Types of gas detectors and situations when they are appropriate
Different industrial environments require different types of gas detectors.
A) Fixed gas detector:
This is a detector that is widely used in industrial devices and production processes. It can be installed on a specific detection point to detect specific gas leaks. The fixed detector is generally a two-body type. The detection head composed of sensors and transmitters is installed on the detection site as a whole, and the secondary instrument composed of circuits, power supplies and display alarm devices is installed in a safe place as a whole, which is convenient for monitoring. Its detection principle is the same as that mentioned in the previous section, but it is more suitable for the characteristics of continuous and long-term stability required by fixed detection in terms of process and technology. They should also be selected according to the type and concentration of the on-site gas. At the same time, attention should be paid to installing them in the part where the specific gas is most likely to leak. For example, the most effective height of the sensor installation should be selected according to the specific gravity of the gas.
B) Portable gas detector:
Because the portable instrument is easy to operate and small in size, it can be carried to different production sites. The electrochemical detector is powered by alkaline batteries and can be used continuously for 1000 hours; the new LEL detector, PID and composite instruments use rechargeable batteries (some have been Using memoryless Ni-MH or lithium-ion batteries), they can generally work continuously for nearly 12 hours. Therefore, as such instruments, they are more and more widely used in various factories and health departments.
If this type of instrument is used as a safety alarm in an open place, such as an open workshop, a portable diffusion gas detector can be used because it can continuously, 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 hearing the alarm in noisy environments, and install computer chips to record peak, STEL (15-minute short-term exposure level) and TWA (8-hour statistical weighted average) --- provides specific guidance for worker health and safety.
If entering a confined space, such as reaction tanks, storage tanks or containers, sewers or other underground pipes, underground facilities, agricultural closed granaries, railway tank cars, shipping cargo holds, tunnels and other workplaces, inspections must be carried out before personnel enter , and the detection should be carried out outside the confined space. At this time, it is necessary to choose a multi-gas [Industrial Electrical Network-cnelc] detector with a built-in sampling pump. Because the gas distribution and gas types in different parts (upper, middle and lower) in the confined space are very different. For example: the specific gravity of combustible gases in the general sense is relatively light, and most of them are distributed in the upper part of the confined space; The lower part of the space (as shown). At the same time, oxygen concentration is also one of the types that must be detected. In addition, if the volatilization and leakage of possible organic substances in the tank are considered, a detector that can detect organic gases is also required. Therefore, a complete gas detector in a confined space should have a built-in pumping function - so that it can be detected in non-contact and sub-sites; it has a multi-gas detection function - to detect dangerous gases distributed in different spaces, including inorganic Gases and organic gases; Oxygen detection function - prevent hypoxia or oxygen enrichment; Small size, portable instrument that does not affect workers' work. Only in this way can the absolute safety of the staff entering the confined space be guaranteed.
In addition, after entering the confined space, the gas composition in it must be continuously detected to avoid changes in the concentration of volatile organic compounds or other toxic and harmful gases due to personnel entry, sudden leakage, and temperature changes.
If it is used for emergency accidents, leak detection and patrolling, pump-suction instruments with short response time, high sensitivity and resolution should be used, so that the location of the leak point can be easily judged.
In the case of industrial hygiene inspection and health investigation, it is very convenient to use instruments with functions such as data recording, statistical calculation and connection with computers.
At present, with the development of manufacturing technology, portable multi-gas (composite) detector is also a new choice for us. Since this detector can be equipped with multiple gas (inorganic/organic) detection sensors required on one host, it has the characteristics of small size, light weight, fast response, and multi-gas concentration display at the same time. More importantly, the price of the pump-suction compound gas detector is cheaper than multiple single-diffusion gas detectors, and it is 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 damage of one sensor from affecting the use of other sensors. At the same time, in order to avoid the blockage of the suction pump due to water inflow, etc., it is safer to choose an instrument designed with a smart pump with a pump stop alarm.
