Classification of pneumatic conveying systems — Part II, Material conveying phase
At present, no industry standards exist for classifying pneumatic conveying systems. As a result, the systems shown throughout engineering literature and in equipment suppliers' brochures are described by various terms -- vacuum, negative pressure, positive pressure, low pressure, medium pressure, high pressure, low velocity, high velocity, dilute phase, dense phase, and medium phase. To aid your understanding of basic pneumatic conveying terms, Part I [March 1989] of this article classified pneumatic systems by the type of airstream used to convey material -- vacuum, pressure, or combination vacuum/pressure. Part II classifies pneumatic systems by the degree of material concentration in the conveying phase.
In addition to system type classification, pneumatic conveying systems can also be described by the way material moves through the conveying line. Dilute phase and dense phase are the two most common conveying phases. Some equipment suppliers also define a third phase, called medium phase or medium dense phase.