IQS Newsroom Articles on Wire Ropes
About Wire Ropes and Wire Rope Suppliers Including: Aircraft
Cables, Cable
Assemblies, Cable
Railing, Plastic Coated Cable, Push
Pull Cable, Stainless
Steel Cable, Steel
Cables, Stranded Cable and Wire, Wire Rope Fittings & Wire Rope Slings.
Wire rope is a machine consisting of multiple strands of wire wound helically around a core, used in various heavy-duty lifting and support applications. First used in the mid 1800's for mining in Germany, wire rope has become a staple in heavy industrial processes such as mining, oil rigging, bridge construction, marine applications and many others. As a versatile, high load capacity alternative to natural fiber ropes such as hemp and manila, wire rope provides motion transmission through nearly all angles, tie down, counterbalance, guidance, control or lift. Also referred to as
stranded cable and wire due to their multiple strand configuration, nearly all wire ropes, or cables, are fabricated from strands of cold drawn carbon steel wires, although
stainless steel cables are manufactured for highly corrosive environments. Various types of steel cables include stainless steel or galvanized
aircraft cables, which are available sizes as small as 3/64" for aircraft control applications;
push pull cable assemblies used in transferring motion between two points; configurations of multiple-rope
cable assemblies equipped with
wire rope fittings for connecting to other cables, and
wire rope slings or eye splices. Wire rope is often manufactured into
plastic coated cable for increased corrosion and wear resistance or for easier handling.
While wire rope's obvious applications lie in multi-ton hoisting and tie-down in industrial manufacturing, construction, ship rigging, oil rigging and mining, many other industries in the manufacturing and consumer sectors use wire rope. Fitness industries use plastic coated cable in most weight machines; theater industries use black powder coated cables for stage rigging; outdoor playground equipment often use plastic coated cables, and many types of electronic equipment, communications devices and medical devices use miniature wire rope and wire rope fittings. Wire rope and steel cables are always connected, fastened and ended with special types of hardware called wire rope fittings. Fittings prevent rope ends from fraying while creating ways for ropes to connect with anchors, equipment or other ropes.
Wire cables and rope are considered machines because their multiple strand configuration acts as multiple "moving parts". The three basic elements of which wire ropes are composed are the individual wires, the strands formed by wires, and the core around which wire strands are wrapped. The configuration of wires, strands and cores varies widely according to a wire rope's application requirements of strength, flexibility, wear and corrosion resistance. Strands can contain as many as 37 wires or as few as 2, and different wire gauges may be included in a strand to increase strength and/or flexibility. Ropes may be right hand lay, twisting strands clockwise, or they may be left hand lay, twisting strands counter-clockwise. Individual strands are twisted in the opposite direction of the lay of the entire rope of strands to increase tension and to prevent the rope from coming unwound.
One of wire ropes' most versatile features is the center core; changing the composition and/or arrangement of the core can make a wire rope suitable for very different applications. Manila fiber cores cushion wires against one another and are valued for their flexibility in medium to low load applications. Aircraft cables and small wire ropes have cotton fiber cores; asbestos cores are used in high heat, or oven applications; polypropylene, polyvinyl chloride (PVC) and plastic impregnated fiber cores provide medium load bearing with mid to high flexibility and wear resistance. Cores may also be another strand of wire called an independent wire rope core (IWRC); wire rope cores maintain a considerable amount of flexibility while increasing strength by at least 7.5% over the strength of fiber core wire ropes. Pure fiber ropes, such as manila, sisal and hemp ropes, have superior flexibility and cushioning, but the strength of natural fiber or polymer rope can't compare to the strength of wire rope in lifting, hoisting and tie-down applications.
Wire Rope Types
-
are strands, cords and wire ropes composed of special strength wire.
Aircraft cables are mainly for aircraft controls and various aircraft
industry uses.
- are fittings which are attached to the end of bundled wires.
- is used in the barriers that run along the edge of stairs and landings, especially in industrial or outdoor locations.
- Plastic coated wire rope is usually coated with a vinyl or nylon-type polymer for ease of handling and extra corrosion resistance in a range of outdoor and indoor fitness cable applications.
- are used as remote-access latch release cables and safety break cables.
- is
resistant to corrosion.
- are strong metal ropes used for various applications.
-
is composed of non-galvanized carbon steel (bright), stainless steel
wire, or galvanized carbon steel. The scope of diameters and compositions
of steel wire rope include 1/16 inch to five inches or greater. But,
whichever the kind of steel, diameter, or the specific composition,
all stainless steel wire has the same physical construction of multiple
strands of wire wound helically about a central core.
- consists of a cable that is made up of strands of wires and is identified by the number of strands and the amount of wires per strand; a 7 x 18 cable would have seven strands with 18 wires in each strand.
-
are wires ropes that have their ends changed through a splice or fittings
add-on. Their uses include running controls, incorporation into machinery
and equipment or as slings or hoists.
-
are hoists that use wire ropes as the means for lifting and consist
of a rope storage drum, motors, gearbox and braking system. A trolley
suspends the hoist from a bridge beam or monorail, although a stationary
mounting is also possible.
-
are short lengths of wire rope made especially to accommodate lifting
attachments. Slings use Independent Wire Rope Cores (IWRC) and may consist
of Improved Plow Steel, Extra Improved Steel, or Extra, Extra Improved
Plow Steel.
Wire Rope Terms
- A calculation of the load necessary to break a wire rope that
is in tension.
- Element of a wire rope
around which the strands are helically laid. The core could be made of
fiber (cloth), independent wire rope or wire strand.
- A round and flanged barrel,
which is tapered or uniform in diameter for storage or operation, around
which rope is wound.
-
Steel that is designed for applications, which require greater safety
features with no increase in diameter size and the highest resistance
to abrasive wear. This steel is fifteen percent stronger than Improved
Plow Steel, and the tensile strength of this grade ranges from 280,000
to 340,000 psi.
- To coat with zinc
for the protection of the wire, strand or rope from corrosion.
- A classification according
to breaking strength.
- Steel wire or strand,
typically galvanized, that braces or supports a structure.
-
A high-carbon steel having a tensile strength of approximately 260,000
psi that is roughly fifteen percent stronger than Plow Steel. Most commercial
wires are made from IPS.
- Wire rope that serves as the core for a greater rope.
- A low carbon steel wire
of approximately 10,000 psi, which is pliable and capable of repeated
stresses from bending around small sheaves. This grade is effective
for tillers, guys and sash ropes.
- The manner in which
the wires are helically wound to form rope. Lay refers specifically
to the direction of the helical path of the strands in a wire rope;
for example, if the helix of the strands are like the threads of a right-hand
screw, the lay is known as a right lay, or right-hand, but if the strands
go to the left, it is a left lay, or left-hand.
- A classification
of wire rope according to its breaking strength. The rank of grades according
to increasing breaking strengths is as follows: Iron, Traction, Mild Plow
Steel, Plow Steel, Improved Steel, Extra Improved Steel.
- A pulley wheel with
a channel, mounted in a frame, that guides or alters the direction of
the cable or rope.
- An assembly of wires
that are helically wound around an axis, fiber or wire center (core) to
create a symmetrical portion.
- Classification
of strands according to breaking strength. The ranking of increasing breaking
strengths is as follows: Common, Siemens Martin, High Strength and Extra-High
Strength; a utility's grade strand is available for certain requirements.
- The act of fastening
a termination to a wire rope through physical deformation of the termination
about the rope via a hydraulic press or hammering. The strength is one
hundred percent of the wire rope rating.
- Fittings into
which wire rope can be inserted and fastened through a cold flow method.
- A grade of
rope material that has a tensile strength range of 180,000 to 190,000
psi. Traction steel has great resistance to bending fatigue with a minimum
of abrasive force on sheaves and drums, which contributes to its long
use in elevators, from which the steel gets its name.
- A continual span of metal
that has been cold drawn from a rod.
Wire Rope Fittings - essential parts of cable assemblies, wire rope assemblies and wire rope slings that assist spliced or swagged rope ends in connecting to other cables and keeping cables and rope from unraveling.
Wire rope from Wikipedia,
the free encyclopedia
Wire rope consists of several strands laid (or 'twisted')
together like a helix. Each strand is likewise made of metal wires laid
together like a helix. Initially wrought iron wires were used, but today
steel is the main material used for wire ropes.
Lay of wire rope
The lay of a wire rope describes the manner in which
either the wires in a strand, or the strands in the rope, are laid in
a helix.
Left and right hand lay
|
Left-hand ordinary lay
(LHOL) wire rope (close-up). Right-hand lay strands are laid
into a left-hand lay rope. |
|
Right-hand Lang's lay
(RHLL) wire rope (close-up). Right-hand lay strands are laid
into a right-hand lay rope. |
Left hand lay or right hand lay describe the manner
in which the strands are laid to form the rope. To determine the lay
of strands in the rope, a viewer looks at the rope as it points away
from them. If the strands appear to turn in a clockwise direction, or
like a right-hand thread, as the strands progress away from the viewer,
the rope has a right hand lay. The picture of steel wire rope on this
page shows a rope with right hand lay. If the strands appear to turn
in an anti-clockwise direction, or like a left-hand thread, as the strands
progress away from the viewer, the rope has a left hand lay.
Ordinary, Lang's and alternate lay
Ordinary and Lang's lay describe the manner in which
the wires are laid to form a strand of the wire rope. To determine which
has been used first identify if left or right hand lay has been used
to make the rope. Then identify if a right or left hand lay has been
used to twist the wires in each strand.
Ordinary lay: The lay of wires in each strand is in
the opposite direction to the lay of the strands that form the wire.
Lang's lay: The lay of wires in each strand is in the
same direction as the lay of the strands that form the wire.
Alternate lay: The lay of wires in the strands alternate
around the rope between being in the opposite and same direction to the
lay of the strands that form the wire rope.
Regular lay: Alternate term for ordinary lay.
Albert's lay: Archaic term for Lang's lay.
Reverse lay: Alternate term for alternate lay.
Spring lay: This is not a term used to classify a lay
as defined in this section. It refers to a specific construction type
of wire.
Construction and specification
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
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.
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.