The wood dust used as an eroded material came from a dust extractor situated in a loading point of white wood pellet. The particle solid density was 443 kg/m3 measured by a gas pycnometer. Particle size was analyzed before erosion test by the Laser diffraction method (Malvern Mastersizer), giving a median size of 45 ไมโครm (see Fig. 4). Hardness of the wood pellets from which the dust was extracted was about 2.0 on a Mohs Scale measurement, which in principle should not cause wear on a steel pipeline; however, evidence from several sites was that wood dust punctured thin walled steel bends in extraction pipelines regularly. The reason for its apparently much higher evasiveness than the ‘‘Moh’’ hardness would suggest was conjectured to be the inclusion of harder mineral traces from the growth or forestry processes. A single batch of approx. 1.3 m3 was used.