1、 Air supply cleanliness
To ensure that the cleanliness of air supply meets the requirements, the key is the performance and installation of the final filter of the purification system.
When selecting the filter for the final stage of the purification system, it should not only meet the requirements of air supply cleanliness, but also consider economy and rationality. Considering the cleanliness requirements, the principle is to select low-performance filters for low-level clean rooms and high-performance filters for high-level clean rooms. Each cleanliness level seems to have two types of filters to choose from, high performance or low performance, depending on the specific situation. When the environment is seriously polluted, or the indoor air exhaust ratio is large, or the clean room is particularly important, and a large safety factor is required, in these or one of these cases, a higher class filter shall be selected; Conversely, lower performance filters can be selected.
2、 Air distribution
The air distribution of the clean room is different from that of the general air-conditioned room. It requires that the cleanest air be sent to the operating part first. Its role is to limit and reduce the pollution to the processed products.
Different air distribution has its own characteristics and scope:
(1) Vertical unidirectional flow: uniform downward airflow can be obtained, which is convenient for the layout of process equipment, has strong self purification capacity, and can simplify the common facilities such as personal purification facilities
The four air supply modes also have their own advantages and disadvantages: full distribution of high-efficiency filters has the advantages of low resistance and long filter replacement cycle, but the ceiling structure is complex and the cost is high; The advantages and disadvantages of side mounted high-efficiency filter top feeding and full orifice plate top feeding are opposite to those of full mounted high-efficiency filter top feeding. When the system is in discontinuous operation, the inner surface of the orifice plate is prone to dust accumulation and poor maintenance, which has some impact on the cleanliness; The top delivery of dense diffusers is only applicable to large clean rooms with a height of more than 4m due to the need for a mixing layer. Its characteristics are similar to the top delivery of full orifice plates; For the air return mode of evenly arranging air return outlets at the bottom of the grating on both sides and the wall on both sides, it is only applicable to the clean rooms with a clear spacing of less than 6m on both sides; The air return vent at the lower part of one side wall is only applicable to clean rooms with small wall spacing (such as ≤ <2~3m).
(2) Horizontal unidirectional flow: it only reaches class 100 cleanliness in the first working area. When the air flows to the other side, the dust concentration gradually increases, so it is only applicable to clean rooms with different cleanliness requirements in the same room; The local distribution of high-efficiency filters in the air supply wall can reduce the consumption of high-efficiency filters and save initial investment compared with the full distribution of horizontal air supply, but there are eddies in local areas.
(3) Turbulent air flow: the characteristics of orifice plate top feeding and dense diffuser top feeding are the same as the above. The advantages of side feeding are easy to arrange the pipeline, no technical interlayer is required, and the cost is low, which is conducive to the transformation of the old plant. The disadvantages are that the wind speed in the working area is large, and the dust concentration in the downwind side is higher than that in the upwind side; The high efficiency filter tuyere top feeding has the advantages of simple system, no pipe after the high efficiency filter, and the clean air flow is directly delivered to the work area, but the clean air flow diffuses slowly and the air flow in the work area is relatively uniform; However, when multiple tuyeres are uniformly arranged or the high-efficiency filter tuyere with diffuser is adopted, the air flow in the working area can also be more uniform; However, in the case of non continuous operation of the system, the diffuser is easy to accumulate dust.
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