The empty state is qualified but the dynamic state exceeds the standard. How to check FFU and personnel process load?
Why are there differences between empty state and dynamic state?
In clean room testing, empty state, static state and dynamic state are three different operating states. Empty state means that the equipment has been installed but no personnel and production equipment are running, static means that the equipment is running but no personnel are operating, and dynamic means normal production status. Many projects have qualified data during empty or static testing, but after entering dynamic production, the particle concentration rises and exceeds the standard.
This difference does not necessarily indicate a problem with FFU itself. In dynamic conditions, movement of personnel, equipment operation, material handling, process dust generation, and airflow disturbances will change particle levels in the clean room. Without these pollution sources during air condition detection, it is naturally easier for the air cleanliness to meet the standards.
Therefore, when the air condition is qualified but the dynamic condition exceeds the standard, the investigation direction should not only focus on the FFU wind speed or filter efficiency, but should start from the dynamic pollution sources, air supply coverage and air flow organization at the same time. Aili Industrial has complete production capabilities in FFU complete machines and clean air supply solutions, and can cooperate with projects to analyze air supply coverage issues under dynamic working conditions. For the basic structure of the FFU machine, please refer toAili Industrial FFU fan filter unit。
First confirm whether the detection status and detection method are consistent
Before checking for dynamic excess, you must first confirm whether the empty state and dynamic detection conditions are comparable. Whether the detection positions are the same, whether the height of the measuring points is consistent, whether the sampling time covers the complete production cycle, whether the number of personnel and production status are recorded, and whether the detection instruments are calibrated.
If the empty state detection only measures a few points and the dynamic detection measures more locations, the data difference may come from the distribution of measurement points rather than changes in cleanliness itself. If the dynamic detection is carried out when people are concentrated in the operation, and the empty detection is carried out in an unmanned state, the difference in particle concentration is also a normal phenomenon.
It is recommended to sort out the empty and dynamic detection records before troubleshooting, mark the status, location, time and personnel activities, and confirm whether the differences are systemic or local.
How pollution sources change under dynamic conditions
Pollution sources in the dynamic state are more complex than in the empty state. Personnel is an important source of particles in the clean room. Personnel will produce particles when moving, operating, and talking. Process equipment may generate particles during operation, such as friction, cutting, conveying, welding, cleaning and other processes. Material handling and packaging opening may also release particles.
If the dynamic exceedance is concentrated in a specific area, you can first observe the activities in that area during production. For example, the FFU air supply above a certain workstation is normal, but operators frequently pick and place materials at this location. The particles may come from operating actions rather than insufficient air supply. If the exceedance occurs near the equipment, you can check whether the exhaust of the equipment is normal, whether particles are produced inside the equipment, and whether the equipment maintenance door is sealed.
The investigation of pollution sources needs to combine the production process and personnel movement, and cannot just look at FFU data.
How does FFU air supply coverage change dynamically?
The air supply coverage of FFU may appear uniform when in the empty state, but under dynamic conditions people, equipment and materials will change the airflow path. When people stand under the air supply area, their bodies will block the air flow; the heating of the equipment will generate updrafts, interfering with the downward air supply; and material handling may bring in surrounding air.
If the dynamic exceedance occurs at a key workstation, the wind speed and airflow direction at that location can be measured under production status, instead of only measuring the wind speed on the FFU outlet surface in the air. If the wind speed on the air outlet surface is qualified, it does not mean that the airflow still meets the requirements after reaching the process location. Equipment occlusion, air supply distance and lateral disturbance will all affect the actual protection effect.
For local protection areas, you can check whether the FFU layout covers key operating points, whether the return air path is smooth, and whether there is lateral airflow interference around it. If the air supply coverage is insufficient, it may be necessary to adjust the position of the FFU, increase the air supply area, or optimize the envelope structure.
Whether the return air and pressure difference cooperate with dynamic operation
Under dynamic conditions, process exhaust, equipment exhaust and personnel entry and exit will change the room pressure difference and air flow balance. If the return air path is blocked by equipment or materials, airflow stagnation or backflow may occur in local areas. If the process exhaust air volume changes greatly, the FFU air supply effect may also be affected when the room supplementary air is insufficient.
During the inspection, the room pressure difference, return air volume and process exhaust status during dynamic operation can be recorded to confirm whether the system is operating under design conditions. If the exhaust air volume increases during dynamic operation and the supplemental air is not adjusted accordingly, the room airflow organization may deviate from the design state.
Impact of personnel management and operating practices
Dynamic cleanliness depends not only on equipment and systems, but also on personnel management and operating practices. The number of personnel, operating movements, clothing changes, frequency of entry and exit, and material cleaning methods will all affect particle levels. If the dynamic exceedance is concentrated in areas with frequent human activities, you can first check whether the operating specifications are implemented in place.
For clean room projects, it is recommended to incorporate personnel training, operating procedures and dynamic monitoring into daily management, rather than just focusing on data during acceptance.
Checking sequence and recording method
Dynamic excessive inspection can be carried out in the following order. First confirm whether the empty state and dynamic detection conditions are comparable, then analyze whether the exceeding standard location is local or the whole room, then check the pollution sources and operating activities at this location, then measure the air flow and supply air coverage in the dynamic state, and finally check the return air, pressure difference and process exhaust status.
During the investigation process, it is recommended to keep the following records: detection status and time, location and height of measuring points, number of personnel and production status, equipment operating status, wind speed and pressure difference data, on-site photos or videos. These records can help determine the source of the problem and provide a basis for subsequent adjustments.
If after investigation it is found that the FFU air supply coverage is insufficient or the layout needs to be adjusted, you can combineFFU air flow and air volume design (Note: This link is an example of the FFU product page, please refer to the corresponding page on the site for specific air flow design related content) to understand the air supply configuration ideas. Aili Industry has complete production capabilities in FFU complete machines and filtration and control supporting equipment, and can cooperate with the project to check the air supply plan under dynamic working conditions.
in conclusion
If the air condition is qualified but the dynamic exceeds the standard, it is usually not a single FFU problem, but the result of the joint action of dynamic pollution sources, supply air coverage, air flow organization, return air pressure difference and personnel operations. When troubleshooting, you should first confirm whether the testing conditions are comparable, and then analyze the location of the pollution source and the air flow state, instead of just re-testing the air FFU wind speed.
Aili Industrial has complete production capabilities in FFU complete machines and clean air supply solutions, and can cooperate with projects to analyze air supply coverage and system coordination issues under dynamic working conditions. If you are dealing with dynamic cleanliness exceedances, you can start withAili Industrial FFU fan filter unit to learn about the complete machine configuration, you can also refer toFFU Frequently Asked Questions and Selection Guide to understand system troubleshooting ideas.
