A combustion air fan is part of the burner safety chain. It interfaces with the Burner Management System, it must hold its operating point through ignition, flame establishment and steady load, and a fan trip ripples through every safety interlock downstream. We build combustion-air fans across oil & gas, petrochemical and process plants — often to API 673 because that is what the EPC tender specifies.
An FD fan supplies bulk combustion air to a boiler train against load demand. A combustion-air fan is dedicated to one burner, fired heater or process oven — often one fan per burner, often inside the burner OEM's control package — and the duty is defined by the BMS it answers to.
Flow to the BMS before light-off — a start permissive and flow-proven contact, with a low-air-flow trip at typically −10 to −20% of rated flow wired to the burner shutdown.
The operating point through the ignition transient — the fan must not surge or stall as burner light-off changes the downstream resistance against 200–1,200 mmWC system rise.
Continuously at one point — often binary on/off control rather than modulating turndown — for L10h ≥ 40,000 h on unmanned refinery and gas-turbine packages.
Clean air is the easy part. What separates a combustion-air fan from a generic blower is what happens at light-off, on a flow-proving fault, and inside a hazardous-area envelope. Design for those, and the fan holds the burner online; design only for the duty point, and it nuisance-trips the BMS or stalls in the first ignition swing.
At light-off the burner resistance shifts fast. A curve sized too close to its peak lets the operating point cross into stall — flow collapses and the BMS trips the burner mid-start.
How we engineer it outThe curve is sized to operate well to the right of the peak so ignition-transient flow swings stay on the stable branch — documented on the curve we issue.
A mis-set or mis-located differential-pressure tapping gives a false low-air-flow signal — a nuisance trip that takes the heater offline — or worse, masks a genuine low-flow condition.
How we engineer it outAirflow proving by DP switch across the fan or in the discharge duct, plus a second DP switch at a lower setpoint on the trip line — both wired to the BMS start permissive and shutdown.
In refinery and petrochem service the fan sits inside a Zone 2 envelope — any rub spark, static discharge or non-Ex motor is a potential ignition source.
How we engineer it outAluminium impeller, bronze rub rings, bonded earthing, anti-static coatings and an Ex-rated motor (Ex e / Ex nA), to ATEX Zone 2 self-declared per 2014/34/EU.
We don't sell a catalogue near-fit. The fan is engineered to your duty point, your inlet-air condition and the burner OEM's BMS interface.
No catalogue fan forced onto your spec. Your operating point is engineered to the right of the wheel's peak so ignition-transient swings stay stable — then verified on the 200 HP VFD test rig to the AMCA 210 / ISO 5801 method before dispatch.
| Parameter | Standard | On application |
|---|---|---|
| Volume flow | 5,000–80,000 CMH typical | up to 1,50,000 CMH on application |
| Static pressure | 200–1,200 mmWC | up to 1,800 mmWC for high-resistance burner trains |
| Inlet air temperature | ambient to 350 °C (APH-preheated) | higher with special metallurgy on enquiry |
| Drive power | up to 200 HP | up to 400 HP with custom motor sourcing |
| Sound | <85 dB(A) @ 1 m | <80 dB(A) on application |
| Speed | 600–1,800 RPM typical | per duty + sound limits |
| Balance quality | ISO 21940 G6.3 | G2.5 / G1.0 on application |
| Bearing life (design target) | L10h ≥ 40,000 h continuous | longer L10 on application |
The envelope above covers the great majority of combustion-air-fan duty. For duty beyond it, we engineer to spec and quote on enquiry. API 673 is the default documentation envelope on refinery / petrochem duty; ATEX Zone 2 self-declared where the area classification calls for it, Zone 1 via a Notified Body on application.
The same engineering language carries from your enquiry to the GA drawing to the nameplate — expressed in the standard AMCA conventions.
| 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) — selected by drive, burner-train access and inlet-air temperature. |
| Width / inlet | SWSI (single width, single inlet) default for dedicated combustion-air duty; DWDI (double width, double inlet) for high flow at moderate pressure. |
| Wheel type | Backward-curved (default, best efficiency) / airfoil-bladed (highest efficiency, clean air) — single-stage, since combustion-air pressure rise is moderate. |
| 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. |
| Materials of construction | MS + epoxy (ambient air) / SS for humid coastal sites or APH-preheated air to 350 °C / aluminium impeller with bronze rub rings and anti-static coatings for ATEX Zone 2 refinery and petrochem service. |
| Drive | Direct-coupled / V-belt / VFD. Often binary on/off control on a fixed duty point. Drive up to 200 HP standard (400 HP with custom motor sourcing); speed typically 600-1,800 RPM. |
| BMS interface scope | Airflow proving DP switch (start permissive) / current-sensing fan-running relay / second DP switch on the low-air trip / inlet temperature transmitter where APH-preheated. Supplied loose for site-wiring into the burner OEM panel, or pre-wired on a junction box on application. |
| 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 the burner take-off and installed footprint. |
Every job's performance is verified at our works on the 200 HP VFD test rig, to the AMCA 210 / ISO 5801 method, before dispatch.
Refinery fired-heater combustion-air fans, gas-turbine inlet air for small turbines, well-pad fired equipment.
Process-heater combustion air, reformer and cracker burner trains, RTO / RCO burner supply.
Gas-fired peaking plants and smaller boilers without separate PA / FD fans.
Dryer and kiln burner-train combustion air on captive fired equipment.
Kiln and furnace burner combustion-air supply on fired lines.
Furnace and forehearth burner combustion air on fired melting lines.
Captive fired heaters and process-oven burner trains across fired duty.
45 application/duty types engineered. Tell us yours.
What our marks mean, in the words that survive an audit.
Tested to the AMCA 210 / ISO 5801 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 (Module A). 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 20816 evaluation; ISO 14694 for fan-specific limits.
| Stage | Standard duty | API-673 / engineered |
|---|---|---|
| Offer / quotation | 3 working days — always | 7–10 working days |
| GA drawing for approval | 2–3 weeks from PO | 3–4 weeks from PO |
| Manufacture + balance + paint | 6–10 weeks | 10–14 weeks |
| Performance test + witnessed FAT | ~1 week | 1–2 weeks |
| Order-to-dispatch (total) | 9–14 weeks | 14–20 weeks |
Shutdown-driven replacements: we have shipped fans within 6 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.
No model numbers needed. Give us the operating conditions — flow, static, gas temperature, composition, particulate, and any tender standard — and our application engineers size the fan and quote it. Attach a spec or GA if you have one.
+91 90110 09155 · mihir.jitamitra@gmail.com