cracked leaf chain link plate due to dynamic impulse or shock loadDynamic impulse or shock loads should not be exerted on forklift truck leaf chain as it can impose abnormally high loads above the fatigue endurance limit of leaf chain.

These types of loads are induced in leaf chain when high velocity movement of the load is followed by sudden abrupt stops.  This adverse movement can be as a result of simply carrying the load suspended by the leaf chain over irregular surfaces such as tracks, potholes and general rough terrain.  Attempting to 'inch' loads which are beyond the rated capacity of the forklift truck chain or lifting mechanism will also seriously damage leaf chain.

It should be noted that continual operation of leaf chain that results in “bounce”, under otherwise normal and apparently safe operation, will cause cyclic (impulse) loading that can result in fatigue failure.  This cyclic loading on the forklift truck chain is further exacerbated when the operation is at high speed.  Under these conditions the actual load on the leaf chain will be approximately doubled.

The more frequently a leaf chain is loaded above its fatigue endurance limit the more likely it is that it will suffer from premature fatigue cracking. As shown in the image. The fatigue endurance limit of leaf chain is difficult to determine but it is invariably going to be less than the certified SWL of the forklift truck chain.  Under normal circumstances leaf chains will elongate (wear out) long before fatigue sets in.  It is generally only when continuous impulse loading is present that a leaf chain fatigue failure will ensue.

Fatigue cracks may not always will become visible and are a result of repeated cyclic (on/ off) loading beyond the leaf chains fatigue endurance limit.  The magnitude of the load, frequency of its occurrence and the endurance limit are factors that determine when a forklift truck chain fatigue failure will occur.

These types of load cycles and environmental conditions make it impossible to predict leaf chain life. It is therefore necessary to conduct frequent inspections until a satisfactory assessment of forklift truck chain replacement life can be predicted.