The base of any round rope is the strands that lay around central element — the core. The core, can be made from fiber (organic or synthetic), metal (arranged as a wire strand or as an independent wire rope), solid polymer or combination of materials. The strands of the rope consist of an assembly of wires of appropriate shape and dimensions laid helically in the same direction in one or more layers around a center.
The rope performance, its fatigue resistance, abrasive wear resistance and radial rigidity (crush resistance, for example, in case of multi-layer lay on drum) depend on the choice of strand and rope construction.
A parallel lay strand construction which contains of at least two layers with the same number of wires of different diameters laid in one operation and in the same direction.
Parallel lay strand construction having an outer layer containing alternately large and small wires and twice the number of wires as the inner layer.
Parallel lay strand construction having an outer layer containing twice the number of wires than the inner layer, with filler wires laid in the interstices between the layers.
Parallel lay strand construction having three or more layers laid in one operation and formed from a combination of strand types Warrington and Seale.
Constructions of the strand laid in several operations in which wires of superimposed layers cross one another and have a point contact.
A construction of a strand laid in several operations that has at least three layers of wires, the outer layer of which is laid onto the central construction of the parallel lay.
Increasing the number of wires and reducing their diameter allows to increase the fatigue resistance of the rope, but it reduces the abrasive wear resistance. Reducing the number of wires in the strands and increasing their diameter allows to increase the abrasive wear resistance, but it reduces the fatigue resistance of the rope. By choosing a six-strand cross-lay rope with a metal core, we get increased crush resistance during a multi-layer lay on the drum, unlike the multi-strand ropes, ropes with a fiber core or lang-lay ropes which are poorly resistant to radial loads. Ropes with polymer coating of a metal core can be used at wider angles of deviation than regular ropes.
That is why the choice of rope, as well as choice of any other equipment, should be made precisely and very carefully. It is necessary to take into account all the working conditions and parameters of the rope.
The fiber core of the rope can be made of natural or synthetic fibers. The fiber core works like a sponge and keeps the lubricant well in the cross section of the rope. The main disadvantage of ropes with a fiber core is that at high specific pressure between the strands and the core, the core gradually collapses and the strands lose support. Therefore, it is not recommended for multi-layer winding on a drum.
A steel core of ropes is a strand (WC), an independent wire rope (IWRC) or a strand wrapped by wire strands (CWRC). The use of a steel core provides the rope with greater strength, increases resistance to lateral compression and reduces the elongation of the rope under load compared to a fiber core.
An independent wire rope core provides even better structural support and increased metallic area. It is most commonly used in demanding applications where crush resistance and fatigue life are critical.
Ropes with polymer coating of a metal core can be used at wider angles of deviation than regular ropes. The plastic fill between the IWRC and outer strands reduces internal wear.
