Snap back arrestor approved by DNV

Mooring lines snap at up to 800 km/h, making vessel mooring one of the most dangerous tasks crew perform. Snap back accounts for 53% of mooring accidents, with one in seven of those accidents resulting in fatalities.

DNV’s thorough qualification process has taken more than four years and involved an extensive qualification process, performed in accordance with DNV’s recommended practice A203. The process provided a systematic approach to identify, verify and mitigate all possible threats and failure modes of the SBA technology.

Established in year 1772 Timm Ropes is now part of the Wilhelmsen group. The company has previously evaluated, tested, and discarded several flawed designs it says are available on the market from other manufacturers. For its solution, the SBA core rope is placed in the centre of the main 12-strand rope in a way that allows full utilisation of its elongation properties. The method for securing the SBA core to the mooring eyes has been specially developed.

The SBA is non-load-bearing during normal rope operation. In the event of rope breakage, its higher elongation means it will absorb part of the energy released and guide the broken strand(s) along the current axis of the rope, resulting in a significant reduction of snap back. The SBA is not capable of sustaining high loads and will therefore release much less energy if it breaks.

“Wilhelmsen Ships Service have with their Snap Back Arrestor developed new technology going beyond existing standards. The intension of the technology is to increase safety in maritime by minimizing the effect of snap-back in case of rope failure. DNV have assisted Wilhelmsen Ships Service through the process of technology qualification as the world’s first snap-back technology qualified by DNV, that is now proven to function within specified limits with an acceptable level of confidence,” says Ingrid Skutle Høgsæt, Principal Engineer from DNV.