WHAT IS A WIRE ROPE
In general, a wire rope consists of a number of wire strands formed helically about a central axis. The most populalropes have six or eight strands supported by an axial member known as the core. There are other constructions, buthey are less common. Each strand is composed of a number of individual wires which have been formed helicallabout an axial member called the center. This center supporting member of the strand is generally once or morewires, however, it may be natural fibers (cotton, hemp, sisal, etc.) or synthetic fibers (rayon, nylon, polypropylene).
RAW MATERIALS
Ungalvanized (Bright) Steel Wire
Bright steel wire is chiefly used for wire ropes of which the (rope) life is determined by wear and deterioration rathelthan by corrosion. When comparing the effects of wear and deterioration with that of corrosion one should bear inmind that even a bright wire rope can to some extent be protected from corrosion by adequate lubrication andmaintenance with a suitable wire rope lubricant.
Drawn Galvanized Steel Wire
The wire is drawn to a diameter larger than the required final diameter, then it is hot dip galvanized and afterwardsdrawn to the right size, During this last phase the wire is drawn cold and thereby the guality of the bright raw materiawhich was partially lost by the galvanizing process is restored, Therefore the international standards do not make adistinction between bright wire and drawn galvanized wire where resistance to bending and torsion is concernedMoreover, the smoothness and density of the zinc coating are improved by post drawing so that it offers for betterprotection than a zinc coating of the same thickness applied by drawing after galvanizing.
Stainless Steel Wire
Wire ropes made of stainless steel wire are extremely resistant to corrosion and moreover, to temperature up to 105'C .Originally only the AlSl types 304 and 302 were used for rope making but today almost all our stainless steel wirropes are made of steel according to AlSl type 316 which has better mechanical properties and a higher resistanceelectrolytic corrosion which increased resistance to seawater.
WHAT IS A WIRE ROPE
Steel wire is made in various tensile strength to meet the differentrequirements of a particular job. For the production of our ropes, weuse wire in the following tensile strength ranges:
- 1470 N/mm²(=150 kgf/ mm²)
- 1570 N/mm²(=160 kgf/ mm²)
- 1770 N/mm²(=180 kgf/ mm²)
- 1960 N/mm²(=200 kgf/ mm²)
- 2160 N/mm²(=220 kgf/ mm²)
In the U.S.A. the various grades are designated as follows:
- Traction Steel
- Mild Plow Steel (MPS)
- Plow Steel (PS)
- Improved Plow Steel (lPS )
- Extra lmproved Plow Steel (EIPS)
The most common grades is “lmproved Plow Steel" which comes
STRAND
Components of the strand
A strand consists of a strand core and a layer or a number of layers of round wires. Theround wire are laid helically around the strand core. The strand core consists either of awire (core wire) or a number of wires or even fiber yarns.
STRAND CONSTRUCTION
Two different types of laying the strand are Equal Lay and Cross Lay.
According to different laying methods, it includes:
- Filler type
- Seale type
- Warrington type
- Warrington-Seale type
ROPE CORES
Ropes are supplied either with fiber or steel core, the choice being largely dependent on the application.
Fiber core
Fiber cores are mainly made from polypropylene. This materialhas the advantage that it neither absorbs nor retains moisture,and thus it eliminates conditions creating internal corrosion. Polypropylene core will have small variations in size and weightand are less susceptible to damage, especially under moistconditions.
The following precautions must be taken during use:
● Do not use fiber core ropes where these are exposed to hightemperatures, i.e. above 90, this will damage the filber core
● The fiber core ropes should not be used when muti-layerwinding is required as the fiber cores susceptible to crushing.
Steel core
The steel core is designated lWRC (independentWire Rope Core) and normal construction is 7x7Steel core proves advantageous in severe workingconditions involving a low factor of safety, smalldrums and sheaves, high operational speeds andwide fleet angles. Steel core tends to preserve thecircular cross-section of the rope when it iscrushed by over -winding on drums. it alsoprevents the strands from bridging,(beingforcibly against each other)which can result infatigue failure of wires.
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