(ii) troughing idler set consisting of 2, 3 or 5 rollers arranged in the form of trough to support the belt in a troughed belt conveyor. Fig. 6.1.7 shows sketch and photograph of a 3-roll idler.
Idler construction: Idlers are generally made from steel tubes conforming to IS 9295:1983,uniformly machined all over at the outer diameter and at the two ends of the inner diameter. The tubes are mounted on antifriction bearings over a fixed steel spindle. The ends of the spindles are flat machined to standard dimensions for quick fixing in slots of idler structure. The idlers may be made of heavy steel tubes for severe service condition (like in material loading section) or cast iron in corrosive application (handling coke etc.).
Fig. 6.1.8 shows different designs of roller mountings on antifriction bearings.