Effects of selected factors on sawmill residue wood chip quality

This study examined the effects of disk speed, temperature and anvil condition on chip size from sawmill residues of Loblolly pine (Pinus taeda L.). Objectives were: 1) to document the effects of disk speed, temperature and anvil condition on the amount of over thick, oversize, accept, pin and fine chips produced from edgings, 6"x6" cants and trim blocks and 2) to recommend changes in processing sawmill residues to minimize the production of over thick, pin and fine chips. Ten trials were conducted at the Chesapeake Corporation's West Point, Virginia hardwood sawmill using a Fulghum Industries 60-in. (152-cm) diameter, six-knife, vertical disk chipper.

Tests were conducted at approximately 80, 70, 60, 50 and 40% of the full disk speed of 707 rpm for the three material types. It was found that decreasing disk speed decreases the amount of pin and fine chips and increases the amount of over thick chips for all material types. The maximum amount of accept and oversize chips was obtained at 50% disk speed. If 50% efficient secondary processing of the over thick chips is achieved, the maximum amount of oversize and accept chips would be produced at 40% disk speed.

All frozen and chilled residue types tended to produce less oversize chips and significantly more pins and fines than wood at ambient temperature.

A worn anvil caused a significant increase in pins and fines while causing a significant decrease in oversize chips from the cants.

Design changes are suggested to reduce the amount of over thick chips produced by vertical disk chippers.