We should be able to reduce project costs by using the following 10 cost factors to provide alternative design options, improve the basic clean room design and standards, and meet the needs of the plant as much as possible. It is suitable for clean room planning and construction in bio-pharmaceutical, microelectronics and food processing industries.
1. Number of air changes
The ratio of pollutants in the room and actual particulate production are the main factors affecting the number of air changes in the clean room.
The speed with which particles can be removed is very important in the production process without any effect on other factors.
Other factors that may affect the amount of recirculated air are the structure of the room, the location of equipment, surface temperature of equipment, air convection, type of airflow, operating space and regulations, materials and chemicals used, etc.
A unidirectional, turbulent, vertical or horizontal flow
In many cases, unidirectional airflow is used only in sensitive areas of small Spaces and clean rooms and uses a microenvironment. The source of contamination may be in glove boxes, filtration modules, etc.
Most of the schemes designed to clean the outdoor area with integral unidirectional air flow can only achieve unidirectional air flow when there are no operators, production equipment and exhaust devices in these areas.
Depending on the structure of the room and where the equipment is placed, turbulence can carry pollutants away.
3. Air filtration
Depending on the purpose of the clean room, other equipment may also be selected. For example, in a circulating air plus fresh air treatment system, A HEPA filter is used to treat VOC and electrostatic filtration chambers with a synthetic filter with carbon adsorption or similar functions.
Fan filtration is no longer a new product in the cleanroom market, and when applied correctly it can provide an excellent and economical solution for many high-level cleanrooms, especially in buildings with limited ceiling heights.
4. Air processor
Fresh Air Treatment The air conditioning cabinet provides the necessary fresh air for the clean room.
Multiple circulation air conditioning units feed air into the clean room through the air ducts and through ULPA filters or HEPA filters, which are usually 100% covered on the suspended ceiling of the clean room on classes 10 and 1.
The vertical unidirectional air flow goes down through the clean room and enters the return air space under the floor through the aerial floor tile with holes, and then goes up through the vertical return air channel and enters the return air static pressure box on the ceiling.
Then, the air enters the circulation air conditioning box again, the above air circulation is repeated again.
5. Air pressure difference
Clean room pressurization is necessary to ensure that the clean room is away from pollution in its immediate vicinity, to control the flow of harmful pollutants, to prevent cross-contamination between different areas, and to help maintain the required temperature and humidity levels.
The pressure differential between the clean room and the associated corridor and other areas within the facility should be maintained between 0.25 and 0.005 inches of water (in.w.G.).
Generally, the pressure difference required by pharmaceutical enterprises is higher than this, and the pressure difference between different areas is adopted to avoid cross contamination.
A series of cascade airlocks and positive pressure doors that allow air to diffuse rapidly between different areas are installed to create pressure differentials.
6. Temperature control
The change of temperature and humidity can lead to the error of production equipment, thus affecting the repeatability of production process, and finally leading to the reduction of product qualification rate and increase of waste.
Therefore, the strict temperature control requirements for clean rooms are obvious, and this cost is necessary.
In general, engineers are required to reduce the cost of construction in the design, and to control the temperature accurately over a large area. If there are strict requirements for hvAC, power professional equipment and control systems in the clean room, there will be a local automatic thermostat to control the design temperature within each clean room area. It can drive the local reheat or recold coil installed on the air duct to work to meet the requirements of humidity and heat in the room.
7. Humidity control
The relative humidity of each clean room is controlled by a local humidity regulator.
When precise humidity control must be met, it is usually achieved by the adiabatic humidification effect of fresh air in the air conditioning cabinet. Local changes in humidity level can be controlled by an ultrasonic humidity regulator located in the air duct static pressure chamber prior to final filtration.
8. Exhaust system
Quality air treatment equipment minimizes exhaust emissions, thus reducing engineering costs and energy waste during implementation.
It is important to maintain a balance between the potential demand for increased exhaust volume and the economic value required to expand production and install these stand-by supplies.
9. Electrostatic charges on the surface of air and objects
Static electricity is the result of two separate surfaces touching each other.
Charges generated by different surfaces, if not transmitted to the surface quickly enough, then gather and spread over the surface of the material, which is "static electricity".
The residual electrostatic charge in many areas of industry can be dangerous and cause problems.
It can cause the combustion of flammable gases and electrocution in humans. It can cause thin films and light fibers to adhere, adsorb dust and debris in the air, damage semiconductor equipment and interfere with the operation of microelectronic equipment.
The most basic way to avoid the effects of electrostatic discharge on a microelectronic system is to place the device in a good electrostatic and magnetic field shielding area, appropriately reducing all input and output connections.
10. Form and Function
The strict cleanliness of a clean room is associated with its inherent high production costs. However, if planned in advance, costs can be greatly reduced:
Define cleanroom level accurately to meet process requirements.
Define air temperature and humidity in clean room accurately to meet process requirements.
The exhaust volume outside the clean room should meet the minimum requirements of the process, and the exhaust air management procedure should be carried out at the beginning.
Reduce the pressure drop of the air duct and pipeline by determining the maximum and minimum of the equipment wind speed and implement these guidelines throughout the construction process.