How will the air supply effect of FFU be affected if the return air outlet of the clean room is blocked?
Blocked return air vents are not just a local problem
The clean room return air outlet is an important part of air circulation. FFU sends clean air from the air supply side. After the air passes through the process area, it needs to return to the mezzanine or return air channel through the return air outlet before entering the next round of circulation. If the return air vent is blocked by equipment, materials or structures, the air return path is blocked and the entire air circulation may be affected.
Blocking the return air outlet may not immediately lead to excessive cleanliness. In the initial stage, it may just be a local wind speed change or a deviation in the direction of the air flow. However, over time, airflow stagnation, backflow or low ventilation may develop in local areas, affecting particle control.
Therefore, return air outlet obstruction needs to be identified and dealt with in time. Aili Industrial has complete production capabilities in FFU complete machines and clean engineering supporting equipment, and can cooperate with the project to analyze return air problems. For the basic structure of the FFU machine, you can refer toAili Industrial FFU fan filter unit。
How occlusion changes airflow paths
When the return air outlet is blocked, air cannot return smoothly. Positive pressure may build up in nearby areas, and airflow may find other paths, such as backflow through door cracks, gaps, or adjacent areas. This will cause the originally designed airflow direction to change.
If multiple return air outlets are blocked, the system resistance may increase, the FFU operating point changes, and the air volume may decrease. If the local return air outlet is blocked, the air supply from nearby FFU may not be able to effectively take away particles, forming an airflow dead zone.
Blocking may also affect room pressure differentials. When the return air is not smooth, the room may not be able to maintain the design pressure difference.
How to identify occlusion on site
To identify return air outlet blockage, you can first visually inspect it. Confirm whether the return air outlet is blocked by equipment, materials, shelves, pipelines or structures. Check whether the return air grille is clean and free of dust. Check whether there are any temporary piles near the return air outlet.
If the return air vent is behind or at the bottom of the device, it may not be easily visible directly. You can view the layout diagram to confirm the relative position of the equipment and the return air vent. The device can be moved or inspected using endoscopic equipment if necessary.
How to do area measurement
If you suspect that the return air vent is blocked and affects the airflow, you can measure it in the area. The measurement contents include: wind speed and air flow direction near the return air outlet; wind speed on the FFU outlet surface; wind speed and air flow direction in the process area; and room pressure difference.
If the wind speed near the return air outlet is obviously low, or the air flow direction does not match the design, it may mean that the return air is blocked. If the wind speed on the FFU outlet surface is normal but the wind speed in the process area is low, it may also be related to the return air.
Anemometers, smoke devices or wires can be used for measurements. Record measurement locations and results for easy comparison.
What are the rectification methods?
The method of rectifying the return air vent blockage depends on the reason for the blockage. If equipment or materials are blocking it, you can adjust the location of the equipment or move the materials. If the return air outlet position design is unreasonable, you can adjust the return air outlet position or add a return air outlet. If the return air grille is collecting dust, it can be cleaned or replaced. If the return air path is blocked in the mezzanine, you can clean the mezzanine or adjust the return air channel.
After rectification, the measurement should be re-measured to confirm that the airflow has been restored. If the problem is more complex, comprehensive judgment can be made based on the FFU operating status and pressure difference data.
What are the preventive measures?
To prevent blockage of return air vents, we can start with design and management. When designing, avoid arranging fixed equipment or shelves in front of the return air vent. Specify a material storage area during operation to avoid temporary stacking near the return air outlet. Regularly check the status of the return air vent and include it in daily maintenance.
For areas where equipment layout may change, space for return air vent adjustment can be reserved. If the equipment needs to be close to the return air outlet, you can set up diversion or adjust the return air direction.
Issues that should be confirmed in advance during project communication
During the clean room return air inlet obstruction investigation and rectification stage, it is recommended to confirm the following with the designer and FFU manufacturer: return air inlet location and design air volume; obstruction conditions and reasons; airflow path and area measurement results; FFU operating status; room pressure difference; rectification plan; verification method; preventive management measures.
If you are dealing with the problem of blocking the return air vent in the clean room, you can visitAili Industrial FFU fan filter unit to learn about the complete machine configuration, you can also contact Aili Industrial to obtain engineering support.
in conclusion
Blocking the return air outlet will change the airflow path and system resistance, causing backflow or low ventilation in local areas. The wind speed on the FFU outlet surface is normal, which does not mean that the room airflow still meets the design. Identifying obstructions, area measurement and rectification verification are the steps in dealing with return air issues. Preventative measures can reduce the occurrence of occlusion.
Aili Industrial has complete production capabilities in FFU complete machines and clean engineering supporting equipment, and can cooperate with the project to analyze return air problems. If you need to know more about clean room return air design, you can visitAili Industrial FFU fan filter unit , you are also welcome to contact Aili Industrial for project support.
