Pneumatic Tube Transportation

the set of equipment and systems used to convey bulk and piece goods by means of air or a gas; one of the types of industrial transportation. Pneumatic tube transportation equipment may be of the suction, pressure, or combined type, depending on the means of creating the airstream and the conditions of its motion in the tube together with the material or on the means of generating a pressure gradient in the pipe.

The advantages of pneumatic tube transportation include air-tightness of the system, the possibility of adaptation to various production conditions and automation of the operation of pneumatic equipment, use of the pneumatic equipment to dry, heat, or cool the material being transported, and the possibility of installing pipelines in any configuration. All types of pneumatic tube transportation have the common disadvantages of relatively high consumption of power and metal. In installations that move goods in a mixture with air, rapid wear of the equipment is experienced when transporting highly abrasive materials, and it is difficult to move moist materials.

Pneumatic tube transportation installations are used to load bins and for the controlled delivery of materials from them, to transfer materials from storerooms to production shops and between shops, to unload and load railroad cars, ships, and trucks, to fill worked-out spaces in mines with rock, to remove production wastes, such as ash and metal and wood chips, and to suck up dust. The capacity of pneumatic tube transportation installations ranges from several kilograms up to hundreds of tons per hour, and the transportation distance may be up to several kilometers. Tubes 70–1,200 mm in diameter are in use. In high-pressure systems the pressure of the air or gas reaches 0.8 meganewton per sq m (MN/m²), or 8 kilograms-force per sq cm (kgf/cm²), and the specific power consumption may be up to 5 kilowatt-hours per ton.

Bulk materials are transported through a tube by putting the solid particles of the material into a state of suspension with a stream of air or by saturating the material with air so that it becomes fluid.

Piece goods are transported through a tube by the action of a pressure gradient created by blowers or suction equipment. In this case the dimensions of the load must match the internal cross section of the pipe. The load actually performs the function of a piston in a cylinder. This kind of pneumatic tube transportation, called pneumatic dispatch, has become very popular for conveying various documents or small objects such as instruments, tools, specimens of materials, and semifinished parts in enterprises, institutions, and librairies.

Pneumatic tube transportation of piece goods is developing further in the form of container (capsule) transport systems, in which single containers on wheels or trains of containers are moved through a tube by the air pressure created by blowers. Only a small pressure gradient—of the order of 10⁴ N/m²—is necessary to develop the force that moves the transportation units along horizontal segments. Container systems may have continuous or periodic operation. A system that operates in a continuous mode has two pipelines: loaded containers are moved through one and empty containers are returned in the other. In a periodic-operation system the shuttling movements of loaded and empty containers or trains take place in one pipeline—that is, only a single transportation unit can be present in the pipeline at a time. Capsule pneumatic tube transportation has also found application in plans for transport systems to carry passengers in special compartments.