Breaking strength is one of the most frequently quoted specifications in fall protection equipment, yet it is also one of the most misunderstood. Many users assume that a higher breaking strength automatically means safer equipment, but this is only partially true. While the value indicates the ultimate load a product can withstand before failure, it does not represent the force that can be applied during normal operation, nor does it define the safe working load of the equipment.
Within the work at height industry, breaking strength is used to assess the structural capacity of components such as ropes, connectors, anchor devices, lanyards, webbing, slings and hardware. Manufacturers determine this value through destructive laboratory testing, where the product is loaded until permanent structural failure occurs. These results help engineers design reliable systems and demonstrate compliance with European and international standards, but they should always be interpreted alongside other technical parameters such as working load limits, dynamic performance and safety factors.
How Breaking Strength Is Measured
Breaking strength is established through controlled mechanical testing using calibrated tensile testing machines. During the test, the component is subjected to steadily increasing force until one or more structural elements fail. The maximum force recorded immediately before failure becomes the product’s breaking strength.
Most values are expressed in kilonewtons (kN), the standard unit used throughout the fall protection industry. One kilonewton is equivalent to approximately 100 kg of static force under Earth’s gravity, although direct conversion should be avoided because fall protection equipment is designed to withstand dynamic rather than purely static loading. For example, a connector with a breaking strength of 25 kN has demonstrated the ability to resist approximately 2.5 tonnes of static tensile force during laboratory testing before failure occurred.
Testing procedures vary according to the product type and the applicable standard. Connectors certified to EN 362, anchor devices tested under EN 795 and textile components evaluated under other European standards all undergo specific loading methods intended to represent their expected service conditions. Some products are tested in multiple orientations because loading direction can significantly affect ultimate strength.
The published breaking strength reflects the performance of new equipment tested under controlled laboratory conditions. Ageing, corrosion, ultraviolet exposure, chemical contamination, abrasion or improper storage may all reduce the actual strength of equipment in service, making routine inspection essential throughout its working life.
Breaking Strength Is Not the Same as Safe Working Load
One of the most common misunderstandings is confusing breaking strength with safe working load or working load limit. Although these values are related, they describe completely different aspects of equipment performance.
Breaking strength represents the point at which structural failure occurs. Safe working load is the maximum load that equipment is intended to support during normal operation while maintaining an appropriate margin of safety below its ultimate strength. The difference between these two values is determined by applying a safety factor that accounts for uncertainties such as material variability, manufacturing tolerances, repeated loading, wear and unexpected operating conditions.
For lifting equipment, safety factors of 4:1, 5:1 or higher are commonly applied depending on the equipment type and applicable standards. Although personal fall protection equipment follows different design principles because it is intended to arrest dynamic falls rather than support suspended loads continuously, the same fundamental concept applies. Equipment should never be used close to its breaking strength during normal operation.
Another important distinction involves fall arrest forces. Modern energy absorbers certified to EN 355 are designed to limit the maximum force transmitted to the user to 6 kN during dynamic testing. This value is dramatically lower than the breaking strength of the equipment because the objective is to protect the worker long before any structural component approaches failure.
Understanding this difference helps prevent dangerous assumptions. A connector with a breaking strength of 25 kN should never be subjected to loads approaching that value during normal use simply because laboratory testing demonstrated structural failure at that point.
Typical Breaking Strength Values in Fall Protection Equipment
Different components within a personal fall protection system are designed to withstand different levels of loading depending on their intended function. Although exact values vary between manufacturers, many certified products fall within well established performance ranges.
Typical examples include:
- Karabiners and connectors certified to EN 362 commonly have major axis breaking strengths between 20 and 30 kN.
- Textile anchor slings often have minimum breaking strengths of 22 kN or greater.
- Low stretch kernmantle ropes used for rope access under EN 1891 typically have minimum breaking strengths above 22 kN depending on rope diameter and termination method.
- Full body harness attachment points tested under EN 361 must withstand substantial dynamic and static loads during certification testing.
- Permanent and temporary anchor devices tested under EN 795 are required to resist demanding static and dynamic loading scenarios depending on their classification.
These values should not be compared without understanding the associated test methods. Different standards use different loading directions, test masses and acceptance criteria, meaning that identical numerical values do not necessarily indicate equivalent performance.
It is also important to recognise that the strength of an assembled system is limited by its weakest compatible component. Connecting a 30 kN karabiner to an unsuitable anchor or damaged sling does not produce a 30 kN system if another component fails at a significantly lower load.
Factors That Can Reduce Breaking Strength
The published breaking strength applies only to equipment that remains in its original certified condition. During service, numerous environmental and operational factors can reduce structural capacity, sometimes without immediately visible damage.
Mechanical wear is one of the most common causes of strength reduction. Repeated abrasion gradually removes fibres from textile equipment and can create grooves in metal hardware. While the equipment may continue functioning normally, its ultimate strength may no longer correspond to the manufacturer’s published value.
Sharp edges present another significant hazard. Textile lanyards, ropes and slings loaded over unprotected edges may experience severe localised damage. Even relatively small cuts can reduce residual strength considerably because modern synthetic fibres rely on load sharing across thousands of individual filaments.
Environmental exposure should also be considered. Ultraviolet radiation gradually degrades many synthetic materials, while chemicals, oils, acids and alkalis may weaken fibres or cause corrosion in metallic components. High temperatures generated by friction or welding operations can permanently alter the properties of webbing, rope and certain metal alloys.
The following conditions require particular attention during inspection:
- Cuts, abrasion or broken fibres in ropes and webbing.
- Corrosion, cracks or deformation in metal hardware.
- Heat damage, burns or welding spatter.
- Chemical contamination or prolonged ultraviolet exposure.
- Previous fall arrest loading or unknown service history.
Any equipment showing signs of significant damage should be removed from service immediately because its original breaking strength can no longer be guaranteed.
Why Breaking Strength Must Be Considered Within the Entire Safety System
Breaking strength is an important engineering parameter, but it should never be used as the sole criterion when selecting fall protection equipment. A system with exceptionally high structural capacity may still perform poorly if components are incompatible, incorrectly installed or unsuitable for the intended application.
Anchor location provides a good example. A certified anchor capable of resisting more than 20 kN may still create an unsafe system if positioned below the worker, increasing free fall distance and arrest distance beyond the available clearance. Similarly, a high strength connector offers little protection if attached to a structure that has never been assessed as a suitable anchorage.
Dynamic behaviour is equally important. During a fall, energy absorbers, self retracting lifelines and harnesses work together to control arrest forces. The objective is not simply to prevent structural failure but to reduce the forces acting on the worker to survivable levels while maintaining system integrity. This explains why modern fall protection standards place equal emphasis on dynamic testing, arrest force limits and equipment compatibility alongside ultimate strength.
Inspection and maintenance complete the picture. Products that initially met all certification requirements may gradually lose strength through wear, corrosion or environmental exposure. Regular examination in accordance with EN 365 and the manufacturer’s instructions ensures that the equipment continues to provide the performance established during certification testing.
Breaking strength should therefore be viewed as a measure of structural capacity rather than a guarantee of operational safety. When interpreted alongside working load limits, dynamic performance, applicable standards, inspection requirements and correct system design, it becomes an essential engineering value that helps ensure fall protection equipment performs reliably throughout its service life.