make a strong statement in this regard by referring in a considerable number of its sections to the
need for preventing pollution from ships navigating the Arctic Regions.
These are just some of the issues that must be tackled by designers as they develop the new
Feature 1 | Tankers of T
generation
he 21s
of polar class tankers for the new whitefield energy developments in the Arctic. A
multitude of research
T Cen
projects
Tury
being undertaken in Finland, Russia and Canada, many in
cooperation with the leading class societies, will provide the necessary technical understanding
to tackle these design challenges with confidence.
In looking to the Arctic, class has already scantling requirements is that the FSICR
taken a leadership role with the development frame strength requirement is based on the
of the new IACS Polar Class Rules that took elastic section modulus and in the Polar
effect at the beginning of March. The new Rules on the plastic section modulus. The
Rules, jointly developed by the IACS member FSICR require brackets at the connection
societies, grew from the acceptance that vessels of a side longitudinal to a web frame
operating in the Arctic region are exposed to a
•
Polar Class includes longitudinal strength
number of unique demands. The presence of requirements for ramming, whereas the
first year and multi-year ice imposes additional FSICR does not
loads on the hull, propulsion system, and
•
Polar Class machinery requirements
appendages. Low temperatures impact the include ice loads and failure criteria but
ship, and the cold, the lack of light and visibility the detailed scantling design is to be done
affect the crew. In addition, the protection of either using advanced analysis methods or
the unique Arctic environment is of particular PPolar class descriptions (source: IACS).olar Class Descriptions (Source: IACS) accepted industry engineering practice.
concern as the resources in this new frontier The FSICR include scantling equations
are exploited.
Pic: Vasily Dinkov, the first in a series of 70,000dw
•
t
P
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tankers specifically
ar requirements for
To promote the safety of navigation and
designed to operate in the ice covered waters of the Arctic polar region north of Russia.
material class selections to prevent material
to prevent pollution from ship operations in
•
The definition of the ice belt, which defines failure in low temperature, while FSICR
Arctic ice-covered waters, the Marine Safety
Pic:
t
Vessels
he exten
operating
t of reinfo
in
rc
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eme
Arctic
nt, is d
region
ifferen
are
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exposed to a number of unique dem
does not include such require
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ents
Committee (MSC) and Marine Environment the two rule sets. The FSICR divides the
Protection Committee (MEPC) of IMO ship into three regions: forward, midship, The average and extreme temperatures
approved the Guidelines for Ships Operating and aft. The forward region is further in the Arctic are lower than in the Baltic
in Arctic Ice-Covered Waters in October 2002. divided into three vertical sections: upper and the design and the operation must
These Guidelines are recommendatory rather forward ice belt, ice belt, and fore foot. be adjusted to these temperatures.
than mandatory for vessels traveling in the This means that for the midship and aft The reliability and the redundancy of
Arctic ice-covered waters. regions, the sections below the ice belt the machinery and safety equipment,
IMO Guidelines refer to the IACS Unified are not reinforced. And the extent of insulation of spaces, and ergonomic
Requirements (UR) for Polar Class for structural reinforcement for side shell plating and considerations are some of the issues that
design and construction. Since the existing framing are different in the FSICR. The need to be addressed. Since these aspects
generation of tankers intended for Baltic winter Polar Class requirements divide the hull are not covered by the traditional ice
operation is generally built in accordance with into four sections longitudinally: bow, class requirements, classification societies
the Finnish-Swedish Ice Class Rules (FSICR), bow intermediate, midbody, stern; and have developed additional criteria for
designers are familiar with those Rules and have three sections vertically: bottom, lower, winterisation and cold weather operations
been looking to the class societies to help them and icebelt region (eg the ABS Guide for Vessels Operating in
understand the differences between the FSICR
•
The ice load definition in the Polar Class Low Temperature Environments).
and the new Polar Ice Class requirements. requirements depends on hullform angles Design considerations critical for cold
These are significant even though the lowest whereas the FSICR load does not. The weather operations of tankers but not
two Polar Ice Classes (PC6 and PC7) are FSICR load depends on propulsion power, covered by Ice Class Rules may include
considered to be generally equivalent (but not whereas the Polar Class requirement does such items as material and coatings
exactly so) to the two highest Finnish-Swedish not. The Polar Class ice load model is selection; hull construction/arrangement
ice classes (1A Super and 1A respectively). Ice based on theoretical analysis models for and equipment that takes account of the
classes 1A and 1A Super are based on 0.8m and the glancing (tangential impact) ship/ice likelihood of tank contents freezing, the
1.0m ice thicknesses respectively. interaction, while the FSICR ice load is need for protection of the personnel and
There are seven Polar Ice Classes and their based on experimental measurements the impact of ice accumulations on vessel
assumed operational profile varies from a in the Baltic Sea. In the Polar Class stability.
‘year-round operation in all Polar waters’ for requirements, peak pressure factors Machinery arrangements may be
the highest ice class PC1 to ‘summer/autumn are used to account for the pressure required to be modified as a result of low
operation in thin first-year ice which may concentration on local structural members ambient temperatures. Sea water supplies
include old ice inclusions’ for the lowest ice class when the ice load is applied to determine for essential operational systems and
PC7. The Polar Class requirements are based on scantlings, while in the FSICR, the pressure safety systems must be provided during
the assumption that the ship is able to operate is assumed uniform inside the load patch navigation and at port in ice-covered
independently (ie without icebreaker support)
•
In the FSICR, the corrosion margin is a waters. Essential equipment and systems
in the designated ice condition. constant 2mm, whereas in the Polar Class must be available at all times and in any
Some of the main differences between the corrosion/abrasion margin depends temperature conditions.
the approaches adopted by the two rule sets on the location, ice class, and coatings Heating of spaces and equipments must
include:
•
The main difference in the approach to the be considered. The definition of the design
22 The Naval Architect March 2008
NA Mar 08 - p20+22+
23.indd 22 10/03/2008 14:10:35
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