Chipper Performance Improved Through Analysis of Critical Angles, 1997 Pulping Conference Proceedings

Chipper parameters critical to the production of quality chips include spout angle, knife edge angle, Lambda angle, knife speed, and chip length setting. The uniformity of chip size and the percentages of each chip size fraction produced by a chipper are keys to pulping performance. Pulp production, pulp strength and pulp quality are directly tied to chip size and chip quality. Reducing the chipper spout angle to 35° had the benefit of reducing overthick (+8 mm) in pine and oak log pilot plant tests, and of shifting the proportion of small accepts (+7 m round hole, -4 mm thick) into large accepts (+4 mm thick, -8 m thick. Reducing knife speed reduced the amount of pin chips produced (-7 mm round hole, +3 mm round hole), regardless of chipper spout angle. Over-size (+45 mm round hole) and fines (-3 mm round hole) were poor indicators of chipper performance, as they were strongly affected by log characteristics. Field performance of a chipper configured with a 35° spout and optimized hardware angles produced hardwood chip quality similar to pilot plant trials...