,
If the H force fluctuation signal P is detected, it means that gas leakage has occurred upstream of the gas meter 12 and the display section 16
The process ends by displaying that there is waste leakage on the upstream side.

On the other hand, when the flow rate signal Q is detected, the pressure fluctuation point 1
Determine the presence or absence of No. P.

Here, the location number where the pressure fluctuation signal 1) was detected.

Since a gas leak has occurred either on the upstream side or on the downstream side of the gas meter 12, the 1 display section j6 will temporarily indicate that a gas leak has occurred on the downstream side (2. End. On the other hand, if 1-1 is not even detected in the pressure fluctuation signal, it means that the pressure sensor 11 is abnormal, so the display @
The process is terminated by displaying on Jl 16 that an abnormality has occurred in the pressure sensor 11, and a second embodiment of the gas leak determination process will be described with reference to the 70-chart in FIG. In addition to the judgment process of the first embodiment, the second embodiment detects whether the flow rate signal Q is detected and the pressure fluctuation signal P is detected. This is to determine whether there is a leak.

Therefore, only the determination of whether there is a leak on the upstream side or the downstream side of the gas meter 12 will be described, and a description of the determination process similar to that of the first embodiment will be omitted.

When the flow rate signal Q is detected and the pressure fluctuation signal P is detected, it is tentatively displayed that a gas leak has occurred on the downstream side. Then, when the gas appliance user or the like who has learned of the alarm closes the cutoff valve 10, the presence or absence of the pressure fluctuation signal P is determined again.

If the pressure fluctuation signal P is detected, this means that a gas leak has occurred upstream of the gas meter 12, so a message indicating that a gas leak has occurred upstream is displayed on the display section 16 and processing is performed. finish. On the other hand, if the pressure fluctuation signal P is not detected, a gas leak has occurred on the downstream side of the gas meter 12, so the display section 16 displays a message indicating that a gas leak has occurred on the downstream side, and processing is performed. finish.

A third embodiment of the gas leak determination process will be described with reference to the time chart of FIG. 9 and the flow chart of FIG. 10.

This third embodiment automatically performs the judgment process, and
It also determines whether a pilot flame is used, and if a gas leak occurs downstream of the gas meter 12, the shutoff valve 10 is automatically operated.

In the microcomputer 14, when the combustion appliance is not used and the flow rate signal from the flow rate signal transmitter 15 is not detected for a predetermined fixed signal reception start time, for example, 30 minutes, the pressure fluctuation from the pressure signal transmitter 13 is detected. The signal receiver begins to notice. When a pressure fluctuation signal is detected, the pressure fluctuation signal is started and the pressure fluctuation signal is continuously detected (0) within a predetermined signal interval time, for example, 30 minutes.

If so, it continues counting, and when the signal interval time is reached, a leakage signal is transmitted. On the other hand, if no pressure fluctuation signal is detected within the signal interval time, the count is cleared, the timer is reset, and the above process is repeated.

Further, if the use of the combustion appliance is restarted within the signal interval time and a flow rate signal from the flow rate signal transmitter 15 is detected, the previous count value is cleared and counting is stopped.
Return to the initial stage of processing.

The reason for setting the above signal interval time is to prevent a leak signal from being generated due to pressure fluctuations that are not due to gas leakage, such as pressure fluctuations due to expansion of gas piping due to sunlight or temperature changes. Such pressure fluctuations not based on gas leakage occur in a longer period than pressure fluctuations due to gas leakage. Therefore, by setting a certain signal interval time, pressure fluctuations that occur continuously within the signal interval time are assumed to be due to gas leaks, and pressure fluctuations that occur beyond the signal interval time period are caused by factors other than gas leaks. It has been determined that the pressure fluctuation was caused by

Note that both the signal reception start time and the signal interval time can be changed as appropriate.

The determination process starts, and if no rise in the flow rate signal is detected, the presence or absence of the pressure fluctuation signal P is determined.

Here, if the pressure fluctuation signal P is not detected, it means that no gas leakage has occurred, and therefore the display section 16 displays that it is normal and the process ends. On the other hand, when the pressure fluctuation signal P is detected, a gas leak has occurred upstream of the gas meter 12, so the display section 16 displays a message that a gas leak has occurred upstream, and processing is performed. finish.

On the other hand, when the flow rate signal Q is detected, the pressure fluctuation signal P
Determine whether or not there is.

Here, if the pressure fluctuation signal P is not detected, it means that the pressure sensor 11 is abnormal, so that the display unit 16 displays that an abnormality has occurred in the pressure sensor 11, and the process ends.

On the other hand, if the pressure fluctuation signal P is detected, it is determined whether the flow rate signal Q is less than 21β/h.

Here, the reason for determining whether the flow rate signal Q is less than 21β/h is because when a starter is used in a gas appliance, normally about 21 g/h of gas is in the gas flow path 9. This is to distinguish between the flow of gas caused by the use of the pilot flame and the flow of gas caused by gas leakage.

If the flow rate signal Q is 21° C./h or more, it is assumed that there is no micro-leakage of gas, and the display unit 16 indicates that the gas is normal, and the process ends.

On the other hand, if the flow rate signal Q is less than 21ρ/h, it is determined whether the pilot flame is in use.

If the pilot flame is in use, it is assumed that there is no minute leakage of gas, and the display section 16 displays that it is normal, and the process ends.

On the other hand, if the pilot flame is not in use, a small leakage of gas is determined.

If no microleakage has occurred here, the display section 16
Displays that the process is normal and ends the process. On the other hand, if a minute leak has occurred, the display unit 16 displays that a gas leak has occurred downstream of the gas meter 12, and the shutoff valve 10 is shut off so that the flow rate signal Q is not detected. Return to the case processing step and perform subsequent processing.

Note that the present invention can be applied not only when using LP gas but also when using city gas or convenience gas. In this case, when performing a leak test, the shutoff valve is closed and pressure fluctuations are measured. Then, usually with a changeover switch,
All you have to do is cancel the signal processing.

<Effects of the Invention> As explained above, the present invention provides a flow rate sensor on the downstream side of a cutoff valve, a pressure sensor on the upstream side of the cutoff valve, and a flow rate signal transmitter electrically connected to the flow rate sensor. A calculation means compares and calculates the flow rate signal transmitted by the pressure sensor with a pressure fluctuation signal transmitted by a pressure signal transmitter electrically connected to the pressure sensor. If a pressure fluctuation signal is input even though the gas appliance is not in use, and a flow rate signal is input, gas leakage may occur on the upstream or downstream side of the flow sensor. Furthermore, if a pressure fluctuation signal is input but a flow rate signal is not input, it is assumed that a gas leak has occurred upstream of the flow rate sensor, and a leak signal is transmitted.

Therefore, in facilities such as hospitals and schools, the distance between the gas storage facility and the gas usage facility is long, and the distance between them is connected by a gas pipe buried underground, and the flow rate sensor is installed in the gas meter of the gas usage facility. Even if the sensor is fixed to the wall of a gas-using facility, gas leaks on the upstream side of the flow sensor, such as in a buried pipe, can be reliably detected.

Furthermore, since gas leakage can be easily determined, gas leakage can be detected early, and serious accidents can be prevented from occurring.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a schematic block diagram showing a gas leak detection device of the present invention, FIG. 2 is a schematic block diagram showing a conventional gas cutoff device, and FIG. 3 is a schematic block diagram showing a conventional gas cutoff device. A side view showing the internal structure of the pressure regulator, Figures 4 and 5 are graphs showing pressure fluctuation patterns at the time of minute leaks, and Figure 4 shows pressure fluctuation patterns when using a single-stage pressure regulator. Figure 5 is the pressure fluctuation pattern when using an automatic switching pressure regulator, Figure 6 is an explanatory diagram of the criteria for determining gas leakage, and Figure 7 is
8 is a flowchart of the second embodiment, FIG. 9 is a time chart of the third embodiment, and FIG. 10 is a flowchart of the third embodiment. In the figure, 8... gas leak detection device, 9... gas flow path,
10... Shutoff valve, 11... Pressure sensor, 12 Gas meter, 13 Pressure signal transmitter, 14... Microcomputer, 15... Flow rate signal transmitter.

Claims (1)

[Scope of Claims] In a gas flow path equipped with a cutoff valve, a flow rate sensor that is provided downstream of the cutoff valve and detects the flow rate of gas flowing into the gas flow path; and when the flow rate sensor detects the flow of gas. A flow signal transmitter that sends a flow signal to the gas flow path, a pressure sensor installed upstream of the shutoff valve that detects the gas pressure in the gas flow path, and a pressure sensor that sends a pressure fluctuation signal when the pressure sensor detects a fluctuation in gas pressure. It is electrically connected to the pressure signal transmitter, the flow rate signal transmitter, and the pressure signal transmitter, and detects the gas leakage state by comparing and calculating the signals from both transmitters.
1. A gas leak detection device comprising: arithmetic means for generating a leak signal.