An auxiliary fan can either be used attached to suitable ducting, ventilation tubing, pressure bulkhead or as a stand-alone fan, that is, ductless. In the latter case, when used in this mode, it is used as a jet fan. Jet fans are used in mine tunnel longitudinal ventilation, either free standing or attached to the ceiling, and usually include a nozzle to direct the air flow better. Their application in mining operations includes to boost pressure and to ventilate development ends. In industrial applications, they are used for tunnel ventilation, cooling of furnaces and ventilation of service tunnels.
A jet fan operates by discharging a jet of air into the area to be ventilated. They can be installed in an airway where there is a weak prevailing air stream, boosting the flow, in some cases to many times the magnitude of their own inlet volume. The connecting airway length can be 15m to over 100m long.
The reasons for a ductless, jet fan, system include that ducts could interfere with mining operations, that there are often restrictions to duct sizes and because of leakage due to damage, that ducts may have to be replaced frequently. Jet fans are also ideal for balancing flows in short interconnecting airways.
Axial flow jet fans designed with the following features:
- 406mm/4kW to 760mm/45kW
- Type IP 55, with Class H insulation, motors
- Cambered plate rotor blades
- Fitted with skids for manoeuvrability or lugs for ceiling installation
- Modular design ensures affordability
- 2.5 – 3 mm blade clearance
- Nozzle parameters calculated for maximum thrust
- Internals finished with corrosion resistant paint
- Externals finished to client-specified colour-scheme