How to troubleshoot insufficient air supply volume of ULPA?

Insufficient air supply volume may be caused by the fan, filter, box, air duct, or control. During on-site inspection, if you only look at the filter element, it is easy to miss the real cause.

It is recommended to start with the fan and control status in the troubleshooting sequence, and then gradually extend to the filter. Because fans and controls are the source of active air supply, their status determines the system's ability to overcome the resistance behind it. First confirm that the source is normal, and then check the resistance distribution, the idea will be clearer.

First look at the fan and control status

Whether the fan is operating normally. Listen to the sound, watch the vibration, and confirm the steering. If the fan makes abnormal noise, vibrates significantly, or reverses, the air volume will naturally not increase. EC fans and DC fans also need to check whether the driver has any alarm or slowdown.

Is the set speed correct? The gear of a certain station in the group control system may be misadjusted. For equipment controlled by a single machine, confirm whether the speed setting value is consistent with the actual output.

Is the power supply normal? Low voltage and poor line contact may affect the fan speed.

Check whether the control signal is normal. If the air volume is adjusted by pressure difference, wind speed or external signal, confirm that there is no fault in the signal link. Abnormal signals may cause the fan to run at reduced speed.

Whether the operating mode corresponds. Some systems have different settings such as production mode, duty mode, night mode, etc. If you are currently in low air volume mode, the measurement results will naturally be low. It is necessary to record the operating mode during measurement and compare it with the design operating conditions. Supporting For the FFU fan filter unit system, the group control parameters and single unit status must be checked together; the equipment-side application is as follows: EFU equipment side fan filter unit , the operating mode of the equipment itself will directly affect the air supply volume, so you must first confirm the equipment status when troubleshooting.

Recheck the air volume measurement method

The air volume data itself may be inaccurate.

Whether the measuring point location is appropriate. When the wind speed distribution is uneven, a single point reading cannot represent the entire unit. Distribute points according to the equal-area grid method, and average multiple points. The distance between the measuring point and the air outlet surface must also be controlled according to the method requirements.

Is the instrument calibrated? The anemometer may drift after long-term use. Use standard instruments for comparison, or send for inspection periodically.

Are the units unified? The reading of the anemometer may be m/s, m/min or ft/min, and the conversion must be unified when calculating the air volume. If the units are mixed up, the results may be dozens of times different.

Is the measurement time sufficient? Each measuring point should wait until the reading is stable before recording to avoid misjudgments caused by instantaneous fluctuations. When the system operating status is unstable, the measurement results are not comparable.

Whether to compare with the design value under the same working condition. The design air volume usually corresponds to a specific fan gear and operating mode. If the working conditions are different during measurement, the data cannot be directly compared. For specific measurement methods, please refer to the relevant instructions for surface wind speed calculation.

Check filter element and installation status

After the air volume measurement method is confirmed to be correct, check the filter and installation links.

Whether the resistance of the filter element exceeds expectations. Take the actual measured pressure difference under the current air volume and compare it with the product resistance curve. If the pressure difference is obviously high, it may be that the filter element is seriously dusty, damp, or its resistance exceeds the standard. involving ULPA ultra high efficiency filter or For the selection of HEPA high-efficiency filters , please refer to the corresponding product information.

Is the filter element installed in place? Installation deviation, uneven pressing, and gasket displacement may affect the air flow. In severe cases, part of the airflow bypasses the effective filtering surface, which is equivalent to reducing the air supply area.

Whether the packaging film has been removed cleanly. Some filters have a protective film that needs to be completely removed before installation. Residual film can significantly increase drag.

Is there any obstruction upstream? If the front of the filter element is blocked by foreign objects, packaging debris or structural parts, it is equivalent to reducing the effective ventilation area and the air volume will decrease.

Is the pre-filter clogged? If the front filter resistance is too high, the terminal air volume will also be affected. Check the pre-filter pressure differential and maintenance records to confirm that the front stage has not become a bottleneck. For specific configuration, please refer to the instructions related to pre-filtering.

Check the box and air duct

There is no problem with the filter and fan, but the air volume is still insufficient. At this time, the system needs to be checked.

Does the box have a bypass? Unsealed holes, cracked seams, and improperly closed access doors will short-circuit some airflow and reduce the effective air supply volume. On-site leak detection can locate these types of problems.

Is the air duct blocked or leaking? Dust accumulation inside the air duct, blockage by foreign objects, and air leakage at the joints will all affect the air volume at the end. Check the pressure loss and sealing status of the air duct.

Is the damper opening correct? If the branch air valve is misadjusted or stuck, it will affect the air volume distribution. Check whether the damper opening of each branch is consistent with the design value.

Whether the total system resistance exceeds expectations. Accumulate the pressure losses of the filter element, pre-filter, air duct, box and terminal, and compare it with the fan curve to see whether the operating point deviates from the design range. If the total resistance is high, the turbine may be operating at its capacity boundary. For specific calculation methods, please refer to the relevant instructions on the resistance curve.

When multiple units are connected in parallel, is the air volume distributed evenly? Different branch resistances will lead to uneven distribution of air volume. Measure the air volume one by one and adjust it through the damper if necessary. involving Products of different grades of HEPA/ULPA air filters have the same air volume distribution method.

Project judgment example

The ULPA air supply volume of a certain equipment dropped from the design value of 800 m³/h to about 620 m³/h.

The troubleshooting process: first check the fan, the speed setting and operating status are normal; then measure the air volume, the measuring point and method are consistent with the design stage; then measure the filter element pressure difference, and find that it is about 60% higher than the initial resistance, but has not yet reached the final resistance; continue to check the pre-filtration, and find that the primary filter has exceeded the replacement cycle, and the resistance is obviously high.

Treatment method: Replace the primary filter, the total resistance of the system decreases, and the terminal air volume returns to approximately 770 m³/h. Although it has not completely reached the design value, it is within a reasonable range. Follow-up tracking records were conducted to confirm that the air volume was stable.

This case shows that the cause of insufficient air volume is not necessarily the end filter element. The failure of the front-stage protection will also affect the terminal air supply. When checking, you should look along the entire air path.

Selection and Acceptance Checklist

About Aili Industrial’s air volume investigation cooperation

To investigate insufficient air supply volume, the fan, filter element and system pressure loss need to be looked at together.

Aili Industrial's manufacturing system covers filters, motors, fans, control systems and complete machine assembly, and can provide ULPA ultra high efficiency filter、HEPA high-efficiency filter and supporting air supply equipment. filter with FFU fan filter unit、When the EFU equipment-end fan filter unit is matched in the same system, the filter element resistance and fan operating point can be calculated together during the planning stage to facilitate comparison and judgment during operation.

When the air supply volume is insufficient on site, it is recommended to record the fan status, air volume measurement data and filter element pressure difference first, and then contact the supplier for verification. The specific handling method shall be subject to on-site inspection results and project maintenance requirements.