It is generally believed that the definition of a gas detector is based on the classification of detection targets, that is to say, any sensor used to detect gas composition and concentration is called a gas sensor, whether it is a physical method or a chemical method. For example, sensors that detect gas flow are not considered gas sensors, but thermal conductivity gas detectors are important gas sensors, although they sometimes use generally consistent detection principles. In daily life and industrial applications, the role of the gas detector is a very important tool, but in the actual installation and application, the use of the gas detector must also pay attention to the following aspects:
1. Installation of gas detector:
1. The gas detector is installed in the area where there may be gas leakage. The gas detector must be installed firmly, and the installation position is determined according to the specific gravity of the measured gas relative to the air. Because the measured gas specific gravity is less than air, the detector should be installed 30 to 60 cm away from the ceiling. Fix the detector on the wall with Φ8 expansion screw.
In order to use the detector correctly and prevent its failure, please do not install it in the following locations:
a. Places directly affected by steam and oil fumes b. Places with large air flow such as air supply vents, ventilating fans and room doors c. Places with a lot of water vapor and water droplets (relative humidity: greater than 90%)
d. The place where the temperature is below -40 ℃ or above 70 ℃ 2. Wiring: the wiring should use highly shielded wires to prevent the electrical signal from being disturbed, put the wires well, and open the top cover.
1. The gas detector generally adopts three-wire transmission, and the positive pole of the power supply is marked ("VCC" terminal), the signal line (the terminal marked "SIG"), and the negative pole of the power supply (terminal marked "GND") are connected respectively. "24V, mA and GND" of a group of terminals marked "4-20mAIN" of the access channel module, the chassis ground (cable shielding network) is well grounded, after connecting the wires, the chassis is fastened.
2. Startup: After wiring, power supply to the detector. Immediately after starting, the reading will go from overrange to stable reading, which takes about 15 minutes.
2. Factors to be considered before using the gas detector 1. Before measuring the safety level of the measuring plant, before entering the restricted space and / or the container, it is necessary to check whether the work area is safe and whether corresponding arrangements need to be made, such as the provision of a set of ventilation device. Are there toxic or explosive substances in the area, and if they do exist, what is the substance? How much oxygen is there? If the security level measurement can be implemented correctly, these two questions can be answered. If the container has been completely emptied, it still plays an important role in the risk assessment regardless of whether there are pollutants releasing gas or dangerous substances entering.
Measuring plant safety levels requires expertise in selecting and applying suitable measurement methods. Similarly, the results can only be reliably evaluated with the correct expertise; it is also important to do comprehensive training and preparation.
2. The main causes of danger in the restricted space are:
Formation and accumulation of explosive substances (combustible gas measurement)
Hypoxia or too much oxygen (oxygen measurement)
Formation and accumulation of toxic substances (measurement of toxic and harmful gases)
Combustible gas measurement and oxygen measurement are mandatory items.
The oxygen concentration in the restricted area is less than 19.0 vol%, indicating the danger of suffocation.
An oxygen concentration exceeding 23.0 vol% indicates that all substances are easily ignited and the temperature of the substance is high, including protective clothing that is resistant to fire in general environments.
3. How to maintain the gas detector 1. Inspection of the whole machine: The detector should be checked regularly at ordinary times. Its signal current in clean air is DC4mA
2. Sensor maintenance: Generally, re-inspection and calibration should be carried out within half a year to one year after installation and use, and the test report shall be issued by the tester.
3. When the sensor of the gas detector loses its sensitivity, it needs to be replaced. Through regular calibration, it will be known whether the sensor has failed. When the calibration value does not reach the calibration gas value, the sensor should be replaced.
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