Pneumatic conveyors are also known as air conveyors as they are devices that use a cushion of air to move materials. These conveyors are designed to move a variety of materials such as abrasive products, yarn, plastic pellets, tablets, etc. They are basically pneumatic tube systems which use low pressure air to either push or pull short closed cylinders through a pipe from one point to another. A compressor is used to deliver the compressed air. Based on the application, the air may need to be dried before it touches the material.
The cylinders or carriers that are conveyed in this conveyor system generally range in size from three inches in diameter by nine inches long and up to six inches in diameter by up to 36 inches long, depending on the items that are to be to be carried. Pneumatic conveyors are quite popular because of their speed, reliability and low cost.
These conveyors use either a positive pressure system or a vacuum system. In a positive pressure system, a positive displacement blower is used to provide the necessary stream of air. Material entry points can be single or multiple, but they have to be downstream. A rotary airlock valve is used to maintain the air pressure. These systems are suitable to move material across both short and long distances.
In vacuum systems, a negative pressure of air is created by a vacuum pump. The material that is to be conveyed is then sucked in and can be deposited where ever it is needed.
Pneumatic conveyors are often used to move hazardous materials and when cleanliness is crucial. Pneumatic conveyors are also used to move simple things such as sending and receiving documents and invoices between a receiving office and the main office, or sending drawings between the engineering department and the shop floor, or transferring document between buildings. Pneumatic tubes are versatile as they can be installed outside as well as inside.
Types of pneumatic conveyors include dense phase and dilute phase, low velocity, high velocity and carrier system.