What does the rated air volume of ULPA filter mean?

Let’s take this word apart first. The rated air volume is a value on the product information, which usually indicates the flow rate of this filter element under specified test conditions. It appears together with efficiency and resistance and constitutes the basic performance description of the product.

But it describes the product conditions, not the air volume when the equipment is actually running.

If you understand this incorrectly, problems will arise in subsequent selection and debugging. The sample says 1000 m³/h, but when installed on the equipment, the actual measurement is 800 m³/h. This is not necessarily a mislabeling, but rather that the system operating point and rated conditions are different.

Rated data should be viewed together with the conditions

Just looking at the air volume number doesn't tell you much.

What is the corresponding resistance. There must be a corresponding resistance value under the rated air volume, and the two are in pairs. Saying 'rated air volume 1000' alone, without mentioning resistance, this data cannot be used for fan selection.

Corresponding efficiency levels and test conditions. For the same product, the efficiency report and air volume report may come from different test conditions. It is necessary to confirm whether these data can be used together.

Corresponding structural configuration. There may be different thicknesses, sealing methods, or media configurations under the same model name, and the ratings may also be different. When selecting, confirm which specific specification the data obtained corresponds to.

The installed air volume is determined by the system

This is where the most confusion arises.

The actual air volume is not determined by the filter element alone, but by the fan curve and the resistance of the entire system. The system includes the filter element, box, air duct, pre-filtration section, and the characteristics of the fan itself.

The large rated air volume of the filter element does not mean that the existing fan can definitely provide such a large flow rate. If the system resistance is high, the fan operating point will move to the left, and the actual air volume may be lower than the rated value.

Conversely, if there is a margin in fan capacity, the actual air volume may exceed the rated value. Whether over-rated operation is appropriate depends on the working range of the product and cannot be taken for granted.

Supporting In the FFU fan filter unit system, the fan and filter element are integrated together, and the matching relationship is relatively easy to check. Centralized air supply system or equipment-side applications such as For the fan filter unit at the EFU equipment end , the resistance of the entire air path must be taken into account.

How to write clearly when purchasing

It is not enough to just write '1000 air volume required' when making an inquiry. The supplier cannot confirm whether the product can meet the requirement.

It is recommended to write these items clearly:

Design air volume : The actual air volume required in the target area or installation location.

Working range : If the speed is adjusted during operation or there are different working conditions, write the range instead of just one point.

Final resistance working condition : The increase in resistance after dust accumulation in the filter element must be taken into consideration. If you only select based on the initial resistance, the air volume may not be enough in the later stage.

Available fan static pressure : This is a key input in determining whether the system can deliver the target air volume. Without this, the supplier can only recommend based on conventional configurations, which may not necessarily match.

Installation space : affects the thickness and effective filtration area of ​​the filter element, and also indirectly affects the air volume capacity.

Only when this information is complete can the supplier provide targeted solutions instead of just reporting one model.

How to check the actual air volume

After installation, the actual air volume must be measured and confirmed.

The measuring point locations must be consistent. The wind speed distribution in different sections is uneven and the locations of the measuring points are different, so the results may be different. Indicate the measuring points when recording.

The operating status must be stable. The fan gear position, air valve opening, and equipment operating mode must be fixed during measurement. Readings under varying operating conditions are not comparable.

Compare with design value. If there is a large gap between the actual measured value and the designed value, the investigation directions include: whether the system resistance exceeds expectations, whether the fan working point is offset, whether the filter element is installed in place, and whether there is a problem with the seal. Do not directly use the total air volume divided by the number of units to estimate the value of a single unit. The branch resistance is different and the distribution is uneven.

Record baseline data. The initial air volume and pressure difference are the basis for subsequent judgment of the filter element status. involving HEPA/ULPA air filter products of different grades have the same verification methods, and the test data are carried out according to the corresponding standards.

Project judgment example

The rated air volume written on the sample is 1000 m³/h, and the actual installed air volume is 800 m³/h.

At this time, do not rush to judge whether it is a labeling error or a product quality problem. First confirm a few conditions: whether the fan gear is at the design point during actual measurement, whether the system resistance exceeds expectations, whether the filter element is installed in the correct direction, and whether the measurement method and measurement points are reasonable.

If these conditions are correct, then compare the fan curve to see if 800 m³/h falls within the normal operating point of the fan under the system resistance. If the deviation from the design value is indeed large, go back and discuss whether it is a selection problem or a system problem.

Selection and Acceptance Checklist

About Aili Industrial’s air volume accounting cooperation

The difference between the rated air volume and the actual air volume is essentially a system matching problem.

Aili Industrial's manufacturing system covers filters, motors, fans, control systems and complete machine assembly, and can provide ULPA ultra-high efficiency filter and supporting air supply equipment. filter with When the FFU fan filter unit and EFU are matched in the same system, the filter element resistance and fan operating point can be calculated together during the planning stage to reduce the occurrence of air volume mismatch after installation.

When enquiring, provide the design air volume, available static pressure, installation space and operating conditions to help confirm the appropriate configuration. Specific performance is subject to the testing data of the corresponding model.