The FFU is running normally, why is dust falling at the workstation?

The FFU running indicator light is on and the control panel display is normal, which is the easiest status to confirm during daily inspections. However, this status only indicates that part of the operation signal of the equipment is valid, and does not mean that the air supply volume, filtration effect and air flow protection are all normal. Dust at the work station may be related to the FFU itself, or it may come from other links.

Fallout is the result, and may be caused by equipment, seals, airflow paths, personnel, materials, or process actions. When troubleshooting, you should start from multiple directions, rather than just looking at whether FFU is running.

Operating status and actual air supply capacity are not the same thing

The FFU control panel displays operation, usually only reflecting fan power on or speed signals. Actual air supply capacity also depends on:

• Filter resistance and dust accumulation status;

• Fan operating point and speed setting;

• Whether the air inlet and return air channels are clear;

• Check whether the installation seal is intact.

If the filter is heavily dusted or the return air is blocked, the fan may still show running, but the actual air volume has dropped. For the difference between the FFU nominal air volume and the actual operating air volume, please refer to Is FFU's nominal air volume tested with a filter? . For the influence of working point offset, please refer to Why should we look at the complete performance curve when selecting FFU?。

Sealed bypass may allow unfiltered air to enter

The FFU installation is not tightly sealed, which may allow unfiltered air to bypass the frame or interface and enter the clean side. At this time, the fan is operating normally and there is no obvious abnormality in the filter, but particles may still appear at the workstation.

During the investigation, you should check:

• Whether the filter frame sealing strip is pressed tightly;

• Whether the installation interface is misaligned;

• Is there air leakage from the ceiling or box connection?

• Is the filter broken or displaced?

Sealing inspection is an important step in troubleshooting dust. For specific methods, please refer to What should be checked when cleaning equipment is accepted?。

Upstream occlusion changes protective airflow

If there are lamps, pipelines, fixtures, tools or materials blocking the air outlet surface of the FFU, the protective airflow may be changed and a weak protection zone may be formed locally at the workstation. At this time, the FFU itself is normal, but the product position cannot be effectively protected.

For the problem of dead corners caused by stacking items on the workbench, please refer to Will stacking items on the workbench create a pollution dead zone? . Interference from operating arms, please refer to How will operating the arm interfere with the air supply to the workbench?。

Personnel clothing and movements may be sources of contamination

Particles may be generated from personal clothing, gloves and movement. If dust appears after personnel enter, or is synchronized with specific actions, personnel-related factors should be checked:

• Whether the clean clothes are worn and changed according to regulations;

• suitability of gloves and wiping materials;

• Whether personnel movements are too frequent or across products;

• Whether the number of personnel exceeds the verification range.

Please refer to the troubleshooting method for particles rising after people enter. How to locate the cause of increased particle number after personnel enter?。

Materials and process actions also generate dust

Particles can be generated by unpacking materials, rotating containers, tool friction and mechanical action. If dust fall is synchronized with material replacement or equipment action, check:

• Material packaging and cleaning status;

• Whether the container is collecting dust;

• Whether tools and fixtures are worn;

• Whether the action of the mechanism produces particles.

For particle fluctuations that occur after product batch changes, please refer to How to troubleshoot particle fluctuations after product batch change? . For the impact after startup of process equipment, please refer to What should I do if the cleanliness of the process equipment drops after it is started?。

Airflow paths and return air conditions should also be checked

The FFU air supply is normal, but the return air channel is blocked or the air flow is short-circuited, and dust may still fall on the workstation. The air does not pass through the product as intended, and contaminants cannot be effectively removed.

During the investigation, you should check:

• Whether the return air outlet is blocked;

• Whether there is an airflow short circuit;

• Whether the workstation is in a backflow or vortex area;

• Whether external cross airflow enters the protected area.

To troubleshoot airflow short circuits, please refer to What particle problems can airflow short circuits cause? , for issues regarding the reflow area, please refer to Why is it easy for contamination to accumulate in the return flow area?。

Distinguish between airborne particles and surface sedimentation

Workstation dust is the result of surface settlement, and airborne particles are another type of indicator. The two are related but not substitutes for each other. When the air test passes, dust may still appear on the surface due to long-term settling or direct contact.

When making judgments, air particle data and surface conditions should be recorded separately, and analyzed in combination with time, location and operating conditions. Please refer to the difference between dust accumulation on the equipment surface and excessive air particles. How to distinguish between dust accumulation on the surface of equipment and excessive air particles?。

Suggestions for troubleshooting order

If the FFU is running normally but dust is falling on the workstation, you can troubleshoot in the following order:

• Confirm the actual air supply volume and filter pressure difference;

• Check installation seals and bypasses;

• Check the shielding below the wind outlet surface;

• Check personnel and material related factors;

• Check airflow paths and return air conditions;

• Check process actions and mechanism dust generation;

• Combine air and surface data to determine source.

Troubleshooting should be carried out item by item to avoid adjusting multiple variables at the same time. Insufficient maintenance channels will increase subsequent expenditures. This is reflected in what later expenses will be increased due to insufficient maintenance channels . There is a more detailed analysis of

Equipment selection and terminal matching

The troubleshooting involves equipment and filtering configuration, please refer to FFU clean air supply products and EFU equipment side fan filter unit . Filter installation, sealing and leak detection requirements can be learned HEPA and ULPA filters . If you are still unclear about the difference between space rating and filter efficiency, you can read What is the difference between cleanliness level and filtration efficiency?。

Project judgment example

There is dust at a certain workstation, but the FFU is operating normally. The investigation revealed that the filter frame sealing strip was aging and the bypass leaked. Adjustment method: Replace the sealing strip and check for leaks again to solve the dust problem.

The FFU of another project is running normally, but a new tool rack above the work station blocks the air supply, and the product position is in a weak protection zone. Adjustment method: move the tool frame, adjust the air supply direction, and reduce dust.

These two situations illustrate that the normal operating status of the FFU does not mean that the workstation protection is effective. Dust inspection needs to cover multiple aspects of equipment, sealing, air flow, personnel and materials.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

The FFU operates normally but dust accumulates at the workstation. The problem often does not lie with a single piece of equipment. Aili Industrial has collaborative capabilities in fans, motors, filters, control systems and complete machine assembly links. It can cooperate to check the actual air supply volume, filter sealing, air flow path and operation settings during operation inspections, helping to determine whether the source of dust is equipment status, installation conditions or operating factors. Specific models can be viewed FFU clean air supply products , supporting equipment can be viewed EFU equipment end fan filter unit , please refer to the filter package. HEPA and ULPA filters。