Selecting the right pneumatic conveying equipment

05 July, 2023

Pneumatic conveying is a tried and trusted means of transferring powders, granules and dry bulk around manufacturing and process environments. Subsequently, it is used in an incredibly diverse range of industrial applications. Whether flour in bakeries, grain in breweries or chemical compounds in pharmaceutical plants, pneumatic conveying represents a flexible and cost-effective solution for transporting materials to their required destination.

But selecting the right pneumatic conveying equipment can be challenging, with many considerations coming into play. For example, what type of substance is being handled? The size, weight and type of material can significantly affect the flow and pressure required. Also, are the goods being conveyed for human consumption or as a constituent part of a pharmaceutical product? If so, rigorous quality standards will define the purity of the compressed air that can be used. Meanwhile, other factors such as energy and safety are also critical considerations that must be fully understood.

The principles of pneumatic conveying

Before evaluating the selection criteria in greater detail, it is worth looking at the basic principles of pneumatic conveying and how materials can be moved. Pneumatic conveying uses compressed air to transport materials through enclosed pipelines in places like manufacturing and industrial plants using different air pressures. This process can be achieved in two distinct ways.

Pressure conveying, or positive conveying as it is also known, deploys the compressed air from a compressor or blower at the start-point to ‘push’ the material through the pipeline. This method provides a particularly efficient way of covering larger distances. Meanwhile, vacuum or negative conveying uses compressed air to ‘suck’ the bulk material through the pipeline, with the compressor or blower positioned at the endpoint. One benefit is that there is no contact between the compressed air and the material being transported – and hence no contamination – and the product is not exposed to the heat generated in the air compression process. However, the distance that can be covered by vacuum conveying is more limited than by pressure conveying.

Within these two fundamental approaches, there are three phases of pneumatic conveying – dilute, dense, and transient. These phases relate to how different materials move through the pipelines.

Firstly, there is the dilute phase, where a blower or lowpressure compressor is used to send the material through the pipeline as though it is floating without any of it accumulating at the bottom of that pipeline. The dilute phase allows the material to be moved with an air pressure of up to 2.5 bar and at high speed and is a great way to transport a large volume of material quickly.