Extended-casing belt driven axial fans for direct insertion into boiler flues, furnace stacks, drying chamber ducts, and process duct systems requiring the fan to be located within the duct wall thickness. Motor outside extended casing. IS 3588 compliant manufacturer from Mumbai, India.
Belt Driven Long Shell Axial Fan — Manufacturer & Supplier, India
Vayuvents manufactures Belt Driven Long Shell Axial Fans with extended casing for direct boiler flue, furnace stack, and duct insertion service. Motor outside airstream, IS 3588 compliant. Mumbai manufacturer.
A Belt Driven Long Shell Axial Fan is a belt drive fan with an extended-length tubular casing — significantly longer than a standard tube axial fan casing. This extended shell allows the fan to be inserted directly into a boiler flue wall, furnace stack, or thick duct wall, with the fan impeller operating inside the duct and the motor bracket extending outside on the external face.
The long shell casing is particularly suited to retrofit fan insertion into existing boiler induced-draft (ID) and forced-draft (FD) duct systems where the original natural draft is insufficient and a fan must be added without major duct modification. The fan casing is fabricated to match the existing duct bore and inserted through a matching circular penetration.
Vayuvents fabricates long shell axial fans to order — the shell length, diameter, and impeller position are specified by the customer to match the specific duct wall thickness and penetration geometry. Both MS (up to 150°C) and high-temperature alloy (up to 300°C) shell construction are available for boiler and furnace flue service.
Applications include induced-draft ID fan duty on small package boilers, forced-draft FD duty on furnaces and kilns, and induced-draft duty on thermic fluid heaters where a compact retrofit fan is preferred over a large external centrifugal fan.
Key Features & Benefits
Extended Shell Length
Long tubular casing accommodates thick boiler flue walls, furnace brickwork penetrations, and duct wall insertions where standard tube fans are too short.
Motor Outside Shell
Motor bracket extended beyond the shell end — completely outside the hot duct environment regardless of shell length or duct wall thickness.
High Temperature Shell
MS shell rated to 150°C; high-temperature alloy shell for 150°C to 300°C boiler flue and furnace stack service.
Custom Shell Dimensions
Shell length, diameter, and impeller position custom-fabricated to customer specification — matches any existing duct penetration geometry.
Speed via Pulley Ratio
Belt drive speed adjustment — optimise fan airflow for the specific boiler or furnace draught requirement without changing motor.
Heavy-Gauge Construction
Heavier gauge MS shell withstands the thermal cycling, vibration, and thermal expansion stress of boiler and furnace flue service.
Retrofit Installation
Designed for retrofit insertion into existing duct — no major ductwork modification required for boiler draught improvement projects.
IS 3588 Compliant
Tested per IS 3588-1987. Performance certificate supplied confirming airflow and pressure at operating point.
Technical Specifications
| Parameter | Specification |
|---|---|
| Fan Diameter Range | 305 mm to 1,220 mm |
| Shell Length | Custom — per duct wall thickness (standard 400 mm to 1,200 mm) |
| Airflow (Free Air) | 2,300 m³/hr to 69,000 m³/hr |
| Motor Power Range | 0.25 HP to 10 HP |
| Drive Type | V-belt and pulley, motor on external shell bracket |
| Shell Material | MS / High-Temp Alloy |
| Impeller Material | Aluminium / High-Temp Alloy |
| Airstream Temp | Up to 150°C (MS) | Up to 300°C (high-temp) |
| Motor Enclosure | IP55 TEFC |
| Standards | IS 3588-1987 | IS 4894 |
Airflow Performance — Model Range
Free air delivery (m³/hr) at increasing static pressure (mm WG), across the full model range.
| Sr | Model | Dia (mm) | Motor (HP/Pole) | RPM | Free Air (m³/hr) | @10 mmWG | @15 mmWG | @20 mmWG | @25 mmWG | @30 mmWG |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | BD-75-28-120 | 305 | 0.75/2P | 2800 | 2,300 | 2,000 | 1,750 | 1,400 | - | - |
| 2 | BD-50-14-180 | 460 | 0.50/4P | 1440 | 6,750 | 5,500 | 4,400 | - | - | - |
| 3 | BD-100-28-180 | 460 | 1.0/2P | 2880 | 9,000 | 7,500 | 6,200 | - | - | - |
| 4 | BD-100-14-240 | 612 | 1.0/4P | 1440 | 12,000 | 11,000 | 10,900 | 9,500 | - | - |
| 5 | BD-200-28-240 | 612 | 2.0/2P | 2800 | 15,500 | 13,600 | 13,000 | 11,300 | - | - |
| 6 | BD-150-14-280 | 712 | 1.5/4P | 1440 | 17,500 | 15,000 | 13,900 | 12,500 | 11,800 | 10,000 |
| 7 | BD-300-28-280 | 712 | 3.0/2P | 2880 | 20,000 | 18,500 | 16,900 | 16,000 | 15,000 | 14,500 |
| 8 | BD-300-96-360 | 915 | 3.0/6P | 960 | 45,000 | 42,000 | 39,000 | 37,000 | 34,000 | - |
| 9 | BD-500-14-360 | 915 | 5.0/4P | 1440 | 40,000 | - | - | 38,000 | 35,000 | 32,000 |
| 10 | BD-500-96-400 | 1015 | 5.0/6P | 960 | 48,000 | 45,000 | 43,000 | 42,000 | - | - |
| 11 | BD-750-14-400 | 1015 | 7.5/4P | 1440 | 55,000 | 49,000 | 47,000 | - | - | - |
| 12 | BD-750-96-480 | 1220 | 7.5/6P | 960 | 65,000 | - | 58,000 | 55,000 | 34,500 | 30,500 |
| 13 | BD-100-960-480 | 1220 | 10/6P | 960 | 69,000 | - | - | 65,000 | 61,500 | 60,000 |
| 14 | BD-150-960-600 | 1530 | 15/6P | 960 | 75,000 | - | - | - | - | 80,000 |
| 15 | BD-300-14-600 | 1530 | 30/4P | 1440 | 95,000 | - | - | - | - | - |
| 16 | BD-300-96-720 | 1830 | 30/6P | 960 | 1,20,000 | - | - | - | - | - |
| 17 | BD-500-14-720 | 1830 | 50/4P | 1440 | 1,50,000 | - | - | - | - | - |
Fan speed independently adjustable via pulley ratio — airflow customisable without changing motor. Fan selection based on air at 20°C, density 1.2 kg/m³. Performance and tolerance as per IS 3588-1987. Custom sizes and intermediate performance points available on request.
Product Images
Where It Is Used
BOILER & FURNACE DRAUGHT
- Boiler ID Fan Retrofit: Induced-draft fan retrofit for package and fire-tube boilers.
- Boiler FD Fan: Forced-draft combustion air supply for small steam boilers.
- Thermic Fluid Heaters: Induced-draft fan for textile, plywood, and process industry heaters.
- Furnace Draught Fan: Heat treatment and forging furnace draught improvement.
- Kiln Exhaust: Induced-draft fan for ceramic and brick kiln draught improvement.
- Biomass Boilers: Induced-draft fan for rice husk and wood chip boilers.
PROCESS DUCT & DRYER SYSTEMS
- Dryer Exhaust: Direct insertion into drying chamber exhaust duct.
- Chemical Reactor Vent: Direct insertion into reactor vent duct.
- Incinerator Draft: Combustion draught fan for medical waste incinerators.
- Agricultural Dryers: Exhaust duct fan for grain and crop drying systems.
- Marine Boiler Draught: Auxiliary forced draught fan for ship boilers.
- Oven Exhaust: Direct insertion into industrial oven exhaust duct.
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FAQs — Belt Driven Long Shell Axial Fan
The key advantage is that the motor is mounted outside the airstream on a separate bracket. This means the motor never contacts the hot, corrosive, or dust-laden air being handled — dramatically extending motor life in paint shop, chemical plant, high-temperature, and dusty process service where direct-drive motors would overheat or corrode rapidly. Belt drive also allows the fan speed to be set independently of the motor speed by changing pulley diameters.
With the motor outside the airstream and a suitable impeller and casing material, belt driven axial fans handle airstream temperatures up to 300°C continuously. Standard MS impeller and casing are suitable up to 150°C. For 150°C to 300°C, high-temperature alloy impeller and casing with high-temperature grease bearings are used. Above 300°C, centrifugal fans with water-cooled bearings are typically preferred.
Fan speed is adjusted by changing the pulley diameter ratio between the motor pulley and the fan shaft pulley. A larger motor pulley or smaller fan pulley increases fan speed; a smaller motor pulley or larger fan pulley decreases it. Vayuvents supplies fans with the pulley ratio pre-set for the required operating point, and can supply alternative pulleys for field speed adjustment if the airflow requirement changes after installation.
For chemical fume exhaust service, Vayuvents supplies: (1) FRP (fibre-reinforced plastic) impeller and casing for acid fumes, HCl, H2SO4, and general chemical exhaust; (2) PP (polypropylene) impeller for moderate chemical service; (3) SS304 or SS316L impeller and casing for food, pharmaceutical, and moderately corrosive service. The motor remains outside the corrosive airstream regardless of impeller material.
Yes. For Zone 1 and Zone 2 hazardous classified areas, Vayuvents supplies belt driven fans with IS 5572 / ATEX flameproof Ex-d motors and non-sparking aluminium or GRP impellers. The belt drive configuration is advantageous in hazardous areas because it allows the motor to be positioned outside the hazardous zone boundary in some installations, reducing the motor certification requirement.
Belt driven fans require: (1) V-belt tension check every 3 months — a slack belt slips and reduces fan speed, a tight belt overloads motor bearings; (2) V-belt replacement every 12 to 18 months under normal service; (3) fan shaft bearing lubrication every 6 months for re-greasable bearings; (4) impeller cleaning every 3 to 6 months to prevent imbalance from dust accumulation. Belt drive adds modest maintenance compared to direct drive but provides substantial benefits in high-temperature and chemical service.
Contact Vayuvents at enquiry@vayuvents.com or call +91 90961 88703. Share the airstream temperature, chemical composition if corrosive, required airflow in m³/hr, static pressure in mmWG, and any special requirements (flameproof, high-temperature, corrosion-resistant). We will provide a technical selection and commercial proposal within 24 hours.