How to plan clean air supply for closed equipment cavities?

Closed equipment has small cavity space, many mechanisms, and limited openings. Variables such as internal dust generation, heat sources, manipulator blocking, exhaust switching, and door opening maintenance often exist at the same time. Partial cleaning under such conditions cannot be solved by simply installing a fan or high-efficiency filter above the cavity.

Where the clean air comes in, what it passes through, who it protects, where it comes out, and in what state it is verified are the core of planning. Let’s start with several practical aspects.

First define the cavity boundaries and protection objects

Before planning, decide whether to protect the product, the institution, or the entire device. Is it to protect wafers, precision parts, optical components, or the robot movement area? Is it to control the entire cavity, or only protect a local workstation?

Different boundaries will result in different air supply directions, filter locations, air speeds and sampling points. If the product is continuously exposed in the cavity, the protection scope should cover the actual transmission path; if it is only exposed for a short time at a certain work station, local air supply can be evaluated. If you are not sure whether to do the whole cavity or just a part of it, you can first see How to choose between whole room purification and partial purification ? Clarify the selection logic at the program level and then implement it in the cavity.

If hazardous dusts, vapors or bioaerosols are involved, clean air supply cannot replace dedicated exhaust, isolation or safety protection equipment. In this case, it is necessary to first determine the protection plan according to safety requirements, and then consider the clean air supply package.

Identify internal dust generation and external inputs

Sources of contamination in closed chambers usually include: mechanical wear, cable friction, fixture movement, material introduction, personnel opening doors, residual dust accumulation, thermal plumes and process exhaust. Merely improving filter efficiency cannot solve the problem of downstream dust generation or seal bypass.

It is recommended to mark the pollution sources on the cavity diagram to distinguish between upstream pollution and downstream pollution. Clean air should first pass through sensitive products, then pass through the pollution source, and finally be discharged; the air should not be allowed to sweep through the dust-generating mechanism first and then blow toward the product.

Design controllable airflow paths

With only air intake but no reasonable outlet, the air flow will be stranded or discharged from the gaps in an orderly manner. Enclosed cavities should form clear paths:

• Air inlet: Confirm where the filtered air enters and whether it passes through HEPA and ULPA filters , whether the inlet is affected by background contamination.

• Coverage: Let the clean air reach the product, wafer or sensitive surface first and avoid being blocked by robots, fixtures and pipelines.

• Exhaust: Check the exhaust, pressure relief vents, return air channels and gaps to prevent the supply air and process exhaust from competing for air volume.

• Pressure difference: Use the pressure difference direction to prevent background air from flowing back, but the pressure difference target should be determined according to process, safety and equipment requirements, and it is not appropriate to apply a fixed value.

How to match EFU, FFU, filter and group control?

Commonly used equipment-side closed cavities EFU equipment-side fan filter unit , because it is easier to integrate into the equipment, is suitable for locations where space is limited and local protection is required. The background air supply in the room is often provided by FFU clean air supply products are responsible for this. The two can cooperate, but the protection boundaries, wind sources and control linkage must be clearly defined respectively. The logic of this division of labor lies in the division of labor between device-side EFU and room FFU . There is a more detailed explanation on

The selection should not just look at the nominal air volume. It is necessary to check the working point with filter, external static pressure, filter resistance, installation dimensions, sealing method and maintenance direction. If the cavity has multiple sets of EFU or needs to be on duty, partitioned, alarmed and energy-saving operation, it can be combined FFU group control system provides unified management.

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. 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 ? Avoid mixing the two concepts together when making selections.

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. This point is what later expenses will be increased due to insufficient maintenance channels . There is a more specific cost analysis in

Pressure difference, door opening status and internal mechanism

Equipment opening, maintenance, exhaust switching and manipulator movements will change the cavity pressure difference and air flow direction. When planning, it should be clear: who starts and stops first during normal operation, whether to slow down or alarm when opening the door, and how to restore after maintenance. Without linkage logic, background air may be brought into the sensitive area the moment the door is opened.

When the manipulator extends, returns, and waits, it may block the air supply surface, causing wake flow or local backflow. The heat source will lift the air, and the exhaust will remove the protective airflow. Verification should cover real movements, rather than just measuring the static state of the cavity.

Verification and common misunderstandings

It is recommended to verify the closed cavity in stages:

• Check filter seals and bypass leaks after installation;

• Measure air volume, wind speed, pressure difference and air flow direction;

• Observe the air flow during manipulator movement, door opening, exhaust switching, etc.;

• Conduct particle detection according to the agreed particle size, sampling location and operating status;

• Record the recovery time and confirm whether it can return to the protection state after the exception.

Common misunderstandings include: only installing filters without designing air flow outlets; only looking at the nominal air volume of the EFU without looking at the working point with a filter; only measuring static conditions but not door opening and mechanism movement; treating a closed shell as a guarantee of cleanliness; using filter efficiency instead of on-site cleanliness level verification.

Project judgment example

There is a robot inside the cavity of a certain equipment. The original plan only installed one EFU on the top. The static wind speed was normal, but particles occasionally appeared at the product location during production. The investigation found that the manipulator extended out and blocked part of the air supply surface, and the product was located in the weak protection zone behind the blockage.

Adjustment method: slightly shift the EFU position to allow clean air to pass through the product first and then through the manipulator movement area; increase door opening linkage, slow down and alarm when opening the door, and resume after closing the door. After the adjustment, the wind speed was measured again, and the air flow in the protected area returned to stability.

In another project, the cavity space was insufficient, 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: local cleaning of the closed cavity, equipment selection and position adjustment must be considered together.

Key points for selection and acceptance inspection

Aili industrial equipment supporting support

Aili Industry covers motor manufacturing, independent research and development and production of fans, control system development, sheet metal processing, air filter manufacturing and complete machine assembly. For closed equipment cavity projects, EFU, FFU, HEPA/ULPA filters, group control systems, air volume, static pressure, and installation interfaces can be uniformly checked to connect equipment configuration with on-site evaluation boundaries and reduce the disconnect between component parameters and complete machine operating conditions.

learn EFU equipment side fan filter unit；FFU clean air supply products；HEPA and ULPA filters；FFU group control system checks the installation space, operating conditions and filtered air supply configuration.

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