JPS60105932A - Leakage detecting apparatus of gas piping and gas appliance - Google Patents

Abstract

PURPOSE:To enable the instantaneous detection of a leakage, by generating a predetermined signal by processing the signal from ultrasonic sensors arranged in gas pipings at appropriate intervals. CONSTITUTION:Ultrasonic sensors 2... are arranged in gas pipings 1 of gas at appropriate intervals and connected to a corresponding signal generating apparatus 3 provided to a proper place in a room. By this mechanism, the ultrasonic wave due to the gas leakage in the pipe 1 is received by the sensors 2... and an alarm signal can be generated in a sound form by the apparatus 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects gas leakage from piping that transfers flammable gas such as city gas, toxic gas, etc. and from various gas equipment.
This invention relates to a leakage detection device that generates a predetermined response signal, such as an alarm or a shutoff signal for an emergency shutoff valve.

BACKGROUND ART Conventionally, a concentration detection type combustible gas detector has been used to monitor gas leaks in city gas and the like. However, with this method, after a leak occurs, it takes a certain amount of time for the gas concentration near the sensor installation point of the detector to reach the detection level, so there is a time delay in detecting the leak. The longer the distance from the installation location, the more significant it is. FIG. 5 shows an example of a temporal change in the indoor gas concentration when a leak occurs, where A indicates the lower explosion limit and B indicates the detection level of the combustible gas detector. According to this figure, when the leakage amount is Nm3/b, the concentration reaches the detection level of the detector a long time after the leakage occurs, but does not reach the lower explosive limit, and 3,5 Nm
”/h, it can be seen that the lower explosive limit is reached a long time after reaching the detection level.In the case of a leak of this magnitude, even if there is a time delay in detecting the leak, the lower explosive limit is reached after a long time after reaching the detection level. There is a margin because there is a large difference between the time to reach the limit and the time to reach the detection level.However, if the leakage amount is 5
At Nm3/h, the lower explosive limit is reached in about 20 minutes, but it takes about 5 minutes to detect this leak, and the time from detecting the leak to reaching the lower explosive limit is I know it's short. By the way, FIG. 5 was drawn on the assumption that the leaked gas instantaneously mixes with L or about -, and in reality, explosive gas is locally generated within 5 minutes until detection. The same local explosion occurs even when the amount of leakage is small.

As mentioned above, conventional concentration detection type combustible gas detectors are
Since there is a time delay in detecting a leak, there is a high risk of explosion air occurring before detection, and a high degree of safety cannot be ensured. Leak detection equipment is required.

The present invention was made based on the knowledge that when gas is ejected from a microscopic hole, it generates ultrasonic waves.In other words, the ultrasonic waves are received by a sensor and can be used to issue alarms, shut-off signals for emergency shut-off valves, etc. By generating a corresponding signal, the shortcomings of conventional concentration detection methods are completely resolved and leakage can be detected instantaneously.Furthermore, under normal environments, noise in the ultrasonic range is eliminated. Since this is extremely small, reliable operation can be achieved.The present invention will now be described in detail based on examples.

In FIG. 1, reference numeral 1 is a gas pipe for transporting flammable gas, toxic gas, etc. such as city gas, and inside the gas pipe 1,
Ultrasonic sensors 2, 2, . . . are installed at appropriate intervals. The ultrasonic sensors 2, 2, . . . are connected to a corresponding signal generating device 3 installed at a suitable location, such as indoors.

The corresponding signal generating device 3 is the ultrasonic sensor 2, 2...
The structure is such that the signal from the controller is processed appropriately to generate a predetermined corresponding signal, such as an alarm signal or a shutoff signal for an emergency shutoff valve. Reference numeral 4 indicates various gas appliances.

In such a configuration, when gas leakage occurs in the piping 1 or various devices 4 due to cracks, pinholes, loosening of flanges or screws, etc., ultrasonic waves are generated at the same time and are received by the ultrasonic sensors 2. The corresponding signal generator 3
By generating an alarm signal in the form of sound or light or a cutoff signal for an emergency cutoff valve, it is possible to prevent accidents caused by gas leakage. Since the present invention detects gas leaks using the ultrasonic waves generated when the gas leaks, it is possible to instantly detect and respond to leaks as shown in Figure 2, resulting in a high level of safety. can be achieved.

Figure 3 shows an example of the spectrum of the sound that occurs accompanying gas leakage, that is, the leakage sound.As can be seen from this figure, although the overall shape of leakage sound changes depending on the amount of leakage, leakage Q
The sound pressure level in the ultrasonic region is higher than in a state where there is no noise (background noise), so the presence or absence of ultrasonic waves is detected by focusing on ultrasonic waves in an appropriate frequency range, for example, 30 to 40 kHz in the embodiment. It can be seen that the presence or absence of leakage can be detected satisfactorily. Figure 4 fa) shows the change in the sound pressure level of an ultrasonic wave with a frequency of 40 kHz depending on the amount of leakage.From the figure, if there is a leakage of about 0.1 Nm"/h, for example, the sound pressure level will be about 40 dB. This ultrasonic leakage sound is generated, and the flow noise is about OdB, so it can be seen that such an ultrasonic leakage sound can be clearly identified.The sound pressure level of the ultrasonic leakage sound shown in Fig. 4 is The sound pressure level is measured at a point approximately 5 Crn away from the sound source inside the sound source, and the sound pressure level increases as the distance from the sound source increases, for example in Figure 4 (1).
)) Attenuates with the amount of attenuation shown in Further, the sound pressure level of the leakage sound becomes higher when the gas pressure inside the pipe 1 is higher, even for the same amount of leakage.

The longest detection distance was derived based on the above various conditions, and as described above, taking the longest detection distance into consideration, the gas piping 1 in Figure 4
By installing ultrasonic sensors 2.2 at appropriate intervals within the gas pipe 1, it is possible to reliably detect leaks occurring anywhere in the gas piping 1 and various gas equipment 4. . Noise and flow noise from equipment such as combustion equipment and governors may also reach the ultrasonic sensors 2, 2... in the gas pipe 1, but as a preventive measure against malfunction due to such noise, for example, ultrasonic The signals from the sensors 2, 2, etc. are processed with a filter in the corresponding signal generator 3 to narrow the frequency range of interest, or more advanced signal processing is performed using a microcomputer, etc., as appropriate. This can be done through signal processing.

As described above, the present invention detects the leakage by detecting the ultrasonic waves generated due to the gas leakage using the ultrasonic sensors installed at appropriate intervals in the gas piping.
Unlike conventional concentration detection methods, there is no time delay in detecting leaks, and leaks can be detected instantly, and appropriate countermeasures can be taken, such as warnings and shutting off emergency shutoff valves. It has the feature of being able to reliably prevent accidents caused by leakage. In particular, since the present invention provides an ultrasonic sensor in a gas pipe, it is not affected by walls even when the pipe spans multiple rooms, and is also resistant to external noise. .

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing one embodiment of the configuration of the present invention, Fig. 2 is an explanatory diagram of operation, Fig. 6 is an explanatory diagram showing an example of the spectrum of the amount of gas leakage, and Fig. 4 (a) is an explanatory diagram showing an example of the spectrum of the amount of gas leakage. Figure 4 is an explanatory diagram showing changes in sound pressure level with respect to quantity (l is an explanatory diagram showing changes in sound pressure level with respect to distance, and Figure 5 shows temporal changes in indoor gas concentration when a gas leak occurs) It is an explanatory diagram. Code 1: Gas piping, 2, 2-: Ultrasonic sensor, 3.
... Compatible signal generator, 4. Gas equipment. Figure 1 Figure 9 Progress #Review → Figure 3 01 Number of eyebrows kHz Figure 4 (a) L ○O Leakage amount N branch h

Claims (1)

[Claims] Gas piping, characterized in that it is provided with ultrasonic sensors installed at appropriate intervals in the gas piping, and a corresponding signal generator that appropriately processes signals from the ultrasonic sensors and generates predetermined corresponding signals. Leak detection device for gas equipment