Construction and specification
 |
In
the above example, each individual
wire is arranges around a central
wire to form a 7-wire strand. Six of
these strands are formed around a
central core to make a wire rope.
The rope is specified as 6x7 (6/1) –
i.e. six strands each of seven
wires. |
The specification of a wire rope type –
including the number of wires per strand, the
number of strands, and the lay of the rope – is
documented using a commonly accepted coding
system, consisting of a number of abbreviations.
This is easily demonstrated with a simple
example. The rope shown in the figure "Wire rope
construction" is designated thus: 6x19 FC RH
OL FSWR
| 6 |
Number of strands that
make up the rope |
| 19 |
Number of wires that
make up each strand |
| FC |
Fibre core |
| RH |
Right hand lay |
| OL |
Ordinary lay |
| FSWR |
Flexible steel wire rope |
Each of the sections of the wire rope
designation described above is variable. There
are therefore a large number of combinations of
wire rope that can be specified in this manner.
The following abbreviations are commonly used to
specify a wire rope.
| Abbr. |
Description |
| FC |
Fibre core |
| FSWR |
Flexible steel wire
rope |
| FW |
Filler wire |
| IWR |
Independent wire
rope |
| IWRC |
Independent wire
rope core |
| J |
Jute (fibre) |
| LH |
Left hand lay |
| LL |
Lang's lay |
| NR |
Non-rotating |
| OL |
Ordinary lay |
| RH |
Right hand lay |
| S |
Seale |
| SF |
Seale filler wire |
| SW |
Seale Warrington |
| SWL |
Safe working load |
| TS |
Triangular strand |
| W |
Warrington |
| WF |
Warriflex |
| WLL |
Working load limit |
| WS |
Warrington Seale |
Terminations
RHOL wire rope terminated in a loop
with a thimble and talurit splice
The end of a wire rope tends to fray readily,
and cannot be easily connected to plant and
equipment. A number of different mechanisms
exist to secure the ends of wire ropes to make
them more useful. The most common and useful
type of end fitting for a wire rope is when the
end is turned back to form a loop. The loose end
is then fixed by any number of methods back to
the wire rope.
Thimbles
When the wire rope is terminated with a loop,
there is a risk that the wire rope can bend too
tightly, especially when the loop is connected
to a device that spreads the load over a
relatively small area. A thimble can be
installed inside the loop to preserve the
natural shape of the loop, and protect the cable
from pinching and abrasion on the inside of the
loop. The use of thimbles in loops is industry
best practice. The thimble prevents the load
from coming into direct contact with the wires.
Wire rope clamps
(DOG CLAMPS)
A wire rope clamp, also called a clip, is
used to fix the loose end of the loop back to
the wire rope. It usually consists of a u-shaped
bolt, a forged saddle and two nuts. The two
layers of wire rope are placed in the u-bolt.
The saddle is then fitted over the ropes on to
the bolt (the saddle includes two holes to fit
to the u-bolt). The nuts secure the arrangement
in place. Three or more clamps are usually used
to terminate a wire rope.
Swaged
terminations
Swaging is a method of wire rope termination
that refers to the installation technique. The
purpose of swaging wire rope fittings is to
connect two wire rope ends together, or to
otherwise terminate one end of wire rope to
something else. A mechanical or hydraulic swager
is used to compress and deform the fitting,
creating a permanent connection. There are many
types of swaged fittings. Threaded Studs,
Ferrules, Sockets, and Sleeves a few examples.
Sockets
A socket termination is useful when the
fitting needs to be replaced frequently. For
example, if the end of a wire rope is in a
high-wear region, the rope may be periodically
trimmed, requiring the termination hardware to
be removed and reapplied. An example of this is
on the ends of the drag ropes on a dragline. The
end loop of the wire rope enters a tapered
opening in the socket, wrapped around a separate
component called the wedge. The arrangement is
knocked in place, and load gradually eased onto
the rope. As the load increases on the wire
rope, the wedge become more secure, gripping the
rope tighter.
Eye splice
| The ends of individual strands of
this eye splice used aboard a cargo ship
are seized with natural fiber cord after
the splicing is complete. This helps
protect seaman's hands when handling.
An eye splice may be used to terminate
the loose end of a wire rope when
forming a loop. The strands of the end
of a wire rope are unwound a certain
distance, and plaited back into the wire
rope, forming the loop, or an eye,
called an eye splice.
|
 |
