How to locate ULPA leaks?

When leak detection reveals abnormal readings, many people's first reaction is 'the filter element is broken.' This judgment may be correct, but if you deal with it directly in this direction, it is easy to misjudge air leakage at the interface, box bypass or measurement fluctuation as a filter material problem.

The core of leak location is not to find 'whether there is a leak', but to determine which layer the leak is on and which category it belongs to. When ULPA is installed in the system, air may bypass the filter material, edge sealing, frame sealing surface, box seams or pipe interfaces. Each layer is treated differently, and if the positioning is wrong, changing the filter element will not solve the problem.

First do a basic action: mark the abnormal readings on the filter element number and location map. Record the leak point coordinates, signal repeatability, distance from the edge, as well as the air volume and operating mode during detection. This information is more useful than a 'failed' conclusion. For specific detection boundaries, please refer to the relevant instructions on the difference between factory leak detection and on-site leak detection.

The first level: filter surface inspection

Abnormalities on the filter surface usually manifest as high local readings, which are located inside the filter material surface and not close to the frame or glue seams.

Inspection content: Whether the filter material is damaged, pinholes, tears or pleated damage. Check whether the roots of the pleats and the surface of the filter material are crushed by foreign matter. If it is a densely folded structure, it also depends on whether the local channel collapses. Slight discoloration on the surface does not necessarily indicate a problem, but if there are obvious holes or tears, it should be treated as filter material damage.

Note: Passing the center of the filter surface does not mean passing the entire filter surface. When scanning, the root of the pleat must be covered, not just the flat part. If the abnormality is concentrated in a small area, you can mark the location first and do not touch it with your hands or tools.

involving The structural inspection of ULPA ultra-high efficiency filter can be checked with the product information of the corresponding model.

Second level: Checking the borders and glue seams

The junction between the frame and the filter material is a high-risk area for leaks, and it is also a section that is easily skipped during scanning.

Inspection contents: Whether the edge sealing glue is continuous and whether the joint surface between the glue seam, the filter material and the outer frame is cracked or peeled off. The four corners are locations where colloids are prone to discontinuities and need to be confirmed individually. Check whether the outer frame is deformed or warped, and whether the pressing surface is flat.

Judgment method: If the abnormality occurs continuously along a section of the edge, the glue seam or sealing surface should be suspected first; if it is only a single point, it may be a local defect or installation damage. When no cracks are visible on the surface of the glue joint, you can observe it with a magnifying glass or confirm the colloid state from the back. For specific inspection methods, please refer to the relevant instructions for leak detection at the interface between the filter material and the frame.

If it is confirmed that it is a glue seam problem, the treatment method shall be carried out according to the model description and project acceptance conditions. It is not recommended to continue to use it after filling the glue without permission.

The third level: Installation sealing surface inspection

The filter element body is qualified, but it may still leak after installation. The sealing surface is the connection layer between the filter element and the installation frame. Gasket compression or liquid tank matching are all on this layer.

Check content: Whether the gasket is displaced, broken, hardened or loses rebound. Check whether the blade edge of the liquid tank seal matches the tank body continuously, and whether the insertion depth is in place. Check whether the pressing parts are evenly distributed and whether there are any loose spots at the four corners.

Judgment method: If the abnormality is concentrated at the contact position between the frame and the installation frame, adjust the compression structure and retest. If the abnormality disappears, it means that the problem is with the sealing surface rather than the filter element itself. If it still exists after adjustment, go back and check the filter element frame and glue seam. For specific sealing methods, please refer to the relevant instructions for liquid tank sealing.

Supporting The FFU fan filter unit system and the interface between the unit and the ceiling or box should also be included in this level of investigation.

The fourth level: Checking the interface between the box and the pipeline

There is no problem with the filter element and the installation frame. The leakage point may be in the more peripheral box or pipeline.

Inspection contents: box joints, flange connection surfaces, access doors, cable penetrations, and unsealed holes. If there is a bypass at these locations, the air will bypass the filter element and enter directly into the clean side. Air duct connections, valve flanges, and hose joints should also be inspected.

Judgment method: If the abnormal location is not near the filter element, but close to the box joints or pipeline interfaces, prioritize these structures. Leak detection methods can be used to confirm step by step under operating conditions, or pressure difference and air volume data can be combined to assist in judgment.

Device-side applications such as The EFU equipment-side fan filter unit has a compact internal space, and the robotic arm, cables and transmission parts may block some interfaces. The scanning path must be planned in advance, and the locations that cannot be scanned should be clearly stated in the record and cannot be qualified by default. involving HEPA/ULPA air filters have the same positioning logic. Products of different grades of

What to do after positioning

After locating a certain layer, the processing method is divided by layer.

Filter material problems: Evaluate repair or replacement according to the allowable scope of the project. Obvious tears or extensive damage usually require replacement.

Glue joint problems: If repairs are allowed in a small area, they should be dealt with according to regulations and re-tested; if large areas are degummed or accompanied by structural deformation, evaluation and replacement should be carried out.

Sealing surface problems: Adjust the pressing structure, replace the sealing gasket or repair the liquid tank fit and then retest. Do not just increase the pressing force to avoid deformation of the outer frame.

Box or pipeline problems: Repair the seal, close the hole, or adjust the connection structure before retesting. If this kind of problem is not dealt with, it will be useless no matter how many times you replace the filter element.

After rectification, retest under the same working conditions, and retain the leak point coordinates and detection conditions before and after treatment. involving HEPA high-efficiency filter is the same, and the criteria are implemented according to the corresponding standards. The method for locating leakage of

Project judgment example

The ULPA on-site leak inspection of a certain equipment found a persistent abnormality, located on the right side of the frame near the corner.

It is initially suspected that the filter material is damaged. After disassembly and inspection, there was no obvious damage to the filter material surface, and no cracks were visible on the glue seam surface. Upon further inspection of the installation frame, it was found that the compression piece at the corner was loose and the sealing gasket was slightly displaced at the corner. After readjusting the pressing parts and replacing the sealing gasket, the abnormality disappeared.

This case shows that abnormal readings do not mean that the filter material is damaged. When positioning, check the filter surface, glue seam, sealing surface, and box interface layer by layer, which is more effective than directly replacing the filter element.

Selection and Acceptance Checklist

About Aili Industrial’s leak location package

The difficulty in locating leaks often lies not in the detection itself, but in which layer the leak belongs to and who should handle it. If product information, installation records and leak detection data can be matched, positioning will be much faster.

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 interface size and sealing structure can be uniformly checked at the planning stage to reduce on-site leaks caused by interface mismatch. For projects that require on-site leak detection, product testing data and record cooperation can be provided as agreed.

Providing leakage point records, installation methods and operating data during inquiry or troubleshooting will help confirm the appropriate treatment direction. The specific testing methods and judgment standards are subject to the project plan.