Appendix
70
GLOBAL
INDUSTRIES, INC.
Drag Conveyors
10230011
2016-06-14
(1) cause of severe overload can be jams.
Freezing of the load to the conveyor bottom,
or a stone or other material becoming lodged
between the chain and sprocket, or an
incorrect sprocket profi le.
C
METAL FATIGUE
Sometimes an overload is not enough to
cause tensile failure. However, continuous
running in overloaded conditions may cause
metal fatigue. A typical example of metal
fatigue is shown at right. This type of fatigue
failure can occur in a few weeks or a few
years, depending on the amount of overload
experienced.
Causes of metal fatigue could be the result
of the exceptionally heavy loads, sprocket
interaction problems, or chain overtightening.
If all the cracks are in (1) direction, it normally
indicates a sprocket problem. If cracks are
both up and down, it normally indicates an
overloading problem.
The presence of corrosion as well as the
presence of hydrogen within the carried load can
accelerate the problem. If metal fatigue is evident,
it is recommended that the entire chain be
replaced because the chain contains microscopic
cracks, and breakage problems will continue
even if the overload conditions are halted.
oblong hole
split barrel
rotated pin
crack
