This article advances ideas and presents experiments on the flow characteristics of concentrated emulsions of Venezuelan bitumen in water plus surfactant. These emulsions are studied under a variety of flow conditions, namely, between rotating cylinders, in a colloid mill, and in pipes. The ideas advanced here concern the modeling of the highly viscous bitumen drops as solid spheres and their fracture under contact forces between neighboring drops, as in comminution, rather than break-up by hydrodynamic forces. Further, we observe and discuss the local inversion of an emulsion due to local increases of the bitumen fraction induced by flow and the conditions that lead to slip flow, in which the drag is reduced by the formation of a lubricating layer of water at the wall. We believe that the results presented here unveil mechanisms that take place in the pumping and pipelining of oil-in-water emulsions and therefore contribute to the understanding of the dynamic stability of these systems.