ldler bearings are designed to provide a minimum operating life of 30,000 hours, on the basis that they are normally working in an uncontaminated environment.
Experience has shown that roller fatigue does not normally result from bearing fatigue, but from the wearing of the seal itself. Such wearing can lead to contamination from the build up of material around, or under rollers preventing them from turning.
As a rule, idlers should be spaced more closely at the feed points. The actual pitch of the idlers is dependent upon both the feed rate and the size of the material (the size should not normally exceed 450mm, but may be as close as 200mm). The material feed should always be just in front of one of the idlers. Also, the first idler in front of the tail drum should be positioned so that the belt is forming a true trough prior to the feeding of the material. It is also an advantage if fine materials are fed onto a belt prior to any large lumps, as this may cushion the load. This may be achieved by incorporating a grid in the feed chute. Standard troughing idlers are normally satisfactory at feed points for materials up to a maximum size of 60mm and the rubber covered rollers up to a maximum size of 100mm. Above this heavy duty impact idlers should be used. For high capacities or larger lumps please consult Universal Conveyors. To avoid damage it is essential that material is allowed to slide onto the belt and not dropped on from any height.
For applications where material is liable to build up on the idlers, both troughing and return disc idlers are available. Whilst such idlers will reduce the possibility of build up, it should be‘noted that material can accumulate between discs, so regular cleaning is advised.
Particular attention should always be paid to the correct tracking of the belt, to prevent the possibility of the belt moving to one side. Allowing the belt to foul the end discs can cause belt damage.
Self aligning idlers of both troughing and return type are generally manufactured for use on long conveyors and are not normally necessary on short conveyors. To be effective they must be kept clean from spillage. For very long conveyors vee type return idlers may be fitted to assist belt tracking.
Picking belt idlers provide a thinner and wider spread of material which aids inspection and sorting. Picking idlers have longer centre rollers to allow the material to be spread. Belt speed is usually in the range of 0.25 to 0.5 metres per second.
Where the belt changes alignment i.e. from incline to horizontal, it is advisable to fit idlers at a close pitch to maintain the belt profile. To avoid belt distortion, deep troughing is not recommended on this type of conveyor. Return idlers should be fitted at closer pitch.
Other roller diameters and spindle diameters can be made to special order.
Return idlers are only suitable for light belt snubbing. A range of conveyor drums is offered for heavier duties.