1. Introduction
Pneumatic conveying of cork stoppers has been used in some steps of the cork industry, where the basic approach for the design of the conveying systems is purely empirical, and the technical and scientific data on such matter is scarce. There were however some studies on the horizontal conveying of cork stoppers, Neto and Pinho (1998), Pinho (1999) and Pinho (2001). Afterwards, the work moved towards the study of steady state vertical conveying, Barbosa and Pinho (2004), while in the present paper results on the transient acceleration regime in vertical pneumatic transportation are presented and discussed.