Pneumatic conveying systems are widely used in a variety of industrial settings since different types of materials can be conveyed. There are some classifications of flow modes for conveying of powders and bulk solid particles based on mean particle size, density, and inter particle cohesion forces. In this paper, three different cases which are vertical (test case 1), horizontal (test case 2) and continuous conveying test case are constructed and considered in order to determine the flow modes in pneumatic conveying systems. Seven solid particles are used with the range of 200 kg/m3 < ρblp < 2400 kg/ m3 and 150 μm < dp < 2750 μm in these three cases. In vertical test set-up unstable zone and fluidized dense phase is occurred, then in the horizontal test set-up slug flow and plug flow is observed and lastly plug flow and dilute phase is occurred visually in continuous conveying test case. Finally, all obtained data are considered for the classification according to flow modes in pneumatic conveying systems. The observed flow modes are considered and tabulated with respect to all test cases.