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ICE NAVIGATION
HISTORY
Sea ice has posed a problem to the navigator since
antiquity. During a voyage from the Mediterranean to
England and Norway sometime between 350 B.C. and 300
B.C., Pytheas of Massalia sighted a strange substance
which he described as “neither land nor air nor water”
floating upon and covering the northern sea over which the
summer Sun barely set. Pytheas named this lonely region
Thule, hence Ultima Thule (farthest north or land’s end).
Thus began over 20 centuries of polar exploration.
FORMATION &TYPES OF SEA ICE
OPEN
WATER ICE
PANCAKE ICE
GREASE ICE
NILAS
Frazil ice
In rough water, fresh sea ice is formed by the cooling
of the ocean as heat is lost into the atmosphere.
The uppermost layer of the ocean is super cooled to
slightly below the freezing point, at which time tiny
ice platelets, known as frazil ice,
form. As more frazil ice forms, the ice forms a mushy
surface layer, known as grease ice
Frazil ice formation may also be started by snowfall,
rather than supercooling.
slush is a floating mass formed initially from snow
and water.
Shuga is formed in agitated conditions by
accumulation of slush or grease ice into spongy
pieces several inches in size.
Waves and wind then act to compress these ice
particles into larger plates, of several meters in
diameter, called pancake ice.
ICEBERGS
An iceberg is a large piece of ice from freshwater that has broken off from a snow-formed glacier or ice
shelf and is floating in open water. It may subsequently become frozen into pack ice. Alternatively, it may
come to rest on the seabed in shallower water, causing ice scour (also known as ice gouging) or
becoming an ice island
Although icebergs float on ocean waters, they are composed of freshwater.
An iceberg is simply an extraordinarily large mass of ice that has broken off from an ice cap
or glacier where it met the sea. The first stage of iceberg formation occurs
when part of a glacier or ice cap that has been pushed into the sea,
begins to float on the water. Tides and wave action subsequently cause stress fractures,
causing a piece of the glacier to break off and a new iceberg is born! This process is calving.
An iceberg’s extraordinary blue and white coloration is a reminder of its glacial origins.
Glacial ice appears blue because pure ice absorbs other colors more rapidly than blue.
This colour appears in the deepest layers of the ice that are under such high pressure that
all of the air bubbles have been forced out of the ice.
By contrast the surface layers of the iceberg are white
because the air bubbles trapped in the snow layers reflect much of the incident light.
These air bubbles also result in iceberg fizz.
As an iceberg melts, fizzing results from the release of gases that have been held
under pressure, trapped in bubbles for thousands of years!
FORMATION Although icebergs float on ocean waters, they are composed of
freshwater.
An iceberg is simply an extraordinarily large mass of ice that has
broken off from an ice cap or glacier where it met the sea. The
first stage of iceberg formation occurs when part of a glacier or
ice cap that has been pushed into the sea, begins to float on the
water. Tides and wave action subsequently cause stress
fractures, causing a piece of the glacier to break off and a new
iceberg is born! This process is calving.
An iceberg’s extraordinary blue and
white coloration is a reminder of its glacial origins. Glacial ice
appears blue because pure ice absorbs other colors more rapidly
than blue.This colour appears in the deepest layers of the ice that
are under such high pressure that all of the air bubbles have
been forced out of the ice.
By contrast the surface layers of the iceberg are white
because the air bubbles trapped in the snow layers reflect much
of the incident light. These air bubbles also result in iceberg fizz.
As an iceberg melts, fizzing results from the release of gases that
have been held under pressure, trapped in bubbles for
thousands of years!
DRIFTING OF ICEBERGS
Iceberg movement is influenced by direct wind push on its exposed area to an extent far
greater than commonly assumed. Although the bulk of the iceberg is below water, in many
situations wind has a dominant influence on the movement.
In addition to windage on the iceberg and the ocean gradient current, the wind-induced
surface current has the effect of increasing drift speed by about 10 percent for small
icebergs and increasing the angle of drift direction.
The wind force on an iceberg does not result in movement directly downwind, but, because
of the rotation of the Earth (Coriolis effect), windage on an iceberg is 30 to 50 to the right in
the Northern Hemisphere and to the left in the Southern Hemisphere.
They move at speeds of 1 knot, or 24 nautical miles per day.
This iceberg moved 140 kilometres at as much as 3 knots across the Labrador Current and
resulted in an emergency move of the North Atlantic shipping lanes to the south
ICE BREAKERS An ice breaker is a special-purpose ship or boat designed to
move and navigate through ice-covered waters.
For a ship to be considered an icebreaker, it requires three traits most normal ships lack:
a strengthened hull,
an ice-clearing shape,
the power to push through ice-covered waters.
PRINCIPLE:
it uses its momentum to break the ice
High strength hull
Powerful engine
Azimuth thrusters
Icebreakers are constructed with a double hull and watertight compartments in case of a breach.
The ship's hull is thicker than normal, especially at the bow, stern, and waterline, using special steel that
has optimum performance at low temperatures. The thicker steel at the waterline typically extends about 1 m above
and below the waterline and is reinforced with extra internal ribbing, sometimes twice the ribbing of a normal ship.
The bow is rounded rather than pointed, allowing the vessel to ride up over the ice, breaking it with the weight of
the vessel. The hull has no appendages likely to be damaged by the ice,and the rudder and propeller are protected
by the shape of the hull. The propeller blades are strengthened, and the vessel has the ability to inspect and
replace blades while at sea.
DESIGN AND CONSTRUCTION
The optimal shape for moving through ice makes icebreakers uncomfortable in open water
and gives them poor fuel efficiency.
In open-water travel, icebreakers tend to roll side to side to the discomfort of the crew. Some new icebreakers,
such as the USCGC Healy, make use of anti-roll tanks, incompletely filled ballast tanks which span the beam of
the vessel. Ballast water in these tanks is allowed to move side to side, or slosh, as a free surface
A greater concern is how well a ship cuts through waves.The ability of a ship to cut through waves can
greatly affect its fuel efficiency and even its safety in a storm. Most ships use a sharp or bulbous bow
to cut through waves and help prevent waves from slamming the bow of the ship.
DOUBLE ACTING SHIPS
Double acting ship (DAS) is a type of icebreaking merchant ship designed to run ahead in open water
and astern in ice.
Such ships can operate independently in severe ice conditions without icebreaker assistance
but retain better open water performance than traditional icebreaking vessels.
How Double Acting Tankers Work?
A double acting tanker sails in normal sea in the ahead direction, just like any other vessel.
However, when it comes to ice breaking,the astern movement of the ship is utilised.
The aft or stern part of the ship hull structure is therefore made up of special reinforced double skin with a fatigue
life of around 40 years.Moreover, the conventional rudder and propeller is replaced by Azipod system
with fixed pitch propeller and an electric motor of Mega Wattrating.
The azipod system is capable of rotating 360 and the normal ahead speed is above 15 knots.
Additional bow thrusters are also fitted to provide excellent manoeuvrability in narrow channels and ports.
ICE PATROL The International Ice Patrol is an organization with the purpose of monitoring the
presence of icebergs in the Atlantic and Arctic Oceans and reporting their movements for safety purposes. It is operated by United States Coast Guard but is funded by the 13 nations interested in trans-Atlantic navigation.
It was established in 1914 in response to the sinking of the RMS Titanic. "The primary mission of the Ice Patrol is to alert any seacraft traveling the great circle shipping lanes between Europe and the major ports of the United States and Canada of the presence of any icebergs there."
Size Category Height Length
Growler Less than 1 metre (3.3 ft) Less than 5 metres (16 ft)
Bergy Bit 1–5 metres (3.3–16 ft) 5–15 metres (16–49 ft)
Small 5–15 metres (16–49 ft) 15–60 metres (49–200 ft)
Medium 15–45 metres (49–148 ft) 60–120 metres (200–390 ft)
Large 45–75 metres (148–246 ft) 120–200 metres (390–660 ft)
Very Large Over 75 metres (246 ft) Over 200 metres (660 ft)
ICE ACCREATION
Rudder
Inner Bot.
Bulkhead
Fore&Aft
Deck
Bottom
Hull
Unspec/
Ship Side
ICE CLASSES SIGNIFICANCE
Not all ships are built to an ice class. Building a ship to an ice class means that the hull must be thicker,
and more scantlings (aggregate of girders, beams, and bulkheads resulting in stronger structure) must be in place.
Sea chests (openings in the hull for seawater intake) may need to be arranged differently depending on the class.
Sea bays may also be required to ensure that the sea chest does not become blocked with ice.
Most of the stronger classes require several forms of rudder and propeller protection.
Two rudder pintles are usually required, and strengthened propeller tips are often required in the stronger ice classes.
More watertight bulkheads, in addition to those required by a ship's normal class, are usually required.
In addition, heating arrangements for fuel tanks, ballast tanks, and other tanks vital to the ship's operation
may also be required depending on the class.
ARCTIC CLASSES
FINNISH SWEDISH CLASSES
POLAR CLASSES
The following areas are subject to requirements depending on the ice
class selected.
BALTIC ICE CLASSES
- Hull – ice belt
- Machinery output
- Shaft – system
- Propeller
- Mooring
- Heating ballast tanks
- Sea chest
- Air capacity for starting compressor (1A*)
- Rudder and steering gear
- Corrosion protection
ARCTIC ICE NOTATION (ADDITIONAL SCOPE)
- Hull girder transverse strength, line loads due to vessel being trapped
between
moving ice flows.
ARCTIC POLAR AND ICEBREAKER NOTATION (ADDITIONAL
SCOPE)
- Hull materials exposed to low temperatures (DAT-notation)
- Subdivision, intact and damage stability (additional requirements)
- Hull girder longitudinal strength due to beaching and ramming
- General
Items covered by Ice-Class Notation (Baltic, Arctic and
Polar)
ICE CLASS RULES AND OTHER
REQUIREMENTS CLASS
NOTIFICATIONS
EQUIVALENT
BALTICS ICE
CLASSES
VESSEL TYPE ICE CONDITIONS ICE LIMITS
ICE C
ICE 1C
ICE 1B
ICE 1A
ICE 1A*
ICE 1A F*
1C
1B
1A
1A SUPER
ALL SHIP
TYPES
VERY LIGHT ICE
CONDITIONS
- First year ice and
broken channel
0.4 m ice thickness
0.6 m ice thickness
0.8 m ice thickness
1.0 m ice thickness
1.0 m ice thickness
NO RAMMING
ICE O5
ICE 10
ICE 15
POLAR 10
POLAR 20
POLAR 30
ICE BREAKER
Vessels intended
for ice
breaking
-Built for another
main purpose
-ICE BREAKING IS
MAIN PURPOSE
First year ice with
pressure ridges
Multi year ice with
glacial inclusions
ACCIDENTAL
RAMMING
REPEATED
RAMMING
North Atlantic • No ice
• -20 deg c
Baltic sea •1 m ice
• -15 deg c
Barents sea •1.2 m ice • -30 deg c
Kara sea • 2 m ice • -40 deg c
•Multi year ice
THICKNESS OF ICE IN VARIOUS AREAS
CASPIAN 70
WHITE 80
Typical hazards when operating
in cold climate Overstress of hull
• Lack of good ice reports/routing
• Ice restriction vs. commercial pressure on
master
Propulsion failure
• Stuck in ice, crushing of hull or drifting
Aground
• Remote from rescue and spare parts
Icing (stability, safety functions, cargo
operations)
•Black-out ( freezing of ship, crew, difficult restart).
Evacuation problems in ice
Malfunction of fire fighting
Experience/competence
Crew fatigue (additional work load, low
temperature, noise/vibrations, 24 hrs
ICING
A SERIOUS CHALLNGE High Wind Speed
Usually above 18 kts or 9 m/s but
sometimes lower
Low Air Temperature
Below freezing (-1.7 deg c)
Low Water Temperature
Usually below + 7 deg c
Ice accretion on the various
equipment/areas has unequal importance
on the vessel safety.
- Category I : to be kept completely ice
free
- Category II : shall have de-icing
arrangements removing ice within a
reasonable period of time (4-6 hours)
ICE ACCREATION =
WIND+
WAVES+
LOW AIR TEMPERATURE+
OPEN WATER =
ICING
REPORTED ICE DAMAGES
Rudder
Inner Bot.
Bulkhead
Fore&Aft
Deck
Bottom
Hull
Unspec/
Ship Side
Ships side
65%
Rudder
7%
Bottom
10%
Fore&aft
8%
Inner bottom 1%
Bulk head 4%
Deck 2%
TOTAL NO. OF DAMAGES REPORTED
486
FORCES FROM
DRIFT ICE
FORCES FROM
DRIFT ICE
FORCES FROM
DRIFT ICE
FORCES FROM
DRIFT ICE
MANAGING OF COLD CLIMATE RISKS CROSS SECTIONS OF FRAM’ BUILT 1892
Ice forces would lift the vessels out of
the ice, and save her.
A brilliant example of practical risk
management
Protected location. Also with heating (i.e.
adjacent to heated spaces or hot air
ventilation).
Protective covers
Electric tracing (Note ex-requirements)
Heating coils (steam/hot water)
Ice-repellant coating
Self-draining piping/operating procedures
Circulation of liquids (e.g. hydr.oil)
AVOIDING ICING PROBLEMS - METHODS
MEMBRANE LNGC
PROTECTION AGAINST
ICE PRESSURE DAMAGE
Collision with Growlers and
Bergy Bits in open waters Uncouple the containment system
and the
ship side leaving space for indentation
of
the side without damage/deformation
of the
containment system
Increase double hull width
Design for increased energy
absorption
capability of the double hull
Traversing through ice
channel or the ship
completely frozen in Design hull to lift the ship rather than
pushing it down due to the ice pressure
Increase double hull width
Design a stronger protective outer
hull,
stiffer – less deformation
• DA (double acting) - where the ship operates with the stern first when operating in ice. This saves on installed power, and fuel, and makes it possible to optimize the bow of the ship for open water performance. The DAS was made possible through the development of azimuthing electric propulsion--another system which was developed by AARC, together with ABB (Azipod).
• A very new develpoment is the Oblique Icebreaker. By using azimuthing electric propulsion, it breaks ice by moving sideways, utilizing its entire length for breaking a wide channel. This makes it possible to use a relatively small and narrow icebreaker to assist large and wide cargo ships.
Challenges – human factors
Competence and performance of crew is essential for safe
operations
• Availability of experienced personnel?
• Training/experience!
• Increased manning?
• Extreme low temperatures
• 24 hours darkness
• Noise and vibrations in ice
HUMAN FATIGUE
UNDERSTANDING THE
CHALLENGES
CAPTAIN
CHIEF ENG
CADET
Summary…..
Ship operations in cold climate is
much more
than ice strengthening of the ship
alone.
Compliance with basic ice class
rules and
regulations may be insufficient for safe
and
effective ship operations in cold
climate
Risk evaluation for specific trades
and adequate
“winterization” for safe and reliable
operations
must be carried out.
ANY QUESTIONS
THANK YOU
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