Comparing pneumatic conveying system types In this column, we'll
return to a topic covered in the March 1991 column: types of
pneumatic conveying systems. The types include vacuum, pressure,
and combination vacuum-pressure systems. We'll describe each,
along with its advantages and disadvantages, to help you
understand what each system includes and how systems of each
type are designed. Before discussing each system, let's examine
some common misconceptions about how the systems work. Many
people believe that a vacuum system draws material into the
conveying line's center and separates the material, and that a
pressure system forces material toward the conveying line walls
and compacts the material. However, neither is true. At any
point in either a vacuum or pressure system, the air's dynamic
action on the material is the same. The particles are moved
through the conveying line by the airflow, which is established
by a pressure differential. In a vacuum system, air flows from
atmospheric pressure to a reduce