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Tension fatigue

Mooring is a complex operation that can place severe wear and stress on the lines used for securing vessels. Wind, waves and currents mean that even when docked, ships are in constant motion. This means that the tension placed through mooring lines is changing all the time – contributing to material fatigue and reducing service life. When lines are used in high ambient temperatures, such as the Middle East, for example, the effects are even more severe.

FAQs

Q: How do lines made with Dyneema® SK78 compare to generic HMPE alternatives when it comes to tension fatigue? 
A: DSM has engineered Dyneema SK78 fiber in such way that it offers at least 3x the fatigue performance of generic HMPE fibers. The rope temperature models developed by DSM allow for accurate prediction of rope core temperatures in static and dynamic conditions. Thanks to this model, ropes made with Dyneema® SK78 can be used at higher operating temperatures then generic HMPE, without the danger of line failure due to tension fatigue. 

Q: What makes mooring lines made with Dyneema® SK78 safer and more efficient to use?
A: Not only is the fiber designed in such a way that is more than 3x more resilient to fatigue, DSM has developed a tool to predict line behavior and inform maintenance. Using information such as rope diameter, rope construction, minimum breaking load, and metocean data, DSM’s accurate modelling can better predict the fatigue life of mooring rope under varying conditions – reducing the chance of dangerous line failures.

Q: What other factors contribute to tension fatigue? 
A: As well as wear and stress placed on the lines through constant movement, yarns and strands are continuously rubbing against each other and being subject to changing bending angles, e.g. in the fairlead. The effects of this are more severe at higher ambient temperatures – making accurate modelling essential. 

Q: What is the effect of a slack line or shock loads?
A: Because of factors like wind, waves and passing vessels, a vessel will move constantly at its berth. This movement is translated into tensions in the moorings lines. The line tensions can go from slack, having no tension at all, to high loads and vise versa within seconds. This leads to axial compression fatigue in the fibers. Dyneema® is the only HMPE fiber that is engineered to withstand the tension differences that can damage generic HMPE fibers and lead to premature failure.

Find out more

For more information on the exceptional tension fatigue properties delivered by Dyneema® SK78, download our new whitepaper.

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Work smarter. Choose Dyneema® SK78

To read more about what gives mooring lines made with Dyneema® SK78 their superior service life and exceptional performance, click on the proof points below.

Renowned and certified

Dyneema® SK78 fiber is renowned for its quality, consistency and performance. This has resulted in an Approval of Manufacturing Certificate by DNV GL, and in a Notification for Approval of Filament by ClassNK. If you want to know more about our certifications, please contact us.