How do the pleat pitch and filter material area of ​​ULPA affect resistance?

Two opinions are often heard when selecting a filter: one is that 'the more pleats, the larger the filtration area, and the lower the resistance'; the other is that 'the pleats are too dense, the channel is narrow, and the resistance is high.' The two statements sound contradictory, but each has its own conditions.

The influence of pleat pitch and filter material area on resistance does not act alone, but is determined together with the airflow channel, support structure, and passing wind speed. Increasing the area of ​​the filter material can reduce the wind speed through which the medium passes, which is theoretically beneficial to reducing resistance; however, if the pleat pitch is too small, the friction loss in the inter-pleat channel will increase. There is a balance point between the two, and this balance point depends on the type of filter material, the pleating process and the actual air volume.

ULPA filter material is usually folded more densely than HEPA because it has higher efficiency requirements and requires a larger filter area to control the passing wind speed. But the side effect of dense folding is that the channel narrows. When the airflow passes through the pleat channel, in addition to the resistance of passing through the medium itself, there is also friction and pressure loss caused by flowing along the channel. The smaller the pleat pitch, the greater the proportion of pressure loss in this part of the channel. So we can't just look at 'how much the filter area has increased', but also look at 'how much the channel loss has increased' . involving For the structural design of ULPA ultra-high efficiency filter , please refer to the corresponding product information.

The relationship between filter material area and pleat pitch can be understood in a simplified way. Under the same external dimensions, as the number of pleats increases, the height of a single pleat may decrease, and the total unfolded area may increase. However, if the pleat distance is reduced to close to the thickness of the filter material, the channel will be almost crushed, making it difficult for the airflow to pass through each pleat evenly, and the actual effective area may be reduced. Moreover, overly dense pleats are more likely to deform during the manufacturing and transportation processes, and local channel collapse will cause uneven distribution of resistance. Therefore, when designing pleats, you need to find a balance between area and channels, rather than simply pursuing the maximum number of pleats.。

When actually comparing different structures, it is necessary to compare the resistance curves of the complete finished product under the same frame size, the same air volume and the same level. You cannot take a sample with a 'larger expansion area' and compare it with another sample with a single point resistance, because the channel design may be completely different. For the comparison method, please refer to the relevant instructions on the resistance curve. Supporting FFU fan filter unit or the fan filter unit at the EFU equipment end , the resistance of the filter element must be checked together with the working point of the fan. You cannot just look at the parameters of the filter element itself. When using

Wrinkle deformation, colloid occupancy, and support differences also affect actual performance. The glue line or spacer support itself occupies a part of the channel space. If the distribution is uneven, it may cause the local channel to be narrow or wide. During mass production, the status of the pleating equipment, glue volume control and curing conditions will all affect the structural consistency. After the structural parameters are confirmed, it is recommended to record key process data to facilitate subsequent batch comparison. For specific testing items, please refer to the relevant instructions for factory testing.

Device-side applications have more specific structural requirements. When the installation space is limited, the filter element thickness and pleat pitch design must be considered together. We cannot only pursue low resistance and ignore assembly feasibility. When detecting leaks, the edge of the densely folded structure and the position of the glue line are the focus of scanning. Whether the probe can reach it needs to be confirmed in advance. The matching dimensions of the liquid tank or gasket seal should also correspond to the structural design. For projects with special working conditions, such as high humidity or corrosive environments, filter material selection and structural design need to be evaluated at the same time. involving HEPA/ULPA air filter products of different grades have the same structure comparison method.

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About Aili Industrial’s folding structure packages

The resistance performance of ULPA is often determined in the pleat design stage. Once the parameters of pleat pitch, area, and glue line layout are determined, the space for subsequent adjustments is limited.

Aili Industry has independent manufacturing capabilities in filters, fans, control systems and sheet metal processing, and can provide ULPA ultra high efficiency filter、HEPA high-efficiency filter and supporting air supply equipment. For structural selection, the installation space, target air volume and filtration level can be combined to help check the matching of folding parameters and resistance requirements. When the filter is matched with equipment such as FFU and EFU, the filter element resistance and fan operating point can also be evaluated together during the planning stage to reduce repeated adjustments due to structural mismatch after installation.

When enquiring, provide the outer frame size, target air volume, grade requirements and installation conditions to help confirm the appropriate folding structure solution. Specific specifications are subject to the technical documents and testing data confirmed by the project.