1 clean room definition
Clean room is the space for the activity of the air that meets the specified level of cleanliness. Its function is to control the particle pollution.
In order to achieve the required level of cleanliness and to effectively control the pollution of particles so that people can conduct sophisticated production and scientific experiments in them, the clean room is by no means limited to "clean" but must be a thermal, noise, illumination, Electrostatic, micro-vibration have considerable requirements of the multi-functional complex, is a set of architectural decoration, air purification, pure water pure, electrical control and other professional and technical expertise in one product.
2 clean room classification
First, by use classification
By use can be divided into two categories:
(1) Industrial clean room - with inanimate particles as the control object. The main control of non-living particles of the work of pollution, internal generally maintain positive pressure. It is suitable for precision industry, electronics industry, aerospace industry, atomic energy industry, printing industry, photography industry and other departments.
(2) biological clean room - to live particles as the control object, can be divided into:
① general biological clean room. The main control of life particles on the work of object pollution. At the same time the internal material to withstand a variety of sterilization agent erosion, the internal general to maintain positive pressure. Can be used in pharmaceutical industry, food industry, medical facilities, experimental facilities.
② biological safety clean room. Mainly control the life of the work of the particles of pollution to the outside world and people, the internal need to maintain negative pressure. For experimental facilities, bio-engineering, medical facilities and so on.
Second, by air flow classification
By air can be divided into four categories:
⑴ one-way flow clean room
⑵ non-one-way flow clean room (turbulent clean room)
⑶ angle corner flow clean room
⑷ mixed-flow clean room (local one-way flow clean room)
Third, the principle and characteristics of one-way flow clean room
A unidirectional flow cleanroom is a clean room through which airflow flows at a uniform cross-sectional velocity across a section of the chamber in a single direction along parallel flow lines.
Unidirectional flow clean room by the air flow "piston" -like extrusion, the rapid discharge of indoor pollution.
To ensure the realization of the role of the piston, the most important point is that high efficiency filters must be covered. Of course, the filter has a border, the ceiling also has a border, it is impossible to 100% to filter. Full cloth to measure the extent of the filter over:
Under normal circumstances covered cloth up to 80%. Vertical unidirectional flow should not be less than 60% of the cloth, horizontal unidirectional flow should be less than 40%, otherwise it is a local unidirectional flow.
⑶ characteristics of indicators
① streamline parallelism (streamline parallelism)
The parallel effect of flow lines is to ensure that the dust particles emitted by the dust source do not propagate perpendicular to the flow direction. It is required that the flow lines should be parallel (the angle between the inner lines can not be less than 15 ° at a distance of 0.5m) and the flow lines should be as perpendicular as possible to the air supply surface (the inclination angle can not be less than 65 °).
② turbulence (speed unevenness)
The effect of uniform speed is to ensure the lateral exchange of particles between the streamline minimum. Turbulence is defined as the concentration or dispersion of the velocity field.
③ lower limit wind speed
This is to ensure that the cleanroom can control the minimum wind speed for the following four types of pollution:
a. When the polluting air flow is distributed in different directions, the air flow should be able to effectively control the pollution range;
b. When the polluted air flow and air flow in the same direction, the air flow to be able to effectively control the flow of pollutants to reach the downstream diffusion range;
c. When the polluted air flow and the supply air flow reverse, the supply air flow can inhibit the pollution flow within the necessary distance;
d. In the case of contaminated rooms, sufficient room to quickly self-clean the indoor air at the right time.
Lower limit Wind speed Recommended value
Third, the principle of turbulent clean room and features
Turbulent clean room is: air flow at a non-uniform velocity was non-parallel flow, with a clean room or backflow eddy current.
Turbulent clean room by the air flow constantly dilute the indoor air, the indoor pollution gradually discharged, to achieve balance. To ensure that the dilution effect is well achieved, the most important point is that the indoor air flow spread as quickly as possible.
⑶ characteristics of indicators
① ventilation frequency
The role of ventilation is to ensure that there is sufficient dilution of clean air.
The number of ventilation should be based on calculations and experience to determine.
② air flow organization
The role of air flow organization is to ensure uniform supply air and return air, give full play to the dilution effect of clean air. Therefore, a single outlet requires a sufficient diffusion effect, uniform return air room layout, the number of more good, to minimize turbulence and air maneuvering.
③ self-purification time
Self-purification time is a reflection of the ability of the clean room to recover from a contaminated state to a steady state. The shorter the better. It can also be specified as the time from a contaminated state to a clean state.
Turbidity clean room self-purification time is generally not more than 30min.