And the main advantage seems to be you can add as many bearings to the rotating part as you want and none of them can be contaminated by the product. Try that on the screw conveyor.,(reply>), Yes, this operates in a similar fashion to medical pumps in that by pushing the fluid externally through the pipes by essentially squeezing the liquid forward with pressure differences, the liquid inside does not go through a pump. This olds elevator also does not touch the contents inside with anything new from the outside.,(reply>), @Kevin Martin and the rotating cylinder has no limits on thickness, so it can be scaled up more.,(reply>), @jl3423l4jsdf That's fine for a very short conveyor, but once it gets longer the central rotating screw will start to whip. The faster it rotates, the shorter/stiffer it has to be to avoid this.,(reply>), Put your bearings and rotating parts at the top of the screw not the bottom?,(reply>), Thank you - I was wondering about this, the screw model seemed equally good but indeed I could imagine that with this you can keep any moving parts away from the material (or water!)