How to do on-site leak detection of high-efficiency filter?

When it comes to on-site leak detection, many people think that it is just a matter of scanning around with a probe. But what really determines whether the leak detection results are meaningful is whether the several conditions before the start of the detection are in place.

Whether the fan is stable, the upstream dust emission is uneven, the instrument is not calibrated, and the scan path coverage is incomplete—these are not confirmed, and the scanned readings cannot explain the problem. Re-inspection due to insufficient conditions during project acceptance is more common than the leak itself.

Confirm operating conditions before testing

On-site leak detection is performed under operating conditions, and the conditions are unstable, so the results are incomparable.

Air volume : Record the current system air volume and fan operating gear. Leak detection should be carried out under the design air volume or the air volume agreed upon by the project. Air volume deviation will affect the concentration relationship between the upstream and downstream.

Upstream challenge conditions : Confirm that the aerosol generation device is working properly and the upstream concentration reaches and stabilizes within the range required by the detection method. The upstream concentration is not enough, and even if the downstream probe detects the leakage point, the reading may not be obvious.

Instrument status : Check the calibration validity period and zero point status of the testing instrument. Different detection methods have different requirements for instruments, which are implemented according to the standards adopted by the project.

After confirming these items, start scanning. Device-side applications such as For the EFU equipment-end fan filter unit , the internal operating status of the equipment may affect the air flow. Before leak detection, make sure the equipment is in a working mode consistent with the acceptance conditions. Supporting For the FFU fan filter unit system, the unit gear position must also be recorded to facilitate the restoration of the same conditions during subsequent re-inspections.

The scan path must be completely covered

Scanning is not just about scanning the surface of the filter material.

Filter material surface : Move the probe according to the path and speed specified in the project plan, covering the entire filter surface. The filter surface of the V-shaped structure is inclined, and the scanning path is different from that of the flat-plate structure, which needs to be specified in the plan.

The junction between the filter material and the frame : the location of the glue filling line is an area prone to local problems.

The sealing surface between the frame and the installation frame : the position where the gasket is pressed or the liquid tank is sealed. This is the installation interface and is usually not covered by factory inspection.

Accessible box seams : box seams, access doors, and flange connection surfaces. If there are bypasses in these locations, it will also affect the air supply quality.

If the diffuser or equipment structure blocks part of the interface, the accessibility must be stated in the plan and the inaccessible locations must be recorded. Locations that cannot be scanned cannot be qualified by default. involving For products with different levels of HEPA/ULPA air filters , the scanning methods and judgment standards may be different, and shall be implemented according to the corresponding project documents.

What to do after a leak is discovered

Mark the location, distinguish the type of leakage point, and then decide on the treatment method.

Damage to the filter material : handle according to the project acceptance requirements and the scope allowed by the supplier.

Edge sealing problem : Check the status of the glue filling line to determine whether it is a product problem or installation damage.

Air leakage from the interface : Check the status of the pressing parts, sealing gaskets or liquid tanks. The treatment direction is different from the filter material problem. For the verification method of the liquid tank structure, please refer to the relevant instructions on the knife edge size verification.

After repair or replacement, re-inspect within the specified range, and keep records of leak location and treatment. Repairing the filter paper without positioning it or replacing the filter element repeatedly will prolong the problem.

Records must support review

Leak detection records are not just 'pass' or 'fail'.

Contents that need to be recorded include: filter number, installation location, operating air volume, upstream challenge conditions, scan path, location of discovered leaks, handling measures and re-inspection results.

The purpose of this set of records is to allow subsequent maintenance personnel to review the same location. If an abnormality occurs in a certain filter again, by comparing the last leak detection record, it can be determined whether the problem occurs repeatedly at the same location or whether it is a new situation.

It is recommended to keep the leak detection records corresponding to the product number and installation location ledger. In batch projects, they are numbered uniformly according to the position number to facilitate quick positioning.

About Aili Industrial’s leak detection cooperation

Aili Industry can provide high-efficiency filter product information and structural cooperation according to project requirements. filter with FFU fan filter unit、The EFU equipment-end fan filter unit is matched in the same manufacturing system, and the interface size and sealing structure can be uniformly checked during the planning stage.

The method and criteria for on-site leak detection shall be specified in the project plan, and the filter element number shall correspond to the installation location and processing records. The specific testing methods and judgment standards are subject to the project plan.