How to establish a local clean area in an open workstation?

The open workstation has no enclosure and people and materials can enter and exit freely. Partial cleaning under such conditions cannot be solved by simply hanging an FFU above the work station.

When the clean air comes down from the air supply surface, it must first pass through the product and then take away the surrounding particles. If the airflow direction is wrong or interfered with by side winds, no matter how large the air supply volume is, it may not be able to protect key locations. Let’s start with several practical aspects.

Let clean air cover the actual operating area

The protection scope of the local clean area is not the workstation surface, but the small area where the product is actually exposed.

Determining this area depends on the position of the workpiece, the range of movement of the operating arm, and the way the tools are placed. Some workstation products are placed in the middle, and the protected area is the center of the table; some workstation products are on the fixture and may be skewed to one side, and the air supply surface must be skewed accordingly.

The distance between the air supply surface and the work station is also important. If the distance is too far, the airflow will have spread by the time it reaches the workpiece; if the distance is too close, the operation may be affected or even the tools or parts will be blown. This distance generally requires on-site testing to see if the airflow can cover it stably without interfering with normal operations.

If there are lighting, pipelines or mechanical structures above the workstation, also make sure that these objects do not block the air supply surface. If an FFU is installed above the workstation, and the air outlet surface is partially blocked by the beam, the actual coverage will be reduced.

Open borders require on-site verification

The boundaries of the open workstation are virtual. Whether the airflow can be maintained needs to be seen in practice.

Side curtains or soft curtains can block some cross-wind winds, but they will change the airflow exit path. After adding a curtain, the air supply may be restricted within the curtain, or it may be rolled outward from the curtain opening. It is difficult to completely predict these changes by calculation. It is recommended to observe the air flow under normal operating conditions.

When observing, pay attention to several time points: when people approach the workstation, when tools are inserted from the side, and when products are put in or taken out from one side. These actions will change the local airflow, and passing the static test does not mean that the dynamic test is also qualified.

If there are air-conditioning vents, exhaust hoods or frequently opened and closed doors next to the workstation, the airflow from these locations will directly hit the protected area. First record the source and direction of these external interferences, and then decide how to install local equipment.

Lateral interference must be dealt with separately

Side wind is a common source of interference for local cleaning of open workstations.

It may come from air conditioning supply, exhaust air from adjacent workstations, airflow caused by people moving around, or the cooling fan of the equipment itself. The lateral wind does not need to be very large. As long as the direction is facing the protected area, the clean air may be blown away and particles may enter the product location.

There are several ways to deal with it: adjust the direction of the air-conditioning outlet so that the main airflow does not blow directly into the workstation; add baffles or soft curtains to the side of the workstation to change the airflow path; slightly increase the local air supply surface to allow the protection range to cover the locations affected by interference.

These adjustments need to be selected based on site conditions, and there is no fixed answer. Sometimes it is more effective to move the workstation to another location than to add equipment in place.

How to Choose Between Whole Room Purification and Partial Purification , the protection boundary of the local plan should correspond to the actual exposure path. As mentioned in For open workstations, special attention must be paid to airflow interference outside the boundary. Otherwise, no matter how well the boundary is drawn, it cannot be maintained.

Equipment selection and installation location

Commonly used equipment in local clean areas include FFU, EFU and clean workbench.

The FFU is installed above the workstation, suitable for occasions with suspended ceilings or brackets. When selecting, check the size of the air outlet surface, air volume and external static pressure to ensure that the required air speed can be maintained at the height of the workstation. The FFU clean air supply product page has standard and customized plans.

EFUs are typically used inside equipment or in tight space locations. If the workstation is next to the equipment, or the space above it is limited, an EFU may be more suitable. The EFU equipment side fan filter unit page has instructions for different structures.

The clean workbench comes with its own air supply and enclosure, which is suitable for workstations with concentrated operating areas. However, the protection scope of the workbench is limited, and products still need other protection when being transported outside the bench.

Filter selection should correspond to the target particle size and cleanliness level. The HEPA and ULPA filter pages have parameters for different levels of products. When selecting, check the efficiency of the specific model at the target air volume.

The installation location should be away from obstructions and should be convenient for filter element replacement and maintenance. If the equipment is installed too high or too far inside, maintenance will be troublesome.

Operation and maintenance

After the local clean area is built, the operating status needs to be confirmed regularly.

Wind speed and airflow direction will change due to dust accumulation on the filter element, aging of the fan, or external interference. It is recommended to regularly measure the wind speed at key locations of the workstation and observe whether there is any deviation in the direction of the airflow. If the protection effect is found to be reduced, first check the filter element resistance and installation seal, and then check for external interference.

The filter element replacement cycle is judged based on the operating pressure difference and outlet concentration, not just time. As mentioned in What is the Difference Between Cleanliness Grade and Filtration Efficiency ? Space grade and filter efficiency are two different things and should be recorded separately during maintenance.

If multiple local devices need to be managed uniformly, group control can be considered. The FFU group control system can configure operation strategies by region and time period to facilitate on-duty and troubleshooting.

Project judgment example

An electronic assembly station is located in an open workshop. There is an air-conditioning outlet above the station and a personnel passage on the side.

The original plan installed an FFU above the workstation, and the static wind speed was normal. However, during production, workers reported that there were occasional particles in the product position. The investigation found that the air-conditioning air blew from the side and biased the FFU's air supply airflow. The product position was exactly in the weak protection zone after the deflection.

Adjustment method: Deflect the direction of the air-conditioning outlet to reduce direct blowing to the workstation; add a transparent baffle on one side of the workstation to block the airflow caused by people moving around. After the adjustment, the wind speed was measured again, and the air flow in the protected area returned to stability.

In another project, there was insufficient space above the workstation, so the EFU was installed on the side of the equipment, with the air supply direction aligned with the operating position. After installation, check the wind speed and coverage to confirm that the requirements are met.

These two situations illustrate that: partial cleaning of open workstations, equipment selection and position adjustment must be considered together.

Key points for selection and acceptance inspection