JP2001034863A - Air blow-type fire alarm system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fire alarm system which prevents the rapid sensitivity deterioration of a smoke sensor caused by dirt to enhance reliability by providing an air feeding tube supplying clean dry air to the respective smoke sensors, periodically spraying or blowing air to the smoke sensor from the air feeding tube provided with an air source, thereby removing dust entered into the smoke sensor. SOLUTION: An air source 1 has a filter for cleaning air compressed by a compressor and an air drier for dehumidifying and drying the compressed air. In an air feeding tube 2, branch tubes 2b are formed of nylon tubes, air directly flows from the opened terminal of the tube to be allowed to collide on sensors 8 and 9. As for air blowing, high pressure air is sprayed to the smoke sensors 8 and 9 in short time under environment where dusts large in particle size and apt to deposit are entered into the smoke sensors 8 and 9, and low pressure air is slowly blown under environment where dusts small in particle size and apt to float are entered into the smoke sensors 8 and 9, thereby ventilating the inside of the smoke sensors 8 and 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire alarm system suitable for use in factories or the like where airborne dust is generated, and more specifically, to improve reliability by preventing a decrease in sensitivity due to contamination of a smoke detector. About the system.

[0002]

2. Description of the Related Art Clear automatic fire alarm systems (hereinafter abbreviated as self-fire alarm systems) have clear installation standards defined by the Fire Service Law. Among the self-fire alarm equipment installed in accordance with this law, those that detect a sudden rise in indoor temperature with a differential distribution type sensor and activate the alarm will detect the initial fire before flaming. It may not be detected effectively.

For this reason, in factories and the like that use a differential distribution type sensor as a statutory self-fire alarm system, it is considered that voluntary equipment using a smoke detector is used to complement the statutory system. Have been.

[0004]

There are two types of smoke detectors: ion detectors and photoelectric detectors.

[0005] As shown in FIG.
An external ion chamber 21 through which air can freely enter and exit and an internal ion chamber 22 through which air does not easily enter are electrically connected in series by an external electrode 23, an intermediate electrode 24, and an internal electrode 25. The change (decrease) in the ion current is converted into a voltage and detected. When the voltage rise in the external ion chamber 21 exceeds a certain value, the switching circuit operates and the sensor operates.

There are two types of photoelectric smoke detectors: a scattered light type and a dimming type. Among them, in the former, as shown in FIG. 7, the projection light from the light emitting element 25 is scattered by particles flowing into the dark box 26, and the state of the scattering is detected by the light receiving element 27, and the amount of received light is more than a certain value. On the other hand, the latter activates when the amount of light transmitted through the smoke is reduced and the amount of light received by the light receiving element exceeds a certain value.

As described above, since the smoke detector detects the fine particles in the air flowing into the device by natural convection, a fire is generated at the stage where smoke, which is a collection of fine particles, is generated (before the flame is generated). Can be detected.

However, in a factory where a large amount of dust or the like floats, there is a concern that the smoke detector may suddenly lose sensitivity due to fouling.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fire alarm system (equipment) having improved reliability by preventing a sudden decrease in sensitivity of a smoke detector due to fouling.

[0010]

In order to solve the above-mentioned problems, in the present invention, air blowing of a smoke detector is performed. Specifically, in a fire alarm system that installs a smoke detector indoors to detect smoke generated by a fire and activates an alarm based on a signal from the smoke detector, the smoke detector is cleaned toward each smoke detector. An air supply pipe for supplying dry air is provided, and air is periodically blown or blown into the smoke detector from the air supply pipe provided with an air source to remove dust entering the smoke detector.

In this air blow, high-pressure air is blown to the smoke detector for a short time in an environment where dust having a large particle diameter and easily accumulates enters the smoke detector, and the dust having a small particle diameter and easily floating is detected by the smoke detector. In the environment where the gas enters the gas detector, the low pressure air is blown slowly to ventilate the detector, or the air supply pipe is directly connected to each smoke detector, and the air is blown into the smoke detector from the air supply pipe for the required time A better effect can be expected if the sensor is ventilated.

When a photoelectric smoke detector is used as the smoke detector, it is preferable to blow and blow air to the photoelectric smoke detector from the side opposite to the confirmation light.

Further, it is preferable to provide an electromagnetic valve for individually opening and closing each air outlet of the air supply pipe, and to blow or blow air to each smoke detector with a time difference.

[0014]

Dust that has entered the smoke detector is blown off by the air blow, which reduces contamination of the detector and prevents a sharp drop in sensitivity.

If air blow is performed continuously continuously, smoke flowing into the sensor by natural convection is also blown off,
Since the detection is not performed and the normal fire notification is hindered, the spraying time is shortened and the spraying is performed intermittently with a certain time interval.

If the supplied air is dirty air or air containing moisture, the effect may be adversely affected. Therefore, the air to be used is clean dry air.

Further, in an environment in which dust having a large particle diameter and easily accumulates enters the smoke detector, the accumulated dust can be blown off by blowing high-pressure air for several seconds, and good results can be obtained. In an environment in which dust having a small particle size and easily floats enters the smoke detector, if air is strongly blown, the floating dust is blown to the sensor and adheres thereto, which further promotes fouling. Therefore, in the latter environment, the inside of the sensor is ventilated by slowly blowing low-pressure air so that floating dust is not sprayed.

[0018] Even when the ventilation pipe is directly connected to the smoke detector to ventilate the interior of the detector, it is preferable to make a difference between the pressure of the blown air and the blowing time according to the environmental conditions. In addition, if the air pipe is directly connected to the smoke detector, it will not meet the structural standards stipulated by the Fire Service Law. However, if it is equipment installed voluntarily to supplement legal equipment, it will not conflict with the law.

In addition, when the air blow to the photoelectric smoke detector is performed from the opposite side of the confirmation light, dust floating in the air is not blown toward the light emitting portion and the light receiving portion of the sensor, and the sensitivity is reduced. The effect of maintenance increases. Since the ionization type smoke detector does not include an optical element, changing the direction of the air blow does not change the effect.

If the air blow of each smoke detector is performed with a time difference, the capacity of the air source may be small, and the equipment cost can be reduced. When air blowing of each smoke detector is performed at the same time,
In the meantime, a normal fire alarm is not made and a blank time zone occurs. However, if air blowing is performed with a time difference, this problem is solved, and the reliability of the system is further improved.

[0021]

FIG. 1 shows an embodiment of a fire alarm system according to the present invention. In the figure, 1 is an air source, 2 is a main pipe 2
a, an air supply pipe composed of a and a branch pipe 2b, 3 an electromagnetic valve unit provided in the middle of each branch pipe 2b, 6 a speed controller for adjusting the flow rate, and 7 a sensor unit.

The air source 1 includes a compressor (not shown), a filter for purifying air compressed by the compressor, an air dryer for dehumidifying and drying the compressed air, and an air tank.

The solenoid valve unit 3 includes a filter regulator 4 having a filter for drain / tar removal.
And a solenoid valve 5 for opening and closing the passage.
The opening and closing of each solenoid valve 5 is performed by a command from the control panel 10.

Since the operational characteristics of the smoke detector 7 are different as shown in FIG. 2, the ionizing smoke detector 8 and the photoelectric detector (scattered light type) 9 having different detection areas are combined. And expanded the detection area.

Signals from the two detectors 8 and 9 flow to the receiver 11 to activate the alarm. The annunciator issues an alarm and displays a lamp so that it is possible to determine which sensor has been activated.

In the air supply pipe 2, the branch pipe 2b is formed of a nylon tube, and air is blown directly from the open end of the tube to the detectors 8 and 9 as shown in FIG. A nozzle may be attached to the terminal of 2b. In some cases, it may be more effective to slowly blow air into the interior from the immediate vicinity of the sensor.

FIG. 4 shows the inside of an optical bench of an optical smoke detector (scattered light type). In the figure, reference numeral 28 denotes a light projecting section having a light emitting element built therein, 29 denotes a light receiving section having a light receiving element built therein, 30 denotes a labyrinth, and 31 denotes a confirmation lamp. When air blowing is performed on the photoelectric smoke detector from the confirmation light 31 side, the surrounding floating particles are entrained in the air current and thrown, and are blown into the light receiving portion. Is good.

Table 1 shows the results of a test for confirming the effect of air blowing. FIG. 5 shows a system adopted in the test.
The flow meter 12 was used when adjusting the flow rate by the speed controller, and was removed after the adjustment.

The test was performed according to the following procedure. Test voltage measurement to determine the initial sensitivity of the smoke detector. Inject dust into the smoke detector to intentionally lower sensitivity,
Test voltage measurement after drop. Perform air blow and measure the test voltage after that. The effect of air blow is determined by how close the test voltage after the air blow is to the initial value.

The dust used was fly ash (concrete material JIS-Z8901 SiO ₂ 45% or more,
Al ₂ O ₃ 20% or more). The pressure on the compressor side during air supply was 7 to 8 kgf / cm ³ .

Incidentally, the ionization type smoke detector cannot measure the voltage by the sensitivity tester even if dust is put inside,
Since it contains radioactive substances, it cannot be disassembled and its internal state cannot be confirmed, so the photoelectric detector (scattered light type) that does not hinder the test was used.

[0032]

[Table 1] From this test result, the effect does not change much if the distance from the air outlet of the air supply pipe to the smoke detector is changed (comparison between Samples 2 and 4), but the effect diminishes if the flow rate of the blowing air is too small ( Comparison of Samples 3 and 7)
Even if the flow rate is increased unnecessarily, the effect does not change drastically (comparison between Samples 1 and 6). It was found that the effect was increased by increasing the time (comparison of samples 3 and 5, and 7 and 8). In addition, both the photoelectric smoke detector and the ionization smoke detector have a flow rate of 220 l / min,
No malfunction occurred even with a spraying time of 10 seconds.

Next, for the verification test, one ionization type smoke detector and one photoelectric type smoke detector were placed near the differential distribution type sensors of a total of 30 legal facilities installed in the factory. 1 was constructed by newly adding a sensing unit consisting of the following, and air blowing of each sensing unit was performed sequentially at one-minute intervals for 3 seconds from the one with the highest warning zone number. In this case, since the total number of the sensing units is 30, each sensing unit is periodically blown at intervals of 30 minutes.

In this verification test, the state of fouling of air-blown detectors after one year and the smoke detectors left without air blows due to suspended particles was examined.

As a result, the sensor without air blow was overall dirty on the whole, whereas the sensor with air blow had less overall stain than the former. However, a partial blackening that was not present in the former was recognized on the cover. The cause of the blackening is that the particle size of the dust generated in the factory is actually smaller than originally expected, and the surrounding floating dust is entrained in the high-pressure air flow blown out from the air duct and sprayed on the cover. It seems to have been attached.

Then, when the open end of the air supply pipe was brought into contact with the air inlet of the sensor and low-pressure air was slowly blown from there, it was found that contamination could be suppressed without blackening. Was.

Ventilation in the smoke detector can also be performed by a method in which an air supply pipe is directly connected to the detector. In this case, better results can be expected because external floating dust is not involved. The air blowing pressure and the blowing time may be determined in consideration of the particle size of the suspended dust and the behavior around the smoke detector. This direct connection does not meet the structural standards stipulated by the Fire Service Law, but can be used for non-statutory independent facilities.

[0038]

As described above, the fire alarm system according to the present invention suppresses the pollution of the smoke detector due to the floating dust by performing air blowing, thereby preventing a sudden decrease in the sensitivity of the detector due to the contamination. Reliability and the replacement time of the sensor can be extended.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a system flow of a fire alarm system of the present invention.

FIG. 2 is a diagram showing a relationship between operating characteristics of a smoke detector and smoke particles detected.

FIG. 3 is a diagram showing an example of a method of air blowing.

FIG. 4 is a diagram showing the inside of an optical bench of an optical smoke detector (scattered light type).

FIG. 5 is a diagram showing a system flow adopted in an effect confirmation test.

FIG. 6 is a sectional view showing the internal structure of the ion type smoke detector.

FIG. 7 is a circuit diagram of an optical smoke detector (scattered light type).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air source 2 Air supply pipe 2a Main pipe 2b Branch pipe 3 Solenoid valve unit 4 Filter regulator 5 Solenoid valve 6 Speed controller 7 Sensor unit 8 Ionization type smoke detector 9 Photoelectric type smoke detector 10 Control panel 11 Receiver

Claims (5)

[Claims] 1. A fire alarm system for detecting smoke generated by a fire by providing a smoke detector indoors and activating an alarm based on a signal from the smoke detector. Air blower for supplying dry air, and periodically blowing or blowing air to the smoke detector from the air supply tube provided with an air source to remove dust entering the smoke detector. Fire alarm system. 2. In an environment in which dust having a large particle size and easily accumulates enters the smoke sensor, high-pressure air is blown onto the smoke sensor for a short time, and dust having a small particle size and easily floated is applied to the smoke sensor. 2. An air blow type fire alarm system according to claim 1, wherein low pressure air is slowly blown into the detector in an invading environment to ventilate the detector. 3. An air blow type fire alarm according to claim 1, wherein an air supply pipe is directly connected to each of the smoke detectors, and air is blown from the air supply pipe into the smoke detector for a required time to ventilate the inside of the smoke detector. system. 4. A photoelectric smoke detector is used as the smoke detector, and air is blown and blown to the photoelectric smoke detector from the side opposite to the confirmation light.
An air blow type fire alarm system according to any one of the above. 5. An air valve for individually opening and closing each air outlet of an air supply pipe, wherein air is blown or blown to each smoke detector with a time difference.
An air blow type fire alarm system according to any one of the above.