Standard for Determining the Replacement of Explosion-proof FFU Filters (Enforced in explosion-proof workshops, divided into 4 levels, with differential pressure as the primary basis)
1. Core determination: Differential pressure standard (the most authoritative and priority execution)
1.1 Resistance value threshold
New HEPA initial differential pressure: 130～180 Pa
General explosion-proof workshop alarm value: 280 Pa (warning, arrange for planned replacement)
Mandatory replacement differential pressure: 300～350 Pa
Lithium battery, electrolyte, high solvent explosion-proof workshop: Replace directly if the pressure exceeds 280 Pa, do not wait until 350 Pa
Explosion-proof key: Excessive differential pressure causes the fan load to soar, motor temperature to rise beyond the limit, easily forming an ignition source, and there is an explosion hazard.
1.2 Special situations of differential pressure abnormality
Short-term rapid increase in differential pressure (increase by more than 80 Pa within one week), indicating a sudden increase in dust/oil mist concentration in the workshop, even if it is not yet 300 Pa, it is necessary to replace immediately.
2. Operating condition determination (differential pressure not exceeding the standard, but the following situations must be replaced)
Same speed fan significantly smaller, laminar flow effect in the clean area deteriorates, particle concentration continues to exceed the standard;
FFU fan noise increases, the body vibrates violently, the motor casing is obviously hot;
The fan operating current far exceeds the rated standard, long-term overload.
3. Intuitive appearance determination (open the cover for inspection, must be powered off)
Large areas of blackening on the filter material surface, accumulation of lithium battery powder, medicine powder, oil stains, electrolyte crystallization;
Filter material is damaged, cracked, leaking, the edge frame sealing sponge is aging and falling off;
The filter material adsorbs a large amount of alcohol, organic solvent mist, the filter paper is soaked and sticky (flammable pollutants attached, explosion risk extremely high, immediate replacement).
4. Time reference determination (auxiliary reference when no differential pressure gauge, cannot be used as the sole basis)
Low dust explosion-proof laboratory, sterile pharmaceutical area: recommended replacement after 8 months;
Electronic explosion-proof workshop: recommended replacement after 5 months;
Lithium battery coating, injection, daily chemical solvent workshop: mandatory inspection after 3 months, mostly need to be replaced.
5. Exclusive hard replacement rules for explosion-proof scenarios (red line, ignore differential pressure and time duration)
Workshop leakage (electrolyte, organic solvent, flammable dust spreading) contaminates the filter;
Clean area fire, solvent emission exceeds the standard, filter material adsorbs flammable and explosive media;
FFU has long-term failure shutdown and is restarted, filter screen is severely damp, condensation plate hardens;
Pre-filter completely fails, large coarse dust directly penetrates the high-efficiency filter material.
6. Summary of rapid determination
Differential pressure ≥ 300 Pa → Immediately replace
Differential pressure 280～300 Pa → Complete replacement within 3 days
Fan performance decline, motor overheating, filter oil stain/damage → Immediately stop and replace
Adsorbing electrolyte, flammable solvent dust → Unconditionally replace