Negative pressure systems generally comprise similar equipment to the positive pressure system. Negative pressure systems have an advantage that any system leakage is inward, so the escape of dust into the atmosphere is much reduced.

Negative pressure pneumatic conveying systems are commonly used to convey material from a multiple inlet points such as unloading rail cars, bulk trucks and discharging product into a single point. These systems are used when a variety of feed configurations may be required, and are almost always used when handling toxic materials to avoid accidental discharge to the atmosphere. When required, step line conveying systems can be employed to provide relatively constant conveying velocities to minimize product degradation during the conveying cycle.

• Conveying pressures up to -0.5 bar
• Low product/air ratio, generally up to 15:1