Radial Tipped Centrifugal Fans

Blade geometry

Blade form	Radial at the tip, sloping toward rotation at the root
Exit blade angle	90°
Number of blades	6 to 12
Air leaving the impeller	Radially, at a velocity close to the blade tip speed. The blade shape guides the gas into the passage with lower entry loss than a straight radial blade.

Where it is used

• Mildly erosive gas such as flue gas with fly ash
• ID fan and process fan duties with light dust
• High pressure duties where a straight radial blade would cost too much power

Where the dust is heavy or sticky the straight radial type is chosen. Where the gas is clean the backward curved or aerofoil type gives lower power.

Applications selected with this blade

Application	What it does	Type usually selected
ID Fan	Sits at the outlet of a boiler, kiln or furnace and draws the flue gas through the plant to the stack. It handles hot, dust-laden gas at large volume, so it is sized at the hot condition and checked at cold start.	Backward curved, backward inclined and radial tipped
PA Fan	Supplies the air that dries the pulverised fuel in the mill and carries it to the burners. Runs at higher pressure than the FD fan because it must overcome the mill and the fuel piping.	Backward curved and radial tipped
Raw Mill Fan	Draws hot kiln gas through the raw mill and separator, drying the raw meal on the way and carrying the fine product to the collector. Heavy fine dust, so wear protection on the impeller is standard.	Backward curved and radial tipped
Cooler Vent Fan	Exhausts the surplus hot air from the clinker cooler after the secondary and tertiary air have been taken off, drawing it through the cooler dust collector.	Backward curved and radial tipped
Coal Mill Fan	Draws hot gas through the coal mill to dry and convey the pulverised coal to the burner or the fine coal bin. Built spark resistant because the gas carries combustible dust.	Backward curved and radial tipped
Bag Filter Fan	Pulls the process gas through the filter bags and discharges the cleaned gas to the stack. Works on the clean side, so the blade can be chosen for efficiency, with the filter pressure drop added to the duty.	Backward curved and radial tipped
Preheater Fan	Draws the kiln exhaust gas through the preheater cyclone stages. The largest fan in a cement line and the one that sets the kiln draft.	Backward curved and radial tipped
Cooler Compartment Fan	Blows ambient air up through the grate of the clinker cooler. Each compartment has its own fan set for the pressure that bed needs.	Backward curved and radial tipped
Air Slide Blower	Supplies low pressure aeration air to the fabric of an air slide, fluidising cement, raw meal or gypsum so it flows down the slide.	Backward curved and radial tipped
High Pressure Blower	Delivers combustion, aeration and conveying air where the system resistance runs to several thousand millimetres of water column in a single stage.	Backward curved and radial tipped
Combustion Air Blower	Feeds a burner with air at the pressure the burner register needs. Sized for the burner turndown range, and often fitted with an inlet silencer.	Backward curved and radial tipped
Cooler ID Fan	Draws the clinker cooler exhaust through the cooler dust collector to the stack, holding the cooler hood under a slight negative pressure.	Backward curved and radial tipped
Fume Exhaust System	Hoods, ducting and an exhaust fan that capture fume at source and deliver it to a scrubber, bag filter or stack. Fan material follows the fume: stainless steel, PP-FRP or rubber lined where it is corrosive.	Backward inclined and radial tipped
Dust Collector Fan	The fan behind a bag filter, cyclone or multiclone on a dust extraction system. Placed on the clean side where possible so the blade can be chosen for efficiency.	Backward inclined and radial tipped

Industries

Drive and construction

Offered direct mounted on the motor shaft, direct coupled, or belt driven. Material of construction follows the medium and temperature: mild steel, stainless steel, PP-FRP lined, MS FRP lined or MS rubber lined.

Testing and balancing

Performance tested as per IS 4894, BS 848 Part I, or as per customer standards. Rotors are statically and dynamically balanced to grade G 6.3 or G 2.5 as per ISO 21940-11.

Information needed to select or quote

1. Duty point. Volume flow and static pressure at the fan inlet, with the gas density and temperature or the conditions to derive it.
2. Operating conditions. Site altitude, normal operating temperature and continuous or intermittent duty.
3. Gas stream. Dust loading and particle size, corrosive species, moisture, upset temperature and any tendency of the material to deposit on the impeller.
4. Mechanical. Rotation viewed from the drive end, discharge orientation and motor power.