Solid particle erosion caused by rice grains

The processing of rice involves many tribological processes as the husk is removed and the rice is polished to remove the outer bran layer for a white appearance and it is finally sorted to remove broken or discoloured grains. As a result many wear issues can arise in the equipment used during the different stages of the procedure. This work centred on the anodised aluminium chute used in a rice sorting machine. The purpose of the chute is to separate the grains and provide a controlled distribution. Rice grains drop onto the chute and slide down. At the bottom of the chute the grains are examined optically and contaminants or defective grains are removed from the stream by jets of air. In a previous study [1] a failure analysis was carried out on a chute that indicated the main wear mechanisms occurring on the chute were erosion and abrasion. Tests were carried out to study friction and sliding wear behaviour of rice grains against untreated aluminium and aluminium with a variety of surface treatments and the performances were ranked. In the work described in this paper testing was moved on to study the erosive wear performance of the same materials. A new test set-up was developed to fire rice particles at a counterface surface. Tests were carried out at different angles and impact velocities. High speed video filming was used to accurately determine impact velocities and analyse the rice grain behaviour on impact with the counterface. (C) 2009 Elsevier B.V. All rights reserved.