Clean room control refers to a series of design, operation and maintenance measures to ensure that the air quality, temperature and humidity, pressure and other key environmental parameters in the clean room are strictly controlled and meet the prescribed standards. Clean rooms are mainly used in applications that are highly sensitive to microorganisms, particulate matter and other sources of contamination, such as semiconductor manufacturing, pharmaceutical production, biological laboratories, etc.
Clean room control involves the following aspects:
HVAC is an important aspect of a cleanroom because heating, ventilation, and air conditioning (HVAC) systems perform air-related functions. Different types of control elements are used to control the characteristics of the air. mainly include:
- Variable frequency drive
- Air flow sensor
- Differential pressure sensor
- Temperature and humidity sensor
Particulate matter control
Control and reduce the concentration of particulate matter in the air through a high-efficiency air filtration system. Filter selection and maintenance are key to ensuring particulate matter control.
Through strict environmental control, air filtration and clean room hygiene measures, we prevent and reduce the presence of microorganisms and ensure that the level of microorganisms in the clean room meets the prescribed standards.
Air flow sensor
Airflow sensors monitor air movement inside and outside the cleanroom. Feedback from these sensors is then used to control the speed of the supply fan operated by the VFD.
If the air supply volume is less than the preset value, the VFD will increase the fan speed, causing the air volume to increase. Similarly, if the air volume is greater than the preset value, the inverter will reduce the fan speed, resulting in a reduction in air volume.
The feedback signal can be 4-20mA current or 0-10V. Air flow sensors are installed on the fresh air and return air supply ducts closest to the control area.
Temperature and humidity sensor
Every manufacturing industry strictly controls the temperature and humidity conditions in clean rooms. Any deviation from these parameters can significantly affect the manufacturing process, leading to defects in the product.
Temperature and humidity sensors are used to monitor these two physical values. The sensors of both values are built into the same housing and the signals are transmitted by separate conductors.
4 – 20mA 0r 0 – 10V can all be used as signals and fed to the main controller. Some sensors also come with a display attached to the sensor for field data visualization. These sensors continuously measure temperature and humidity values. Any deviation from the preset value triggers an alarm. The system remains in alarm state until control conditions are restored.
Pressure difference control
Differential pressure sensors measure the difference between two points rather than actual or absolute pressure. In clean room technology, the internal areas of the clean room should be under positive pressure and the outside areas should be under negative pressure. This is because positive pressure prevents foreign objects from entering the controlled area.
A differential pressure sensor monitors positive pressure in a controlled area and alerts the system when the differential pressure becomes negative. These are also used in filter assemblies for clean rooms. Its purpose is to measure the condition of the filter, indicating the effectiveness of its filtering capabilities. In this case, it is installed on both sides of the filter.
Implement personnel access control measures, such as clean room clothing, air showers, etc., to reduce particles and microorganisms introduced by personnel.
Control the operation of equipment in the clean room to ensure that it does not introduce contaminants, and perform regular equipment maintenance.
Monitoring and alarm system
Install a monitoring system to monitor key parameters in real time, and set up an alarm system to issue an alarm when the specified range is exceeded to ensure that control measures are taken quickly.
Cleaning and maintenance schedule
Develop a regular cleaning and maintenance schedule, including air filter replacement, floor cleaning, etc., to ensure long-term clean room performance and cleanliness.
Combining the above control measures, clean room control aims to create and maintain a highly clean and stable working environment to meet the extremely high requirements for air quality and environmental conditions in specific industries.