Mooring lines: don’t be afraid of creep

Every material creeps. One material generally used in mooring lines, HMPE, is more sensitive to this phenomenon, and suppliers are standing up to design fiber types that take away creep as a potential failure mechanism for mooring lines. 
Creep means that a material is sensitive to long-term static loads and will elongate proportionally with time.
The amount of creep in HMPE fibers is influenced by ambient temperatures, applied loads, time and the type of HMPE fiber. Very high loads and high temperatures can accelerate creep but in practice failures due to creep are rare.

As an ultra-high molecular weight polyethylene, the specially formulated Dyneema® SK78 fiber has at least three times higher creep performance versus generic HMPE. This means that ropes made with Dyneema® SK78 fiber can be used at least 3 times longer and in harsher environments without the fear of premature failure.

Making mooring operations safer for ships and crews is the focus of new IMO regulations and industry guidelines following serious and even fatal accidents involving seafarers and terminal operators. These accidents typically involve the manual handling of equipment or mooring line breakage.
According to the European Harbour Masters’ Committee 95% of injuries are caused by failures of ropes or wires, and 60% of those incidents happen during mooring operations. Additionally, movements of a badly moored vessel can cause property damage or environmental harm, and a ship breaking lose from its moorings can result in catastrophic damage in port.

Starting 1 January 2024, all ships will be required to have a Line Management Plan (LMP) under the new IMO Safety of Life at Sea (SOLAS) MSC.1/Circ. 1620 regulation. The health of lines including hours of use, and how they are stowed, tested, inspected, retired and certified should be recorded in the LMP.
When the fourth edition of the Mooring Equipment Guidelines, known as MEG4, was published by OCIMF in 2018, it, too, set new and higher safety standards. In publishing MEG4, OCIMF recognised that lines had to rise to the challenge of faster port turnarounds, ever-larger vessels and widely varying conditions including the effect of extreme heat and cold on lines.
Avient (former DSM Dyneema), which was closely involved in the development of the MEG 4 guidelines, welcomes these higher standards. Their Dyneema® SK78 fiber is purpose built to meet head-on the challenges of this new era in mooring.

MEG4 requires a much broader approach to the design of mooring rope than previously. As well as breaking load, rope diameter and other characteristics obvious at purchase, the guidelines encompassed a whole new range of parameters such as angled endurance, material breaking force at high temperatures and axial compression resistance.

In short, lifetime performance.

Mooring ropes should be made to last and provide comfort to ship operators, not least the crew. The challenge is, of course, that no ship, port, or crew is the same. So, in partnership with manufacturers of premium mooring ropes, Avient has long been working towards use-specific lines. That’s why mooring ropes made with Dyneema® SK78 fiber are designed to handle the endless stresses and strains imposed during mooring operations. Strains from Fatigue, Abrasion, Creep and Temperature. Any one of these “FACTs” can lead to failures. 
The mooring experts at Dyneema® have put together a video series about the FACTs to consider when selecting mooring lines. Their Creep video below explains how and why they have engineered Dyneema® SK78 fiber so that it offers at least three times the resistance to creep compared to generic alternatives. When it comes to creep, there is nothing to fear with mooring lines made with Dyneema® SK78 fiber.

Want more information?

Talk to Dyneema’s experts by clicking this link