What does the nominal breaking strength of a chain mean in practice?

When selecting conveyor chains, breaking strength is one of the most fundamental technical parameters, but its true significance in practical applications often remains unclear. Particularly in demanding industrial processes, such as metal processing and conveyor systems operating at high temperatures, the nominal breaking strength of the chain can be a crucial factor for production continuity.

When a maintenance manager wonders why conveyor chains wear out faster than expected or why a new chain costs more than the previous one, the answer is often found in the relationship between tensile strength and actual operating conditions. Forged conveyor chains they offer a solution to these challenges when their breaking strength is correctly dimensioned for the operating conditions .

What does the nominal breaking strength of a chain mean?

The nominal breaking strength of a chain indicates the maximum tensile load that the chain can withstand before breaking under laboratory conditions at room temperature. It is measured in kilonewtons (kN) or tonnes and is determined in standardised tests where the chain is subjected to a steadily increasing force until it breaks.

Nominal breaking strength serves as a benchmark between different chain types, but it doesn't tell the whole story about a chain's actual performance in practical applications. For instance, the nominal breaking strength of a 142V type chain is 520 kN, while the more robust 216W chain has a breaking strength of 750 kN. This 44% difference is significant, especially under demanding operating conditions.

In industrial applications, however, the chain does not operate under laboratory conditions but is exposed to high temperatures, shock loads and abrasive materials. Therefore, nominal breaking strength alone is not sufficient as a selection criterion for the chain, but it is essential to understand how different factors practically affect this value.

How does the nominal breaking strength of a chain affect practical applications?

In practical applications, the nominal breaking strength of a chain determines the safety margin and operational reliability, but actual performance depends on the operating conditions. High nominal breaking strength allows for greater load-bearing capacity and extends the chain's service life under demanding conditions.

In metal refining plants and the heat recovery boilers of smelters, the chain operates under a continuous tensile load, which can represent a significant portion of its nominal breaking strength. If the operating temperature rises to 300–400 degrees Celsius, the tensile strength of steel decreases considerably. In this situation, a higher nominal breaking strength provides a necessary safety margin.

Sudden loads, such as the fall of large material accumulations onto a chain, can momentarily exceed the continuous load many times over. A chain with a higher nominal breaking strength will cope better with these situations without permanent deformation or fracture.

In practice, this is seen in longer service intervals and reduced maintenance requirements. When the chain's breaking strength is dimensioned according to actual loads with a sufficient safety factor, the process can operate reliably without unexpected downtime.

What factors influence the actual breaking strength of a chain in use?

The actual breaking strength of a chain in use is primarily influenced by temperature, material properties, load type, and environmental conditions. High temperatures significantly reduce the tensile strength of steel, while the correct material selection can compensate for this degradation.

The effect of temperature is one of the most critical factors. When the temperature rises above 200 degrees Celsius, the tensile strength of ordinary manganese steel begins to decrease rapidly. Boron steel, on the other hand, retains its mechanical properties better at high temperatures, making it a superior choice for demanding applications.

The type of load significantly affects the actual durability of the chain. A continuous steady load is less harmful to the chain than repeated shock loads or fatigue-inducing, variable loads. Therefore, it is important to understand the load profile of the process when selecting a chain.

Environmental conditions such as corrosive gases and particles can degrade the chain structure over time. If the internal temperature of the conveyor drops below the acid dew point, sulfuric acid will form, which accelerates corrosion and weakens the chain's tensile strength.

During use, the chain is also exposed to wear, which reduces the cross-sectional area and thus lowers the actual breaking strength. The advantage of a boron steel chain is that its hardness does not change with surface wear, so the reduction in breaking strength is slower than with traditional materials.

To optimise the breaking strength of a chain in practical applications, the entire conveyor system must be considered. Thermal expansion control, insulation, protection of the chain from impacts, and correct operating parameters are just as important as the choice of chain material itself. When these factors are considered comprehensively, the actual performance of the chain will better match its rated values.

If you are wondering whether the durability of the conveyor chains used in your process could be improved, or if you want to be sure that your next chain selection is the correct one, Get in touch, so let's work together to find the best solutions for your specific application. Forged conveyor chains provide a reliable solution even for the most demanding operating conditions.