The most basic explanation of pneumatic conveying is that it involves the movement of suspended bulk such as chemicals, pellets, tablets, fine powders and other small elements in a uniform stream from a supply source to a point of delivery transported through pipes or hoses. An application of air, which is supplied through a blower or vacuum pump, forms a high air velocity and low solids-to-air ratio which moves the materials through the piping or hoses. The presence of the vacuum stops any chance of the product from being released into the environment in the event of a leakage.
There are two types of vacuum conveyor:
– Dilute Phase Conveying: the material is drawn into the air stream in equal parts product to air. This is a great way of conveying powders such as flour or sugar.
– Dense Phase Vacuum Conveying: materials are transferred in slugs within the convey tubing. This is a slower process and is suitable for a blend of powders or friable products.
– The loading of the material from containers into the vacuum conveyor.
– Vacuum conveying.
– Discharge position: the material is discharged and put into packaging machines.
A pump creates a vacuum in the Vacuum Conveyors separator tank. Air flushes through a hose from a feeding point and into the suction inlet. From here the material is aspirated and transported in this air stream.
A separator tank reduces the velocity, and the material collects above the conveyor’s discharge valve. A filter, which is located inside the separator tank, removes dust and airborne particles from the product and the air. The material is then collected into the separator.
Once the material has passed into the separator and it is full, the vacuum turns off and the material is discharged out of the conveyor through a discharge element. It falls into a tank, where it can then be loaded.
The filter is automatically cleaned by a blast of air, and there may be cases when the filter unit discharges the odd filter cake. Piston vibrators along with fluidising units are available which help improve the process of discharging for materials that are sticky or have bad flowing characteristics.
Once the product has been unloaded, the discharge valve is shut off and the vacuum cycle process starts afresh.