The Backward-Curved (BC) wheel is the everyday workhorse for moderate-pressure air handling: solid blades that curve away from rotation, giving high efficiency and a power curve that cannot overload the motor. It tolerates light dust — one step more rugged than a hollow aerofoil, one step more efficient than a plate or radial wheel. We build BC fans for forced-draft, primary and secondary air, bag-filter draught, dilute conveying, drying and combustion-air duty — each one engineered to its operating point, across the envelope below.
A sample of units we've engineered, built and dispatched — each to a customer's duty point. Customer names and identifying marks are withheld. Click any photo to enlarge.
In a Backward-Curved fan the solid plate blades curve backward, away from the direction the wheel spins. That single geometric choice sets its whole character: air leaves the blade tip with less turbulence, so more motor power becomes useful pressure, and the power demand peaks then falls instead of climbing without limit. It is the efficient, self-protecting, general-purpose centrifugal wheel.
The backward-leaning blade sheds air cleanly — peak static efficiency second only to the Aerofoil in our range, so a given duty is met on the least motor power.
Power is non-overloading — it rises with flow, peaks, then falls. If the duct resistance drops and flow runs out, the motor cannot be driven into overload.
The solid plate blade is tougher than a hollow aerofoil, so it carries light particulate — general industrial air, not just filtered HVAC air.
The Backward-Curved fan is picked for efficiency, drive safety and light-dust capability. Push it past any of the three and a different family is the honest answer. We size to where the BC wheel is genuinely strong — and tell you when to step up to the Backward-Curved Plate family, the Radial-Tip family or the Radial family — rather than overselling one wheel into every duty.
A fan running thousands of hours a year is mostly an electricity bill. An over-sized or low-efficiency wheel wastes power every hour and can sit in stall.
How we engineer it outThe backward-curved blade delivers one of the highest peak static efficiencies in our range; we select the wheel near its best-efficiency point on the duty, not the nearest oversized box.
If the real system resistance is lower than calculated, flow runs out and a forward-curved or radial wheel can pull the motor past its rating.
How we engineer it outThe backward characteristic is non-overloading — power peaks then falls — so the motor stays protected even when the duct opens up.
Once dust rises beyond a light loading, the airstream starts to erode a high-efficiency blade and shorten wheel life — efficiency is no longer the right thing to optimise.
How we engineer it outWe hold BC to its light-dust gate and move heavier or abrasive dust to the Radial-Tip family (built for high dust) or the wear-plated Radial family (the toughest in the range) — the right wheel for the wear mode.
We don't sell a catalogue near-fit. The BC fan is engineered to your flow, pressure, temperature, dust load and gas — then specified in plain construction terms on the drawing.
No catalogue fan forced onto your spec. Your operating point is engineered onto the stable, best-efficiency region of the selected BC wheel — well clear of stall — then verified on the 200 HP VFD test rig to the IS 4894 / ISO 5801 / AMCA 210 method before dispatch.
| Parameter | Standard | On application |
|---|---|---|
| Volume flow | up to 2,25,000 CMH | higher on enquiry |
| Static pressure | up to ~800 mmWC | to 2,000 mmWC envelope with the higher-pressure Backward-Curved Plate family |
| Continuous gas / air temperature | 10–350 °C typical | to 500 °C with HT construction + shaft cooling |
| Inlet dust loading | clean to light dust | above the gate, step to the Radial-Tip or Radial family |
| Peak static efficiency | high — second only to the Aerofoil family (exact figures shared with your enquiry) | selected near best-efficiency point per duty |
| Drive power | up to 425 HP | higher with custom motor sourcing |
| Balance quality | ISO 21940 G6.3 | G2.5 on application |
| Bearing life (design target) | L10h ≥ 40,000 h continuous | longer L10 on application |
The BC wheel is job-proven across 1,337–100,000 CMH and 25–610 mmWC on real builds; the published ~800 mmWC ceiling is the engineering-validated structural figure, and flow / power to the canon envelope is engineered-to-order on enquiry. Once dust becomes more than a light loading, or where the duty needs higher pressure at a given size, the honest pick is the Backward-Curved Plate family or a Radial-family wheel — we will tell you which.
The same engineering language carries from your enquiry to the GA drawing to the nameplate — expressed in the standard AMCA conventions, with the BC family's own width, class, MOC and construction-suffix choices.
| Specification field | Options |
|---|---|
| Arrangement (AMCA 99) | Arr. 1 (overhung, fan bearings) / Arr. 4 (direct, motor on base) / Arr. 8 (overhung on common base) / Arr. 9 (overhung, motor side) / Arr. 10 (overhung, motor inside base) — plus plug/plenum (unhoused) for AHU and fan-array builds; selected by drive, access and temperature. |
| Width / inlet | SWSI (single width, single inlet) for higher pressure; DWDI (double width, double inlet) for high volume in a compact height. |
| Wheel type | Solid backward-curved plate blade — the efficient, non-overloading general-purpose wheel for clean to light-dust air. (The Aerofoil family for maximum efficiency on clean air; the Backward-Curved Plate family for higher pressure.) |
| Class (by pressure / outlet velocity) | Class I / II / III selected from the duty point on the pressure-vs-outlet-velocity limits; higher class = heavier construction for higher pressure and tip speed (welded build to ~110 m/s tip). |
| Materials of construction | MS (standard) / SS304 or SS316 (full or airstream-only) / FRP (F suffix) / Corten or duplex for corrosive air / wear-plated (WP) where light dust creeps toward the family's dust gate. |
| Construction suffix | HT (high-temperature build + shaft cooling disc above ~150 °C, to 500 °C) / SR (spark-resistant, AMCA 99 Type A/B/C, ATEX-ready) / F (FRP airstream) / WP (wear-plated) — added only as the duty requires. |
| Drive | Direct-coupled / V-belt / VFD with shaft-earthing ring. Drive up to 425 HP across the envelope; SWSI or DWDI to suit pressure-vs-volume. |
| Discharge & rotation (AMCA orientation) | Rotation CW or CCW (viewed from drive side) with discharge angle per AMCA — e.g. TH/BH/UB/DB — set to match your duct take-off and installed footprint. |
Every job's performance is verified at our works on the 200 HP VFD test rig, to the IS 4894 / ISO 5801 / AMCA 210 method, before dispatch.
Forced-draft, primary, secondary / overfire air; seal and cooling-air duty on package and cogen boilers.
Bag-filter and pulse-jet draught, clean-side filter fans for OEM dust-collection skids.
Coal-mill primary air, process and combustion air on the lightly-dusty side of the plant.
Spray, fluid-bed and flash drying; dilute pneumatic conveying of flour and powders.
Combustion / process-air blowers, drying and quench / tempering-air duty (SS / FRP for corrosive air).
Process drying, dilute conveying and clean-side draught — SR construction where the area is ATEX-classified.
Plant ventilation, combustion-air supply and light-dust process draught across mixed industrial duty.
10 application/duty types this family serves. Tell us yours.
What our marks mean, in the words that survive an audit.
Tested to the IS 4894 / ISO 5801 / AMCA 210 method, in-house on our 200 HP VFD rig. Tested-to-method — not AMCA-certified.
ISO 9001:2015 — third-party certified. Our only third-party certification.
Self-declared per 2006/42/EC + 2014/35/EU. A self-declaration, not a notified-body certificate.
Self-declared, Zone 2/22, Category 3, per 2014/34/EU, where the area classification calls for it.
Designed and built to API 673 as project-specific scope.
ASME Sec IX qualified welders + WPS for every joint.
ISO 21940 — G6.3 minimum, G2.5 / G1.0 on application.
ISO 14694 fan-specific limits; ISO 20816 general evaluation method.
| Stage | Standard duty | CE / ATEX / API / AMCA |
|---|---|---|
| Offer / quotation | 3 working days | 5 to 7 working days |
| GA drawing for approval | 3 days from customer PO | 5 to 7 days from customer PO |
| Manufacture + balance + paint | 2 to 3 weeks from PO + PI + approved GAD | 4 to 5 weeks from PO + PI + approved GAD |
| Performance test + witnessed FAT | ~1 week | ~1 week |
| Order-to-dispatch (total) | 4 to 6 weeks | 7 – 9 weeks |
Shutdown-driven replacements: we have shipped fans within 3 weeks of a clean PO. Tell us your shutdown window and we commit to a dated plan.
The same engineering, viewed three ways — by fan family, by duty, and by industry. Follow the cross-references.
Flow, static, gas temperature, application — or attach a spec, GA drawing or a multi-fan schedule. Engineer to engineer.
ISO 9001:2015 quality system · performance-tested to IS 4894 / ISO 5801 / AMCA 210 method · witnessed FAT on request, at no cost.
*For our standard range, additional days required for special projects
