How to check ULPA bypass air leakage? Flange, housing and mounting interface

ULPA filter bypass air leakage refers to the path where air enters the downstream without filtering material. It is necessary to check the flange, shell, seams and installation seals. The higher the efficiency of the filter material, the more attention should be paid to these bypass paths. If the filter element body passes the leak test, it does not mean that the system does not have a bypass - air bypasses the entire filter material and enters the clean side from the flange seam or shell seam, which will also cause the regional particle concentration to deviate from the target. Aili Industrial uses the bypass path as a design input in the box sheet metal seal design: flanges, access doors, perforations and joints are clearly defined in the structural planning stage as to which airtight boundaries are and how to seal them, so that the bypass inspection has a structural basis instead of guessing one by one on site.

1. Find interfaces along the air boundary: first draw which parts belong to the airtight boundary

Identify the box connections, access doors, perforations and filter frame seals from the upstream to the clean side, and confirm which parts belong to the airtight boundary of this project.

The scope of bypass inspection is not the entire box, but those connection surfaces that should be airtight by design. Aili Industry isEFU equipment end fan filter unit andThe box structure description of the FFU fan filter unit will indicate the locations of flange connections, access doors, cable penetrations and filter frame seals. The project team can use this to determine the airtight boundaries that need to be inspected, instead of treating every seam of the box as a suspect. The relationship between levels and filtering requirements can be found inISO cleanliness level comparison。

2. Distinguish between body leakage and bypass: signal location and repeatability will give clues

Combined with signal location, repeatability and structural inspection and positioning, do not misjudge the entire interface abnormality as multiple pinholes in the filter material.

The signal from the pinhole of the filter material is usually limited to local points, and the position is stable during repeated scanning; the signal from the flange or seam bypass often appears continuously along the entire interface, or changes with the opening and closing of the door or the rotation speed of the fan. During the entire machine assembly process, Aili Industrial will separately record the leak detection of the filter element body and the inspection of the box interface. This set of sub-inspections can help on-site determine whether the abnormality comes from the filter material or the installation boundary. Please refer to the combination of sealing and leak detection methods.HEPA FAQs and Selection Guide。

3. The sealing of the flange and shell joints has been determined at the design stage.

The sealing methods of flange connections and shell joints are determined during the box structure design. On-site inspections are to confirm whether the sealing is effective, rather than temporarily deciding how to seal. In the sheet metal processing of supporting boxes, Aili Industry has process requirements for flange connection surfaces, inspection door seals and seam processing.The tank interfaces corresponding to the liquid tank sealed ULPA filter and the mechanical compression structure are matched and verified before leaving the factory to reduce on-site bypasses caused by the unsealed structure itself. For the interface seal installed inside the equipment, please refer toEFU FAQ and technical support。

4. After rectification, cover the relevant paths and record the location instead of just writing 'Glue has been patched'

After repairing a connection or seal, verify it in actual operating condition and check whether the treatment affects other seams. Recording the location is easier to trace than simply writing 'glue repaired'.

After patching, you should confirm which path is patched and whether it affects the sealing state of adjacent joints. Aili Industry isIn the structural design of non-standard ULPA filters and supporting boxes, an airtight boundary diagram can be provided according to project requirements to facilitate comparison of recording locations during rectification; the retest results after rectification are archived correspondingly with the rectification content to facilitate subsequent traceability. Please refer to the key points for dividing the sealed boundary.ULPA ultra-high efficiency filter FAQ and selection guide。

5. Related questions and answers

Can bypasses be eliminated by testing only the filter surface?
cannot. Relevant installation seals and connections that may bypass the filter material should be covered according to the system boundary. Passing the filter surface leakage test does not mean that the flange and joints are airtight.

The leak detection of the filter element is normal but there is an abnormality on the edge of the access door. How to judge?
The connection between the door seal and the box should be checked instead of directly upgrading the filter element level. The abnormal position is at the edge of the door body, pointing to the installation boundary rather than the filter material.

Is the treatment completed after the glue is applied?
It should be re-inspected under actual operating conditions and checked to see if the treatment affects other joints. Just writing 'Glue patched' cannot indicate which path was patched.

6. Related articles

ULPA ultra-high efficiency filter FAQ and selection guide

EFU equipped with ULPA ultra-high efficiency filter

Liquid tank seal ULPA ultra high efficiency filter

HEPA FAQs and Selection Guide

7. Key points for selection and acceptance inspection

8. Product matching and technical support from Aili Industrial

Aili Industry isEFU equipment end fan filter unit andThe box structure description of the FFU fan filter unit indicates the airtight boundary locations such as flange connections, access doors, cable penetrations, and filter frame seals to facilitate on-site determination of the bypass inspection scope; the supporting box sheet metal processing has process requirements for flange connection surfaces, access door seals, and seam processing.The cabinet interfaces corresponding to the liquid tank seal, ULPA filter and other structures must be matched and checked before leaving the factory.Non-standard ULPA filter projects can provide a schematic diagram of the airtight boundary as required. The leak detection of the filter element body and the box interface inspection are recorded separately during the assembly process of the whole machine. Provide process objectives, installation drawings, operating conditions and acceptance requirements for further communicationULPA ultra-high efficiency filters . Standard specifications, non-standard interfaces, samples and batch matching of The specific parameters and test range are based on the confirmed model and technical documents.