What should be noted in the calibration of combustible gas detectors and toxic gas detectors
Everyone knows that a gas detector is an instrument that detects gas concentration. Suitable for hazardous areas with flammable or toxic gases, capable of continuously detecting the lower explosive limit of the measured gas in the air for a long time. In the process of calibrating combustible gas detectors, it is inevitable to use flammable and explosive gas reference materials. Therefore, in this work, explosion-proof is more important than the calibration work itself. The three elements of gas explosion are explosive substances, ignition sources, and auxiliary gases. Explosive substances include substances that can react with oxygen (air), including gases, liquids, and solids. Gas: hydrogen, acetylene, methane, etc; Liquids: alcohol, gasoline; Solid: dust, fiber dust, etc.
In the process of calibrating toxic gas detectors, in order to prevent occupational hazards to personnel during work, it is necessary to first pay attention to personnel protection and use high-efficiency exhaust facilities. If conditions permit, all detection equipment should be installed in the exhaust system and air flow balance ports should be set up to facilitate the rapid diffusion of harmful gases to the outside or into the waste gas treatment system. If an automated detection system can be used, personnel can achieve computer-controlled gas on/off, which is a great protection for personnel.
In all calibration work using toxic and harmful gas standard substances, it is best for calibration personnel to wear portable gas alarms to ensure their own safety.
The characteristics of toxic and harmful gases vary, some have adsorption properties, while others are highly soluble in water. In order to avoid affecting the accuracy of measurement values when standard gases pass through, stainless steel pipes should be selected as much as possible, kept dry, and the length of the pipeline should be reduced to ensure gas flow rate and pressure. Meanwhile, due to the varying densities of each gas relative to air, different exhaust methods are required.
Different gases: Hydrogen sulfide is a colorless gas that is irritating and suffocating, and is corrosive to metal materials. Hydrogen embrittlement often causes instrument explosions, accelerating the aging of non-metallic materials. Therefore, when calibrating the gas pipeline of the hydrogen sulfide detector, it is necessary to avoid using metal pipelines and use polytetrafluoroethylene pipelines. Polytetrafluoroethylene is widely used in the detection of gas detectors due to its excellent chemical stability, corrosion resistance, sealing, high lubrication, non viscosity, electrical insulation and good anti-aging endurance. However, due to the hardness of polytetrafluoroethylene pipes, latex pipes need to be used for connection between different gas paths. When connecting, the latex pipes should be used as auxiliary connections outside the polytetrafluoroethylene pipes to avoid contact with gas and prevent corrosion and aging. The density of hydrogen sulfide gas is 1.19 times that of air, slightly heavier than air, so it is advisable to use lower exhaust.
Carbon monoxide is a colorless, odorless, tasteless, and insoluble gas in water. At the same time, carbon monoxide is a toxic and explosive gas. When testing gas detectors for this type of gas, such as ammonia detectors, benzene detectors, hydrogen sulfide detectors, etc., special attention should be paid to safety. After carbon monoxide is absorbed by the human body, it can cause symptoms such as fatigue, shortness of breath, nausea, dizziness, and dizziness. Inhaling too much carbon monoxide can cause brain damage and even death. The melting point of carbon monoxide is -205.1 ℃, the boiling point is -191.5 ℃, and the gas density under standard conditions is 1.25g/L, which is very close to the air density (1.293g/L under standard conditions). This is also one of the factors that are prone to carbon monoxide poisoning.
