Application of Toxic and Harmful Gas Detection Alarm

  The use of harmful gas detection alarm instrument, the harmful gas detection alarm instrument is a special safety and health detector, used to detect the flammable or toxic gas and vapor content in the air inside the chemical work place or equipment and alarm.

   In addition, the air hypoxia detector also belongs to this kind of instrument.

   The detection of harmful gases in hazardous chemical places mainly includes the following situations:

   Leak detection: alarms for leakage of harmful gas or liquid (vapor) on the equipment pipeline, leak detection of equipment pipeline operation.

   Maintenance inspection: After the equipment is replaced, it is necessary to detect the residual harmful gas or liquid (vapor), especially before the fire.

   Emergency detection: When an abnormal situation occurs in the production site or an accident is handled, for the sake of safety and hygiene, a detection of harmful gases or liquids (vapors) is required.

   Entry detection: When workers enter the hazardous substance isolation operation room, enter the sewage ditch, cable trench or equipment in the dangerous place to operate, they should detect harmful gas or liquid vapor.

   Itinerant testing: During the safety and health inspection, harmful gases or liquid vapors should be detected.

Dangerous chemicals must strengthen safety management, improve safety measures, and control hidden dangers of accidents. However, it is impossible to achieve absolute security, and there is still a possibility of a panic. Therefore, the detection and alarm of hidden dangers, and the detection and alarm of harmful gases or liquids (vapors) in hazardous chemical locations are very necessary.

It is of great significance to avoid and control accidents.

   First, the classification of harmful gas detection alarm

   1. Classified by usage method:

   ① The portable harmful gas detection and alarm instrument integrates sensors, measuring circuits, displays, alarms, rechargeable batteries, air pumps, etc. into a single housing, which is compact, lightweight, and easy to carry. Pump suction sampling can be anywhere Check it out. Pocket instrument is a kind of portable instrument. Generally, there is no suction pump diffusion sampling. It is powered by dry batteries and has a small body.

   ② Fixed harmful gas detection and alarm instrument This type of instrument is fixed on the scene and continuously detects the corresponding harmful gas (steam) automatically. The harmful gas exceeds the limit and it automatically alarms. Some can also automatically control the exhaust fan.

Fixed instruments are divided into two types: integrated and split.

   Integrated fixed harmful gas detection and alarm device: Like portable instruments, the difference is that it is installed on the scene, 220V AC power supply, continuous automatic detection and alarm, and most are diffusion sampling.

   Split fixed harmful gas detection and alarm device: The sensor and signal transmission circuit are assembled in an explosion-proof housing, commonly known as a probe, installed on the scene (dangerous place); the second part includes data processing, secondary display, alarm control and power supply, assembly Into a controller, commonly known as a secondary instrument, installed in the control room (safe place), probe diffusion sampling detection, secondary instrument display alarm.

   2. Classify according to the measured object and sensor principle

   ① Combustible gas detection and alarm instrument (referred to as explosion detector, one instrument detects multiple combustible gases) Catalytic combustion type combustible gas detection and alarm instrument detects various combustible gases or vapors. Electrochemical toxic gas detection alarm device, detecting CO, H2S, NO, NO2, CL2, HCN, NH3, PH3 and many toxic organic compounds, infrared flammable gas detection alarm device, detecting various flammable gases (depending on filtering technology), semiconductor-type flammable gas detection alarm device, detect a variety of flammable gases. Thermal conductivity type combustible gas detection alarm device, detecting hydrogen gas with large difference between thermal conductivity and air, Toxic gas detection and alarm device (referred to as poison tester, an instrument for detecting a toxic gas) Photoionization type toxic gas detection and alarm device, which detects organic and inorganic compounds with an ionization potential of less than 11.7eV, infrared toxic gas detection alarm device, detecting CO, CO2, etc, semiconductor-type toxic gas detection alarm, detection of CO, etc.

   Second, the selection principle of harmful gas detection alarm instrument

  1. Define the detection purpose and select the type of instrument. In short, the detection of harmful gases has two purposes, the first is to detect explosions, and the second is to detect poisons. The so-called explosion detection is to detect the flammable gas content in dangerous places, and alarm is exceeded to avoid the occurrence of explosion accidents; the drug detection is to detect the toxic gas content in dangerous areas, and the alarm is exceeded to avoid staff poisoning. The test range is 0 to 100% LEL, and the test range is 0 to tens (or hundreds) ppm, which is very different. There are three cases of hazardous gases in hazardous places: first, non-toxic (or low-toxic) flammable, second, non-flammable and toxic, and third, combustible and toxic. The first two cases are easy to determine. The first test is the second test, the second test is the third test. If the third party is exposed to the test, the third party can test the explosion if no one is exposed. For the explosion test, select a flammable gas detection and alarm device, and for the poison test, select a toxic gas detection and alarm device.

   2. Select the type of instrument for clear testing purpose (portable or fixed). Leak detection for long-term operation of production or storage positions should use fixed detection alarm; other inspections such as maintenance testing, emergency detection, entry detection, and patrol testing should be portable (or compact) instrument. The instrument model contains three main contents: manufacturer, function index and detection principle.

   3. Identify the test objects, select the best model and choose the model of the instrument. Consider the following principles when selecting the model of the instrument:

① The manufacturer speaks integrity, has a good reputation, and the quality of production is guaranteed. It has passed the ISO9002 quality system certification, has a CMC production license issued by the technical supervision department, and has fire and explosion certification.

② The function index of the selected model must meet the requirements of national standards GB12358-90, GB15322-94, GB16808-1997 and other standards.

③ The test principle of the instrument should be adapted to the requirements of the test object and test environment.

   Third, the harmful gas sensor and its characteristics

   Overview of Harmful Gas Sensing: Harmful gas sensors are devices that convert the content of harmful gases in the air into electrical signals. The electrical signals generated by the sensors are processed by electronic circuits, amplified, and used in the field by the sensors. They can withstand the influence of various harsh environments and atmospheres, especially the sensors of fixed instruments, which are continuously operated for a long time, and have explosion-proof and power supply capacity restrictions. The requirements for hazardous gas sensors are very strict. After conversion, display and alarm of harmful gas content is realized. It can be seen that the sensor is the basic and core component of the harmful gas detection alarm device, and its quality determines the quality and functional indicators of the harmful gas detection alarm device.

   General inspection sensors have the following items: Detection range and resolution; Ability to resist environmental (temperature and humidity) influence; safety, explosion-proof performance; interchangeability and convenient maintenance; small size, light weight; small current, good power saving.

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