How to calculate EFU working static pressure? How to add the resistance of filters, air inlets and equipment air ducts

How to calculate the EFU working static pressure? You can't just calculate the filter resistance. When the EFU is working, the resistance that the fan must overcome comes from multiple links: filter resistance, air inlet resistance, box internal air duct resistance, air outlet structure resistance, and the resistance of the air outlet path inside the equipment. The sum of these resistances is the working static pressure that the fan needs to provide. If only the filter resistance is calculated, the fan selection may be too small and the air volume after installation may be insufficient; if all resistances are roughly estimated as a total, the fan selection may be too large and the efficiency range deviates. Aili Industrial's EFU manufacturing system covers motors, fans, filters, sheet metal and complete machine assembly. System resistance decomposition and fan operating points can be checked according to equipment drawings within the same manufacturing system. There is no need to transfer parameters back and forth between filter factories, fan factories and complete machine factories. This is why many equipment manufacturers refer to Aili Industrial configuration instructions when calculating EFU operating static pressure.

Filter resistance: initial resistance and operating resistance are calculated separately

Filter resistance is the main part of system resistance, but it must be calculated in two values. The initial resistance is the pressure difference of the new filter at the target air volume, and the operating resistance is the pressure difference when the dust accumulates to the replacement condition. When calculating the working static pressure, if only the initial resistance is calculated, the fan may have insufficient air volume in the latter part of the maintenance cycle; if only the operating resistance is calculated, the fan selection is too large and the efficiency range deviates from the initial installation. A reasonable approach is to count both values, corresponding to the working points at the initial installation and at the end of operation.

For confirmation methods of filter initial resistance and operating resistance, please refer toHow to confirm the initial resistance of EFU filter? rated air volume, test conditions and fan matching . Verification steps for Filter packages can be viewedthe HEPA vs. ULPA air filters page.Rating descriptions on

Air inlet resistance: headroom and structure affect inlet pressure drop

The air inlet resistance comes from the inlet structure, air inlet clearance and surrounding occlusion when air enters the EFU. The air inlet is blocked by structures, cables or adjacent components, and the inlet resistance increases; the inlet structure design is unreasonable, the air flow is turbulent, and the pressure drop increases. When calculating the working static pressure, the air inlet resistance cannot be ignored, especially for projects with compact internal space and limited air inlet clearance.

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

Box air duct resistance: pressure drop caused by internal structure

The resistance of the air duct inside the box comes from the steering, flow distribution structure and cross-sectional changes of the air flow in the box. When there is a flow equalizing plate, flow guide structure or control module inside the box, the airflow path becomes complicated and the pressure drop increases. The internal space of ultra-thin or compact boxes is small, and the air duct resistance may account for a higher proportion. When calculating the working static pressure, the box air duct resistance must be confirmed according to the structure of the whole machine, and cannot be estimated based on the filter resistance alone.

Ai Li industrialEFU products and customized configurations list the complete machine structure and supporting instructions by model. When checking the box air duct resistance, the equipment manufacturer can directly correspond to the specific model and put the internal structure and resistance data in the same table for analysis. For the air duct resistance of ultra-thin models, please refer toHow to choose ultra-thin EFU? space, air volume, static pressure, heat dissipation and maintenance points .Checking methods in

Air outlet and equipment path resistance: fully reflected after installation

The resistance of the air outlet structure and the resistance of the air outlet path inside the equipment are easily overlooked parts in the calculation of working static pressure. When the EFU air outlet has a flange, flow-sharing structure or connector, the air outlet resistance increases; the air outlet path inside the equipment is narrow, blocked or diverted, and the back pressure increases. This part of the resistance may not be fully reflected during the EFU unit test, and will fully appear after installation. When calculating the working static pressure, the resistance of the air outlet path inside the equipment must also be taken into consideration.

For the relationship between the air outlet direction and the installation position, please refer toWhat should we pay attention to in the direction of EFU air outlet? structural, electrical, commissioning and rectification points .Checking methods in

Addition of resistance: Each resistance is superimposed according to the same air volume condition

Various resistances must be superimposed under the same air volume conditions. The filter resistance, air inlet resistance, box air duct resistance and air outlet resistance all change with the air volume. When calculating the working static pressure, first determine the target air volume, then confirm each resistance separately at this air volume, and finally add them up to obtain the total system resistance. The resistance under different air volumes cannot be added directly, otherwise the calculation of the working point will be biased.

For the calculation relationship between air volume and resistance, please refer toHow to calculate EFU rated air volume? the air supply area, target wind speed and unit conversion method .The calculation caliber in

Match the fan operating point: the total resistance is placed on the fan curve

After the total resistance of the system is calculated, it should be placed on the fan curve to see whether the operating point corresponding to the target air volume falls within the effective range of the fan. The initial installation resistance and operating resistance correspond to two working points respectively, and both working points must be within the fan adjustment range. Only counting one working point, it is impossible to judge the stability of the air volume during the maintenance cycle.

Regarding the relationship between the fan working point and the matching of the whole machine, please refer toHow to choose EFU centrifugal fan? working point, power, temperature rise and continuous operation requirements . Checking methods for For projects that require DC speed regulation solutions, please refer toSpeed the DC speed adjustment EFU equipment fan filter unit page.​​adjustment instructions on

Installation retest: Comparison of measured static pressure with calculated value

After the working static pressure calculation is completed, the installed machine must be retested and verified. Measure the pressure difference before and after the filter, the air inlet pressure difference and the air outlet static pressure at the target air volume, and compare with the calculated results. When the difference is large, check the air inlet clearance, filter status, internal structure of the box and air outlet path instead of directly judging that there is a problem with the fan. The retest data should be archived as a baseline for subsequent maintenance and mass production.

In the EFU project, Aili Industry organized installation retest according to the equipment drawings and agreed working conditions, and verified the filter pressure difference, air inlet pressure difference, outlet static pressure and complete machine air volume together. Related machines can be referred tothe EFU equipment fan filter unit page.Structural description on

Aili Industrial's EFU system resistance package

Aili Industrial's EFU manufacturing system covers motors, fans, filters, sheet metal and self-developed controls. System resistance breakdown and fan operating points can be checked according to equipment drawings within the same manufacturing system, and filters, boxes, air inlets and air outlet structures do not need to be transferred between multiple suppliers. For equipment with clear requirements for working static pressure, Aili Industrial can organize prototype testing and batch curing according to the confirmation diagram, and reduce the sub-resistance, total resistance and fan working point to verifiable complete machine data. Non-standard interfaces can be referred toCustomize EFU page.Customization instructions in the

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 filter resistance, air inlet resistance, box air duct resistance, air outlet resistance and fan working point to the supplementary list, and organize a comparison after the supplier responds. The confirmed system resistance, complete machine configuration and interface are used for order execution, and sample parameters 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 filter, box, fan and control correspond one by one according to the order list, which facilitates the equipment factory to calculate the working static pressure and settle it on the verifiable complete machine conditions.

Misunderstandings to avoid

It should be avoided to only calculate the filter resistance, to avoid the direct addition of resistance data under different air volumes, to avoid ignoring the resistance of the air inlet and air outlet path, to avoid counting only the initial resistance but not the operating resistance, and to avoid not re-testing and verifying after the calculation is completed. The core of the calculation of EFU working static pressure is not to add a few numbers, but to decompose and superimpose various resistances under the same air volume conditions, and then place them on the fan curve to confirm the working point. Aili Industrial can first form a to-be-confirmed list according to the equipment drawings, and list the sub-item resistance and fan conditions together.

Related questions and answers

Can EFU selection be completed by providing only air volume?

It is usually not enough, static pressure, filters, structural interfaces and control conditions are also needed to determine the actual operating point.

How to advance the EFU working static pressure calculation 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 sub-item resistance and fan conditions together.

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

Prepare current project information around filtration efficiency, resistance, sealing and leak detection. 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 calculating the EFU working static pressure, 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. System resistance breakdown and fan operating points can be checked according to equipment drawings within the same manufacturing system, and filters, boxes, air inlets and air outlet structures do not need to be transferred between multiple suppliers. The equipment factory completes the working static pressure calculation and complete machine matching within the same system, which makes it easier to maintain data consistency 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 . Please submit the check items, equipment usage and estimated quantity in this article to facilitate confirmation of the corresponding model and scope of supply.