When the chemical filter is located in the positive pressure section, check whether the box, access door and connection interface are leaking outward, and whether the leakage occurs before or after the filter section. Different locations have different effects. You cannot ignore the box seal just because the indoor pressure difference is normal. The air is leaking out of the positive pressure section, but which section of the air is leaking is very different.

Direction and risk of positive pressure section leakage

When the chemical filter section is installed on the outlet side of the fan, the pressure inside the box is higher than the surrounding environment. Once there is a gap, the air inside the box leaks out instead of the outside air being sucked in. If the leak occurs before the filter section, the leaked air is untreated air, which may contaminate the surrounding area of ​​the equipment or adjacent areas; if the leak occurs after the filter section, the leaked air is treated air, and the main impact is the loss of air supply volume and energy consumption, and the impact on gas control is relatively small. To determine the risk of leakage, you must first determine which side of the filter section the leakage point is on, rather than just looking at whether there is air leakage.

The sealing of the box before the filter section is the key

The most important thing to pay attention to in the positive pressure section is the sealing of the box before the filter section, including seams, flanges, access doors and air duct interfaces. If these locations are not tightly sealed, the untreated air containing the target gas will leak directly to the outside of the box. For chemical filtration sections installed near equipment or in clean rooms, this leakage may increase the gas concentration in the surrounding area, which may not be reflected by the room's differential pressure gauge. During the inspection, the box structure diagram should be combined to confirm which joints are located upstream of the filter section and be prioritized.

Leakage after the filter section must also be checked

Although the leakage after the filter section is treated air, it will affect the air supply volume and system balance. A large amount of leakage may lead to insufficient air volume at the end, requiring the fan to increase speed compensation and increase energy consumption. In addition, if there are particle filters or other functional sections after the filter section, leaks may cause the operating conditions of these sections to deviate from the design. During the inspection, the location of the leakage point and the amount of air leakage should be recorded to determine whether it is within the acceptable range.

The leak detection method under positive pressure is different from that under negative pressure

Leak detection in the positive pressure section is relatively intuitive. Leakage can be observed on the outside of the joint by smoke, soapy water or anemometer scanning. However, it should be noted that leak detection should be carried out under normal operating air volume and pressure difference. When the pressure difference between the inside and outside of the box disappears in the shutdown state, the leakage point may not be visible. For large boxes, inspection should be carried out section by section to avoid missing corners and high seams. When detecting leaks, the ambient wind speed should also be recorded to avoid misjudging the ambient air flow as a leak. For ideas on comparative inspection of the negative pressure section, please refer toHow to prevent external air leakage when a chemical filter is installed in the negative pressure section?。

After correction, review the air volume and surrounding gas

After the seal is corrected, the air supply volume, fan operating point and gas concentration in the surrounding area should be reviewed. After the leakage is reduced, the system resistance may change, and the air volume distribution needs to be re-confirmed; if the original leakage in front of the filter section is obvious, the surrounding gas concentration should be improved after correction. The correction record should retain the leakage point location and treatment method for subsequent maintenance reference. Aili Industry can provide selection packages for box-type, flat-plate and V-type chemical filtration products. For box-type MAU packages, please refer toMAU box type chemical filter , product series can be viewedChemical filter product range . Device-side applications can useChemical filter FFU form, integrated chemical adsorption layer withHEPA/ULPA filter particle filtration. When installing the positive pressure section, the box joints and interface seals can be checked together during the matching stage. The manufacturing end covers sheet metal, frame and complete machine assembly, and non-standard cabinets can be adjusted according to on-site interfaces. The specific gas effect, sealing performance and replacement cycle still need to be verified based on the corresponding configuration data and on-site working conditions. The actual results are subject to on-site leak detection and gas detection results.

Related questions and answers

There is air leakage in the positive pressure section and the room pressure difference is normal. Does it still need to be dealt with?
need. The room pressure difference reflects the relationship between the room and adjacent areas, and does not mean that the box is properly sealed. Leakage in front of the filter section may leak untreated air to the surrounding area, which may not be visible on the differential pressure gauge.

Which one has greater impact, air leakage behind the filter section or air leakage in front of the filter section?
What leaks out before the filter section is untreated air, which may affect the surrounding gas concentration; what leaks out after the filter section is treated air, which mainly affects air supply volume and energy consumption. The former usually has a more direct impact on gas control.

Can Aili Industrial help check the sealing of the box in the positive pressure section?
The sealing scheme of the joints and the access door can be checked based on the box structure, filter section position and interface form. The specific plan needs to be confirmed based on product data and on-site working conditions.

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