Lull 644E-42 Operation Manual - Manual (Page 160)

158 Model 644E Origin 3/04
General Maintenance
Cracked Plates
Inspect the chains very carefully, front and back as well as side to side, for any
evidence of cracked plates. If any one crack is discovered, the chain should be
replaced in its entirety.
it is important, however to determine the cause of the crack before installing a
new chain so the condition does not repeat itself.
The types of cracks are:
ï Fatigue Cracking - Fatigue cracks
(1) are a result of repeated cyclic
loading beyond the chainís
endurance limit.
ï Stress Corrosion Cracking - The
outside link plates are particularly
susceptible to stress corrosion
cracking (2).
ï Corrosion Fatigue Cracking -
Corrosion fatigue cracks are very similar to fatigue cracks in
appearance. Corrosion fatigue is the combined action of an aggressive
environment and cyclic stress.
Other Modes of Failure
ï Ultimate Strength Failure - These
types of failures are caused by
overloads far in excess of the
design load. Either fractured plates
(3) or enlarged holes (4) can occur.
If either of these failures occurs, the
chain should be replaced
immediately.
ï Tight Joints - All joints in the
chain should flex freely. Tight
joints (5) resist flexing.
If the problem is caused by dirt
or foreign substance packed in
the joints, clean and lubricate
thoroughly before re-installing
the chain. If the problem is
caused by corrosion and rust or bent pins, replace the chain.
MM2070
1
MM2080
2
MM2100
3
MM2090
4
MM2110
5