How to determine the protection area for a two-person clean workbench?

The double clean workbench looks like it just widens the workbench, allowing two people to operate it at the same time. But the determination of the protection area does not mean dividing the table in two from the middle. When two people operate at the same time, the positions of arms, tools, materials, and bodies will affect each other, and the airflow boundaries will also change. If the protection zone is determined only based on a single manual station, it may happen that one side is well protected and the other side has high particles.

To determine the protection area of ​​the two-person workbench, first look at the effective air outlet range, then look at the workpiece position, operating actions and material transfer paths, and finally verify it under representative actions. The following will focus on the air outlet range, personnel movements, material handover, layout division, and verification methods.

First look at the effective air outlet range, not the table size.

The effective protection area of ​​the workbench is not equal to the entire area of ​​the workbench, nor is it equal to the overall dimensions of the air outlet surface. It depends on the effective air outlet area of ​​the filter, the airflow direction and the table structure. If a two-person workstation has only one air outlet surface, the airflow in the middle area and the edge area may be different.

When judging the effective range, the wind speed distribution at different locations on the wind outlet should be measured, and attention should be paid to whether the airflow corresponding to the two operating positions is stable. The area diameter can be referred to How should we look at the effective air outlet area of ​​FFU? , wind speed conversion can be referred to How to convert face wind speed and air volume?。

If the wind speed at the edge of the air outlet surface is obviously low, you cannot make up for it by widening the table. It should be confirmed whether the effective protection area can cover the actual operating position of two people, rather than the machine being divided equally according to the table area.

The movements of two people may cause cross interference

When two people are working at the same time, one person's arm, tool, or material may be upstream of the other workpiece. If the flow table is horizontal, the airflow flows from back to front, and items on the windward side will block the downstream; if the flow table is vertical, the arms or tools above may create airflow shadows.

Specific interference includes:

• One person's arm spans the other person's operating area;

• Tools or materials are placed between two people to block the air supply;

• Two people reach into the workbench at the same time to change the direction of local airflow;

• The wake created by one person's actions affects another person's workpiece.

These interferences may not occur when a single person operates. The verification should be based on the actual actions of two people operating at the same time. The influence of operating arms can be referred to How will operating the arm interfere with the air supply to the workbench?。

Material handover is a weak link that is easily overlooked

Two-person workstations often involve the transfer of workpieces between two stations, or the sharing of tools, fixtures and boxes. If the handover position is located upstream of a workpiece, or the handover action blocks the air supply path, particles may be brought near the product.

When judging, please pay attention to:

• Whether the handover position is within the protection zone of the two persons;

• Whether the handover action crosses the other party's protective range;

• Whether the shared tool rack blocks the air supply;

• Whether the material box or container is placed in the air outlet path.

Stacking items on the workbench will create airflow dead spots. Please refer to the relevant judgments. Will stacking items on the workbench create a pollution dead zone? . If handovers are frequent, it is recommended to demarcate working areas and handover positions for two people instead of sharing the entire table.

The division of work areas should be combined with action paths

Mechanically dividing the table into equal parts may not necessarily be consistent with actual operation. A reasonable division method is determined according to the position of the workpiece and the action path:

• Each person has a clear working area and tool location;

• Keep a gap between two people that does not block the air supply;

• Place shared tools or material boxes in a location that does not affect both parties;

• The handover action has a fixed route and does not cross the upstream of the other party's workpiece.

If two people are operating the same workpiece, or the workpiece needs to be continuously passed between two people, special checks should be made to see if the air flow direction is interrupted by the handover action. In this case, please refer to Does the double clean workbench protect the product or the operator? , first confirm the protection objects and operation methods.

External cross-flow also affects the protected area

Two-person workstations are typically larger and have wider openings, making them more susceptible to external lateral airflow. Air conditioning vents, movement of people, exhaust from adjacent workstations, and opening and closing of doors and windows may all change the airflow boundary at the edge of the workbench.

If the workbench is located in an open workshop, the source and direction of external interference should be recorded before deciding on the workbench location and operating settings. For background condition assessment, please refer to Can an ordinary factory building become a clean workshop by installing FFU? , the lateral interference treatment of open workstations can be referred to How to establish a local clean area in an open workstation?。

The influence of front window height and countertop size

Front window height changes openings and external air exchange, affecting local airflow. If the two people working on a two-person workstation are operating at different heights, they may need to check the airflow status at their respective locations. Related analysis can refer to Will the height of the workbench front window affect the clean airflow?。

The size of the countertop should match the workpiece, fixtures, tools and operating paths, and leave space that does not block airflow. For specific judgment, please refer to How does the size of the workbench match the actual operation? . When choosing the size of a two-person workbench, you should not only check whether the two people can stand apart, but also confirm whether the effective protection area can cover the operating positions of the two people.

Verification method: Two people operate the test at the same time

The verification of the two-person workbench should be carried out with two people operating at the same time. Suggestions include:

• Measure the wind speed and air flow direction at the two-person operating position;

• Observe the changes in airflow when arms are extended simultaneously;

• Record the local air flow during material handover;

• Detect under normal tool placement and material box position;

• Conduct particle detection according to the agreed particle size and sampling position;

• Record front window height, operating settings and personnel positions.

The sampling point layout should cover the actual product exposure locations of two people, rather than just choosing the middle or below the air supply outlet. Related methods can be found in Why can’t the sampling point be located just below the air supply outlet? . The cleanliness level must indicate the particle size and state. For details, please refer to Why must the particle size be indicated in the cleanliness grade?。

Equipment selection and terminal matching

If it is determined after evaluation that partial protection for two persons is required, please refer to Clean benches understand the different structures. Please refer to the room background air supply FFU clean air supply products , please refer to the local protection of the equipment side. EFU equipment side fan filter unit . The logic of division of labor between the two lies in The division of labor between device-side EFU and room FFU is explained in detail.

Filter selection should correspond to target particle size and actual resistance.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. 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?。

If multiple local devices need to be managed uniformly, they can be combined FFU group control system provides unified management.

Project judgment example

The original plan for a two-person assembly workbench was to bisect the tabletop in the middle. During actual production, it was found that one operator's tool rack blocked the airflow of another operator, causing the workpiece particles on one side to be higher. Adjustment method: remove the middle tool rack, set tool positions for two people, and adjust the material transfer path. After adjustment, the airflow on both sides returned to stability.

In another project, two people operate the same workpiece, and the workpiece needs to be transferred between the two people. The original plan only tested static airflow. Dynamic testing found that the handover action interrupted the air supply path on one side. Adjustment method: Adjust the workpiece transfer direction and handover position, and re-measure the protective boundary of the two-person operating position. Adjusted dynamic grain reduction.

These two situations illustrate that the protection area of ​​the two-person worktable must be comprehensively determined based on the air outlet range, movement path and material transfer, and the table surface cannot be divided mechanically.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

The protected area of ​​a double workstation is not the size of a single workstation multiplied by two. Aili Industrial provides clean workbench, clean booth, clean screen and related air supply and filtration packages. It can combine the two-person operating position, workpiece handover path and background air flow conditions to check the effective protection range, airflow direction and filter configuration of the workbench to help determine whether the table layout, tool position and operation settings match the actual two-person operation, rather than selecting based solely on the size of the table. Specific equipment can be viewed Clean workbench , local air supply can be referred to FFU clean air supply products , please refer to the filtration package HEPA and ULPA filters。