Pneumatic conveyors transport bulk dry goods through a pipeline by using gas pressure differentials. Flour, sand, pellets or cement are frequently transported in this way. Pastes, sticky materials and slurries are not usually suited to pneumatic conveying, as they can block the pipeline. The system’s air mover (typically a fan) creates a plenum of pressurized air at the starting end of the pipeline, or a vacuum at the terminating end, thus creating a pushing or pulling force to move the materials. Positive-pressure systems operating at high pressures can handle higher material flows over longer distances than negative-pressure systems.

There are two main types of pneumatic conveying processes. Dilute or lean phase conveying blows the particles through the pipeline, much like wind picking up dust, whereas dense phase conveying pushes a mass through the pipe like a sausage into its skin. Dilute phase systems can convey a wide range of materials for short distances and have a relatively low capital cost. They are also easy to operate, as they are less subject to plugging than dense phase systems. However, power requirements, wear on the pipes and stresses on the product are higher. For this reason, abrasive materials or products such as food items that may be easily damaged are best conveyed by a dense phase system.

Pneumatic conveying systems are energy intensive and require large dust collectors at the end. However, they have several advantages over mechanical conveyors:

• They take up less space.
• They tend to have fewer moving parts, as they do not require motors for every change of direction.
• They allow greater layout flexibility and can thus be used at any place a pipeline can run.
• They are enclosed and therefore do not generate loose dust when conveying powders, making them easier to maintain, as well as cleaner and more environmentally acceptable. This also makes them attractive wherever bulk food ingredients or products are to be conveyed, since the ingredients are safeguarded from contamination.
• As distances increase, the energy efficiency of pneumatic systems relative to mechanical systems also increases.
• These characteristics mean that they are often more cost-effective to install and operate.

Being enclosed and integrated, pneumatic systems are suitable for conveying combustible dusts and fines. Factory incidents involving dust explosions can cause extensive damage. While pneumatic conveying systems do not eliminate this risk, the risks are easier to manage if proper design and operating procedures are followed. Devices to suppress explosion propagation in pneumatic systems can be installed, and in particularly dangerous situations nitrogen can be used for conveying instead of air.

Because maintenance costs can vary widely depending on the system’s design and use, it is important to obtain professional advice or services when selecting the components for the system. Choosing unsuitable valves, for example, can lead to unnecessary downtimes and maintenance costs and reduce the overall performance of the conveying system.

CFW builds dilute-phase pneumatic conveyance systems that are ideal for transportation of bulk materials such as tea, sugar or sawdust. These systems are versatile and have a low capital cost. They are especially suitable where materials are to be conveyed from multiple locations. Both positive and negative pressure systems are available.

We also offer components and accessories such as blowers, material handling fans, rotary and diverter valves and anti-bridging devices. We supply cyclones for separating the entrained bulk material from the air.