Troughed belt conveyor is that in which the belt forms a trough on the carrying side while running over idler rollers which are either in set of 5 rolls, 3 rolls or 2rolls. The troughing angle adopted are: 15°, 20° , 25° , 30° , 35° , 40° , 45° .
Return idlers are usually straight roller type.
Transverse flexibility or rigidity of the belt is another significant consideration.
It is important that the belt trough properly.
The empty conveyor belt must make sufficient contact with the center roll in order to track properly.