Experienced supplier of Initial pressure drop VS Final Pressure drop (for a filter)

Initial pressure drop VS Final Pressure drop (for a filter)

Filters create resistance to airflow. The filter accumulates dust and the resistance increases. When the resistance increases to a certain value, the filter is scrapped.

The resistance of the new filter is called "initial resistance", and the resistance value corresponding to the discarded filter is called "final resistance".

When designing, a resistance value is often required to calculate the air volume design of the system. This value becomes the "design resistance". The usual method is to take the average value of the initial resistance and the final resistance.

In most cases, the final resistance of the filter on site is 2-4 times the initial resistance.

The dirtier the filter, the faster the resistance builds. Excessive final resistance value does not mean that the service life of the filter will be significantly extended, but it will sharply reduce the air volume of the air conditioning system. Therefore, there is no need to set the final resistance value too high.

Low-efficiency filters try to use coarse fiber filter materials with a diameter ≥ 10 microns. Due to the large gap between the fibers, the excessive resistance may blow away the dust on the filter. At this time, the resistance will no longer increase, but the filtration efficiency will drop to zero. Therefore, the final resistance value of the filter below G4 should be strictly limited.

The table below gives some suggested final resistance values, derived from actual experience.

Recommended value of final resistance
Filter efficiency	Suggested final resistance (Pa)
G3 (coarse)	100—200
G4(coarse)	150—250
F5—F6 (Medium)	250—300
F7—F9 (Medium)	300—400
H10—H11(EPA)	400—450
H13-U16(HEPA&ULPA)	400—600

Each filter should be fitted with a resistance monitoring device. The final resistance should be judged by the instrument, not just by the operator's feeling.

High temperature resistant Minipleat filter

Various Cardboard Frame Prefilters

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