Standard troughing idlers have three rolls of equal length and diameter. They are usually mounted at 20°, 35° or 45° angles and roll on anti-friction bearings. Roll diameters vary from 4" to 7". Diameters below 5" are generally used where lighter duty is evident or where clearances are close. Larger diameters are usually required for heavier-duty applications.
trough conveyor idlers for belt conveyors
The carrying capacity of a system can often be altered by changing the length of the center roll to widen or narrow the trough. Rolls of unequal length may also be specified, but only after the effects of this type of idler on material flow and belt performance have been studied.
In an offset idler, the center roll is positioned behind the concentrating rolls. The most common use is in installations with minimal clearances. Offset idlers offer more protection against idler junction fatigue than the inline type.
Although 20°troughing idlers were once standard, angles of 35°and 45°are now more commonly in use. The benefits of deeper troughs, inline or offset, are:
1. Greater cross section for more tons per hour.
2. Less cover wear per ton of material carried.
3. Use of a narrower belt is possible - for savings on belting and hardware.
4. Reduced potential for material spills.
5. With most materials, a deeper trough allows for more distance between idlers.
In choosing a deep-trough over a 20° trough, it must be kept in mind that deep-trough idlers require a larger curve radius and longer transition distances for optimum belt performance.
belt conveyor idler bracket for idlers
Catenary idlers are most often used in handling light-to-medium materials such as coal and grain, and are mounted at each edge of the conveyor. They offer less of a jolt to transversing loads than standard idlers.
Return idlers are generally flat, with the same roll diameters as the carrying idlers. They should be at least three inches longer than the width of the belt to allow for lateral movement. Use of longer idlers will further reduce the risk of belt edge damage.
Because the belt is especially prone to wandering on this return side, self-aligning return idlers are a good investment, especially where the belt crosses the tail pulley. In this area, it is critical that the belt enter on center.