The UK’s Marine Accident Investigation Branch (MAIB) has issued a safety bulletin to the cruise industry to highlight the importance of using anchoring equipment within its intended design parameters.
Due to COVID-19, many cruise vessels have anchored off the UK’s south coast.
Since October, 2020, MAIB has been made aware of several anchor losses associated with riding out winter storms. Also blamed was the use of the anchoring equipment beyond its intended design parameters.
For example, one cruise ship lost both anchors within a week.
MAIB said it had identified a trend in anchoring equipment failures and had released a safety bulletin to the cruise industry to mitigate against further losses both in the short term and when the vessels return to normal operations.
The safety issues highlighted included:
– Ship’s Masters should be proactive in heading to sea and not wait for the anchor to drag in strong winds before acting.
– The choice of anchor and amount of cable chosen should be varied to avoid single point loading.
– Ship’s Masters should ensure they and their crew are aware of the reporting procedures to the coastal state in the event of losing an anchor.
– The anchoring equipment should be assessed before returning to normal service, due to the greater use of the anchors during this extraordinary period.
MAIB further explained that the anchoring equipment’s strength is defined by the ship’s classification rules and it is intended for temporary mooring of a ship within a harbour or sheltered area.
In good holding ground, the anchoring equipment should be able to hold the ship to a maximum wind strength of 48 knots in fat water, but this reduces to a maximum of 21 knots wind strength in seas with a significant wave height of 2 m.
The International Association of Classification Societies (IACS) has advised that the anchoring equipment is not designed to hold a ship off fully exposed coasts in rough weather or to stop a ship that is moving or drifting.
In these conditions, the loads on the anchoring equipment increase to such a degree that its components may be damaged or fail, due to the high energy forces generated, particularly with ships with high windage.
Failures have occurred in joining links, anchor chain common links, D-links and across the anchor crown causing the fukes to be lost. Of the failures reported thus far, the most frequent was the failure of the joining links connecting two shackles of cable, often when a significant amount of cable was out, in some cases as much as 11 shackles on deck, MAIB said.
Although the additional weight of the cable can prevent the vessel dragging anchor, in adverse conditions it will also increase the forces acting on the cable and anchor. When combined with the significant yawing caused in high winds, and cable lying in a chain locker since the last time it was used, it is unsurprising that several anchor equipment failures have occurred.
This issue is further exacerbated when the scope of cable remains constant, causing a single point of loading and wear, for example, where the cable is in contact with the hawse pipe.
The indications are that anchor equipment had been failing, due to operational issues rather that fabrication defects, MAIB concluded.