Pneumatic Conveyors

Pneumatic conveyors are probably the most versatile of all, but they are also the most expensive. They have virtually no limit on capacity, product type, distance, or routing. Lean phase versions in which the ratio of material to air is very low. Lean phase conveyors can typically move 1 lb of air for every pound of materiel. This is important because air velocity is between 60 and 75 feet per minute with the material traveling at about 70 percent of the speed due to slip factor.

Dense phase or plug flow versions can move slugs of material at lower speeds with minimal degradation to the product. They move about 100 lb of material for every pound of air. Slugs move between 10 and 30 feet per second. Positive pressure models are generally used to move materials from one place to one or several different destinations. They are normally used for major tasks like quickly emptying road and rail tankers into storage tank or moving material from one storage unit into large-scale production processes.

The two main disadvantages of pneumatic conveyors are a relatively high initial installation cost and the amount of filtration required. The high cost is due to the need for an expensive blower or compressor. Not to mention the pressure-tested pipe, supporting the larger pipes, and filtering the large volume of air used. As with vacuum conveyors, self-cleaning reverse-jet filters are a big help in reducing maintenance. High levels of maintenance is needed to ensure these systems are leak free for best efficiency.