normally caused by improper, infrequent, or no
lubrication, the internal wires of the rope are often
subject to extreme friction and wear. This type of
internal and often invisible destruction of the wires is
one of the most frequent causes of unexpected and
sudden wire rope failure. To safeguard against this
occurring, you should always keep the rope well
lubricated and handle and store it properly.
CLEANING AND LUBRICATING
Wire rope should always be cleaned carefully
before lubrication. Scraping or steaming removes
most of the dirt and grit that has accumulated on used
wire rope. Rust should be removed at regular intervals
by wire brushing. The objective of cleaning is to
remove all foreign material and old lubricant from the
Figure 5-27.Types of wire rope cutters: A. Hydraulic; B.
strands, then the strength of the rope maybe seriously
reduced. When 4 percent of the total number of wires
in the rope are found to have breaks within the length
of one lay of the rope, the rope is considered unsafe.
Consider the rope unsafe when three broken wires are
found in one strand of 6 by 7 rope, six broken wires in
one strand of 6 b y 19 rope, or nine broken wires in one
strand of 6 by 37 rope.
Overloading a rope will reduce the diameter.
Additionally, failure to lubricate wire rope will reduce
the diameter. This occurs because the hemp core will
eventually dry out and collapse or shrink. The
surrounding strands are therefore deprived of support,
and the strength and dependability of the rope are
equally reduced. Rope that is 75 percent of its original
diameter should be removed from service.
When wide-spread pitting and corrosion of the
wires are visible through inspection, the rope should
be removed from service. Special care should be taken
to examine the valleys and small spaces between the
strands for rust and corrosion. Since corrosion is
valleys between the strands as well as the spaces
between the outer wires. This allows the new lubricant
to flow into the rope.
Wire rope bending around hoist drums and
sheaves will wear like any other metal article, so
lubrication is just as important to an operating wire
rope as it is to any other piece of working machinery.
For a wire rope to work right, the wires and strands
must be free to move. Friction from corrosion or lack
of lubrication shortens the service life of wire rope.
Deterioration from corrosion is more dangerous
than that from wear because corrosion ruins the inside
wires a process hard to detect by inspection.
Deterioration caused by wear can be detected by
examining the outside wires of the wire rope because
these wires become flattened and reduced in diameter
as the wire rope wears.
Both internal and external lubrication protects a
wire rope against wear and corrosion. Internal
lubrication can be properly applied only when the wire
rope is being manufactured, and manufacturers
customarily coat every wire with a rust-inhibiting
lubricant, as it is laid into the strand. The core is also
lubricated in manufacturing,
Lubrication that is applied in the field is designed
not only to maintain surface lubrication but also to
prevent the loss of the internal lubrication provided by
the manufacturer. The Navy issues an asphaltic
petroleum oil that must be heated before using. This
lubricant is known as Lubricating Oil for Chain, Wire
Rope, and Exposed Gear and comes in two types: