As the basis of pollution control, clean room can remove pollutants such as particles, harmful air and bacteria in the air within a certain space, and control indoor temperature, cleanliness, indoor pressure, airflow velocity and airflow distribution, noise, vibration and lighting, and static electricity within a certain demand range.
The degree of cleanliness and the continuous stability of pollution control are the core standards to test the quality of clean room. The standard will be divided into several grades according to regional environment, purification degree and other factors. The commonly used standards are international standards and domestic regional industry standards. To meet the cleanroom rating standards, the following four requirements should be met:
One, air supply cleanliness
In terms of air supply cleanliness, the key to meet the requirements is the performance and installation of the final filter of the purification system. The final stage filter of the purification system is usually a hepa filter or a sub-hePA filter.
Therefore, it should be considered that low performance filter should be used for low grade clean room and high performance filter should be used for high grade clean room.
However, to select a good filter, the characteristics of the clean room, the filter characteristics and the purification system characteristics should be considered comprehensively. To ensure the cleanliness of the air supply, only qualified filter is not enough, but also to ensure that the transport, installation process does not damage the filter, to ensure that the installation is tight.
The air distribution in a clean room is different from that in an air-conditioned room. It requires the cleanest air to be sent to the operating area first. Its function is to limit and reduce the pollution to the processed materials. To this end, the following principles should be considered when designing air distribution:
First, to minimize turbulence, to avoid pollution outside the work area into the work area;
Secondly, as far as possible to prevent the dust of the secondary flying to reduce the dust of the workpiece pollution opportunities;
Finally, the airflow in the working area should be as uniform as possible, and its wind speed should meet the technical and sanitary requirements. When the airflow flows to the return air outlet, the dust in the air should be effectively removed.
Air delivery/wind speed
Adequate ventilation and ventilation is to dilute and eliminate indoor air pollution. Depending on different cleanliness requirements, the number of air changes can be increased appropriately when the clean room is of high purity.
Among them, the ventilation rate of class 1 million clean rooms is considered as the high and middle efficiency purification system, while the rest are considered as the high efficiency purification system. When the 100,000-level clean room HEPA filter is centralized in the machine room or the end of the system to adopt the sub-hePA filter, the ventilation frequency can be appropriately increased by 10-20%.
Static pressure difference
Maintaining a certain positive pressure in a clean room is one of the essential conditions to ensure that it is free from or less polluted and to maintain the level of design cleanliness. Even for a negative pressure clean room, there must be adjacent rooms or suites at least of its cleanliness level to maintain a certain positive pressure to maintain the cleanliness of the negative pressure clean room.
According to China’s clean room design code, the static pressure difference between clean rooms of different grades and between clean and non-clean areas should not be less than 0.5mmH2O(~5Pa), and the static pressure difference between clean areas and outdoor areas should not be less than 1.OmmH20(~l0Pa).
In addition to meeting grade criteria, the following points should be noted when using a clean room:
1. Operators shall have the standard of dress and meet the hygienic requirements; To carry out regular cleaning and fire fighting work;
2. Regularly replace disinfectants to prevent microbial resistance;
3. To ensure that the safety door must be able to open at any time, the safety channel is prohibited from piling up debris, safety fire equipment should often check.
In addition, good operating and maintenance habits are essential to maximize the effectiveness of a clean room.
Post time: Jan-25-2021