How to check FFU air supply and pressure difference recovery when the clean room door is frequently opened
Why does opening the door change pressure differential and airflow?
Clean rooms usually maintain a certain pressure difference through supply air, return air and exhaust air. The function of the pressure difference is to control the flow of air from clean areas to non-clean areas to prevent external contamination from entering. When the door is opened, a channel is formed between the rooms, air may flow from one side to the other, and the pressure difference changes.
When the door is opened frequently, the pressure difference may fluctuate repeatedly. Each time the door is opened, the pressure difference may drop or reverse, and it will take some time to recover after closing the door. If the recovery time is too long or the pressure difference cannot return to the set value, it may affect the pollution control of the clean room.
FFU is part of the air supply system, which provides circulating filtered air supply. However, pressure difference recovery also depends on the management of make-up air, return air, exhaust air and doors. FFU itself cannot solve the pressure difference problem alone. Aili Industry has complete production capabilities in FFU complete machines and clean engineering supporting equipment, and can cooperate with the project to analyze the relationship between air supply and pressure difference. For the basic structure of the FFU machine, you can refer toAili Industrial FFU fan filter unit。
Record door opening conditions
Before inspection, the opening conditions should be recorded. Including: door type and location; door opening frequency and duration; personnel entry and exit methods; material entry and exit methods; whether the door has an air curtain or buffer; pressure difference set value and actual value.
Logging can be done by time period, such as production peaks and off-peaks. If the frequency of opening the door varies greatly in different periods, it can be recorded separately.
How to record pressure difference changes
The pressure difference record should include the values before opening the door, when opening the door and after closing the door. Continuous recording can be done using a differential pressure gauge or differential pressure sensor. The record content can include: initial value of pressure difference; pressure difference change when opening the door; pressure difference recovery time after closing the door; and stable value after recovery.
If the pressure difference recovery takes a long time, the reason can be analyzed. It may be due to insufficient air supply, poor return air, excessive exhaust air or door sealing problems.
How to check air supply and airflow
Air supply and air flow inspection includes FFU operating status, air supply volume, air flow direction and return air path. Confirm whether the FFU is operating normally and whether the rotation speed or control settings are stable. Confirm whether the air supply volume meets the room ventilation or coverage requirements.
When opening the door, observe whether the direction of airflow changes. If outside air is entering through the door, it may indicate insufficient positive pressure in the room or excessive exhaust air. If airflow is flowing out of the room, the positive pressure may be normal. Smoke or ribbons can be used to observe the direction of airflow.
How to check supplementary air and exhaust air
Supply air and exhaust air are important links in pressure difference recovery. Check whether the air supply system is operating normally and whether the air supply volume is sufficient. Check whether the exhaust system is stable and whether the exhaust volume changes. Check whether the return air path is smooth.
If the exhaust air volume changes greatly when the door is opened, the pressure difference may be affected. If the supplementary air response is slow, the differential pressure recovery time may be extended.
How to adjust and improve
If the pressure difference recovery is not ideal, it can be adjusted in several directions. Adjust the air supply volume or air supply response so that the air supply can keep up in time after opening the door. Adjust the exhaust air volume to avoid a drop in pressure difference caused by excessive exhaust air. Optimize door management, such as adding air curtains, buffer rooms or controlling door opening time. Adjust the FFU operating status and confirm that the air supply is stable.
After adjustment, the pressure difference changes and recovery time should be recorded again to confirm the improvement effect.
Issues that should be confirmed in advance during project communication
During the clean room pressure differential and FFU air supply inspection stage, it is recommended to confirm the following with the designer and FFU manufacturer: pressure differential setting value and allowable range; door type and opening frequency; air supply and exhaust system configuration; return air path; FFU operating status and control method; airflow direction when opening the door; pressure differential recovery time requirements; adjustment measures and verification methods.
If you are dealing with cleanroom differential pressure recovery issues, you can visitAili Industrial FFU fan filter unit to learn about the complete machine configuration, you can also refer toFFU/EFU group control touch screen controller andFFU computer group control system to learn about the control scheme, or contact Aili Industrial for engineering support.
in conclusion
Frequent opening of the clean room door will affect the pressure difference and air flow. The recovery of the pressure difference depends on the joint effects of supplementary air, return air, exhaust air, door management and FFU air supply. During the inspection, the opening conditions, pressure difference changes, air supply status and supplementary air exhaust status should be recorded. Adjustments can start with supplementary air, exhaust air, door management and FFU operation.
Aili Industry has complete production capabilities in FFU complete machines and clean engineering supporting equipment, and can cooperate with the project to analyze the relationship between air supply and pressure difference. If you need to know more about clean room pressure differential recovery inspection, you can visitAili Industrial FFU fan filter unit , you are also welcome to contact Aili Industrial for project support.
