CUTTING
& SEIZING WIRE ROPE
There
are numerous ways to cut wire rope - use only appropriate
tools specifically designed to cut wire rope. Safety goggles
and work gloves must always be worn. Observe other
precautions peculiar to the tools used. Wire rope should be
properly seized on both sides of the cut with wire or strand.
Seizing wire diameter and the number and length of the
seizings will depend on the diameter of the wire rope, and
whether or not it is preformed.
BREAKING
IN NEW WIRE ROPE
Since
wire rope is a machine with many moving parts, it requires
careful installation and breaking in procedures for maximum
safety and long service life. After proper installation, allow
the wire rope to run through a cycle of operation at a very
low speed. Keep a close watch on the wire rope, its
attachments and any working parts such as sheaves, drums,
rollers, etc. to make certain that the wire rope runs freely.
If no problems appear at this stage, run the wire rope through
several cycles of operation under light load at reduced speed.
This procedure allows the component parts of the new rope to
make a gradual adjustment to the actual operating conditions.
Wire
rope will develop 100% efficiency, that is, break at or above
minimum acceptance strength (not less than 2 1/2% below
nominal breaking strength) under controlled laboratory
conditions. Once fittings such as sleeves, clips, sockets,
etc. are attached and/or the wire rope passes over a curved
surface such as sheaves, pins, etc. its strength is
decreased. In the case of wire rope passing over a curved
surface this decrease in strength depends on the severity of
the bend. In the case of wire rope fittings, the decrease in
wire rope strength will depend on the type of fittings used.
The wire rope efficiency usually ranges from 70% - 100%. For
more detailed information consult the strength efficiency of
wire rope graph on page 61 in the block section. Note, that
hand spliced wire rope, while not using any fittings, has less
efficiency than properly flemished and swaged wire rope. There
are other factors, depending on the application of wire rope,
that can cause a decrease in nominal wire rope strength. They
must be considered when choosing a design factor. Refer to the
Wire Rope Users Manual and/or other qualified sources for
details.
ELASTIC
PROPERTIES OF WIRE ROPE
Wire
rope is an elastic member; it stretches or elongates under
load. This elongation can be permanent or recoverable. The
extent of elongation will depend on the wire rope used and the
design factor chosen. While it may be acceptable for many wire
rope uses to neglect its elastic properties, they are of
critical importance for some uses. When in doubt about the
importance of wire rope elongation consult professional help.
Pre-stretching wire rope will only remove some of the
constructional stretch and will not totally eliminate
elongation under load.
WINDING
WIRE ROPE ON DRUMS
Installation
of wire rope on a plain or grooved drum requires a great deal
of care. Make certain the wire rope is properly attached to
the drum. Keep adequate tension on the wire rope as it is
wound onto the drum. Guide each wrap as close to the preceding
wrap as possible, or follow the groove in case of a grooved
drum. No blanket recommendations can be given concerning
direction of winding, desirable drum diameter, fleet angle,
etc. Consult the Wire Rope Users Manual for this and other
important technical information.
Refer
to ASME standard B30.9 and OSHA standard 1910.184 for design
factors and other important information. Other standards and
information may apply.
