Researchers investigated chipper knife wear on the efficiency of biomass processing.A long-term study investigated chipper knife wear at a waste wood recycling facility. A Biber 70, trailer-mounted, tractor-driven drum chipper was used. A 150 kW (204 hp) tractor was the power source for the chipper. The chipper had an 860 mm (33.9 in) steel drum. The drum length was divided into six sections, with each carrying two knives in opposite positions. Each knife carries out one cut for a full rotation of the drum. The staggered knife design is suitable for large logs and results in less knife damage. The chipper was used to process wood residues from nearby sawmills. The residues consisted of slabs with a length of between one and four metres. The main species were pine, spruce, fir, poplar and aspen. The moisture content of the material during chipping varied between 18 and 40% on a wet basis. During use, knives are usually wet sharpened after removal from the chipper. However, they can also be sharpened with a portable angle grinder without removing them from the chipper (dry sharpening).
When rotating knives (as is normal practiced), the average knife lasted 1,176 scheduled machine hours, and was sharpened 49 times. The anvil was expected to last 60% longer than the knives. The results showed that knife wear resulted in a productivity drop of more than 20%, and also reduced chip quality. Dry sharpening helped to reduce these productivity losses, but did not have the same effect as wet sharpening. Increasing the frequency of wet sharpening increased chipper knife costs, but this additional cost was offset by the increased productivity and product quality. Therefore, more frequent wet sharpening must take place.
This research was titled “Managing chipper knife wear to increase chip quality and reduce cost”, and was published in Biomass and Bioenergy, Vol. 62 (2014). The authors were R Spinelli, S Glushkov and I Markov. Source: http://www.sciencedirect.com/science/article/pii/S0961953414000087