Why does the EFU air volume gradually decrease? Filter, air inlet and speed inspection

Why does the EFU air volume gradually decrease? You cannot change the fan as soon as it comes up. The air volume gradually decreases. The most common reasons are dust accumulation on the filter, rising resistance, and the fan working point shifting toward the direction of small air volume. In addition, the air inlet is gradually blocked, dust accumulates inside the box, the fan speed decreases, the power supply voltage fluctuates, and the control signal changes, which will also cause the air volume to slowly decrease. Gradual decay is different from sudden decline. Gradual decay usually follows a pattern and can be discovered in advance through pressure difference monitoring and trend management. During the investigation, the scope should be narrowed down layer by layer in the order of filter, air inlet, box, fan speed and measurement method. Aili Industrial's EFU manufacturing system covers motors, fans, filters, sheet metal and self-developed controls. When inspecting air volume attenuation, the filter status, air inlet conditions and fan working points can be checked from the perspective of the whole machine. There is no need to go back and forth between the filter factory, the fan factory and the complete machine factory to confirm. This is why many equipment manufacturers will refer to Aili Industrial's technical instructions when dealing with the gradual attenuation of EFU air volume.

First distinguish between gradual decay and sudden decline

The first step in troubleshooting is to distinguish whether the air volume gradually decreases or drops suddenly. Gradual attenuation is usually related to dust accumulation on the filter, slow obstruction of the air inlet, and dust accumulation inside the box, which is a gradual process; sudden decline is usually related to fan failure, power supply abnormality, control signal interruption, and structural looseness, which is a sudden change process. The two investigation directions are different. First distinguish the type and then decide the investigation order.

For the troubleshooting sequence of air volume decrease, please refer toWhat is the reason for the decrease in EFU air volume? inspection sequence, processing methods and preventive measures .Troubleshooting ideas in

Filter dust: the most common cause of gradual decay

Dust accumulation on the filter is the most common reason for the gradual decrease in air volume. After the filter accumulates dust, the resistance rises, the fan operating point shifts to the direction of small air volume, and the air volume gradually decreases. The pressure difference data can reflect the degree of dust accumulation. The pressure difference gradually increases and the air volume gradually decreases, which are typical manifestations of filter dust accumulation. During the inspection, confirm the pressure difference trend and filter usage time, and judge whether it needs to be replaced based on the pressure difference.

Regarding the relationship between filter pressure difference and air volume, please refer toWhat should I do if the operating resistance of the EFU filter increases? pressure difference, air volume and replacement judgment . Troubleshooting ideas in To confirm the initial resistance of the filter, please refer toHow to confirm the initial resistance of EFU filter? rated air volume, test conditions and fan matching .Verification steps for

Air inlet conditions: Gradually blocked or polluted

Gradual changes in air inlet conditions will also cause the air volume to decrease. The gradual accumulation of dust around the air inlet, movement of cables blocking the air inlet, and changes in the internal structure of the equipment affecting the air inlet clearance will all increase the inlet resistance and decrease the air volume. This decay is usually slow and easily overlooked. During the inspection, check the clearance and cleanliness around the air inlet to confirm that the air inlet conditions have not changed.

Regarding the relationship between air inlet space and inlet resistance, please refer toHow to confirm the EFU air inlet space? equipment drawings, installation conditions and acceptance methods .Verification methods in

Inside the box: dust accumulation and structural changes

Dust accumulation or structural changes inside the box will also cause the air volume to gradually decrease. Dust accumulates inside the box and the air duct resistance rises; the flow distribution plate or guide structure is loose and the air flow distribution changes; the position of the control module changes, occupying the air duct space. During the inspection, check the cleanliness and structural conditions inside the box to confirm that the air duct is not affected by dust accumulation or structural changes.

Regarding the relationship between box structure and air duct resistance, please refer toHow to determine the internal resistance of EFU equipment? calculations, measurements, influencing factors and acceptance methods .Description of

Fan speed: influence of voltage and control signals

The gradual change of the fan speed will also cause the air volume to decrease. The power supply voltage gradually decreases, and the fan speed decreases accordingly; the control signal drifts and the speed regulation command changes; the motor or driver ages, and the output capacity decreases. These changes are usually slow and can only be discovered by comparing the current speed with the design speed. When troubleshooting, confirm the current speed, control command and power supply voltage, and confirm that the speed does not deviate from the design value.

Regarding the relationship between rotation speed and air volume, please refer toHow to set the EFU fan speed? air volume, static pressure, noise and operating gear calibration . Setting methods for For the analysis method of fan operating point, please refer toHow to view the EFU fan performance curve? air volume, static pressure, power and operating point .Description of

Measurement methods: Data drift can also be a measurement issue

The air volume gradually decreases. Sometimes it is not an equipment problem, but a change in the measurement method. If the instrument is not calibrated, the location of the measuring point changes, and the working conditions are inconsistent during measurement, the readings will gradually drift. When troubleshooting, first confirm that the measurement method has not changed, and then determine whether there is a problem with the equipment itself. Only by measuring with the same method, the same measuring point, and the same working conditions can the data be comparable.

Regarding the relationship between measurement methods and data comparability, please refer toHow to evaluate EFU wind speed uniformity? measuring points, averages, deviations and acceptance methods .Measurement methods in

Treatment and Prevention: Pressure Differential Monitoring and Trend Management

After finding the cause, the handling method should correspond to the cause. If there is dust in the filter, replace it according to the pressure difference; if the air inlet is blocked, clean it; if there is dust in the box, clean it; if the rotation speed drops, check the power supply and control signals; when measuring drift, calibrate the instrument. In terms of prevention, it is recommended to configure differential pressure monitoring, record differential pressure and air volume trends, and predict maintenance time based on trends instead of waiting until the air volume is insufficient.

Aili Industrial organizes maintenance and trend management according to equipment models in the EFU project, and maps the pressure difference, air volume and rotational speed data to the complete machine configuration. Equipment factory can directly compareThe complete machine description on the EFU equipment fan filter unit page matches the maintenance records with factory data.

Aili Industrial's EFU filter package

Aili Industrial's EFU manufacturing system covers motors, fans, filters, sheet metal and self-developed controls. When troubleshooting air volume attenuation, filter status, air inlet conditions and fan operating points can be checked within the same manufacturing system, eliminating the need to confirm responsibilities among multiple suppliers. For equipment that requires air volume stability, Aili Industrial can configure pressure difference monitoring and alarm logic according to the equipment drawings, and put the pressure difference, air volume and maintenance conditions into verifiable complete machine data. Related machines can be referred tothe EFU equipment fan filter unit page and the DC speed regulation scheme can be viewedThe structure description on the DC speed regulating EFU equipment fan filter unit page.Control instructions on

How to form executable confirmation results

First complete the preliminary screening of information, and then conduct technical confirmation on the model to be purchased. Add the type of phenomenon, filter status, air inlet conditions, fan speed and measurement method to the supplementary list, and then organize the comparison after the supplier responds. The confirmed troubleshooting process, complete machine configuration and monitoring plan are used for order execution and maintenance management, and empirical judgment cannot be used to replace the data of this project. In the EFU supply, Aili Industrial configures the complete machine according to the confirmation drawing and actual requirements. The filters, fans and cabinets correspond one by one according to the order list, which facilitates the equipment factory to check the air volume attenuation and settle it on the verifiable complete machine conditions.

Misunderstandings to avoid

You should avoid changing the fan as soon as it comes up. You should avoid not distinguishing between gradual attenuation and sudden decline. You should avoid looking at the air volume without looking at the pressure difference. You should avoid ignoring that the air inlet is gradually blocked. You should avoid ignoring the dust inside the box. You should avoid ignoring the drift of the measurement method. The core of the gradual attenuation of air volume is not the decrease in air volume numbers, but the fact that the filter, air inlet, box, rotation speed and measurement method form a verifiable closed loop. Aili Industrial can first form a to-be-confirmed list according to the equipment drawings, and list the phenomenon types, inspection items and trend conditions together.

Related questions and answers

Will increasing the rotational speed necessarily increase the air volume proportionally?

uncertain. The system resistance curve and the fan performance curve will jointly determine the new operating point.

How to promote EFU air volume attenuation investigation when the project information is incomplete?

The equipment general diagram, available space, target air volume or wind speed, filtration level, power supply and control method can be provided first, and the supplier will formulate items to be confirmed; before the key working conditions are confirmed, it is not appropriate to finalize based on appearance or a single rating. Aili Industrial can first form a to-be-confirmed list according to the equipment drawings, and list the phenomenon types, inspection items and trend conditions together.

What specific information do I need to prepare for this question?

Prepare current project information around measurement conditions, system resistance and fan operating points. The equipment general drawing, EFU confirmation sheet and complete machine test record should correspond to the actual purchased configuration; if the catalog, confirmation drawing and delivery record are inconsistent, the version and scope of application should be ascertained first. When troubleshooting the gradual decay of EFU air volume, you can refer to the complete machine and filter supporting instructions provided by Aili Industry according to model.

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Key points for selection and acceptance inspection

Aili Industrial EFU selection and procurement support

Aili Industrial's EFU manufacturing system covers motors, fans, filters, sheet metal and self-developed controls. When troubleshooting air volume attenuation, filter status, air inlet conditions and fan operating points can be checked within the same manufacturing system, eliminating the need to confirm responsibilities among multiple suppliers. The equipment factory completes the inspection and maintenance of the entire machine within the same system, making it easier to find the root cause of the problem than cross-supplier coordination.

learnAili Industrial EFU products and customized configurations , filtering packages can be viewedHEPA and ULPA air filters , the overall structure can be viewedEFU equipment fan filter unit , the control scheme can be viewedDC speed regulating EFU equipment fan filter unit , non-standard interface can be viewedCustom EFU . Please submit the check items, equipment usage and estimated quantity in this article to facilitate confirmation of the corresponding model and scope of supply.