The process
Withering troughs blow a large volume of ambient or warmed air through green leaf for hours. The trough fan is an axial fan at low pressure, often with a hot air mixer, run for long hours and cleaned often.
The gas at the fan
Warm, humid air through withering troughs and dryers with light leaf dust. Large volume at low pressure; the fan is cleaned often, so access matters.
Selection for this duty
| Blade form | Backward inclined or backward curved; the residual dust does not justify a radial wheel |
| Material of construction | Stainless steel wetted parts, with drains in the casing and a shaft seal |
| Drive and bearings | Direct coupled or belt driven; belt drive where the duty point may need tuning at site |
| Also specified | Casing drain at the lowest point |
| Density at the fan | At about 60°C the gas density is close to 1.06 kg/m³, 88% of standard air. Pressure developed and power drawn fall in the same ratio, so the selection is made at this density and the motor is checked at cold start. |
Moves air through a plant or building for fresh air supply, heat removal and fume dilution where the system is ducted. Low pressure, long hours, so efficiency and noise set the selection. Client-stated blade types for the Ventilation Fan in general: Backward inclined and forward curved.
Industries
Other fans in tea withering troughs
Ventilation Fan in other processes
Bagasse Fired BoilersRice Husk Fired BoilersAFBC BoilersCFBC BoilersPulverised Coal Fired BoilersOil and Gas Fired BoilersBiomass Fired BoilersCement Packing and DispatchElectric Arc Furnace SteelmakingInduction Furnace Melt ShopsHeat Treatment FurnacesForge ShopsAluminium Smelters and Cast HousesIron and Non-ferrous FoundriesGlass Forming and Annealing LehrsBrick and Refractory KilnsChemical Reactor and Tank VentsMVR EvaporatorsEffluent Treatment and Zero Liquid Discharge PlantsPharmaceutical Clean RoomsSolvent Recovery PlantsGas Compressor StationsBelt and Tray DryersTobacco Primary Processing
Services on this fan
Information needed to select or quote
- Duty point. Volume flow and static pressure at the fan inlet, with the gas density and temperature or the conditions to derive it.
- Operating conditions. Site altitude, normal operating temperature and continuous or intermittent duty.
- Gas stream. Dust loading and particle size, corrosive species, moisture, upset temperature and any tendency of the material to deposit on the impeller.
- Mechanical. Rotation viewed from the drive end, discharge orientation and motor power.