First, the classification of ventilation systems
1. Full ventilation: full air exchange in the whole room. When a large area of toxic and harmful gas is diffused into the space of the test bench, it must be discharged in time, and there must be some fresh air to supplement it. Control toxic and harmful gases within the specified range.
2. Local ventilation: The toxic and harmful gas is partially ventilated through a small operating facility to prevent diffusion to the entire room; forced exhaust can also be selected according to the gas concentration. Forced exhaust can be called mechanical exhaust, and the local wind is used to discharge the generated wind pressure through the ventilation duct.
For the exhaust gas discharged into the air, if the emission standard of the harmful substance exceeds the emission standard stipulated by the state, it cannot be directly discharged into the polluted environment in the atmosphere; it must be absorbed and treated according to the chemical nature of the gas to make it lower than the emission standard. After that, it can be discharged into the atmosphere.
Second, the choice of air volume
The choice of air volume is based on the size of the room exhaust requirements. There are different standard requirements for each profession in each industry. There is no question of how to choose. The choice of fan is related to the speed/power/pressure value. The pressure of the fan is related to the resistance of the ventilation system. Of course, it is very important.
Third, ventilation pipe design points
1. A fume hood and a ventilator are the best way to connect with a single pipe.
2, can not be connected by a single pipe, only the same room in the same floor can be connected to each other.
3. Install the fan as far as possible at the end of the pipe (on the roof).
4. The shorter the pipe length, the better.
5. The fewer ventilators connected to a fume hood, the better. The exhaust passage is as straight as possible, and the higher the passage, the better.
6. If you need to change the wind speed of the air duct, you should configure the corresponding frequency conversion adjustment system.
7. The end of the exhaust passage should avoid the air supply port of the air supply duct as much as possible to prevent the harmful gas discharged from being sent to the fume hood through the exhaust duct.
Fourth, the fan selection
1. Choosing the right fan is an important condition to ensure the normal and economic operation of the ventilation system. The so-called correct selection of the fan mainly refers to selecting the fan for different purposes according to the nature and use of the gas to be transported; the selected fan should meet the required air volume of the system, and the wind pressure of the fan should overcome the resistance of the system, and the efficiency is the highest or Work within the scope of economic use. The specific selection methods and steps are as follows:
2. According to the nature of the gas to be transported, fans of different purposes are selected. For example, when cleaning clean air or dusty gas has been purified through the fan, when the dust concentration does not exceed 150mg/m3, the fan for general ventilation and ventilation can be selected; for conveying corrosive gas, anti-corrosion fan should be selected; When burning, explosive gas or dusty gas, use an explosion-proof fan or a dust-exhausting fan. However, when selecting a specific fan model and specification, it must be determined according to the performance table or characteristic graph on a certain type of fan product sample.
3. Unless any fan is selected to meet the requirements, or the wind pressure and air volume of the fan are required to be greatly changed during use, two or more fans should be avoided in parallel or in series. When two or more fans work together, each fan will perform worse than its own.