What are the differences between HEPA and ULPA leak detection requirements?

The purpose of both leak detection is the same: to confirm that there is no local leakage in the filter body and installation interface. But the same purpose does not mean that the methods can be copied.

HEPA and ULPA belong to different groups in the standard system, and have different allowable penetration limits. This difference will directly affect what instrument, what aerosol, what scanning parameters are used when detecting leaks, and how the judgment limit is determined. If the H14 leak detection solution is directly applied to the U16, the problems that should be discovered may not be detected, and meaningless conclusions may also be drawn.

First confirm the test object and document basis

Before detecting leaks, first confirm clearly 'what to test' and 'what to judge by'.

Detect object. Is it the filter element itself at the factory stage, or is it the system after installation? Factory leak detection mainly covers the filter material, edge sealing and frame. On-site leak detection also includes the sealing interface between the filter element, frame and box. The two have different scopes and different judgment methods.

Standard releases and contract requirements. HEPA and ULPA may reference different standard clauses. The procurement document clearly states which standard, which version, and how to determine the whole and part. Just write 'to detect leaks', which may lead to different understandings during execution.

Source of limit value. Decision limits are not numbers that can be set arbitrarily. It results from the adopted standards, product levels and project acceptance requirements. HEPA and ULPA have different limits and cannot be mixed. HEPA products can be referred to HEPA high-efficiency filter testing data, ULPA can refer to Description of ULPA Ultra High Efficiency Filter .

Instrument capabilities must match the level

This is where HEPA and ULPA leak detection are most likely to go wrong in actual operations.

Allowing lower penetration requires higher sensitivity of the instrument. The local penetration limit of ULPA is stricter than that of HEPA. If the range, resolution or sampling flow rate of the leak detection instrument used on site does not match, 'the measured value is zero, but it cannot be proved to be qualified'.

Zero count does not equal absolutely no penetration. It may simply be below the detection capabilities of current instruments and methods. The report should describe the status of the instrument, background levels and suitability of the test method.

Background control is also critical. Field ambient particle levels are higher than in the laboratory, and background fluctuations may mask signals from small leaks. The leak detection plan must explain how to deal with the background, and cannot directly use the laboratory settings.

The scanning speed, probe distance and sampling flow rate must also be confirmed according to the method requirements of the corresponding level. These parameters are not universally applicable.

Aerosol and material suitability to be checked

The aerosol used for leak detection is not just a random choice.

Different standards may specify different aerosol types. Some use oil aerosols, and some use salt aerosols. Which one to choose depends on the standards adopted by the project.

The suitability of the filter material must also be confirmed. Especially for PTFE membrane materials, certain aerosols or test conditions may have an impact on the material. Before testing, you should confirm with the supplier the leak detection method and aerosol type applicable to this product, and do not replace it yourself.

For membrane media, the suitability of aerosol and materials must also be checked and tested. This needs to be paid more attention to in ULPA projects, because the application of membrane materials is becoming more and more common, and the design differences of different products are also greater.

Scanning parameters cannot be copied

Scanning leak detection looks simple, but the parameter settings are very particular.

Probe distance. If the distance is too large, small leaks may be missed, and if the distance is too close, the filter material may be touched. Control according to method requirements.

Scan speed. If the speed is too fast, the instrument response may not be able to keep up; if it is too slow, the detection efficiency will be low. Set according to the method requirements of the corresponding level.

Path coverage. The filter material surface, edge sealing, sealing surface of the frame and installation frame, as well as the accessible joints of the box must be covered. Parts blocked by diffusers or equipment structures must be explained in the plan and inaccessible locations must be recorded. They cannot be deemed qualified by default.

If the scanning parameters are the same as those used in the H14 project, but the judgment limits have been set according to ULPA, the solution itself may not be valid. Parameters and limits must match. Device-side applications such as The EFU equipment-end fan filter unit has a compact internal space, and the planning of the scanning path needs to be confirmed in the planning stage; supporting For the FFU fan filter unit system, the unit status and air volume conditions must also be recorded to facilitate restoration of the same working conditions during re-inspection.

Project judgment example

A certain site used to do H14 leak detection, but now it needs to be changed to U16. The operator planned to keep the original instrument and scanning parameters and only change the decision limits.

This approach is risky. The allowable penetration of U16 is lower, the original instrument may not be able to distinguish leak points close to the limit, and the background level may also drown out small signals. The correct approach is to first confirm whether the range and sensitivity of the instrument meet the method requirements of U16, replace the detection equipment or adjust the aerosol conditions if necessary, and then reset the scanning parameters according to the corresponding method.

The limit value has been changed, but the method has not. It is equivalent to changing the number but not the detection capability. involving For HEPA/ULPA air filter products of different grades, the leak detection plans should be confirmed individually according to the corresponding standards.

Selection and Acceptance Checklist

About Aili Industrial’s leak detection cooperation

HEPA and ULPA have different leak detection requirements. It is best to put product information, detection methods and instrument conditions together for confirmation when designing the solution.

Aili Industrial's manufacturing system covers filters, motors, fans, control systems and complete machine assembly, and can provide HEPA/ULPA products of different grades and supporting air supply equipment. Can provide testing data as agreed on the project, and assist in checking the leak detection scope, report form and numbering rules during the planning stage. filter with FFU fan filter unit、When the EFU equipment-side fan filter unit is delivered as a package, the boundaries between the complete machine leakage test and the filter element leakage test can also be confirmed uniformly.

When enquiring, clarify the standard version, grade requirements, leak detection methods and instrument conditions, which will help with subsequent acceptance. The specific testing methods and judgment standards are subject to the project plan.