Noise from pellets passing rapidly through transfer pipes and also moving within cyclones often create levels of noise. Typically the noise is due to the internal "scratching" noise breaking out through the pipe walls, but also to the resonant ringing of the pipes.
In this example, analysis showed that the resonant ringing part was dominant.
The pipes and cyclones were covered with a self-adhesive pitch-based damping sheet to eliminate the ringing.
Note that the process is not one of insulation - it is damping down pipe ringing. This treatment is not particularly sensitive to installation quality and 100% coverage is not required.
Pipes prone to ringing are usually circular, thick walled and often welded.
Noise was reduced by at least 6dB.
Cost for self-adhesive damping sheet is around £12 per m2 supply only.