The construction of buildings, bridges and roads, the oil and gas refining and coal industries, sea and river shipping, and other industries cannot do without a steel cable today. Flexible and durable ropes twisted from steel wire are used for lifting and moving various equipment, building materials, structural elements and other loads.
Features of the structure of the cable
Steel rope is a complex metal product, which is the main element in many road-building, earthmoving, hoisting machines and mechanisms. Any cable consists of many wires twisted into strands, braiding a common core of metal or other materials.
The strength and design of the rope depends on the number and thickness of wires in each strand, the number of cores and the material of their manufacture, density and number of strands in the cable. The core of the twisted cable forms a model of the finished product and protects the surface of the rope from being squeezed at high mechanical loads. A metal core increases the structural strength of the cable, while tensioning and at high temperatures it reduces its structural elongation.
Rust control
The main problem of steel cables, corrosion, is solved in three ways:
- The production of the original wire is made of stainless steel. The method is the most reliable and expensive.
- Coating zinc or chrome. The most resistant spraying is designed for several years of operation.
- Combined cables with an organic or synthetic core. Cores of hemp, sisal, manila or cotton, impregnated with special grease, minimize friction between the elements of the rope and extend the terms of its use. A more durable and lighter two-layer core made of polyamide yarns is used in cables for equipment of extreme sports.
In terms of durability - quality - price, galvanized cables with non-metal cores are considered the most optimal. Sometimes
corrosion protection is provided by water-repellent grease (solid oil or nigrol).
Qualitative characteristics of a steel cable
One of the main aspects of evaluating a steel cable is its strength. Determined by the thickness, manufacturing method and design, the strength of the rope determines the permissible load on it. Working strength (allowable force) is determined by the maximum load at which the integrity of the cable is not violated for a long time. The tensile strength is determined by the minimum load that destroys the steel cable. Without breaking, steel ropes 2 ... 10 mm thick withstand a load of 47 to 174 kg. The minimum load for breaking steel cables ranges from 235 kg for thin 2 mm ropes to 5880 kg for ropes with a diameter of 10 mm.
An important criterion when choosing a cable is flexibility. The more wires are twisted into a strand of steel rope, the more flexible it is. In cables of increased flexibility, each of the 6 strands braiding the organic core, a retinue of 144 wires.
A flexible look consists of 72
wires, a product of 42 elements is considered rigid. In the production of steel ropes, a wire 1 ... 8 mm thick is used.
Varieties of Steel Ropes
The classification of the cables is determined by the number of layings:
- With a single lay, the wire is wound in a spiral around the core. Such a rope can be used both as a finished product, and as an element of more complex cables.
- For a double twist, ready-made single strands are used, wrapping the core in a certain sequence. This technique is used for the production of single and multi-layer cables. Special wrapping rules allow double galvanized cables (strands) not only to withstand significant loads, but also not to twist during operation.
- The most durable and reliable ropes receive a triple lay. For their formation, the strands are produced according to a special method.
The direction of the strands when twisting can be either right or left.
Cable marking
The designation of the type of galvanized cable is determined by the type of weaving of the strands. Depending on the way the wires are arranged, the cables are divided into several types:
- LC - linear touch, in which the step of the lay in all layers is the same with a repeating pattern.
- LK-O - when weaving a strand, a wire of the same diameter is used.
- LK-R - the cable is formed by strands woven from wires with different diameters.
- LK-RO - in the manufacture of the rope, strands of various types are woven.
- TK - point contact of wires. With this weaving, each layer of the strand has its own step, and the layers cross each other.
- TLK - a combined cable from strands with both linear and point touch.
The right choice of galvanized wire rope, depending on the operating conditions and its purpose, affects the durability and quality of work of the machines and mechanisms in which it is used. For example, the low density of the internal structure of TC types under dynamic load provokes strong friction of the rope layers and leads to its rapid wear.
The product labeling also indicates the type of coating, diameter, type of lay, purpose, type of twist, straightening, accuracy and strength.
The state standard defines the requirements for a galvanized cable, GOST has each type of steel rope. For example, steel cables of type LK-O of a double lay with a metal core are produced in accordance with standard 3066-80, and with organic - 3069-80, LK-O of a single lay comply with standard 3062-80, cables of LK-R with an organic core are made in compliance with GOST 2688-80 and so on. These documents regulate the purpose, mechanical properties of the grades, types of coating of wires, the direction and method of twisting, the combination in the rope of directions of the lay of its elements, the accuracy of manufacture and the degree of balance. Acceptance rules, technical requirements, labeling, test methods, packaging, transportation and storage standards for cables are determined by GOST 3241-91.
Steel wire rope application
Due to its reliability and practicality, galvanized steel wire ropes are actively used as an integral part of industrial equipment in a wide variety of areas:
- in hoisting-and-transport mechanisms;
- in road-building, earth-moving and mining units;
- in the technology of oil and gas industries;
- in agricultural machinery;
- in shipbuilding and other industrial sectors.
A wide range of cables of different diameters and strengths allows you to purchase the type of steel rope appropriate for a particular equipment.
By designation, steel cables are divided into two groups: designed only for working with goods and for lifting or transporting people and goods.
Benefits of Galvanized Ropes
Coating steel wire with zinc increases the life of the steel rope by 3 times and allows it to be used in aggressive environments. Galvanized cables are characterized by a high level of corrosion resistance, which makes it possible to use them on river and sea vessels. Due to their high wear resistance, they are actively used in all areas of industry.
Zinc coating of steel wire divides the cables according to working conditions into three groups:
- In a harsh aggressive environment.
- In a particularly aggressive harsh environment.
- In a medium-aggressive environment.
Sheathed cable
Modern industry offers galvanized PVC braided wire rope for enhanced corrosion protection. Such ropes are successfully used if necessary to tie a load for immersion in liquid, as stretch marks during installation of antennas and masts, during rigging and loading operations in adverse conditions and at low temperatures. A 3 mm galvanized cable in a PVC sheath is used for overhead communication lines and power supply. Today the assortment of galvanized wire ropes is replenished with products coated with materials that can withstand high temperatures and resist combustion.