How to agree on the ULPA acceptance limit?

Acceptance limits are often written vaguely in project documents. 'The air volume deviation does not exceed 10%' 'The resistance meets the design requirements' 'Leak detection is qualified' - these sentences may seem clear, but they often lead to disagreements during actual implementation.

The problem is missing conditions. 10% is relative to what benchmark? At what air volume is the resistance measured? Which standard, method and limit should be used for leak detection?

The limit value is not a number set on the head, it must be able to correspond to the specific test conditions. The core of the agreement is not 'what value', but 'what value is reached under what conditions'.

First, clearly distinguish the acceptance objects

Before agreeing on limits, make it clear what is being measured.

Product acceptance. For the filter body, verify whether the efficiency, resistance, and integrity meet the contract requirements. Testing information is usually provided by the supplier, factory testing or third-party testing.

Installation acceptance. Based on the status after installation, verify whether the seal is in place and whether the air supply volume reaches the design value. This part is completed by the project party or designated agency.

System acceptance. For the final result of the protected area, verify that the particle concentration or cleanliness meets the design requirements. Involves the comprehensive impact of airflow organization, pollution sources and operating conditions.

The limits of the three types of objects are different, and the determination methods are also different. If the three are mixed together, the boundaries of responsibility will be unclear during acceptance, and it will not be clear whether a problem is a product, installation or system problem. For specific distinction methods, please refer to the relevant instructions of the filter test report.

How to agree on air volume deviation

The air volume limit is usually written as 'design value ±X%', but how to determine this X needs to be combined with the project requirements.

Benchmarks should be clear. Is the deviation relative to the design air volume, the target air volume of a single unit, or the total air volume of the system? Different benchmarks may result in different judgment results.

Test conditions must be clearly stated. In what gear and what operating mode is it tested? What are the measuring point locations and measurement methods? If these are not written clearly, the difference in measurement results may be greater than the limit value itself.

The tolerance range must be reasonable. Some projects copy '±10%' without considering the adjustment capability of the actual system. The air valve opening, branch resistance, and equipment status may affect the air volume. If the tolerance is too small, it will lead to frequent adjustments. If the tolerance is too large, it will lose the meaning of control.

When multiple units are connected in parallel, the consistency requirements for a single unit must be agreed upon. Just because the total air volume meets the standard does not mean that every unit meets the standard. If the wind volume of each typhoon is too different, the coverage of the protected area may be uneven. For specific balancing methods, please refer to the relevant instructions for air volume balancing of multiple units.

How to determine resistance limit

The resistance limit is usually linked to the replacement cycle. Lower is not better, nor is it a fixed value.

Initial resistance limit. When a new filter element is installed, the resistance should not exceed a certain upper limit. This upper limit is determined based on product samples, contract agreements or design requirements. If the initial measured resistance is too high, check the measurement method and installation status first, and then judge whether the product is qualified. For troubleshooting methods, please refer to the relevant instructions on initial resistance abnormality.

Final resistance limit. This is the limit of operation and maintenance, and it needs to be dealt with at this point. The final resistance is usually higher than the initial resistance and depends on the fan capacity, system margins and maintenance strategy. For the setting method and replacement judgment, please refer to the instructions related to the final resistance.

The resistance limit should indicate the test air volume. Resistance numbers are meaningless apart from air volume. The contract states that 'the resistance shall not exceed 250 Pa', but it does not specify at what air volume it is, so it cannot be implemented during acceptance.

The final resistance is the maintenance limit, not the point of product damage. Reaching the final resistance does not mean that the filter element has failed, it just indicates that it needs to be dealt with. This can be explained in the agreement to avoid misjudgments on site.

How to agree on the leak detection limit

Leak detection limits involve three aspects: standards, methods and judgments.

According to which standard. EN 1822 or ISO 29463? Specific version year? The determination terms of different standards may be different. involving For HEPA/ULPA air filter products of different grades, standard references must be clearly written.

What method to use. The aerosol type, detection instrument, scanning speed, and probe distance must be stipulated in the corresponding standards or project plans. The methods and limits must be matched, and schemes of other levels cannot be used.

What is the decision limit? The local penetration limit of ULPA is stricter than that of HEPA, and the same number cannot be used. Specific limits are confirmed according to standard terms and project requirements.

Detection capabilities must match. The instrument's range, sensitivity, and background controls must be able to resolve signals near target limits. Zero count does not mean absolutely no penetration. The detection method and instrument status should be stated in the report. Supporting FFU fan filter unit or For systems with fan filter units at the EFU equipment end , on-site leak detection must also cover the installation interface. For specific differences, please refer to the relevant instructions for leak detection requirements.

What situations require a postponement of judgment?

After the limit value is agreed, there must be room for 'no judgment if the conditions are not met' during execution.

The instrument range is not suitable. If the sensitivity of the on-site instrument is not enough to distinguish signals near the target limit, the measured 'pass' cannot be used as the basis for acceptance.

The working conditions are not stable. When the air volume, temperature or upstream concentration fluctuates greatly, the test results are not comparable. You should wait until it stabilizes before testing again.

Data is missing. When the product number, test report or drawing is incomplete, the correspondence check cannot be completed. Complete the information first and then determine whether the product meets the limits.

Undetected area. If some interfaces cannot be scanned, this should be clearly stated in the record and should not be deemed qualified by default. Whether these locations need to be verified by other methods should be agreed in the acceptance plan.

Suspending the judgment is not to relax the standards, but to ensure that the basis for the judgment is established. If the conditions are not met, a hard decision will be made, and you may have to start over again later.

Project judgment example

The contract for a certain project stated 'ULPA leak detection qualified'. After the goods arrived, it was discovered that the supplier provided batch leak detection reports without records on a unit-by-unit basis.

If this clause is implemented, there will be two understandings: the supplier believes that the batch report can prove compliance, and the project party believes that each unit must have a record. The root cause of the dispute between the two parties is not a product problem, but that the terms themselves do not clearly state the test objects and report forms.

Adjustment method: Supplementary instructions in the technical agreement - what standards, methods, and limits are used for leak detection; whether the report is unit-by-unit or batch-by-unit; what information needs to be included in the report; who is responsible for on-site leak detection and under what conditions.

If the terms are clearly written, there will be no ambiguity in acceptance and execution. involving ULPA ultra high efficiency filter or HEPA high-efficiency filters is the same. The acceptance logic of

Selection and Acceptance Checklist

Regarding the acceptance terms and conditions of Aili Industry

Whether the acceptance limits can be enforced depends on whether the terms are specific enough. Product parameters, test conditions, and report forms are clearly stated at the contract stage, so there will be fewer disputes during subsequent implementation.

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. For projects that need to agree on acceptance limits, we can assist in clarifying test objects, test conditions, report forms and numbering rules during the technical agreement stage. When the filter is delivered together with FFU, EFU and other equipment, the acceptance range of the complete machine and filter element can be confirmed uniformly.

Explaining the testing requirements, acceptance methods and reporting forms during the inquiry will help to clearly spell out the limit terms during the agreement stage. The specific judgment criteria shall be subject to the technical documents and contract agreements confirmed by the project.