Duct reducers are used primarily to change the air speed inside the ducting of industrial dedusting systems. The exact shape and design directly influence the uniformity of air flow inside the ducting.
Group I – small load
Group II – regular load
Group III – heavy load
Duct reducers are used primarily to change the air speed inside the ducting from one of two basic reasons:
- Decrease of air speed in the ducting
Is often used to lower the pressure drop inside the extraction ducting. An example is the requirement of the production machines manufacturers to keep the intake suction speed at v = 30 m / s. We place the reducer directly behind the production machine socket and reduce the extraction air speed to the required v = 20 to 22 m / s. This allows us to optimize the ducting pressure drop.
- Increase of air speed in the ducting
This is used with extraction applications where the dedusting cannot result in undesirable suction of the product. The air speeds are set low on purpose to about 7 – 12 m/s, sometimes even lower (dependent on the product granulometry). The reducer is used to increase the speed to the desired v=20 až 22 m/s.
A still-flow places with a minimal airflow should not form in the reduction or in the ducting in front or after the reducer – the extracted dust could form sediments. The Gidly company offers reducers with an angle of 30°.
On the flow visualizations, there can be seen points with a slower air flow (blue paths) in the sharp reducer. The sedimentation of the extracted dust will occur in this place and that is an undesirable phenomenon in the industrial air extraction. The accumulated dust sediments in the ductings are often causes of baghouse ducting burnings. The correct flow is displayed at the reducer branch. The regular flat reducers are not even mentioned, although they are very often seen in air extraction systems in practice. We consider direct flat reducers as absolutely inappropriate.
The reducers change the extraction air speed, this is accompanied with an undesired phenomenon – abrasion from the extracted material – especially with reducers inducing an increase of air speed. When selecting a reducer (SK I, SK II, SK III) proceed similarly as with branches and wyes.
We have prepared a basic chart for the use of reducers – depending on the extracted dust – by giving examples of the use of different groups for different applications.
|EXAMPLE OF USING A REDUCER IN INDUSTRIAL AIR EXTRACTION|
|BRANCH TYPE||TRANSPORTED AIR PROPERITIES||EXAMPLE OF USE|
|Group I||Minimum of particles
|Welding shops dedusting
|Group II||Medium amount of particles
Coal processing plants
|Group III||Large amount of particles
Offered reducer variants
|Input dimensions||DN 80 to DN 1250|
|Output dimensions||DN 80 to DN 1250|
|Branch dimension||DN 80 to DN 1250|
|Material width||0,5mm – 1mm plumber work – galvanized,
1,5mm, 2,0 mm, 3,0 mm welded
Material design – welded reducers
EN 11 – Sheet metal 11375 with selectable surface finish
EN 17 – Stainless steel 1.4301 for use in food industry
EN 17 – Stainless steel 1.4404 with increased chemical resistance
EN 17 – Stainless steel with increased chemical and thermal resistance
Surface finish for EN 11 – 11375
Powder coated RAL1015 (ivory)
Powder coated RAL5010 (blue)
Powder coated RAL9001 (cream white)
Powder coated RAL9005 (black)
Powder coated RAL9006 (silver – aluminium)