Pneumatic conveying systems are used to transfer dry bulk materials like powders and granules in a convenient and clean way. They are used in a variety of industrial applications, including unloading materials from bulk transport or storage vessels, blending raw materials for plastics, paint or concrete production and in food applications.
The advantage of a pneumatic or vacuum conveyor compared to a more conventional mechanical conveyor is that it’s more compact and can be routed to negotiate tighter corners. Because it’s enclosed, it also prevents dust from escaping and contains material losses. It can also deliver accurately metered flows of material safely to processes with minimal exposure to the atmosphere.
Elements of a Pneumatic Conveyor
A pneumatic or vacuum conveyor system is made up of four main elements. The first of these is a compressor or similar that is used to generate the air or gas flow through the system. Second is the feed mechanism that gets the product to be transported into the airflow – this is usually in the form of an injector valve or powered pump.
The third is the conveyor line itself, which is made up of a series of tubes through which the material is moved. Finally, there is a separation system that recovers the solid material from the conveyor, usually in the form of a filter or centrifugal system.
Types of System
Pneumatic conveyor systems from suppliers like http://www.aptech.uk.com/pneumatic-conveying-systems/vacuum-conveying/ can be either positive or negative pressure, or sometimes a mix of both.
Negative pressure means the system works at less than atmospheric pressure and material is effectively sucked through the system to its destination, rather like a suction pump. In positive pressure systems the gas stream is above atmospheric pressure to keep the flow of material moving.
Negative pressure systems are better suited to collecting material from several locations and delivering it to a single point. Because they are below atmospheric pressure, they are also less prone to leakage. Positive pressure can provide faster flow rates but usually need heavier-duty equipment to maintain the pressures required for smooth operation.
Depending on the process, a combination of techniques are often used – for example, a negative pressure vacuum system for extracting raw materials from containers and a positive pressure system to deliver them to storage or into a production process.