There are various objects to be operated in the clean room, such as electronic products, medicines, health care products, microorganisms, viruses, etc. During the operation, some objects (such as viruses, etc.) will produce aerosols that are harmful to humans or even biologically dangerous. Therefore, whether it is to produce products in a clean room or conduct virus research, it is necessary to protect the products from external contamination, and also to prevent the contamination generated during the operation from leaking out. In addition to the protection of a well-sealed clean room barrier, it is also necessary to use the effect of pressure difference to make the air flow in the specified direction. If the static pressure of the positive pressure clean room is greater than the static pressure of the adjacent room or the environment, the air in the clean room can only flow outward by using this pressure difference, which prevents the pollution of the clean room from the adjacent room or the outdoor environment. Negative pressure clean room is just the opposite. To do some biologically dangerous operations in the clean room, or to produce strong allergenic dust during the operation, it is necessary to use this pressure difference to control the pollutants in the clean room. within a specific range.

Therefore, through the joint action of this pressure difference and the sealed enclosure structure of the clean room, a barrier protection system is formed to achieve the purpose of controlling pollution.

Differential pressure control method

1. Air return control

The return air volume is adjusted by adjusting the airflow passage of the return air louver or the resistance of the damping layer, so as to achieve the purpose of controlling the indoor static pressure. This method is simple and easy, but the amount of adjustment is limited. The positive pressure of the clean room can only be increased by more than 1Pa only by adjusting the angle of the louvers, and even 2Pa can not be reached. By adjusting the resistance of the damping layer (filter cloth), the adjustment range can be larger.

2. Return air valve control

In the design of clean room air conditioning, a regulating valve should be installed on each return air branch pipe, otherwise, the pressure difference is not easy to adjust. In the clean room, the air supply volume is required to be constant. When the exhaust air volume is determined, the indoor pressure difference is realized by adjusting the return air valve on the branch pipe. This adjustment method is very effective in increasing the pressure difference.

3. Automatic control

When designing, place the air outlet as far as possible. This is a very good control method, and there are different control schemes depending on the nature of the clean room. Some control exhaust air, some control return air, and some control fresh air. The principle is: the change of indoor pressure is detected by the sensitive element and transmitted to the controller, the controller sends out adjustment instructions and the actuator adjusts the size of the valve or changes the speed of the fan to achieve the purpose of controlling the pressure difference.

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Suzhou Pharma Machinery Co.,Ltd.

2021/02/13

Birkey