Which parts of FFU and EFU equipped with ULPA should be checked for leaks?

Both FFU and EFU are air supply units with their own fans and ULPA filters installed inside. Many people think that leak detection means scanning the filter element, but in fact, the sealing boundary of the whole machine is the key to determining the actual air supply quality.

If the filter element is factory-qualified, it only means that it has no local leakage under test conditions. After being installed in the FFU or EFU, air may also bypass the interface between the filter element and the box, the seams of the box, access openings, cable holes, etc. If there is a bypass at these locations, unfiltered air will mix into the clean side, and the filter element will not be effective no matter how high the grade is. Therefore, leak detection must cover the complete path from the filter element to the complete machine, and clearly distinguish what belongs to the filter element body and what belongs to the installation and complete machine boundaries. For specific leak detection methods, please refer to ULPA’s instructions on on-site leak detection.

First draw the air path and clearly detect the boundary

Before checking for leaks, first figure out how the air moves through the unit.

FFU : The airflow enters from the top or side air inlet, passes through the fan and the internal channel of the box, and then passes through the ULPA filter and is sent out from the air outlet surface. Locations that need to be checked for leaks include the filter material surface, the sealing surface between the filter element and the box, the splicing of the box, the access door, and any opening that may bypass the filter element.

EFU : Equipment-side fan filter unit, which is more compact and usually installed inside the equipment. The airflow path may be shorter, but the interface is more complex. In addition to the filter element and box, check the connection to the equipment rack, cable penetrations, maintenance doors, etc. Because the internal space of the EFU is small, some interfaces may be blocked by robotic arms and transmission parts, so the leak detection path needs to be planned in the planning stage.

It is important to clarify the boundaries : leakage detection on the filter element body covers the filter material, glue seams, and frame junctions; installation sealing and complete machine interfaces belong to another level. The factory report and the on-site leak detection report must correspond separately and cannot be mixed together. involving For the selection of ULPA ultra-high efficiency filter , the detection boundary should be written into the technical protocol.

Leak detection on the filter element body: filter surface, glue seam and frame

This layer is the same as conventional ULPA leak detection, but accessibility should be paid attention to when installed.

Filter material surface : Scan the pleats to confirm there are no damages or pinholes. Whether the probe can reach all filter surfaces after installation depends on the air outlet structure of the FFU/EFU. If there is a protective net or diffuser on the air outlet surface, the scanning method needs to be stated in the plan.

The joint between the glue seam and the frame : The edge sealing glue between the filter material and the frame is an area with a high risk of leakage points. Cover the edges when scanning, especially the corners. After installation, these locations may be partially blocked by the box structure, and it is necessary to confirm whether the probe can be accessed.

Frame sealing surface : The contact surface between the filter element outer frame and the installation frame, which is the transition area between the filter element body and the complete machine. The matching status of the gasket or liquid tank is reflected here, and it should be checked carefully when detecting leaks. For specific methods, please refer to the relevant instructions for leak detection at the interface between the filter material and the frame.

Install seal: the interface between the filter element and the box

This is the unique focus of leak detection for FFU/EFU, and it is also a layer that is easily overlooked.

The sealing surface between the filter element and the box : After the filter element is installed into the box, the surrounding sealing gasket or liquid tank is pressed against the corresponding structure on the box. When scanning, confirm point by point along this interface. Bypasses can occur here if the seal is displaced, if the compression is uneven, or if the tank level is low. For specific inspection methods, please refer to the relevant instructions on uneven compression of gaskets.

Around the pressing parts : The distribution and tightening sequence of pressing points will affect the force on the sealing surface. When detecting leaks, you can pay attention to whether there are abnormal readings near the compression point.

Flatness of the installation frame : If the box installation frame is deformed, the sealing surface may not fit tightly. This problem is not easy to measure directly in the installed state, but it can be indirectly determined through the leak detection signal.

Complete machine sealing: box, inspection port and interface

The filter element and installation seal are normal, and the leakage point may also be in the box itself.

Box joints : If the FFU/EFU box is made up of multiple panels, the joints need to be sealed. Cover these seams when scanning to confirm there are no bypasses.

Inspection doors and covers : If the maintenance access doors and covers are not properly sealed, air will leak during operation. Check whether the door frame sealing strip is intact and whether it is closed properly.

Cable penetrations and pipe interfaces : The locations where motor cables, sensor cables, air pipes, etc. pass through the box will also become bypasses if there is no seal or the seal fails. There are many cables inside the EFU, so you need to confirm them one by one.

Fan interface : The connection between the fan and the box. If the seal is not good, it may also affect the overall sealing. This layer is usually controlled by the entire machine manufacturing process, but if abnormalities are found during on-site leak detection, they need to be investigated.

Differences between FFU and EFU

The focus of leak detection for the two units is slightly different.

FFU is usually installed on the ceiling or bracket, with the air outlet facing downwards, so there is relatively sufficient operating space when detecting leaks. However, there may be pipelines above the ceiling, and the accessibility of the interface above the filter element needs to be confirmed. Supporting For the FFU fan filter unit system, the sealing boundary between the unit and the ceiling must also be included.

The EFU is installed inside the device, which has a compact space and limited probe accessibility. Before leak detection, make sure that the equipment is in stable operation and that internal mechanical parts will not interfere with scanning. Some EFU filter elements are side-mounted or bottom-mounted, and the scanning angle is limited. It may be necessary to customize the probe or adjust the installation sequence. involving For EFU equipment end fan filter unit projects, it is recommended to confirm the leak detection channel during the planning stage.

Regardless of the type of unit, the actual air volume, operating mode and environmental conditions should be recorded during leak detection. If conditions are unstable, readings will not be comparable. To confirm the specific conditions, please refer to the instructions related to unstable air volume during leak detection.

Recording and retesting

Leak detection results should be able to correspond to specific locations and products.

Record content : filter element number, unit number, installation location, detected air volume, scanning path, leak point coordinates, processing method and retest results. If some interfaces cannot be scanned, this must be noted in the record and cannot be qualified by default.

Retest conditions : When retesting after treatment or adjustment, the air volume and operating mode should be kept the same as the initial test. If the air volume changes, the comparability of the results decreases.

Corresponding to the factory report : the on-site leak detection record and the filter element factory leak detection report should be associated with the same product number, but the detection boundaries should be marked separately. involving HEPA/ULPA air filters are the same. Acceptance and recording requirements for

Project judgment example

An FFU unit is equipped with a ULPA filter, and the downstream particle monitoring is high after operation. During on-site leak detection, only the surface of the filter material was scanned, and no abnormalities were found.

During further investigation, the scanning range was extended to the sealing surface of the filter element and the box, and a continuous abnormal reading was found in one corner. Inspection revealed that the gasket at this corner was slightly displaced during installation, forming a bypass. After adjusting the position of the sealing gasket and retesting, the abnormality disappeared and the particle monitoring returned to normal.

This case shows that it is not enough to just scan the filter element. The sealing boundary of the entire machine must be included in the scope of leak detection. involving For HEPA high-efficiency filter units , the leak detection principles are the same.

Selection and Acceptance Checklist

About Aili Industrial’s complete machine sealing package

The sealing boundary between FFU/EFU and ULPA involves multiple aspects of the filter element, box, and installation interface. If these components are matched in the same manufacturing system, the interface size and sealing structure can be checked uniformly during the planning stage, reducing the difficulty of air leakage inspection on site due to unclear boundaries.

Aili Industry has independent manufacturing capabilities in filters, fans, control systems and sheet metal processing, and can provide ULPA ultra high efficiency filter、HEPA high-efficiency filter and supporting air supply equipment. When the filter is matched with equipment such as FFU and EFU, the filter element sealing surface, box interface and installation matching dimensions can be uniformly confirmed. For projects that require on-site leak detection, product testing data and record cooperation can be provided as agreed.

When enquiring, specify the leak detection requirements, unit structure and acceptance method, which will help confirm the appropriate supporting plan and recording format. The specific testing methods and judgment standards are subject to the project plan.