FUME HOOD FUNCTIONS
Fume hood major function
Fume hood Ventilation cabinet in the main exhaust function, in the chemical laboratory, experimental operation produce harmful gases, odor, moisture and flammable, explosive, corrosive substances, in order to protect a user's security to prevent diffusion of the pollutants to the laboratory, to use ventilation cabinet in the vicinity of pollution source, ventilation cabinet uses fewer units in the past, only in particularly harmful and dangerous gas and produced a large number of experimental heat used in. Ventilation cabinet only responsible for the auxiliary function of the experimental platform. Taking into account the improvement of the experimental environment, the experiment carried out on the experimental stage is gradually transferred to the ventilation cabinet, which requires the ventilation cabinet to have the most suitable for the use of equipment. Especially the most new laboratories are required to have air conditioning, so in the preliminary design stage of construction to ventilation cabinet units will be included in the plan of air conditioning system. Because the ventilation cabinet in the biochemical laboratory occupies very important position, from improving laboratory environment, improve working conditions, improve work efficiency and consideration, ventilation cabinet use units leap to increase. The attendant is ventilation pipes, exhaust piping, wiring, etc. have become an important topic in the construction of laboratory.
Use ventilation cabinet is the biggest purpose is discharged harmful gas produced in the experiment, to protect the health of laboratory personnel, is also said to have a high degree of safety and superior maneuverability, which requires ventilation cabinet should have the following functions:
(5) the function of controlling wind speed: to prevent the harmful gas from escaping in the fume hood, it is required to have a certain intake speed. The factors that determine the inlet velocity of the air inlet of the ventilation cabinet are: the heat generated by the experiment content and the relationship with the number of ventilation. The main contents are the experimental contents and the nature of the harmful substances. National standards, ventilation cabinet surface wind speed of 0.5 m/s + 10%. In order to ensure the wind speed, the air exhaust fan should have the necessary static pressure, that is, the friction resistance of air through the ventilation duct. Determining the wind must also pay attention to the problem of noise. Through the air in the pipe flow to 7 - 10m is limited, more than 10m will produce noise, usually Laboratory (indoor background noise level) noise limit value for 70dba, increase the pipeline cutting area will reduce wind speed (6) heat and acid and alkali corrosion function. Ventilation cabinet to be placed inside the furnace, and some experiments to produce a large number of toxic and harmful gases such as acid and alkali has a strong corrosive. Ventilation cabinet table, lining plate, side plate and the water nozzle, a gas nozzle should have anti-corrosion function etc.. In semiconductor industry or corrosive experiment using sulfuric acid, nitric acid, hydrofluoric acid and other acid but also for ventilation cabinet bulk material must be anti acid, usually by stainless steel, PVC and PP materials manufacturing.
Safety is the maximum duty of the ventilation cabinet, the laboratory use of ventilation cabinet is to ensure the safety of users and to prevent the pollution of the surrounding environment.
1, three section type exhaust structure, effective discharge of harmful gases.
2, streamline hand, hand and glass with a gap between the air due to the flow of air in the table is rotated, from the surface to ensure effective intake.
3, set the window anti drop pin, in case of wire rope off the glass window accident fall under, anti drop pin will catch, prevent bruising personnel.
4, glass windows with glass, glass or even crash accident explosion, no harmful accident.
5, the upper part of the fume hood is provided with a ventilation hole, even if the glass window is closed, the air can be entered, and the negative pressure can be avoided.
matters needing attention
It must be confirmed before the experiment began, ventilation cabinet should be in the running state, to test operation.
We will continue to run before the end of the experiment, at least 5 minutes before they can turn off the fan to discharge the residual gas in the pipeline. Can also consider the installation of exhaust time delay, to ensure that the fan delay operation.
In laboratory construction, the use rate of ventilation cabinet is very high, how to choose the proper, reasonable ventilation cabinet installation position, need to choose the type of ventilation cabinet, material, shape, etc., should be considered. When using organic compounds or other special reagents, the control of wind speed should be considered. Heat source: when using equipment with heat source, the heat over 2000 kcal / hour to consider eduction ventilation quantity of heat required to determine the power of the fan. There are radioactive substances or acid and other experiments: to use a dedicated ventilation cabinet, the surface wind speed must be set greater than 0.5m/s. When the experiment is carried out using large scale equipment: to consider the effective size of the interior, to set aside the necessary space for the exhaust.
Divided into the upper exhaust type, lower exhaust type and up and down at the same time three types of air exhaust. In order to ensure a uniform wind speed of working area, for the cooling process of fume hood should be with a lower air exhaust type, for the thermal process of fume hood with upper air exhaust type, for calorific value is not stable, in the upper and lower are equipped with air outlet with cabinet hair changing heat adjusting row volume ratio to obtain uniform wind.
Full exhaust ventilation cabinet: through the indoor air into the cabinet in the cabinet after the cycle of exhaust, called the full exhaust type, this is a very wide range of applications.
Ventilation cabinet: when the fume hood arranged on the heating and the temperature and humidity control room, in order to save heating, air conditioning energy consumption by from the outdoor supply wind after the ark circulation discharge outdoor called ventilation cabinet.
Variable air volume ventilation cabinet: ordinary constant air volume system needs to manually adjust the fixed blades of the wind valve, adjust the ventilation cabinet exhaust air, when the valve to a certain point of view to achieve the desired surface wind speed.
Can be divided into the lower part of the overall open type, floor type, two sides,