Basic Concept of Dust-free Workshop
A cleanroom, also known as a clean room or purification room, is a working environment that achieves a certain level of cleanliness by controlling the concentration of suspended particles in the air. Its core lies in air purification technology and airflow organization, ensuring that indoor pollutants are effectively eliminated while preventing external pollutants from invading. According to ISO standards, the cleanliness level of cleanrooms ranges from ISO 1 (cleanest) to ISO 9 (dirtier), with each level corresponding to different airborne particle concentration limits.
Definition of Positive and Negative Pressure
-Positive pressure: When the indoor air pressure is higher than the outdoor air pressure, we call the environment a positive pressure environment. In this case, air will flow from indoors to outdoors, effectively preventing external pollutants from entering.
-Negative pressure: Conversely, if the indoor air pressure is lower than the outdoor air pressure, a negative pressure environment will be formed, and external air will be naturally drawn into the room, which is suitable for situations where internal pollutants need to be prevented from leaking out.
The pressure selection logic of dust-free workshop
In most cases, cleanrooms tend to adopt positive pressure design. This is because a positive pressure environment can effectively prevent external pollutants such as dust and microorganisms from flowing into the workshop with the air, maintaining a high level of cleanliness inside. By setting an appropriate positive pressure differential (usually between 5 and 20 Pa), it is possible to ensure that the airflow direction at door gaps, ventilation openings, etc. is always outward, forming an invisible protective barrier.
1、 Positive pressure air volume and air exchange rate 1. Positive pressure in a iso 10000 clean room is achieved by making the supply air volume of the purification system greater than the return air volume and exhaust air volume. The required air volume to maintain positive pressure in the clean room should be determined based on the sealing performance of the enclosure structure. 2. Actual tests have shown that when the positive pressure in the clean room is 5Pa, it can meet the requirements of clean room cleanliness for positive pressure, but this is the minimum positive pressure value. At this positive pressure value, most cleanrooms require a ventilation rate of 2-4 times per hour. In order to save energy, it is recommended to make the enclosure structure as tight as possible, and the required air volume for positive pressure should be selected based on 1-2 air changes per hour. In actual testing, most clean rooms are at a positive pressure value of around 10Pa. It is recommended to use this positive pressure value with an air flow rate of 2-3 times per hour.
Key point 1 of cleanroom positive pressure design: Positive pressure value setting: The positive pressure value of the cleanroom should be set reasonably. Generally, the static pressure difference between cleanrooms of different levels should be at least 5Pa, and the static pressure difference between the cleanroom and the outside should be at least 10Pa to ensure cleanliness and prevent cross contamination. 2. Supply air volume and return air volume control: Maintain positive pressure by making the supply air volume greater than the return air volume and exhaust air volume. The air supply volume should be determined based on the sealing performance of the enclosure structure, and it is usually recommended to exchange air 1-2 times/h or 2-3 times/h to achieve energy-saving effects. 3. Electrical control method: Adopting electrical control methods such as residual pressure valve and PLC control system, the air supply volume is automatically adjusted to maintain the positive pressure in the iso 10000 clean room within a reasonable range. 4. Sealing structure: Pay special attention to the sealing structure of the clean room to ensure that the sealing performance meets the standards and avoid adverse effects on the control of the positive pressure environment.
Suzhou Pharma Machinery Co.,Ltd.
2025/05/14
Gino
