![]() The vacuum generator creates the required negative pressure to pull the material through the conveying line and into the receiver. The basic components of a vacuum conveyor system are the pick-up nozzle, the conveying line, the receiver, and the vacuum generator, which is the power source. Pressure pneumatic conveyors can be fairly costly, however, since they require special equipment, like a rotary valve to introduce material into the air stream at the inlet and extra components to remove the air at the discharge end through a vent system. Pressure pneumatic conveying systems are generally preferable when transporting heavier materials longer distances. When the predetermined low pressure setting is reached at the end of the conveying cycle, the air supply is turned off and the residual air volume purges the pressure vessel and the conveying line. Valves and sensors control the air pressures and velocities. The high-pressure air conveys the material to the receiver, where the air and the material are separated by a filter or other system. Once the pressure vessel is filled, the inlet and vent valves close and seal, and highpressure air is gradually introduced into the pressure vessel. Low-pressure displacement blowers or fans supply a beginning pressure below 15 psig and an ending pressure near atmospheric pressure.įirst, the materials is charged into the pressure vessel through the rotary air lock. Systems using high-pressure compressed air, operate with pressures above 15 psig, usually with a beginning pressure of about 45 psig and an ending pressure near atmospheric pressure. A pressure vessel, the conveying line, and the receiver make-up the balance of the system. The basic components of a pressure system are a rotary air lock feeder valve, a high pressure air compressor system or a low-pressure positive displacement blower or fan to serve as the power source. Material is constantly supplied at the pickup point and is conveyed to the receiver without interruption. Dilute phase systems usually deliver the material continuously. In this type of system, the material is most often fluidized, or suspended in the air flow, and moves at relatively high velocities depending on the particle size and density. Valving systems can be adjusted to reduce the air pockets.ĭillute phase conveying systems have a high air-tomaterial ratio. ![]() Dense phase systems, therefore, move the material through the piping in batches, with discrete dunes or plugs of material separated by pockets of air. Velocities are below the saltation level, the critical velocity at which particles fall from suspension in the pipe. ![]() Pressure and vacuum systems can be used for dense (high pressure/ low velocity) or dilute (low pressure/high velocity) phase operation.ĭense phase conveying systems have a low air-to-material ratio. Pneumatic conveyors can utilize either a pressure system that introduces compressed air at the system inlet in order to push the material through the piping or a vacuum at the delivery end in order to pull the material through the piping. The Differences and Similarities in Pneumatic Conveyors Pneumatic conveyor systems, which use an air stream to move materials through horizontal and/or vertical piping, come in two forms: pressure or vacuum. Choosing a Pneumatic Conveying System: Pressure or Vacuumīecause they are efficient and inherently dust-tight, pneumatic conveying systems provide the most practical method for moving large quantities of dry materials, whether powdered, granulated, or pelletized.
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