The Strength of Elevator Wire Rope

Traction drive elevators subject the wire ropes used in their systems to a high complex of stress factors comprising tension, flexural stress and torsion. These resulting in material fatigue and further abrasion of the wires between the strands.

Elevator suspension ropes are therefore customarily made from bright steel wires, coated with light lubricant. This is sufficient as a protection against corrosion, but should be regularly inspected and renewed.

Strength

The strength of elevator wire rope is a crucial factor when it comes to the safety of your lift. It must be able to withstand a high load without breaking, and it must also have the ability to withstand abrasions and plasticity to ensure its life.

Elevator wire ropes are commonly made from steel. This is a good choice because it is hard-wearing and has a low tendency to untwist when hanging freely in the elevator shaft. They are also easy to mount, so they can be installed in most elevators.

They are designed with a helical structure, which makes them difficult to break. They are also durable and long-lasting, and they can be reused after years of use.

A well-designed rope should have a minimum strand separation and minimal internal strand to strand displacement. This can be achieved by applying a small tensile force to the wires during the production process.

Experienced manufacturers pre-stretch their wires during the manufacturing process by applying a small tensile load to each strand during the stranding process. This reduces the amount of stranding required and increases the wire’s tensile strength.

This pre-stretching process helps to prevent the strands from being damaged during the installation and assembly of your lift. It can also be used to help your wires withstand abrasions.

Several European and international standards (EN 12385-5 [2] and ISO 4344) describe the strength of elevator ropes. These standards define the nominal tensile strengths of the outer wires and inner wires in different rope grades. They also determine the minimum breaking strength of each grade.

A common rope grade for suspension ropes is 1770, which means that the outer wires of the strands have a nominal tensile strength of 1370 N/mm2 and the inner wires of the strands have tensile strengths of 1770 N/mm2. The strength of these ropes is also determined by the wire core material.

Another important elevator wire rope aspect of the rope’s strength is its bending flexibility. This can be affected by a number of factors, including temperature and the sheave material.

A high-quality rope will have a large diameter and an adequate number of outer strands. Moreover, the wires should be made from high-quality, durable steel.

Durability

Elevator wire ropes must be in good condition at all times, inspected for proper tension, wear patterns, rusting, pitting or breaks in strands, sheaves, lubrication and connections. They must also be able to withstand abrasions, plasticity and corrosion.

Several factors affect the durability of elevator ropes, including the type of strand construction, rope nominal diameter and tensile strength. In addition, the use of suitable lubricants can help reduce friction between individual wires.

Ropes can be made from different types of material, including copper, aluminum and steel. They are also available in various colors and finishes. Some of the most popular options include red, white, silver, gold and green.

The tensile strength of elevator ropes is regulated by international standards such as ISO 4344 and EN 12385-5. These standards define the nominal tensile strength of the outer and inner wires in a rope and the minimum breaking strength.

Many elevator wire ropes are constructed with a parallel strand design, which reduces the incidence of abrasion and provides a high fatigue bending life. Additionally, they are less likely to kink or snag and can be easily mounted.

Full steel ropes are another common option for elevator wire ropes, which offer a number of benefits. The biggest advantage is that they are very durable, with a long service life and excellent performance.

Wires of these ropes are usually rated to a minimum breaking strength of 1370 N/mm2. The strength class of the outer wires is defined in terms of their nominal tensile strengths, and the strength of the inner wires is determined by a combination of their nominal tensile strengths.

The outer wires of a rope are often thinner than the inside wires to reduce abrasion damage. However, this can also decrease the tensile strength of the outer wires. This is especially true of elevator wire ropes that have a very high tensile strength.

Some elevator wire ropes are designed to be pre-stretched during production, which can further increase their durability. This process involves applying load to the rope by pull-off during the stranding process. Experienced elevator rope manufacturers can achieve a pre-stretching effect by a number of stretching procedures.

Flexibility

Elevator wire rope is a highly engineered material that has multiple wire strands wrapped together. This makes it flexible strong and gives long service life if properly maintained. It also reduces the risk of damage to elevator cables.

Depending on the intended application, elevator wire ropes may have either a fibre core or a steel wire core. Fiber cores are used because they can store a high quantity of lubricant during manufacture, but this can be a drawback if the lubricant is removed during operation, as it results in a fast rope diameter shrinkage.

Another advantage of fibre cores is that they can be made in a variety of different shapes. This can make it easier to reposition the core in worn grooves.

A steel wire core, on the other hand, can offer more flexibility. It can be shaped to fit grooves with large undercuts, for example. It can be round, for easier adjustments, and it can even have a very thin wire cross section, which offers better fatigue bending properties.

When selecting a rope core, it is important to consider a number of factors, such as the expected load, the bending characteristics of the sheave, and the field of application for the rope. Besides deciding on a suitable rope core, it is also important to choose the right type of strand construction.

In the field of traction drive elevators, the most commonly used strand construction is a 19-wire Seale strand (Fig. 9). Its thick outer wires offer a higher degree of resistance against external wear in use, and the high number of wires enables a higher degree of flexibility.

As an alternative, a Warrington strand can be used. Its thinner outer wires offer better fatigue bending properties and are more resistant to abrasion wear, but they also have less surface contact with the sheave than a Seale strand.

Regardless of the rope core and strand construction, it is vital to ensure that the rope terminates against rotation. This should be done to prevent twisting and untwisting of the rope during installation.

Safety

Elevator wire rope has a wide range of safety features. These include the fact that the wire is lubricated during manufacture, and that the lubricant is applied in a relatively minimal quantity and with extreme care.

In addition, the lubricant should be evenly distributed along the length of the rope. As well as preventing corrosion, lubricants also act to prevent dust and abraded particles from entering the shaft.

It is important that the elevator wire rope be regularly inspected and renewed in order to ensure that it does not break. This can be done by using electromagnetic non-destructive inspection methods or by performing a magnetic test.

Wire ropes with steel wire core are used in elevators because they can be elevator wire rope twisted to provide better axial strength and stiffness. They are also more durable than ropes with fibre cores and they can be easily maintained without changing them.

The wires in the elevator rope are often coated with a light coat of lubricant, but this is not sufficient to protect them from corrosion. In dry lift shafts, this may be adequate, but it is important that ropes are regularly relubricated and inspected to check for any signs of corrosion.

Another way to inspect for corrosion is to wipe a finger over the wires and see whether there are any scratches or other markings. This is an indication of possible problems, and can be corrected immediately.

Ropes are also subject to abrasion during installation and in operation, and it is important that these are protected from abrasion in order to prevent damage. In the case of elevators that are installed in particularly damp climates, ropes should be made from galvanized wires and be relubricated in water-resistant lubricants.

As is the case with all wire ropes, it should be checked for elongation before they are put into use in order to prevent damage. In particular, the elastic elongation of ropes with a steel wire core is increased when they are untwisted and the outer strands are loosened and the load suspended only on the steel core.