Elevator steel wire rope is the main load-bearing and traction part of an elevator. It connects the car and the counterweight and transfers force from the traction sheave. Because of this, the rope has a strong influence on safety, comfort, and service life.
To keep passengers safe, engineers must choose the right elevator steel wire rope and maintain it in the correct way. The sections below explain the structure, markings, inspection rules, damage types, scrapping rules, and lubrication methods in simple language.
Basic Structure of Elevator Steel Wire Rope
Every elevator steel wire rope has three main parts:
- Many fine high-strength steel wires
- Several strands made by twisting the wires together
- A rope core in the centre
The strands are laid around the core in a spiral shape. Makers usually use high-quality carbon steel, such as 45–65, or alloy steel, such as 60Si2Mn. For safety, they use special or No. 1 grade steel wire. The diameter of a single wire is often between 0.3 mm and 1.3 mm.
Common constructions for elevator steel wire rope include Seal type and Warrington type. Modern elevators often use 8-strand or 6-strand ropes, and 8×19 Seal type is a very common choice.
Rope Marks and Identification
Each elevator steel wire rope has a mark that shows its structure and strength. One typical mark looks like this:
8×19S (Seal type) – 16 – 140
This mark means the following:
- 8: the rope has eight strands
- 19S (Seal type): each strand has 19 wires in a Seal-type layout
- 16: the nominal rope diameter is 16 millimetres
- 140: the tensile strength of the wire is 140 kgf/mm²
In many domestic installations, the elevator steel wire rope is usually right-hand lay unless the design calls for something different.
A Seal-type rope with 19+9+9+7+49 wires in its cross-section can have a central wire with a diameter of 1.2 mm, inner wires with a diameter of 0.6 mm, and outer wires with a diameter of 1.05 mm. Because the outer wires are thicker than the inner wires, people often call this design an outer thick steel wire rope.
Contact Between Wires and the Rope Core
When the interlayer steel wires lie parallel and remain in close contact, the elevator steel wire rope has good fatigue resistance. A large contact area increases wear resistance, although it also increases contact stress.
For example, a passenger elevator with a rated load of 1000 kg may use an 8×19S (Seal type)–16–140 rope. In this case:
- 8 is the number of strands
- 19 is the number of wires in each strand
- 16 mm is the nominal rope diameter
- 140 kgf/mm² is the tensile strength of the wire
The rope core is also very important. Many elevator steel wire ropes use a fibre core, such as sisal, that is soaked in lubricating oil. The core supports the strands, keeps them in place, increases the contact area, cushions impact loads, stores oil, and helps with long-term lubrication. As a result, the rope stays flexible and keeps its shape while it bends over sheaves and pulleys.
Safety Factor of Elevator Steel Wire Rope
From a safety point of view, elevator steel wire rope must have a large enough safety factor. Standards such as GB7588 give values for the static safety factor K.
In many cases:
- Elevators with three or more traction ropes use a safety factor K of about 12.
- Elevators with only two traction ropes use a higher safety factor, often about 16.
- Passenger, cargo, and medical elevators normally use at least four working ropes.
Several values go into the calculation:
- The rated load of the elevator
- The dead weight of the car
- The counterweight
- The mass of the elevator steel wire rope itself
- The diameter of the traction sheave and the shape of the groove
When designers choose the correct rope and follow these rules, the elevator steel wire rope has enough strength and fatigue life for safe service.
Daily Inspection and Maintenance
The condition of elevator steel wire rope affects both passenger safety and equipment reliability. Therefore, technicians must inspect the rope on a regular basis. During every inspection they usually do the following:
- Check the number, position, and lay distance of broken wires. They count the broken wires and record where they appear along the rope.
- Measure the rope diameter with a vernier caliper and compare it with the nominal value. A large reduction points to wear or corrosion.
- Check the balance of rope tension. The difference between ropes in the same group must stay within the allowed percentage.
- Look at the rope surface. It should be clean, well lubricated, and free from rust.
- Look for abnormal elongation or deformation, such as kinks, opened strands, or other irregular shapes near the rope head and along the rope.
Because of these checks, maintenance staff can find problems early and fix them before a serious fault appears.
Typical Damage to Elevator Steel Wire Rope
During normal service, elevator steel wire rope faces several harmful effects. These include wear, bending fatigue, corrosion, long-term vibration, and impact. Over time, these effects cause different types of damage.
Wear and Deformation
Pure mechanical wear appears when the rope rubs against the sheave groove and pulleys. Under normal conditions the wear is slow and quite uniform.
Deformation and local wear show up when the groove is eccentric, when there are pits, or when strong vibration or impact happens at the pulleys. These problems can cause local compression and cross-section changes. Even when the total metallic area has not dropped very much, local deformation makes the rope more likely to break.
Internal wear and strand displacement occur because the rope bends many times during service. The steel wires move slightly against each other. As contact pressure grows, the internal wires become thinner. In serious cases, many internal wires break while the outside still looks normal. Sometimes the rope makes a clear clicking sound when the elevator runs. This sound is a warning sign of internal damage.
Rust and Avalanche Break
Rust is another major risk for elevator steel wire rope. Corrosion can happen on the surface or inside the rope. Surface rust may loosen the strands and pit the wires. Internal rust is harder to see and often more dangerous. Both types reduce mechanical strength and can lead to brittle fracture.
One especially dangerous case is the avalanche break. In this situation, strong corrosion and wear cause a large number of wires to fail in a short length of rope. When people see heavy rust or red-coloured oil near the rope head or inside the strands, they should inspect the rope very carefully. If needed, they can cut off the rope head and check the internal condition, then protect the rope or scrap it in time.
How Broken Wires Look
The shape of broken wires gives useful clues about the reason for failure. Typical patterns include:
- Overload broken wire. The fracture has a cup-shaped plastic shrinkage. This pattern shows that the rope once carried an overload or suffered a strong impact. It is rare in normal elevator work.
- Fatigue broken wire. The break often appears on the outer side of the strand, where bending stress is highest. The fracture surface is bright and shows fatigue marks.
- Wear and broken wires. Long-term friction between rope and groove or between wires makes the cross-section thin. The fracture is usually oblique and rough.
- Rust and broken wires. Severe corrosion leaves an irregular pointed fracture.
- Cutting-type breakage. Sharp local contact or impact produces a notch. The fracture may look like it has been sheared.
- Twisted and broken wires. Torsion makes the rope loose and causes the outer wires to twist and break. This problem is not common and usually appears in ropes that already lay unevenly.
When technicians study these patterns, they can find the root cause of the damage and then improve groove shape, lubrication, loading, or installation quality.
When to Scrap Elevator Steel Wire Rope
At some point the elevator steel wire rope becomes unsafe and must be replaced. The main scrapping rules are as follows:
- Excessive surface wear or corrosion. If wear or rust reaches a large share of the wire diameter, often about 30 percent, the rope should be scrapped even when the number of broken wires seems small.
- Too many broken wires in one lay length. Standards set a maximum number of broken wires allowed in one lay. When the lay direction of the rope is the same as the groove, the allowed number is only half of the standard value.
- Large reduction in rope diameter. A diameter reduction of about 10 percent is a clear sign that the rope has reached its limit.
- Severe corrosion, blackening, or looseness. A rope with badly corroded, blackened, pitted, or loose outer strands must be replaced at once.
- Overload signs. When internal lubricant is squeezed out and looks like sweat on the rope surface, the rope has reached an overload state. In this case, technicians must check it carefully and install new ropes when necessary.
When they replace elevator steel wire rope, technicians should change all ropes in the same group. This practice keeps the stretch and performance of each rope similar and makes operation safer.
Lubrication of Elevator Steel Wire Rope
Good lubrication greatly increases the service life of elevator steel wire rope. It reduces friction, slows wear, and protects the wires from rust.
Requirements for Grease
Lubricating grease for elevator steel wire rope should meet several basic requirements:
- It should not contain acid or alkali.
- It should contain no water and should not absorb moisture from the air.
- It should not dry out or crack at low temperature.
- It should keep its properties at high temperature.
- It should have a suitable viscosity so that it can enter the rope interior and also form a thin protective film on the surface without flowing away.
In many good installations, the original lubrication of elevator steel wire rope can last three to five years. However, whenever people see rust or dryness on the rope, they must renew the lubrication at once, no matter how long the rope has been in use.
Lubrication Methods
There are two common methods to lubricate elevator steel wire rope.
- Brushing method. A bristle brush is moved along the running direction of the rope. The mechanic uses it to apply special elevator rope grease or No. 20 oil. This method needs no heating and is easy to use. The amount of oil should stay moderate, because too much oil can reduce traction and contaminate other parts.
- Heating and coating method. First, the mechanic removes dirt with a steel wire brush and wipes the rope with a suitable cleaning liquid. Then a mixture of lubricating oil, such as graphite and Vaseline, is heated to about 80 °C and brushed on the rope. The coating should be even and thin, so that the rope does not slip in the groove and the load torque stays balanced.
Both methods, when used correctly, keep elevator steel wire rope in good condition and protect the sheaves as well.
Conclusion
Elevator steel wire rope is a precision, safety-critical component made of many high-strength steel wires twisted into strands and wrapped around a core. Its safe operation depends on proper selection of structure, material, and diameter; adequate safety factor and correct installation; regular inspection and maintenance; early recognition of wear, corrosion, and broken wires; timely scrapping and replacement; and correct lubrication practices. In addition, choosing elevator steel wire rope from reliable manufacturers and suppliers such as KNKT helps ensure stable quality and consistent performance over the whole service life of the rope.
By following these principles and working with trusted partners like KNKT, elevator owners and maintenance teams can maximise the service life of elevator steel wire rope and ensure that passengers travel safely and smoothly every day.
