Analysis of the function of Gu Ning brand fume hood
Friends who use the Gu Ning brand fume hood know that the most important function of the fume hood is the exhaust function. In the chemical laboratory, various harmful gases, odors, moisture and flammable and explosive are generated during the experimental operation , Corrosive substances, in order to protect the safety of users and prevent the spread of pollutants in the laboratory to the laboratory, use a fume hood near the source of the pollution. In the past, the number of fume hoods was small, only in the case of particularly harmful and dangerous gases and a large amount of Used in hot experiments. The fume hood is only responsible for the auxiliary functions of the laboratory bench. In recent years, considering the improvement of the experimental environment, the experiments carried out on the experimental platform are gradually transferred to the fume hood, which requires the most suitable function of the equipment in the fume hood. In particular, most newly-built laboratories require air conditioning. Therefore, the number of fume hoods must be included in the plan of the air conditioning system during the preliminary design stage of the building. Because the fume hood occupies a very important position in the biochemical laboratory, the number of fume hoods used has increased dramatically in terms of improving the laboratory environment, improving labor conditions, and improving work efficiency. Along with it is the ventilation duct, piping, wiring, exhaust, etc. have become an important subject of laboratory construction.
The biggest purpose of using a fume hood is to exhaust the harmful gases generated in the experiment and protect the health of the experimenters, that is to say, to have a high degree of safety and superior operability, which requires the fume hood to have the following functions:
(1) Isolation function: a glass window that does not slide should be used to separate the inside and outside of the fume hood in front of the fume hood.
(2) Release function: It should be equipped with a mechanism to absorb the harmful gas generated inside the fume hood by absorbing the gas from the outside of the cabinet, so that it can be diluted to exclude the outdoor.
(3) Heat resistance and acid and alkali corrosion resistance: Some of the fume hoods need to be equipped with electric furnaces, and some experiments produce a large amount of toxic and harmful gases such as acids and alkalis, which are extremely corrosive. The countertop of the fume hood, the lining board, the side board and the selected water nozzle and gas nozzle should all have anti-corrosion function. The use of strong acids such as sulfuric acid, nitric acid, and hydrofluoric acid in the semiconductor industry or corrosive experiments also requires that the overall material of the fume hood must be acid and alkali resistant, and must be made of stainless steel or PVC.
(4) Non-reverse flow function: the air flow generated by the exhaust fan inside the fume hood
The function of the body does not flow into the room from the inside of the fume hood. In order to ensure the realization of this function, it is the best way to connect a fume hood to a fan with a single pipe. It cannot be connected with a single pipe, and it is only limited to the same room on the same floor. Installed at the end of the pipeline (or at the top of the floor).
(5) Supplementary function: It should have a passage or substitute device for sucking air from outside the fume hood when discharging harmful gases.
(6) Wind speed control function: To prevent harmful gas from escaping in the fume hood, a certain suction speed is required. The factors that determine the intake speed of the fume hood inlet air are: the heat generated by the experiment and the relationship with the number of ventilations. The main ones are the content of experiments and the nature of harmful substances. It is generally stipulated that the general non-toxic pollutants are 0.25-0.38m / s, the toxic or dangerous harmful substances are 0.4-0.5 m / s, the highly toxic or a small amount of radioactivity is 0.5-0.6m / s, and the gaseous substances are 0.5m / s, granular material is 1m / s. In order to ensure such a wind speed, the exhaust fan should have the necessary static pressure, that is, the frictional resistance of the air when passing through the ventilation duct. When determining the wind speed, you must also pay attention to the noise problem. When the air flows through the pipe, the limit is 7-10m, and more than 10m will produce noise. Usually the laboratory (indoor background noise level) noise limit is 70dBA. Reducing the wind speed will also reduce the noise. Considering the cost and construction of the pipeline, the power of the pipeline and the exhaust fan must be carefully selected.
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