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, noise breaking out from within the pipework was dominant.
This is characterised by the noise being predominantly high frequency and frequently occurs in thin walled pipes.
The solution in this instance was to thermally lag the pipes with a conventional system consisting of a 30 to 50mm mineral wool jacket and a 1mm thick aluminium outer skin.
Noise was reduced by over 15dB.
Cost for this type of lagging is around £12 per m2 supply only.