Page 13 - ConveyorBeltMaintenanceManual2010

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INSTALLATION, MAINTENANCE & TROUBLESHOOTING GUIDE
i n s t a l l a t i o n
Automatic Aligning Devices
Self-aligning conveyor and return idlers have already been described. Center pivoted return idlers are sometimes connected
in groups of two or three to operate together and are actuated by an external mechanism that takes its indication from the belt
position. They have a very strong influence in centering the return belt as it approaches the tail pulley.
A snub pulley also can be arranged to provide the same strong self-aligning influence; however, in place of a center pivot (as
in return rolls), it is usually pivoted at one end of its shaft. The other end is shifted by mechanical, electrical or hydraulic means
as indication is received from the belt position.
Assuring Effectiveness of Training Rolls
Normally, extra pressure is desired on self-aligning idlers, and in some cases, on standard idlers where strong training
influence is required. One way to achieve this is to raise such idlers above the line of adjacent idlers. Idlers or bend pulleys
on convex curves along the return run have extra pressure due to a component of the belt tension, and are therefore effective
training locations. However, carrying side self-aligners should never be located on a convex curve, since their elevated position
can promote idler juncture failure.
Side Guide Rollers
Guides of this type are not recommended for use in making belts run straight. They can be used to assist in training the belt
initially to prevent it from running off the pulleys and damaging itself against the structure of the conveyor system. They also
can be used to afford the same sort of protection to the belt as an emergency measure, provided they do not touch the belt
edge when it is running normally. If they bear on the belt continually, even though free to roll, they tend to wear off the belt
edge and eventually cause ply separation along the edge. Side guide rollers should not be located so that they bear against
the belt edge once the belt is actually on the pulley. At this point, no edge pressure can move the belt laterally (Fig. 12).
Conveyor
Belt
Side Guide
Rollers
Fig. 12