The pneumatic convey rate is directly related to the air flow rate, so the more air that is used, the faster a truck can be unloaded.
However, there is a limit to the amount of air that can be passed through pneumatic convey trucks before over-pressuring them. A common strategy to increase the unload rate is to use a blower that moves more air than a truck is capable of handling, and bypass some of the air from the blower directly to the silo fill line. This effects the convey rate in two ways.First, it allows the operator (or an automatic valve) to maintain the pressure in the truck as high as possible, even as the back-pressure begins to drop as the hopper empties. Second, the air that is bypassed is, in effect, whisking the air away from the truck faster.If you were to dig into the physics behind this phenomenon it would reveal a hybrid dense phase/dilute phase pneumatic conveying.