Effects of oblong-hole screen and round-hole screen on the performance of hammer mill

Hammer mills are widely used for grinding grain products. Screens are one of the important machine components that affect the performance of hammer mills. Generally, round-hole screens are used in hammer mills. In this study, the effects of oblong- and round-hole screens on hammer mill performance were investigated. The results showed that the mean geometric diameter, geometric standard deviation, specific surface area grinding capacity and specific energy consumption varied with the screen type, screen hole size and hammer tip speed. The particle size distribution with the oblong-hole screen was more stable, and its grinding capacity (1.481 t/h) was higher than that of the round-hole screen (1.220 t/h). The specific energy consumption of the oblong-hole screen was lower than that of the round-hole screen. The lowest specific energy consumption (2.805 kWh/t) was measured at a hammer tip speed of 60 m/s for the oblong-hole screen with a hole size of 19.8 x 2.5 mm.