Observations on and the modelling of erosive wear of a long-radius pneumatic conveyor bend

This paper describes the results of an experimental investigation of the erosive wear, and puncture, of a long-radius bend in a pneumatic conveyor when used to convey abrasive particles. Measurements were taken of (a) the local air pressure in the pipe bore (used to obtain values of the local superficial air velocity), (b) the mass of abrasive particles flowing through the pipe with time, (c) the reduction in the thickness of the bend wall and (d) the particle concentration distribution using a simple optical obscuration technique. From analysis of the results it was deduced that an accumulation of the particles against the outside bend wall, and the shape of the pipe bore itself, caused the particles to rebound back towards the pipe bore centre-line after primary impact. This behaviour caused an intensification of particle impacts in the region where secondary impacts predominate, and this is where puncture was found to occur. A simple empirical model is proposed for the prediction of the bend wear life. This is based upon an analogy between the particle dynamics in the bend and the optical aberration of a cylindrical mirror of similar dimensions to the pipe bore.