Negative Pressure (Vacuum) Systems

Negative pressure systems are commonly used for drawing materials from multiple
sources to a single point. There is no adverse pressure difference across the
feeding device in a negative pressure system and so multiple point feeding into a
common line presents few problems. A particular advantage of negative pressure
systems, whether open or closed, in terms of potentially hazardous materials, is
that should a pipeline coupling be inadvertently left un-tightened, or a bend in the
pipeline fail, air will be drawn into a system maintained under vacuum. With a
positive pressure system a considerable amount of dust could be released into the
atmosphere before the plant could be shut down safely.