If the diameter of the sheaves, rollers or drum cannot be increased, a more flexible
rope should be used. But, if the rope in use is already of maximum flexibility, the only
remaining course that will help prolong its service life is to move the rope through the
system, the fatigued sections are moved to less fatiguing areas of the reeving. This
technique is most frequently used in rotary drilling.
14. Broken Wings
The number of broken wires on the outside of a wire rope are 1) an index of its general
condition, and 2) whether or not it must be considered for replacement. Frequent
inspection will help determine the elapsed time between breaks. Ropes should be
replaced as soon as the wire breakage reaches the numbers give in Table 13. Such
action must be taken without regard to the type of fracture.
On occasion, a single wire will break shortly after installation. However, if no other
wires break at that time, there is no need for concern. On the other hand, should more
wires break, the cause should be carefully investigated.
On any installation, valley breaks-i.e., where the wire ruptures between strands-should
be given serious attention. When two or more such conditions are found, the rope
should be replaced immediately.
It is well to remember that once broken wires appear-in normal rope operating under
normal conditions-a good many more will show up within a relatively short period.
Attempting to squeeze the last measure of service from a rope beyond the allowable
number of broken wires (Table 13), will create an intolerably hazardous situation.
A diagnostic guide to some of the most prevalent rope abuses is given in Table 14. On
the following pages these abuses are illustrated and described.
WHEN TO REPLACE WIRE ROPE-BASED ON NUMBER OF BROKEN
WIRES
Number Broken Wires
in Running Ropes
Number Broken Wires
in Standing Ropes
ANSI No. Equipment
In One
Rope Lay
In One
Strand
In One
Rope Lay
In One
Strand
B30.2
Overhead
& Gantry
Cranes
12 4 Not Specified
B30.4
Portal,
Tower &
Pillar
Cranes
6 3 3 2
B30.5
Crawler,
Locomotiv
e & Truck
Cranes
6 3 3 2
B30.6 Derricks 6 3 3 2
321REVISED:
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