Do I need one fan or two for my dryer?
Almost always two, and they are different machines. The supply fan pushes clean, heated air into the chamber at 150 to 350 °C — a thermal duty where efficiency, curve stability and metallurgy matter. The exhaust fan pulls the spent air, laden with fine sticky powder and moisture, to the cyclone or baghouse — a dirty, hygienic duty where self-cleaning wheel geometry, cleanable construction and product capture matter. We engineer and quote them separately, because a fan optimised for one is wrong for the other.
The dried powder builds up on the exhaust wheel and it's my product. What do you do about it?
Fine, sticky, hygroscopic powder accretes on the blade, redistributes mass and unbalances the rotor until it trips protection — and because that powder is often the saleable product, build-up is yield loss and a hygiene breach at once. We default the exhaust fan to a radial-tipped self-cleaning wheel with crevice-free sloped blade faces that encourage shedding, add cleanable coatings and, where the powder allows, water-wash or rapping cleaning provisions with inspection access. We size the geometry to your specific powder, not a generic wheel.
My product is food or pharma. Can your fans meet hygiene and cleanability requirements?
Yes. For food and pharma drying we build in SS304 or SS316 with crevice-free welds ground smooth, cleanable food-safe coatings, hinged inspection doors for access, a wash-down drain, and CIP provision where the process or regulator demands it. The point is a fan you can verify clean, not one you assume is clean — welded-in wheels and painted mild steel that flakes into the product have no place on a hygienic dryer. Tell us your hygiene class and cleaning regime and we build to it.
How hot does the supply-air fan run, and how do you handle it?
The heated drying-air supply fan typically runs 150 to 350 °C. We size the shaft for thermal growth, step the casing to IS 2062 or 16Mo3 on the hot side, fit expansion joints at inlet and outlet, keep the bearings outside the airstream, and add a heat slinger or cooling disc to hold the bearing housing below its lubricant rating. The fan is built for your stated supply temperature and excursion case, not a generic rating.
Should I specify VFD for a drying fan?
Yes, it is our default on both fans. Drying quality depends on air throughput and residence time, which shift across a batch, a product change or a start-up ramp, and VFD tracks that profile smoothly. On the exhaust fan it also avoids the flow swings that unsettle cyclone or baghouse capture and drive more powder onto the wheel. Inlet guide vanes or an outlet damper remain available for legacy retrofit where the existing drive cannot be changed.
Are your drying fans ATEX-rated for combustible food or chemical dust?
Where the dried dust is combustible — many food powders like milk, flour and sugar, and some chemical and pharma powders — ATEX Zone 22 is self-declared per 2014/34/EU, Category 3D, on the product-laden exhaust fan. The build uses aluminium or bronze rub rings to prevent ferrous-on-ferrous contact, bonded earthing, anti-static coatings and T-class bearing-temperature control. To be precise, that is a self-declaration of conformity, not a third-party certification. Zone 21 (Category 2D) is available on application via a Notified-Body partner.
What certifications and test standards actually apply to these fans?
To be exact: CE is self-declared per 2006/42/EC and 2014/35/EU, and ATEX Zone 2/22 is self-declared per 2014/34/EU (Category 3) where the dust classification calls for it — these are self-declarations of conformity, never third-party certifications. Performance is tested in-house to the AMCA 210 / ISO 5801 method on our 200 HP VFD test rig; that is a test method, not an AMCA certification, and we are not an AMCA member. Every fan is dynamically balanced to ISO 21940 G6.3 as standard (G2.5 / G1.0 on application), with a bearing-life design target of L10h at least 40,000 hours. Our only third-party certification is ISO 9001:2015.
What is the lead time for a drying-fan pair?
A standard engineered drying fan runs roughly 9 to 14 weeks order-to-dispatch: offer in 3 to 5 working days, GA drawing 2 to 3 weeks from PO, manufacture, balance and paint 6 to 10 weeks, and performance test plus FAT 1 to 2 weeks. A hygienic all-stainless build with CIP provision, or an ATEX exhaust fan, adds file and finishing work and runs about 12 to 16 weeks. Supplying the supply and exhaust fans as a matched pair does not add time — we schedule them together.
