How to deal with short circuit or backflow of ULPA air supply? Return air and process exhaust layout

If the air supply of the ULPA filter is short-circuited or backflowed, the spatial relationship between the return air and the process exhaust should be adjusted to allow clean air to pass through the protected area as designed. Increasing the level of terminal filtration does not automatically correct incorrect air paths. The essence of the air supply short circuit is that 'the clean air does not go where it should go': after it comes out of the air supply surface, it is directly sucked away by the nearby return air outlet, or is taken away by the equipment exhaust air, without passing through the workpiece and protection area. The essence of backflow is that 'the air that should go out cannot get out': the return air path is blocked, and the airflow flows in the local reverse direction. Both cases point to the same problem - the airflow path is not as designed. Aili Industry isFFU fan filter unit andthe fan filter unit at the EFU equipment end , the air supply direction and return air conditions are checked in the same plan.When matching The FFU computer group control system records the air volume and operating status of the zones. When the air flow path is abnormal, the measured data can be compared with the design plan.

1. First observe the actual path: the supply air is sucked away or it cannot go out.

Combined with wind speed, pressure and applicable flow pattern testing, identify locations where supply air is directly sucked away by return air, obstructive wakes, or local reverse flows.

Short circuit and backflow behave differently, and the focus of observation is also different. During a short circuit, the wind speed near the air supply surface may be normal, but the wind speed in the protected area is low, and the air flow direction is biased toward the return air outlet rather than the workpiece; during return flow, the wind speed in the local area may be reversed, or the pressure distribution may be opposite to the design. When observing, wind speed measurement, pressure distribution and necessary flow pattern testing should be combined to mark abnormal locations. Aili Industry isThe HEPA/ULPA filter matching plan explains the supply air direction and return air matching conditions.The FFU fan filter unit complete machine test records the air volume and pressure distribution of the zones. If the path is abnormal, it can be located according to the test data. The relationship between grade and airflow requirements can be found inISO cleanliness level comparison。

2. Check that all systems are running at the same time: supply air, return air and process exhaust should be looked at together.

The air supply, return air and equipment exhaust should be checked according to the real mode. Door and equipment movements may also change the path, and cannot be judged only when production is stopped.

The airflow path is not determined unilaterally by the air supply system. The negative pressure of the return air outlet, the pulling force of the process exhaust air, and the opening and closing status of the door will all change the direction of the air flow. If you only turn on the supply air but not the return air, or only observe when not producing, the path you see may be completely different from the path during actual operation. Aili Industry isthe EFU equipment end fan filter unit .Confirm the air flow conditions according to the equipment operating mode when matching The FFU computer group control system can record the air volume and status under different operating modes. During the test, the interaction of air supply, return air and exhaust air is checked according to the real operating mode. For the verification conditions of the airflow path at the equipment end, please refer toEFU FAQ and technical support。

3. Rectification through layout and control: adjust the position and parameters together

After adjusting interfaces, obstacles, or air volume distribution, review affected items such as airflow, particles, and pressure to avoid transferring problems to adjacent workstations.

There are two paths to rectify short circuits and reflows: layout adjustment and parameter adjustment. Layout adjustments include changing the position of the return air outlet, increasing the path distance between supply air and return air, and adjusting the location of equipment or obstacles; parameter adjustments include changing the air volume ratio of supply air and return air, adjusting the process exhaust volume, and adjusting the local air supply direction. Layout adjustment changes the airflow path, and parameter adjustment changes the airflow driving force. The two often need to be coordinated. Aili Industry isNon-standard ULPA filters andFFU fan filter unit package, the rectification plan is evaluated according to the equipment layout and return air conditions.In the The FFU fan filter unit supports speed adjustment to facilitate air volume distribution adjustment.The FFU computer group control system records the comparison of operating parameters before and after the rectification. For the coordination between rectification plan and verification, please refer toULPA ultra-high efficiency filter FAQ and selection guide。

4. When the return air outlet is too close and the clean air flow bypasses the workpiece, the return air arrangement should be re-evaluated.

When the return air outlet is too close and the clean air flow bypasses the workpiece, the return air layout and equipment shielding should be re-evaluated instead of blindly increasing the air supply. Increasing the air supply volume will cause more airflow in the short circuit, but the path direction does not change, and the protection at the workpiece is still insufficient.

Aili Industry isFFU fan filter unit andIn the matching solution of the fan filter unit at the EFU equipment end , the air flow path is checked according to the position of the workpiece and the return air outlet. If the return air outlet is too close, adjust it from the layout direction instead of making up for it with the air supply volume. Local protection scenarios on the device side can be combinedthe ultra-thin EFU is configured to allow the airflow to pass through the workpiece and then be discharged. The air outlet direction of The relationship between return air layout and airflow path can be referred toHEPA FAQs and Selection Guide。

5. Related questions and answers

Does the flow pattern test necessarily fail if you see vortices?
It needs to be judged according to the project rules based on the test purpose, location and pollution migration impact, and cannot just look at the shape.

Can the air supply short circuit be solved by increasing the air supply volume?
Usually not. Increasing the air supply volume may allow more short-circuit airflow, and the protection will still be insufficient if the path direction does not change.

Do adjacent areas need to be reviewed after rectification?
need. Airflow adjustments may transfer problems to adjacent workstations and should be reviewed based on the scope of impact.

6. Related articles

ULPA ultra-high efficiency filter FAQ and selection guide

FFU computer group control system

Ultra-thin EFU

HEPA FAQs and Selection Guide

7. Key points for selection and acceptance inspection

8. Product matching and technical support from Aili Industrial

Aili Industry isFFU fan filter unit andthe fan filter unit at the EFU equipment end , the air supply direction and return air conditions are checked in the same plan.When matching The FFU computer group control system records the air volume and operating status of the zones. When the air flow path is abnormal, the measured data can be compared with the design plan.The HEPA/ULPA filter matching plan explains the supply air direction and return air matching conditions.The FFU fan filter unit complete machine test records the regional air volume and pressure distribution;The EFU equipment-side fan filter unit is equipped with a fan filter unit to confirm the air flow conditions according to the equipment operating mode.Non-standard ULPA filters andThe FFU fan filter unit supporting equipment evaluates the rectification plan based on the equipment layout and return air conditions.The FFU fan filter unit supports speed adjustment to facilitate air volume distribution adjustment; when the return air outlet is too close, adjust from the layout direction.The air outlet direction configuration of the ultra-thin EFU allows the airflow to pass through the workpiece and then be discharged. Provide process objectives, installation drawings, operating conditions and acceptance requirements, and can further communicate ULPA standard specifications, non-standard interfaces, samples and batch matching. The specific parameters and test range are based on the confirmed model and technical documents.