This paper describes an industrial on-line wall friction tester developed at The Wolfson Centre to assess coal handleability, sponsored by BCURA and Corus UK. The flow properties of coal are known to be extremely variable, due to large changes in the moisture content, particle size distribution and chemical composition that can occur through a single batch. In this environment traditional powder flow measurements such as shear cells, which are time-consuming and test only a small sample of a few hundred cubic centimetres of material, are of little use in predicting changes in flow behaviour through a batch of coal. This paper reports on the experiences of trialling a prototype on-line wall friction tester at a power station and a steel works. In both trials the tester was located on a coal transfer belt from the stockpile to the first processing step and was utilised as an early warning device to detect changes in the wall friction of the coal that might indicate potential flow problems. During the trials, samples of the coal were taken from the conveyor and these were tested later in the laboratory on a Jenike wall friction tester and compared to the on-line measurements. A reasonable agreement was obtained between the two testers.