Port
Authorities today, most likely require lost anchors to be found and removed,
thereby resulting in a “wreck removal” case. The more serious and very costly
cases occur when dragging anchors leads to collisions, groundings, damage to
subsea -cables and -pipelines, or pollution. Ship operators, Masters and crew
need to be aware of the risks involved and thoroughly assess the limitations of
a vessels’ anchoring equipment. Senior Loss Prevention Executive Jarle Fosen
recently shared Gard’s experience and recommendations at the DNV sponsored
webinar co-hosted by Gard and The Swedish Club.
Background
A growing
number of anchor losses, anchor dragging, and anchor removal cases prompted
DNV, Gard and The Swedish Club to collaborate on an anchor loss awareness
campaign back in 2016. Despite the awareness raised then on the most frequent
technical and operational issues, we are today still seeing an increase in
cases. Might there be some new reasons for the increase in anchor loss and
dragging incidents?
Due to
congestion, ships are spending more time at anchorages and are anchoring in
areas more exposed to extreme and sudden environmental conditions. This is
likely due to the state of our global economy with recent years of economic
downturn and the COVID pandemic with the logistical disruptions that have
followed for both crew changes and cargo handling.
Due to the
pandemic, we have also seen passenger vessels temporarily laid-up in exposed
anchorages. Containerships and car carriers that did not often use their
anchoring equipment now have to use it for extended periods of time while
waiting in the queues outside loading terminals. Climate change also
contributes to losses with more frequent extreme weather events and in
locations previously known to be benign and safe. Climate change has also
resulted in longer periods of high and fast water in river approaches, for
example the Mississippi.
Learning from Gard’s claims data
Similarly, the
vessel movement data revealed that during the same 2015-2020 period, a vessel
with an anchor claim spent on average 18% longer time in bad weather during a
year than a vessel without an anchor claim. Bad weather is defined as wind
forces between Beaufort scale 8 - 12, where 8 equals gale forces and 12
hurricane forces.
Risks and
limitations of a ship’s anchoring equipment
In most of the
anchor claim cases, environmental risk factors, such as weather, strength of
the currents, water depth and holding ground, played a significant role in the
loss. In general, anchoring equipment is designed for temporary mooring in
harbors or sheltered waters, but in today’s real world many anchoring locations
are outside sheltered waters.
We suspect one
of the key issues is a general lack of awareness of the environmental loads for
which anchoring equipment is designed. The anchoring equipment is not designed
to hold a vessel off fully exposed coasts in rough weather or during frequent
anchoring operations in open sea. In such conditions the loads on the anchoring
equipment will increase to such a degree that its components may be damaged or
lost owing to the high energy forces generated.
Through the
International Association of Classification Societies (IACS) Class societies
have agreed to a set of unified requirements for anchoring
equipment (UR A1) and make reference to this in their Class
Rules.
The anchoring
Equipment Number (EN) calculations, as found in UR A1, are based on the
following assumed environmental load conditions:
·
Current
velocity: max. 2.5m/s
·
Wind velocity:
max. 25m/s
·
No waves
(sheltered waters)
·
Length of
chain paid out scope 6-10
·
Good holding
ground
For ships with
an equipment length greater than 135m, an alternative UR A1 environmental
condition may be considered:
·
Current
velocity: 1.54m/s
·
Wind velocity:
11m/s
·
Significant
wave height 2m
The IACS UR A1
has been revised recently and the revised requirements in UR A1, Rev 7,
September 2020 (corrigendum published in September 2021) will apply to ships
contracted for construction from 1 January 2022. The updates in that last
revision include consideration for the front projected area and side projected
area of large funnels in the equipment number calculations to account for their
contribution to anchoring loads. This change may be required following the
addition of scrubbers on many ships which increase the profile of the funnel
and thereby affect how the wind applies force to the vessel.
Dragging
anchor
The most
serious and very costly cases occur when a ship drags its anchor in strong
currents or bad weather, leading to collisions with other nearby anchored
ships, groundings and loss of the ship, pollution or damage to cables and
pipelines on the seabed.
“Dragging
anchor” means the ship drifts without holding power, even though it has been
anchored. It is important to note that it can take some time for the crew to
realize the anchor is dragging and the ship drifting. Once realized, it will
take time to weigh (lift) the anchor, start the engines and restore the ship to
full maneuverable condition, a period during which the ship may run dangerously
close to other ships or structures, or into shoal water.
Where are anchors lost and required to be removed?
For example, the map shows there is a significant number of cases in and around New Orleans and the wider Mississippi River delta. 2019 and 2020 were exceptional years for high river related casualties, due to the extended period of high river conditions in the Mississippi River. When certain areas of the river are considered to have reached high water level, local authorities require all deep draft vessels that are not moored alongside or moored to a buoy to have at minimum three means to hold its position. This may be achieved by using both anchors in addition to the propulsion system or being aided by a tug as the third means of holding position. When using both anchors there is a higher risk of the chains getting crossed, entangled, and damaging the anchor.
The map also
shows that there is a surprising number of anchor claims in and around
Fujairah, UAE. This area is assumed to have benign weather and sea conditions.
However, the water depth at Fujairah anchorage is considered deep waters and
varies from 70-130 meters. ‘Letting Go’ the anchor in such deep water could
cause the brake system to burn out and leave the windlass without control,
damaging the windlass, bitter end, or in some cases resulting in total loss of
the cable and anchor.
One of the key
findings in casualty investigations is the importance of the crew being aware
of the environmental loads their anchoring equipment is designed for. If these
limits are not considered during shipboard anchoring operations, there can be
significant damage to the ship – even beyond the loss of the anchor and the
chain.
Recommendations
Many anchor losses are preventable if
proper maintenance and handling procedures are followed. Performing correct
anchoring operations is vital to the safety of the vessel, and, prior to
anchoring, the Master should take into consideration the following:
Set a policy
for the conditions requiring leaving the anchorage - If a ship is anchored in an area
exposed to weather, it is necessary to have a clear policy as to when to leave.
There have been cases where Masters have been under commercial pressure not to
leave an anchorage, and disasters have followed because the Master was tempted
“to wait and see until the morning”, although the weather forecast was bad.
Respect the
limitations of the anchoring equipment –
Masters must be particularly vigilant when anchoring close to shore in bad
weather or in high rivers with strong currents and poor holding ground. In
making the decision whether to stay or leave, the Master should also be aware
of the design limitations of the anchoring equipment. Some Masters may not have
full knowledge of these limitations; however, they are laid down by the class
societies in their rules for calculating the dimensions, weights and strengths
of the anchoring equipment. With the mentioned limitations in mind, it can be
seen from instances of ships dragging anchors in bad weather that Masters have
at times placed too much trust in their ship’s anchoring equipment. Today’s
weather forecasts are usually very reliable and Masters should more often
choose to weigh anchor and go out to sea in time if heavy weather is forecast.
Train and
mentor crew - Anchoring
a vessel safely can only be carried out with proper planning, a properly
instructed bridge team, and when positive on-board management and leadership
are shown. Owners and managers should ensure that such knowledge is transferred
to junior officers through structured training and by making that knowledge
available. Good seamanship is often best learned on the job whilst at sea.
Proper anchor watches must be maintained which include the use of navigation
equipment in setting up anchor watch alarms and parallel indexing. Extra precautions
such as additional cable paid out and having engines on immediate notice should
also be considered.
Follow below links for tutorial videos.
https://vimeo.com/158315620/73d4146601
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