What is the difference between ULPA factory leak detection and on-site leak detection?

These two aspects are often conflated. Some people think that once the factory report is available, there is no need to re-test on-site; others think that passing the factory does not mean it can be used on-site, and all must be re-tested. Both understandings are biased.

The two detect different objects and answer different questions. The factory leak detection focuses on whether the filter element body - the filter material surface, glue seams, and frame joints are complete. On-site leak detection also depends on the actual conditions of transportation, installation and interfaces. One is completed in the manufacturing plant and the other is completed at the use site. They are not substitutes for each other, but neither are they exactly duplicates.

What does factory leak detection cover?

The object of factory leak detection is the complete filter element, and the detection range usually includes the filter material surface, the edge sealing seam, and the joint between the frame and the filter material.

What it confirms is that in the factory state, the filter element body has no local leakage and the local penetration rate is within the limits specified in the standard or contract.

What it does not cover is: the connection status of the filter element to the installation frame, box, and pipeline after it is installed in the system. These interfaces are not assembled at the factory and cannot be tested.

Factory leak detection is usually carried out under controlled laboratory or workshop conditions. The air volume, aerosol concentration, and background particle levels are relatively stable, and the test results have good repeatability. The report format can be a unit-by-unit record or a batch summary, which shall be implemented according to the project agreement. involving ULPA ultra-high efficiency filters should be written into the technical agreement. The selection and testing requirements of For specific testing items, please refer to the relevant instructions for factory testing.

What does on-site leak detection cover?

The detection object of on-site leak detection is the state after installation, and the coverage is wider than that of the factory.

It needs to check: whether the filter element body is still intact after transportation and installation; whether the connection between the filter element and the installation frame, box, and access port is sealed; whether there are bypasses in other accessible interfaces in the system.

It also confirms whether the air volume, upstream concentration and operating status during testing meet the method requirements. These conditions are controlled by the equipment during factory testing and require additional confirmation in the field. Supporting FFU fan filter unit system, unit gear and operating mode must be recorded; equipment-side applications such as For the fan filter unit at the EFU equipment end , the operating status of the equipment must also be stable for the leak detection results to be valid.

Field conditions are often more complex than laboratory conditions. Background particles, airflow fluctuations, and structural obstructions may affect detection. The detection plan needs to make arrangements for these factors, such as selecting low-interference periods, planning scanning paths, and recording unreachable locations. For specific troubleshooting methods, please refer to the instructions related to unstable air volume during leak detection.

The methods can be the same, but the conditions are different

Factory and on-site leak detection may use the same detection methods and criteria, but the execution conditions are different.

Aerosols and Instruments. Aerosol generation and instrument settings for factory testing are usually standardized. It is necessary to confirm whether the aerosol type, instrument calibration status and measuring range match on site. The local judgment limit of ULPA is stricter than that of HEPA, and the instrument sensitivity must meet the requirements. For specific differences, please refer to the relevant instructions for leak detection requirements.

Air volume conditions. Factory inspection is carried out under the specified test air volume, and on-site leak detection needs to be carried out under the design working conditions or the air volume agreed upon by the project. If the on-site air volume is inconsistent with the factory test air volume, the readings cannot be directly compared.

Scan path. When leaving the factory, the filter element is open all around and the scanning path can be completely covered. After on-site installation, part of the frame may be blocked by structural parts, limiting the scanning range. The occlusion location should be clearly stated in the plan and should not be deemed qualified by default.

Background control. Background particle levels in field environments may be higher than in laboratories, potentially masking signals from small leaks. Confirm the background status before testing and record the background value if necessary.

How to compare files

The two sets of records, factory and on-site, need to be matched in the same traceability chain.

Product Identity. The model number and serial number on the factory report must be consistent with the actual product. On-site leak detection records should indicate the corresponding product number and installation location.

detection conditions. The factory report indicates the test air volume, method, instrument and judgment standards. Field records indicate actual air volume, operating mode and background conditions. If the two conditions are different, the difference should be noted and the values ​​cannot be compared directly.

Results recorded. The factory leak detection conclusion records the integrity of the filter element body. On-site leak detection records the actual sealing status after installation. The two conclusions are filed separately and one cannot be substituted for the other.

Exception handling. If problems are found at the factory, the solution is usually rework or replacement. If a problem is found on site, you must first distinguish whether it is a problem with the filter element itself, transportation and installation damage, or an interface sealing problem, and then decide how to deal with it. For specific troubleshooting methods, please refer to the instructions regarding inconsistencies between factory and on-site test results.

Project judgment example

After the ULPA of a certain equipment arrived, it was discovered that the factory leak detection report was a batch summary and there was no record of each unit. The project required traceability one by one, and on-site leak detection was blocked by the internal structure of the equipment, so some frames could not be scanned.

Processing method: First ask the supplier for leak detection records one by one to confirm that the integrity of each product is supported by data. For locations that cannot be scanned on-site, clearly mark them in the acceptance record, and evaluate whether they need to be re-tested after disassembly or assembly, or use other verification methods according to the project agreement.

The key to this case is: factory leak detection and on-site leak detection each have coverage, and both must be recorded, but the objects and conditions of the records are different. involving HEPA/ULPA air filters are the same. Acceptance and recording requirements for

Selection and Acceptance Checklist

About Aili Industrial’s leak detection information package

Whether the two sets of leak detection records at the factory and on site can be matched depends on whether the product number, testing conditions and report format are unified. If these are clearly agreed upon during the agreement stage, the acceptance will be much smoother.

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. Factory leak detection data can be provided according to the project agreement, indicating the detection objects, test conditions and number correspondence. When the filter is delivered together with equipment such as FFU and EFU, the boundaries and recording requirements for on-site leak detection can be confirmed together during the planning stage.

When enquiring, specify the leak detection requirements, reporting form and acceptance method to help confirm the appropriate supporting information. The specific testing methods and judgment standards are subject to the project plan.