JPS60105931A - Leakage detecting apparatus for gas piping and gas appliance - Google Patents

Abstract

PURPOSE:To enable the instantaneous detection of a gas leakage, by generating a predetermined signal by processing the signal from ultrasonic sensors arranged along gas pipings and gas appliances at appropriate intervals. CONSTITUTION:Ultrasonic sensors 3... are arranged along a gas pipings 1 of gas and gas appliances 2 at appropriate intervals and connected to a corresponding signal generating apparatus 4 arranged at a proper place in a room. By this mechanism, the ultrasonic wave due to the gas leakage generated in the pipe 1 is received by the sensors 3... and an alarm signal can be generated in a sound form by the apparatus 4.

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 appliances, and issues predetermined response signals, such as alarms and emergency shutoff valves. This invention relates to a leakage detection device that generates a cutoff signal and the like.

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. 6 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 Q, 1Nm"/h, the concentration reaches the detection level of the detector after a long time after the leakage occurs, but does not reach the lower explosive limit, and 3. 5
In the case of 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, an explosion will not occur. There is some margin because there is a large difference between the time it takes to reach the lower limit and the time it takes to reach the detection level. However, if the leakage amount is 5 Nm3/h, the lower explosion limit will be reached in about 20 minutes, but it is necessary to prevent this leakage. It takes about 5 minutes to detect the leak, which shows that the time from detecting the leak to reaching the lower explosive limit is short.By the way, Figure 6 shows that the leaked gas is released instantly and uniformly. This is based on the assumption that they will mix, but in reality, explosive air is locally generated within 5 minutes at the detector.

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 that explosive gas will occur before detection, and a high level of safety cannot be ensured. Detection equipment is required. Furthermore, the conventional method described above has the disadvantage that the specific gravity of the gas must be taken into consideration when installing the sensor.

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 drawbacks of the conventional concentration detection method are completely solved, and leakage can be detected instantaneously, and the degree of freedom in the installation location of the sensor is increased. Furthermore, under normal circumstances, noise in the ultrasonic range is extremely low, ensuring reliable operation. The present invention will be described in detail below based on examples.

In Fig. 1, reference numeral 1 indicates gas piping that transfers flammable gas such as city gas, toxic gas, etc., and 2 indicates various gas equipment.
Ultrasonic sensors 3, 3 . ... will be installed. the ultrasonic sensor 3,
3. . . . is connected to a corresponding signal generator 4 installed at an appropriate location such as indoors. The corresponding signal generating device 4 is connected to the ultrasonic sensors 3, 3 . . . . to generate a predetermined corresponding signal, such as an alarm signal or a shutoff signal for an emergency shutoff valve.

In such a configuration, when gas leakage occurs in the piping 1 or various devices 2 due to cracks, pinholes, loosening of flanges or screws, etc., ultrasonic waves are generated at the same time.゜... and generates a warning signal in the form of a sound, light, etc. or a shutoff signal for an emergency shutoff valve to the corresponding signal generator 4, thereby preventing accidents caused by gas leakage. It can be prevented. 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 6, thereby achieving a high degree of safety. can achieve sexuality.

Figure 4 shows an example of the spectrum of the sound generated by gas leakage, that is, the leakage sound. From this figure, it can be seen that although the overall shape of leakage sound changes depending on the amount of leakage, ), the sound pressure level in the ultrasonic range is higher than that in the ultrasonic range. Therefore, by focusing on ultrasonic waves in an appropriate frequency range, for example, 60 to 40 kHz in the example, and detecting the presence or absence of ultrasonic waves, it is possible to detect the presence or absence of leakage. It can be seen that it is possible to detect 1 well. Figure 5 shows the relationship between 60 and 4 depending on the size of the leakage amount.
It shows the change in the sound pressure level of ultrasonic waves in the frequency range of 3 kHz, and from this figure, it can be seen that if there is a leakage of about Q, iNm''/h, an ultrasonic leakage sound of about 4 Q dB will be generated. The sound pressure level of the ultrasonic leak sound shown in Fig. 5 is a value measured at a point 1 m away from the sound source, and the sound pressure level decreases by 6 dB for each doubling of the distance. , 4m, 13m...The 1 pressure level at distant points is 64 dB, 28 dB, 2, respectively.
2 dB,... C in the figure shows the minimum detection sound pressure level (approximately 22 dB) in the embodiment of the detection device of the present invention, and in this case, the maximum detection distance is approximately 8 m as described above.
becomes. By the way, the sound pressure level of the leakage sound will be higher if the gas pressure inside the pipe 1 is higher, even if the amount of leakage is the same.
The maximum detection distance becomes longer.

As described above in consideration of the above longest detection distance, it is possible to reliably detect even if the distance is exceeded at appropriate intervals along the gas piping 1 and the gas equipment 2. The longest detection distance is the maximum detection distance between the ultrasonic sensors 3, 3 . For example, the length can be increased by installing a sound collector 5 as shown in FIG. ．． It is possible to reduce the number of... Furthermore, if the sound collector 5 provides directivity to the reception of ultrasonic waves, the ultrasonic sensors 3, 3. Even if a noise source in the ultrasonic range exists in the vicinity of..., malfunctions can be easily prevented without being affected by the noise source. As a measure to prevent malfunction due to such noise from other places, the ultrasonic sensors 3, 3.・
In addition to the method of imparting directivity to the ultrasonic sensors 3, 3. ... is processed by a filter in the corresponding signal generator 4 to narrow the frequency range of interest, or by performing more advanced signal processing using a microcomputer, etc., as appropriate. be able to.

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 along the gas piping and gas equipment. 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. A major feature is that accidents caused by leaks can be reliably prevented. Furthermore, since the present invention provides an ultrasonic sensor outside gas piping and gas equipment, it can be easily installed on existing gas piping and gas equipment, and can also be installed on existing gas piping and gas equipment. A feature is that when devices are installed in parallel, they can be monitored all at once. Furthermore, since the present invention detects ultrasonic waves as described above,
There is no need to consider the specific gravity of the target gas when installing the sensor, and there is a large degree of freedom in installation.

[Brief explanation of the drawing]

FIG. 1 shows an example of the configuration of the present invention. The explanation is shown in FIG.
a), (b), and (C) are actual side views of the configuration of the present invention, FIG. 6 is an explanatory diagram of the operation, FIG. 4 is an explanatory diagram showing an example of the spectrum of the amount of gas leakage, and FIG. FIG. 6 is an explanatory diagram showing changes in sound pressure level with respect to leakage amount. FIG. 6 is an explanatory diagram showing temporal changes in indoor gas concentration when gas leakage occurs. Code 1...Gas piping, 2...Gas equipment, 3,3.・・・
...Ultrasonic sensor, 4. Compatible signal generator, 5. Sound collector. L..., 7th Figure 3 Elapsed time → Figure 4

Claims (2)

[Claims] (1) Ultrasonic sensors installed at appropriate intervals along gas piping and gas equipment, and a corresponding signal generating device that appropriately processes signals from the ultrasonic sensors and generates predetermined corresponding signals. Leak detection device for gas piping and gas equipment featuring (2) A gas piping leak detection device according to claim 1, characterized in that the ultrasonic sensor is provided with a sound collector.