ID Fan FAQ

An ID (induced draft) fan is a fan placed at the outlet side of a boiler, furnace, dryer or filter system. It pulls flue gas or process exhaust through the equipment and pushes it up the chimney, keeping the system at slightly negative pressure.

An FD (forced draft) fan pushes fresh air into a boiler or furnace. An ID fan pulls the gas out. Balanced-draft boilers use both, so the furnace stays just below atmospheric pressure.

In boilers and power plants, cement and steel plants, spray and fluid-bed dryers, pulp and paper mills, textile and food plants, galvanizing and asphalt plants, wastewater treatment and anywhere hot or dusty gas has to be drawn through filters and scrubbers.

Not quite. An exhaust fan usually moves clean, cool air for ventilation. An ID fan is a process fan: it handles hot, dusty or moist gas at higher pressure, so it needs stronger materials, a suitable blade shape and cooled bearings.

Most are centrifugal: backward-curved or airfoil blades for clean gas, radial or paddle blades for heavy dust. Axial fans are used for very large volumes at low pressure.

Both. AS Engineers designs and builds ID fans and centrifugal blowers in Ahmedabad, India, and publishes this knowledge hub so plant engineers can specify, run and maintain them better.

You need the gas flow (actual m³/hr at operating temperature), the total static pressure the fan must overcome, the gas temperature, the dust and moisture content, the altitude and the drive arrangement. Send what you know and our engineers will work out the rest.

Hot gas is lighter. The same fan produces less pressure on hot gas than on cold air, and the shaft, bearings and impeller materials must handle the temperature. We size the fan on your real operating conditions.

Radial or paddle blades are self-cleaning and wear-resistant, so they suit heavy dust, sticky or abrasive gas. Backward-curved blades are more efficient but better on clean to lightly dusty gas, usually after a dust collector.

Check that the fan is not over-sized, fit a variable frequency drive instead of damper control, keep the impeller clean and balanced, and reduce pressure loss in the ducts and filters. Our duty-point calculator shows what the power costs.

Most often dust build-up or wear on the impeller (imbalance), loose foundation bolts, worn bearings, misalignment or operating far from the design point. Balancing the impeller on site and checking the bearings usually solves it.

Check bearing temperature and vibration every shift, and inspect the impeller, liners and casing at each planned shutdown. Dusty duties need more frequent checks. Our maintenance guides have a practical checklist.

Use the quote form, call or WhatsApp us with your flow, pressure, temperature and gas details. An application engineer replies within one working day with a recommendation and price.

Yes. We repair, modify, upgrade or replace impellers, shafts, blades and housings of any make, and can measure and draw a fan on site if drawings are not available.

Yes. Our service team does on-site balancing, vibration and bearing checks, retrofits and supplies spares, so one team stands behind the fan for its whole life.

Our two units are in GIDC Vatva, Ahmedabad, Gujarat, India. We supply across India and export.