Protecting Your Life:
Wires and Ropes.
UE News H&S, March 1996
WHEN A SLING OR HOIST BREAKS under a load,
the chance of serious injury and loss of life is great. So special precautions need to be
taken to protect the integrity of the wire ropes and metal chains used in these devices.
In the past, fiber ropes were often used for lifting and moving relatively
light industrial loads. But they deteriorate when exposed to acids and caustics or their
vapors, especially under hot, humid conditions. As a result, wire rope or metal chains are
now the materials of choice for hoists and slings.
Wire rope, for example, has greater strength for the same diameter and
weight than fiber. Its strength is the same under wet and dry conditions. It does not
stretch or shrink when weather conditions change, and it is far more resistant to chemical
attack than fibers.
Wire ropes usually consist of six strands of 19 wires each (6x19
classification) or six strands of 37 wire each (6x37), all wrapped around a core, usually
a specially treated, independent wire rope core (IWRC).
Here are some common causes of deterioration of wire ropes:
Corrosion, particularly of the interior core wire, caused by pitting due
to acid and water damage. This is hard to detect and highly dangerous. Regular cleaning of
the wire with a compressed air or steam jet is important, followed by regular lubrication
of the dry wire (if the core is wet the lubricant will trap the moisture). The lubricant
should be dripped or sprayed on, either monthly, quarterly or semiannually, depending on
use.
Wear, on the crown or outside wires.
Kinks, caused by improper installation or hoisting with slack in the
ropes. This causes visible, permanent damage on the surface, including so-called
"bird caging."
Wire fatigue, usually caused by excessive bending through small radius
turns, vibration, pounding and/or excessive twisting under load. Indicated by square,
fracture-like breaks of the outer wire.
With fiber ropes, which are much more sensitive to acid damage, you can
unwind the rope and inspect the inner fibers for damage. Inner threads should be sharp,
clean and unspotted. These inner fibers are especially sensitive to overload situations,
which are indicated by frequent, visible breaks (the greater the overload damage, the more
frequent the breaks).
The OSHA standard for slings (CFR1910.184) requires that all slings,
whether fiber, wire rope or chain, be inspected "each day before being used" by
a "competent person designated by the employer." So occasional inspections are
not enough; a person must be designated, and presumably trained, to do this. Our locals
will of course put in their say about who this designated person is.
Furthermore, "damaged or defective slings shall be immediately
removed from service." (our emphasis) The standard is specific about what constitutes
a defective sling. Wire rope slings should be removed if any of these conditions are
present: Ten randomly distributed broken wires in one rope lay, or five broken wires in
one strand in one rope lay; wear or scraping of one-third the original diameter of outside
individual wires; kinking, crushing, bird caging or any other damage resulting in
distortion of the wire rope structure; evidence of heat damage; end attachments that are
cracked, deformed or worn; hooks that have been opened more than 15 percent of the normal
throat opening measured at the narrowest point or twisted more than 10 degrees from the
plane of the unbent hook; corrosion of the rope or end attachments.
The first conditions give us an especially clear basis for deciding when a
wire rope has seen better days. A designated member of the union health and safety
committee should routinely monitor the condition of the wire to check if there are 10 or
more random breaks in one helical turn of the wire ("one rope lay") or 5 or more
in one single wire strand. If your employer is not in compliance with the 1910.184
standard, the local can raise this in a meeting between the union health and safety
committee and management. If you don’t have a local committee, or if management
doesn’t listen, consider filling a grievance under your contract — either under
one of your safety and health clauses, or under the general clause in most contracts that
union and management agree to comply with all U.S. laws and regulations.
But however you handle it, don’t go to OSHA until you have done
everything possible in the plant, including educating the membership to these dangers. If
you call in OSHA too soon, without educating or mobilizing your membership, the OSHA
inspector may just give the company a slap on the wrist, or even worse, treat the problem
as "minor." The sad fact is that today you have more bargaining leverage with
management by citing the violation to them yourselves, than by actually calling OSHA in.
