Knowledge on purchasing gas detectors

Knowledge on purchasing gas detectors

        1) Confirm the type and concentration range of the gas to be detected: 

        The types of gases encountered in each production department are different. When choosing a gas detector, all possible situations must be considered. If methane and other less toxic alkanes are predominant, it is undoubtedly the most appropriate to choose an LEL detector. This is not only because the principle of the LEL detector is simple and its application is wide, but it is also easy to maintain and calibrate. If there are toxic gases such as carbon monoxide and hydrogen sulfide, it is necessary to give priority to choosing a specific gas detector to ensure the safety of workers. If there are more organic toxic and harmful gases, considering that the concentration that may cause poisoning to personnel is relatively low, such as aromatic hydrocarbons, halogenated hydrocarbons, ammonia (amines), ethers, alcohols, fats, etc., you should choose the photoionization detector introduced in the previous chapter, and never use the LEL detector to deal with it, because it may cause casualties.

        2) Determine the use occasion: 

        Different industrial environments require different types of gas detectors. 

        A) Fixed gas detector: 

        This is a detector that is used more frequently in industrial devices and production processes. It can be installed at a specific detection point to detect specific gas leaks. The fixed detector without horizon is generally a two-body type. The detection head composed of a sensor and a transmitter is installed as a whole at the detection site, and the secondary instrument composed of a circuit, a power supply and a display alarm device is installed as a whole in a safe place for easy monitoring. Its detection principle is the same as described in the previous section, but in terms of process and technology, it is more suitable for the continuous and long-term stability required by fixed detection. They should also be selected according to the type and concentration of the gas on site, and at the same time, they should be installed in the most likely location for a specific gas to leak, such as choosing the most effective height for sensor installation according to the specific gravity of the gas, etc. 

        B) Portable gas detector: 

        Because portable instruments are easy to operate and compact, they can be carried to different production sites. The eye-free electrochemical detector is powered by alkaline batteries and can be used continuously for 1000 hours; new LEL detectors, PID and composite instruments use rechargeable batteries (some have adopted memory-free nickel-metal hydride or lithium-ion batteries), which generally allow them to work continuously for nearly 12 hours. Therefore, this type of instrument is increasingly used in various factories and health departments. 

        If such instruments are used as safety alarms in open places, such as open workshops, a wearable diffusion gas detector can be used because it can continuously, in real time and accurately display the concentration of toxic and harmful gases on site. Some of these new instruments are also equipped with vibration alarm accessories - to avoid not hearing the sound alarm in a noisy environment, and install computer chips to record peak values, STEL (15-minute short-term exposure level) and TWA (8-hour statistical weighted average) - to provide specific guidance for worker health and safety. If you enter a confined space, such as a reaction tank, storage tank or container, sewer or other underground pipeline, underground facilities, agricultural closed granary, railway tank car, ship cargo hold, tunnel and other workplaces, before entering, you must conduct a test, and the test must be conducted outside the confined space. At this time, you must choose a multi-gas detector with a built-in sampling pump. If there are multiple gases in the environment, choosing a composite gas detector may achieve twice the result with half the effort.

        C) Composite gas detector 

        The composite multi-gas detector can be equipped with multiple gas detection sensors required on one instrument, so it has the characteristics of small size, light weight, fast response, and simultaneous multi-gas concentration display. More importantly, the price of the eyeless composite multi-gas detector is cheaper than that of multiple single diffusion gas detectors, and it is also more convenient to use. It should be noted that when choosing this type of detector, it is best to choose an instrument with the function of switching each sensor separately to prevent the use of other sensors from being affected by the damage of one sensor. Many choices of gas detection instruments will produce harmful gases that endanger personal safety or may cause adverse consequences in the environment, and gas detection instruments are often used. And gas detection instruments are indispensable detection instruments for early prevention of environmental pollution and ensuring human life safety. Gas detectors are usually used to detect toxic, harmful or combustible gases. Toxic gas detectors are generally used in biochemical, pharmaceutical, construction and other industries, while combustible gas detectors are commonly used in gas environment detection in coal mines, petroleum, chemical, fuel and other industries. The detection standards for different industries and occasions are different, and the detection standards for different gases are also different. When choosing a good gas detection instrument, you should pay attention to the purpose and occasion of use. First, determine the type of gas to be detected and the concentration standard: 

        The gases to be detected in different environments are different. Before choosing a gas detector, the first thing to do is to determine what kind of gas to be measured, what is the concentration range that this gas is more suitable for, and even consider all possible situations. For example, in an environment with more methane or other less toxic alkanes, it is best to choose an LEL detector; while environmental testing of toxic gases such as CO and H2S must ensure the safety of the testers and the staff in the environment, so a specific gas detector is selected; for environments with more organic harmful gases (such as aromatic hydrocarbons, ammonia, ether, etc.), a photoionization detector must be selected, which can not only obtain more accurate test results, but also avoid the possibility of casualties due to the use of LEL detectors. Finally, if various gases may be mixed in the environment, it is best to choose a composite detector. 

        Secondly, we must also consider the applicable occasions of different detectors: 

        Fixed gas detectors are relatively common detection instruments used in industrial production and equipment. They are installed at fixed monitoring points to detect a fixed gas. The gas monitoring is completed by circuits, sensors, and alarm devices. The height of the sensor installation is selected according to the density of the gas. Portable gas detectors, as the name suggests, are small and light, easy to carry, and can be easily carried to different environments. And because they are powered by alkaline batteries, they have a longer working time, so their applications are becoming more and more widespread.