7 General Observations
The mode of operation within the OLDS elevator would appear to be inherently gentle on the product conveyed. The mechanics of operation dictate that particle elevation is caused by the propagation of shear stress from the wall of the shroud to the bulk material and essentially rolls/drags the bulk material along the flight surface. As a result of this the bulk material will be in a state of low consolidation stress, much lower than for a screw conveyor/feeder/elevator where the bulk material is forced to shear against the wall. This has a significant advantage for the feeding of compressible and cohesive materials which should result in the material not forming clumps as readily as would be seen with a screw feeder. This will directly improve the process and hopefully negate the need for active or passive methods for breaking the clumps before being discharged into the gas stream.
The transport efficiency as determined from the experimental data would appear to be very high. For each tube rotation the material is elevated approximately 0.75 of the flight pitch, Ve=0.75 which seems to support the results presented by Bates [1].