Self-enclosed conveyor belts (pipe, tube or hose conveyor belts) are primarily used where bulk materials must be conveyed along horizontal and vertical curves in confined spaces, and/or where the environment has to be protected resp. where spillage must be avoided.
A pipe belt can negotiate tight horizontal and vertical curves. This eliminates or reduces transfer points, which is a big cost saving.
Inclinations of up to 35° can be dealt with.
The idler supports can be spaced farther apart, because it is self-supporting. An additional conveyor cover is not necessary.
Pipe conveyors were invented in Germany in 1956 (patent of 01.06.56), but have been utilized only in the last three decades.

Pipe belt clsoed

Since a pipe conveyor belt has to close and open at the head and drive pulley (or even at intermediate feeding stations), and be closed at any position along the conveyor for many years or decades, a sophisticated orthotropic carcass system is indispensable.
The belt must not flag so that the edge touches the conveyed material and it must not be too stiff, which would increase motor power resp. energy consumption and lead to premature wear of the belt and the idlers.
The belt must always open and never overlap on the pulleys.

Transparent pipe belt

Some rules of thumb:
- The minimum radius of a textile pipe conveyor belt should be 300 times pipe diameter and of a steel cord pipe belt 600 times the diameter.
- The pipe diameter should be min. 3 times the lump size.
- The filling degree should be between 60 and 75 %.
- The flat-to-pipe transition lengths should be min. 55 times pipe diameter.
- The motion resistance is higher than for troughed belts. Belt types with low indentation rolling resistance should be chosen.
- The belt width is approx. 4 times the pipe diameter.

Pipe conveyor belts are available with diameters of up to 900 mm.

Pipe conveyor with tight curve

A pipe conveyor in a South American port can be seen on Google Earth. It proceeds from the right side of the picture via the top left to the bottom left.

One of the longest pipe conveyor belts worldwide is operating in Lima, Peru.
This extremely demanding application incorporates narrow 3D curves and is used for conveying material simultaneously in the top and bottom runs. The belt is turned at both conveyor ends. For most of its length it is running in a tunnel under the streets of a residential area. Thanks to this unique system, the use of polluting and noisy trucks could be terminated.