Clean shed wind speed description

How to control wind speed in a clean room
The clean room system uses HEPA and ULPA to filter the air, with a dust collection rate of up to 99.97-99.99995%. Therefore, the air filtered by this filter can be said to be very clean. However, in addition to people, there are also sources of dust such as machines inside the shed. Once these generated dust particles spread, it is impossible to maintain a clean space. Therefore, it is necessary to use airflow to quickly remove the generated dust from the outside. And cleanliness is often affected by airflow, in other words, the airflow inside the shed is an important factor affecting the performance of the cleanroom. The movement and diffusion of dust generated by human, machine compartments, building structures, etc. are controlled by airflow.

The airflow velocity in a typical clean room is between 0.25 and 0.5 m/s. This airflow velocity belongs to the gentle wind zone and is easily disturbed and confused by the actions of people, machines, etc. Although increasing the wind speed can suppress the impact of this disturbance and maintain cleanliness, the increase in wind speed will affect the increase in operating costs. Therefore, it is necessary to supply at the most appropriate wind speed while meeting the required cleanliness level, in order to achieve an appropriate wind speed supply and achieve economic benefits. On the other hand, in order to achieve stable cleanliness, maintaining a uniform airflow is also an important factor. If a uniform airflow cannot be maintained, it indicates that the wind speed is different, especially on the wall, where the airflow will generate vortex effects along the wall. In this case, it is actually difficult to achieve high cleanliness.

To maintain uniform airflow in the vertical laminar flow direction, it is necessary to:
1、 The wind speed on the suction surface of the floor return air plate should not have any speed difference.
2、 The wind speed blowing on the surface must not have any difference in speed.

Vortex phenomena occur when the speed is too low or too high (0.2m/s, 0.7m/s), while at a speed of 0.5m/s, the airflow is more uniform. Currently, in general clean rooms, the wind speed is set between 0.25-0.5m/s. There will be eddy currents at the joints of obstacles such as workbenches in the clean room, and the cleanliness near them will be relatively poor. Drilling air return holes on the workbenches will minimize the occurrence of eddy currents; The selection of appropriate assembly materials and the completeness of equipment layout are also important factors in determining whether airflow becomes a vortex phenomenon.

Factors affecting airflow in clean rooms
1. The air flow diversion points on the surface of general workstations or production equipment should be located at a distance of 2/3 between the organizing room space and the partition board, so that when the workers are operating, the air flow can flow from the inside of the process area to the work area, and carry away the fine dust; If the diversion point is installed in front of the process area, it will become an inappropriate airflow diversion. At this time, most of the airflow will flow to the process area, and the dust caused by the operator's operation will be carried to the back of the equipment. As a result, the operation platform will be contaminated and the yield will inevitably decrease. How can cleanroom manufacturers solve the problem of factors affected by airflow.
2. Organizing obstacles such as operation tables indoors will result in vortex phenomena occurring at the junctions, and the organization degree will be relatively poor in the adjacent areas. Drilling air return holes on the operation table will minimize the vortex phenomena; Whether the selection of assembly materials is appropriate and whether the equipment planning is complete are also important factors for whether the airflow becomes a vortex appearance.
3. A clean shed is a simple and efficient organizing room that can be quickly assembled. It has the characteristics of fast installation, short construction period, low cost, and easy mobility. Controlling the primary production process in a smaller environment is also the best choice for organizing room design.
4. The fan sucks in air from the top of the FFU, passes through the primary filter and high-efficiency filter, and the filtered sorted air is uniformly sent out to the greenhouse at a wind speed of 0.45m/s ± 20% on all outlet surfaces. Forming a uniform flow layer, the organized airflow is in a straight and unidirectional direction, ensuring the required level of organization within the operating area.
5. There are many factors that affect the airflow of dust-free equipment, such as process equipment, personnel, assembly materials in the organizing room, lighting fixtures, etc. The diversion point of the airflow above the production equipment should also be considered as a factor to consider.