When there is a bypass channel in the chemical filtration section of the air-conditioning box, the bypass purpose, closing status and sealing should be confirmed, and whether untreated air enters the protected area should be assessed. Just because the main filter element is effective, we cannot ignore the impact of the bypass airflow on the overall effect. The air volume of the bypass is not large, but it takes away unfiltered air.

First find out why the bypass exists

Some of the bypass ducts in the air-conditioning box are reserved during design, and some are left after modification. The reserved bypass may be used to adjust air volume, inspect and isolate, or reduce resistance under certain working conditions; the bypass left over from the transformation may be the opening after adjusting the position of the original filter section. Bypasses from different sources are handled in different ways. The design reserved bypass needs to confirm its operating logic and closing conditions, and the openings left after the renovation need to be evaluated whether they should be blocked. Without first clarifying the function of the bypass, directly blocking it may affect other functions, and leaving it alone may continue to leak air.

Bypass air leakage affects the mixed air

The impact of bypass on gas control depends on the ratio of air leakage volume to the air volume processed by the main filter element. If the bypass accounts for only a small part of the total air volume, the impact on the outlet concentration may be limited; if the bypass ratio is high, or the bypass air comes from a heavily polluted area, the mixed gas concentration may be significantly higher than the filter outlet. During testing, the filter outlet and the mixed air supply should be measured separately. The difference between the two can reflect the contribution of the bypass. Only measuring the outlet of the filter element can easily overestimate the overall effect of the system. Regarding the difference between mixed air and single-point detection, please refer toThe indoor odor is different from the fresh air inlet odor. How should I investigate?。

Valve and seal status should be checked according to operating mode

The closed state, sealing form and actuator of the bypass valve need to be confirmed separately in different operating modes. Some bypass valves are closed during normal operation, but may open when the pressure difference changes or the control signal is abnormal; some valves still have gaps for air leakage after closing. Access doors, flange joints and seams are also common air leakage points. During the inspection, the position of the bypass in normal, on-duty and switching states should be recorded to confirm whether the seal is continuous when closed. Regarding the inspection ideas for air leakage in the positive pressure and negative pressure sections, please refer toHow to prevent external air leakage when a chemical filter is installed in the negative pressure section?。

After correction, review the overall effect

After blocking or adjusting the bypass, the air volume distribution and mixed gas concentration should be reviewed. Closing the bypass may change the total system resistance and air volume distribution. It is necessary to confirm that the fan operating point and the air volume of each branch are still within the controllable range. Gas detection should cover the mixed air supply and key protection locations, not just the filter outlet. If the bypass was originally responsible for the adjustment function, it is necessary to confirm whether other adjustment methods can make up for it after it is closed.

Aili industrial supporting equipment

For problems such as bypass air leakage, we usually recommend that customers confirm the function and operating status of the bypass before deciding to block or adjust it, rather than blocking the problem directly. 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 . The V-shaped structure provides a larger filtration area in the same box space, helping to control the rise in resistance after closing the bypass. Device-side applications can useChemical filter FFU form, integrated chemical adsorption layer withHEPA/ULPA filter particle filtration. The manufacturing end covers independent R&D and production of motors and fans, control systems, sheet metal and complete machine assembly. The bypass structure, valve seals and air volume distribution can be checked in the same package, and non-standard boxes can be adjusted according to on-site air ducts. The specific gas effect, applicable environment 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

The bypass ventilation is not large, can it be left alone?
Depends on the bypass ratio and air source. When the proportion is small and the source is clean, the impact will be limited. When the proportion is high or the source is heavily polluted, it may significantly increase the concentration after mixing. It is recommended to make a judgment after testing.

What should I do if the air volume drops after blocking the bypass?
Blocking will change the system resistance, and the fan operating point and the air volume of each branch need to be rechecked. If the air volume is insufficient, fan adjustment or filter section structural optimization should be evaluated instead of simply restoring bypass.

Can Aili Industrial help check the bypass solution?
It can be combined with the bypass function, valve status and air volume distribution to assist in checking the blocking or adjustment plan and filter section configuration. The specific plan needs to be confirmed based on product data and on-site working conditions.

Related articles

• How to prevent external air leakage when a chemical filter is installed in the negative pressure section?

• How to prevent the leakage of contaminated air when a chemical filter is installed in the positive pressure section?

• How to check the residual pressure outside the machine after MAU adds a chemical filtration section?

• Can I still install a chemical filter if the air conditioning box does not have a reserved filter section?

Key points for selection and acceptance inspection