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Views: 0 Author: Site Editor Publish Time: 2026-03-20 Origin: Site
Wire ropes are critical components in an elevator traction system. They carry the full load of the elevator car, passengers, or cargo, and therefore have a direct impact on operational safety. If the tension of the traction wire ropes is not properly balanced, the system may suffer from abnormal wear, rope slip, vibration, reduced service life, and even serious safety risks.
This article explains the main causes of uneven wire rope tension in elevators, the hazards it creates, and the practical measures that should be taken to prevent premature failure.
Uneven wire rope tension occurs when multiple traction ropes in an elevator do not share the load equally. In a properly adjusted elevator, each rope should carry nearly the same load. When one or more ropes are looser or tighter than the others, load distribution becomes unbalanced.
For example, if an elevator uses four traction wire ropes and one rope is relatively loose, it may appear that all four ropes are installed and working, but in reality only three ropes are carrying most of the load. The loose rope may not truly bear weight and instead moves passively with the others. This creates excessive stress on the working ropes and on the traction sheave grooves.
When rope tension is inconsistent, not all ropes share the load equally. The tighter ropes carry more load, while the looser ropes contribute less or almost nothing. This causes the working ropes to operate under higher stress than intended, increasing the risk of wear, fatigue, and broken wires.
Uneven rope tension increases the compressive stress between the ropes and the traction sheave grooves. As a result:
the wire ropes wear faster
rope diameter gradually becomes smaller
broken wires become more likely
the sheave grooves wear unevenly
groove depth and diameter become inconsistent
Once this happens, both the wire ropes and the traction sheave begin to deteriorate more quickly.
When wire ropes seat in the sheave grooves at different depths, the effective running radius changes. A rope seated deeper in the groove runs on a smaller radius and therefore moves at a slower linear speed. A rope seated more shallowly runs on a larger radius and moves faster.
Since all ropes must travel the same distance during elevator operation, this speed difference causes rope creep or rope slip. The faster rope tends to slide backward, while the slower rope tends to slide forward. This phenomenon is often referred to as rope migration or rope creeping.
As rope slip increases, the elevator car may begin to vibrate or jerk during operation. Passengers may feel impact, hesitation, or uneven motion. This not only affects ride comfort, but also signals mechanical instability within the traction system.
Once rope slip begins, friction increases further. More friction leads to more wear, and more wear increases the difference in groove depth and rope diameter. This creates a vicious cycle that can quickly damage both the wire ropes and the traction sheave, often leading to early replacement or scrapping of components.
In newly installed elevators, uneven wire rope tension is often caused by incorrect adjustment during installation. Common problems include:
adjusting rope tightness by feel or visual judgment rather than by measurement
failing to ensure that all ropes are tensioned consistently
making improper adjustments after slow-speed commissioning runs
allowing different ropes to stretch by different amounts during the initial operating period
Because wire ropes experience structural elongation after installation, inconsistent adjustment at the beginning can lead to significant tension deviation later.
Another limitation is the adjustment travel of the rope fastening assembly. In many cases, the adjusting screw travel is only about 200 mm, which may not be enough to compensate for major differences in rope elongation.
On some construction sites, wire ropes may be installed in batches rather than all at once. If part of the ropes are installed first and the elevator is then run at slow speed before the remaining ropes are installed, the first group of ropes will already have experienced elongation, while the later-installed ropes will not.
This creates a large difference in stretch and tension between ropes, making it difficult or impossible to equalize tension afterward.
In older elevators, uneven tension often occurs when only one or two wire ropes are replaced instead of replacing the full rope set. New ropes and old ropes do not have the same structural elongation characteristics. Even if their initial tension appears similar, they will not behave the same after operation.
Because the adjustment range of the rope end assembly is limited, it is often impossible to fully compensate for the tension difference between old and new ropes. As a result, uneven load sharing develops quickly after installation.
Some installation teams replace ropes one by one by operating the elevator at slow speed. In this method, part of the rope set may already be in service while other ropes are still being replaced. This can create major differences in structural elongation between newly installed ropes and ropes that have already been loaded.
Even if all ropes appear to have equal initial tension at the time of installation, they may soon become uneven after the elevator returns to normal operation.
Wire ropes contain internal rotational stress. If this stress is not fully released during installation, the ropes may twist, rotate, or roll inside the sheave grooves during operation. This can worsen tension imbalance, cause unstable rope seating, and accelerate rope and groove wear.
Proper rope handling during installation is essential to prevent this problem.
Uneven wire rope tension is one of the main causes of abnormal wear in both elevator wire ropes and traction sheaves. It shortens service life, increases maintenance cost, reduces ride quality, and may eventually lead to premature scrapping of expensive components.
More importantly, because elevator wire ropes are directly related to car support and traction performance, tension imbalance is not just a maintenance issue. It is also a safety issue that must be carefully controlled before it develops into a more serious mechanical failure.
Wire rope tension should not be adjusted by hand feel or visual estimation alone. Accurate measuring tools and standardized procedures should be used to ensure that all ropes share the load as evenly as possible.
Whenever possible, all traction wire ropes should be installed together as a complete set. Batch installation can create differences in rope stretch that are difficult to correct later.
In most cases, replacing only one or two ropes in a multi-rope traction system is not recommended. New and old ropes behave differently under load, and this often results in rapid tension imbalance.
Because ropes may settle and elongate after commissioning, tension should be checked again after the elevator has completed its initial running period. Follow-up adjustment is necessary to maintain balanced load distribution.
During installation, care should be taken to release internal torsional stress and prevent rope twisting. Improper handling can cause rope rotation in the grooves, poor seating, and uneven wear.
Routine inspection should include:
rope tension consistency
rope diameter changes
broken wires
groove wear depth
rope slip marks
abnormal car vibration or jerking
Early detection can prevent major damage and reduce repair costs.
Uneven wire rope tension in elevators is a serious issue that can lead to abnormal rope wear, traction sheave damage, rope slip, vibration, reduced service life, and higher safety risk. The main causes include improper adjustment during installation, batch installation, partial rope replacement, slow-speed rope replacement methods, and failure to release internal rope stress.
For elevator manufacturers, installers, and maintenance teams, tension imbalance must be treated as a critical control point. Proper installation, accurate adjustment, complete rope replacement practices, and regular inspection are essential to prevent premature failure and ensure safe elevator operation.
