Regardless of the system type – pressure or vacuum, the general rule is to create a pressure difference between the both ends of the conveying line in order to create gas flow through the system (usually atmospheric air). The velocity of the gas flow is dependent on the pressure difference, as well as length and diameter of the conveying line. High velocity of the gas flow picks up product particles, transporting them throughout the conveying line. In case of hetergeneous product, a particle segregation can occur – lighter particles will be picked up easier than heavier ones.
With pressure conveying, materials are moved through a totally enclosed pipeline using pressurized air generated by a pressure differential blower, pushing the material to its destination. Pressure conveying is extremely efficient because material can be moved in larger quantities and at longer distances.
However you have to keep in mind that compressing air at the start point of the conveying line leads to temperature increase of the conveying medium (air) and therefore increase of the transported product’s temperature. Also additional components like rotary valves (‘aerolocks’), filters and cyclone-filters have to be used. In the event of pipeline failure (loss of airtightness), the conveyed product will be blown with high speed out of the line at the point of failure.
One of the benefits of using the vacuum conveying method is that in the event of pipeline failure the product won’t be blown out of the line – it’s especially important in cases where product might present a threat to health and environment. Also it requires less components such as rotary valves as well as smaller filter sizes.
However the vacuum pump is usually more expensive and the required pipe diameter is higher – this in turn results in lower conveying velocity. It can be good in some applications, but also means that the vacuum system will transport less product and the conveying distance will be lower than in case of pressure system.Back to Coperion page