Choosing the right rope for your application
With each application, your choices of wire ropes can be many. How do you know which one works best for you? Ropes include a combination of properties that give them specific performance abilities. Before you choose, it pays to look closely at each rope’s special properties.
NO SINGLE WIRE ROPE
CAN DO IT ALL
All wire ropes feature design characteristic trade offs. In most cases, a wire rope cannot increase both fatigue resistance and abrasion resistance. For example, when you increase fatigue resistance by selecting a rope with more wires, the rope will have
less abrasion resistance because of its greater number of smaller outer wires.
When you need wire rope with greater abrasion resistance, one choice is a rope with fewer (and larger) outer wires to reduce the effects of surface
wear. But that means the rope’s fatigue resistance will decrease. That’s why you need to choose your wire rope like you would any other machine. Very carefully. You must consider all operating
conditions and rope properties.
THE BASIC PROPERTIES
OF WIRE ROPE
How do you choose the wire rope that’s best suited for your job? Following are the most common properties to be considered when selecting a rope for an application.
STRENGTH: Wire rope strength is usually measured in tons of 2,000 lbs. In published material, wire rope strength is shown as minimum breaking
force (MBF) or nominal catalog)
strength. These refer to calculated strength figures that have been
accepted by the wire rope industry. When placed under tension on a test device, a new rope should break at a figure equal to – or higher than – the
minimum breaking force shown for that rope.
The values in this catalog apply to new, unused rope. A rope should never operate at – or near – the minimum breaking force. During its useful life,
a rope loses strength gradually due to natural causes such as surface wear and metal fatigue.
FATIGUE RESISTANCE: Fatigue resistance involves metal fatigue of the wires that make up a rope. To have high fatigue resistance, wires must be capable of bending repeatedly under stress – for example, a rope passing
over a sheave.
Increased fatigue resistance is achieved in a rope design by using a large number of wires. It involves both the basic metallurgy and the diameters of wires. In general, a rope made of many wires will have greater fatigue resistance than a same-size rope made of fewer, larger wires because smaller wires have greater ability to bend as the rope passes over sheaves or around drums.
To reduce the effects of fatigue, ropes must never bend over sheaves or drums with a diameter so small as to bend wires excessively. There are precise recommendations for sheave and drum sizes to properly accommodate all sizes and types of ropes.
For detailed information about our Wire Rope, go to pages 33-84 in the Full Catalog