How does Taiwan ULPA balance air volume?

Multiple filters are connected in parallel, and the ideal situation is for each filter to bear the same air volume. But in actual systems, this ideal state rarely occurs naturally.

The air volume distribution is determined by the total resistance of each branch, not by the filter model. If the same batch of ULPA is installed on branches with different resistances, the actual air volume may vary greatly. On the side with long air ducts, many elbows, and small valve openings, the air volume will naturally be low.

Therefore, the matter of 'balancing air volume' is essentially to return the resistance relationship of each branch to the design state, rather than making the parameters of each filter element exactly the same.

First confirm whether the imbalance is a system problem or a product problem

If you find that the air volume of several units is inconsistent, don’t rush to adjust it yet. The first step is to determine what the cause is.

Check product parameters. Confirm whether the model, specifications, and resistance data of each ULPA are consistent. If the resistance of the same batch of products is different, you need to first judge whether it is normal according to the tolerance. For specific methods, please refer to the instructions related to the resistance difference of the same batch.

Look at the branch structure. Are the air duct length, number of elbows, and air valve positions of each branch symmetrical? The design may be symmetrical, but construction deviations and later modifications may change the resistance distribution. Supporting The system of the FFU fan filter unit and the local conditions of the air inlet and outlet of the unit also need to be looked at.

Check the installation status. Are the installation directions, pressing force, and gasket compression amount of each unit consistent? Installation deviation or uneven compression will cause the actual resistance to deviate from the product's nominal value.

See control settings. If each machine has an independent speed control device, are the set values ​​consistent? Have the gear parameters of each station in the group control system been adjusted individually?

First figure out whether it is a product difference, installation difference or system difference, and then decide how to adjust it. Directly adjusting the air valve without locating the cause may cover up the product problem.

Several ways to adjust balance

After confirming the source of the imbalance, there are generally several types of treatment methods.

Adjust the branch air valve. This is the most common approach. For a branch with a large air volume, the air valve should be appropriately turned down to increase the resistance of the branch and allow the air volume to be transferred to other branches. The operation should be carried out step by step. After each adjustment, wait until the system is stable before reading. You can't just look at the total air volume reaching the standard, but also make sure that the air volume of each unit is within a reasonable range.

Adjust the single speed. If it is an independently controlled unit, the air volume of each unit can be balanced by speed adjustment. The advantage of this method is fast response and fine adjustment, but attention should be paid to the allowable operating range of the motor. The speed of all units cannot be increased to a very high speed to 'make up' the total air volume, as this will increase energy consumption and noise.

Optimize branch structure. If the resistance of a certain branch is obviously high and the air valve adjustment cannot solve the problem, you may need to check whether the air duct is blocked, whether there are too many elbows, and whether the valve is stuck. This type of problem belongs to the design or construction level and needs to be coordinated with the equipment party or construction party.

Replace filter element configuration. If the air volume at a certain location cannot meet the requirements through adjustment, it may be necessary to evaluate whether the filter element selection at that location is appropriate. For example, if you choose a ULPA structure with a larger effective filtration area, the resistance will be lower under the same air volume. Device-side applications such as The EFU equipment-side fan filter unit has a compact internal space and less room for adjustment. Matching in the selection stage is more important.

When adjusting, pay attention to the uniformity of wind speed simultaneously.

Just because the air volume is leveled does not mean that the actual effect is ideal.

The wind speed distribution on the air outlet surface of a single unit should be even. The total air volume reaches the standard, but the wind speed on a certain side of the air outlet surface is low, and the actual protection effect is still uneven. Measuring the surface wind speed distribution one by one can better reflect the true state than just looking at the total air volume.

Airflow between areas should be reasonable. If multiple filters serve different areas, it is necessary to confirm that the air volume in each area meets their respective design requirements when adjusting. You cannot just look at the total air volume of the entire system.

Check for leaks again after balancing. After adjusting the air valve or speed, the system pressure and flow distribution will change, and the sealing status may need to be re-confirmed. On-site leak detection is a necessary verification step. involving For HEPA/ULPA air filter products of different grades, the leak detection methods and criteria are implemented in accordance with corresponding standards.

How to calibrate the gears in the group control system

When multiple units are managed uniformly by the group control system, the gear parameters need to be calibrated according to the actual situation.

The gears originally adjusted for a certain batch of filter elements may no longer be applicable after replacing the filter elements. If you upgrade from HEPA to ULPA and the resistance increases, the air volume of each unit at the same gear may decrease, but the decrease is not necessarily the same. At this time, it is necessary to re-measure the air volume of each unit and re-confirm the gear settings.

Partial replacement also requires recalibration. If only part of the unit's filter elements are replaced, the difference in resistance between the new and old filter elements will cause changes in air volume distribution. The original group control parameters cannot be used.

Record new baseline. After the adjustment is completed, record the gear settings, measured air volume, pressure difference and operating mode of each unit. This set of data is the baseline for subsequent maintenance. involving ULPA ultra high efficiency filter or For the selection of HEPA high-efficiency filters , please refer to the corresponding product information.

Project judgment example

There are 8 FFUs in a certain clean room, equipped with ULPA filter elements, and adopt group control for unified speed regulation.

After running for a period of time, it was found that the air volume of the four units on the east side was low, and the air volume of the four units on the west side was high. The inspection found that the air duct of the east side branch was about 30% longer than that of the west side, and this difference was not fully considered during the design.

Treatment method: First adjust the branch air valve, appropriately open the east side air valve and appropriately close the west side air valve. After adjustment, the air volume on both sides is similar, but the speed of the unit on the east side is slightly higher than that on the west side. The group control system records the gear parameters of each group separately and no longer sets them uniformly.

This case illustrates: The balanced air volume is not to set all units to be the same, but to allow each unit to achieve its own design air volume under actual working conditions. For a system with an asymmetric structure, it is normal for the parameters to be asymmetric.

Selection and Acceptance Checklist

About Aili Industrial’s multiple supporting solutions

When multiple ULPAs are connected in parallel, the difficulty of air volume balance is related to product consistency, control method, and system design.

Aili Industrial has independent manufacturing capabilities in filters, motors, fans, control systems and sheet metal processing. When multiple devices are matched, the resistance consistency of the filter element and the control parameters of the fans can be checked in the same system. For group control projects, the actual resistance conditions of each branch can be combined to help confirm the gear calibration and air volume distribution plan. When the filter is delivered together with equipment such as FFU and EFU, the corresponding relationship between the detection data and numbers of each unit can be unified.

Providing the branch layout, design air volume and control method of each unit during the inquiry will help to take the balance issue into consideration during the planning stage. The specific configuration is subject to the technical documents confirmed by the project and the on-site debugging results.