Cyclone separators
The Problem
A company manufacturing PVC granules moves the product using pneumatic transport systems terminating in a cyclone separator. The arrangement is typical of the transport systems commonly found in industry. Within each cyclone, the air exhausts through a perforated steel tube. This acts as a sieve, avoiding the small plastic wastage that would otherwise occur. The cyclones were producing a very shrill, penetrating whistle (at 497 Hz). This dominated the entire production area. As well as being extremely annoying, the whistle produced a sound pressure level of 110dB.
The Solution
- It was diagnosed that the whistle was generated by a flow-induced acoustic resonance. This was confirmed by inserting a 10 inch square piece of cardboard into the cyclone. The cardboard broke up the aerodynamic resonance and totally eliminated the whistle, a reduction of 50dB (see figure below).
- The production version of the solution comprised a steel plate fixed inside each cyclone.
- The geometry of each plate was carefully "tuned" to provide maximum performance, matching that of the prototype.
The Results
The overall noise fell by 25dB.
Cyclone separators noise reduction graph
![Cyclone separators noise reduction graph](../assets/images/casestudy041g.jpg)
The Costs
Each steel plate cost less than £1.
Information supplied by
Industrial Noise and Vibration Centre Ltd.