Relationship Between Powder Flowability and Abrasive Discharge in an Industrial Metering Valve

Efficient abrasive blasting requires precise control of abrasive mass flow, which is governed by both the metering system design and the flow properties of the abrasive material. This study investigates the influence of particle size distribution on the flow behaviour of brown fused alumina during discharge through a commercially available Thomson TV II metering valve. Four abrasive fractions (F220, F80, F46 and F24) were characterized in terms of particle size distribution, bulk density, moisture content, angle of internal friction, and flow function. The discharge behaviour was experimentally evaluated using a custom-built test stand for four valve opening positions. The results showed that the smallest valve opening caused unstable flow conditions, arching, and complete flow blockage for the coarsest fraction, whereas stable and repeatable discharge was achieved for various valve openings. Although the finest fraction exhibited the highest flowability according to the flow function, it did not achieve the highest mass flow rate, indicating that flowability alone was insufficient to explain the observed discharge performance. Instead, the F80 fraction provided the highest discharge performance under all stable operating conditions. These findings indicate that laboratory flowability indices alone cannot reliably predict abrasive feeding performance and should be evaluated together with bulk density and particle size distribution. The results provide practical guidelines for optimizing abrasive metering systems and contribute to improved process stability, abrasive utilization, and operational efficiency in automated abrasive blasting applications.