Clean Room Airflow
- View 14
The cleanliness of a clean room is often affected by airflow, in other words, the movement and diffusion of dust generated by people, machine compartments, building structures, etc. is governed by airflow. Clean rooms use HEPA and ULPA to filter the air, and the dust collection rate is 99.97~99.99995%, so the air filtered by these filters can be said to be very clean. However, in addition to people in the clean room, there are also dust generating sources such as machines. Once these dusts spread, it is impossible to maintain a clean space, so airflow must be used to quickly discharge the dusts.
The airflow in the clean room is an important factor that affects the performance of the clean room. Generally, the airflow speed of the clean room is selected between 0.25~0.5m/s. This airflow speed is a breeze area, which is easily disturbed by the movement of people and machines and tends to be chaotic. Therefore, it is necessary to meet the required cleanliness level and supply the most appropriate air speed in order to achieve the appropriate air speed supply to achieve the economic effect.
On the other hand, in order to achieve the cleanliness of the clean room stability effect, uniform airflow maintenance is also an important factor, uniform clean room airflow can not be maintained, it means that the wind speed is different, especially in the wall, clean room airflow will be extended along the wall vortex effect, then to achieve high cleanliness is in fact very difficult.
Vertical laminar flow direction to maintain uniform clean room airflow must be.
(a) blowing out of the surface of the wind speed must not have speed differences.
(b) The air velocity of the inlet side of the floor return plate must not have a difference in velocity.
Speed is too low or too high (0.2m / s, 0.7m / s) are vortex phenomenon, and 0.5m / s speed, the airflow is more uniform, the current general clean room, the air speed are taken in 0.25 ~ 0.5m / s between.
There are many factors that affect the airflow in a clean room, such as process equipment, personnel, clean room assembly materials, lighting, etc. Also, the diversion point of clean room airflow above the production equipment should be included in the consideration.
Generally, clean room airflow diversion point on the surface of the operating table or production equipment should be set at 2/3 of the distance between the clean room space and the partition board, so that when the operator works, the airflow can flow from the inside of the process area to the work area, and the dust will be taken away; if the diversion point is configured in front of the process area, it will become an improper clean room airflow diversion, when most of the airflow will flow to the process area after the dust caused by the operator's operation will be brought to the As a result, the workbench will be contaminated and the yield rate will be reduced.
In the clean room, the work table and other obstacles will have vortex phenomenon at the junction, relatively the cleanliness near it will be poor, drilling the return air holes on the work table will make the vortex phenomenon reduced to a minimum; whether the selection of assembly materials is appropriate, the layout of the equipment is perfect, also for whether the airflow becomes an important factor of the vortex phenomenon.