2.1. Dilute phase
Almost any material can be conveyed in dilute phase, suspension flow through a pipeline,
regardless of the particle size, shape or density. It is often referred to as suspension flow
because the particles are held in suspension in the air as they are blown or sucked through the
pipeline. A relatively high velocity is required and so power requirements can also be high but
there is virtually no limit to the range of materials that can be conveyed.
There will be contact between the conveyed material and the pipeline, and particularly
the bends, and so due consideration must he given to the conveying of both friable and abrasive
materials. With very small particles there will be few impacts but with large particles
gravitational force plays a part and they will tend to “skip” along horizontal pipelines.
Many materials are naturally capable of being conveyed in dense phase flow at low velocity.
These materials can also be conveyed in dilute phase if required. If a high velocity is used to
convey any material such that it is conveyed in suspension in the air, then it is conveyed in
dilute phase.
2.2. Dense