Section
4 Guidance for ice environment
4.1 General
4.1.1 This
section is intended to give guidance on the selection of a suitable
ice class notation for the operation of naval ships in Arctic and
Antarctic regions.
4.1.2 It is
the responsibility of the Owner to determine which notation is most
suitable for their requirements. Ultimately the responsibility rests
with the commanding officer and their assessment of the ice and temperature
conditions at the time.
4.1.3 The
documentation supplied to the ship is to contain the ice class notation
adopted, any operation limits for the ship and guidance on the type
of ice that can be navigated for the nominated ice class.
4.2 Definitions
4.2.1 The
World Meteorological Organisation's, WMO, definitions for sea ice
thickness are given in Table 2.4.1 WMO definition of ice
conditions.
Table 2.4.1 WMO definition of ice
conditions
Ice conditions
|
Ice thickness
|
Medium first year
|
1,2 m
|
Thin first year, second
stage
|
0,7 m
|
Thin first year, first
stage
|
0,5 m
|
Grey-white
|
0,3 m
|
Grey
|
0,15 m
|
4.2.2
Table 2.4.2 Comparison ice standards defines the ice classes
in relation to the Rules and the equivalent Internationally recognised
Standards.
Table 2.4.2 Comparison ice standards
Clasifications Register class
notation
|
Finnish-Swedish Ice-Due
class
|
Canadian type
|
1AS
|
IA Super
|
A
|
1A
|
IA
|
B
|
1B
|
IB
|
C
|
1C
|
IC
|
D
|
1D
|
ID
|
–
|
none
|
none
|
E
|
4.2.3 Extended
periods are defined as those that involve the vessel remaining in
air temperatures below 0oC for more than one week.
4.3 Application
4.3.1 For
naval ships intended for extended periods of operation in Arctic and
Antarctic areas the suggested ice class is 1C. For these
operational limits, the materials used for hull construction are to
be in accordance with Vol 1, Pt 6, Ch 6, 2 Materials.
If a higher ice class is proposed, material requirements are to be
specially considered using a specified design air temperature as defined
in Vol 1, Pt 5, Ch 2, 3.2 Design air temperature.
4.3.3 The
variable nature of ice conditions is such that the average limits
of the conditions are not easily defined. However, it is possible
to plot the probable limits of the ice flows and the ice edge for
each season. Operation with Ice Class 1C may be possible
up to 150 nm inside the 7/10 region shown depending on the severity
of the winter. Operation with Ice Class 1A may be possible
up to 150 nm inside the medium first year ice shown depending on the
severity of the winter. Operation up to the multi year ice is possible
most years with Ice Class 1AS.
4.3.4 Operation
in the region between 7/10 and 1/10 in the arctic is possible with
due care for ships with no ice class. For ships operating for extended
periods in these areas it will be necessary to specify and design
for a minimum temperature for the hull materials. To cover all situations
for a non-ice class ship, the material requirements of Vol 1, Pt 6, Ch 6, 2 Materials are recommended.
4.4 Ice Class notations
4.5 National Authority requirements
4.5.1 Certain
areas of operation may require compliance or demonstration of equivalence
with National Authority requirements. Table 2.4.2 Comparison ice standards gives the equivalence of National Authority requirements.
4.5.2 The
standards of ice strengthening required by the Rules have been accepted
by the Finnish and Swedish Boards of Navigation as being such as to
warrant assignment of the Ice-Due Classes given in Table 2.4.2 Comparison ice standards. For definition of Ice-Due
Classes, see Finnish-Swedish Ice Class Rules, 1985.
4.5.3 Ships
intending to navigate in the Canadian Arctic must comply with the
Canadian Arctic Shipping Pollution Prevention Regulations established
by the Consolidated Regulations of Canada, 1978, Chapter 353, in respect
of which LR is authorised to issue Arctic Pollution Prevention Certificates.
4.5.4 The
Canadian Arctic areas have been divided into zones relative to the
severity of the ice conditions experienced and, in addition to geographic
boundaries, each zone has seasonal limits affecting the necessary
ice class notation required to permit operations at a particular time
of year. It is the responsibility of the Owner to determine which
notation is most suitable for their requirements.
4.6 Ice accretion
4.6.2 As a
minimum a full icing allowance is to be applied to vessels operating
in the following areas, see
Figure 2.4.5 Ice accretion limits Arctic:
- The area north of latitude 65o30’N, between longitude
28oW and the West coast of Iceland; north of the north
coast of Iceland; north of the rhumb line running from latitude 66oN,
longitude 15oW to latitude 73o30’N, longitude
15oE, north of latitude 73o30’N between
longitude 15oE and 35oE, and east of longitude
35oE, as well as north of latitude 56oN in the
Baltic Sea.
- The area north of latitude 43oN bounded in the west
by the North American coast and the east by the rhumb line running
from latitude 43oN, longitude 48oW to latitude
63oN, longitude 28oW and thence along longitude
28oW.
- All sea areas north of the North American continent west of the
areas defined in subparagraphs above.
- The Bering and Okhotsk Seas and the Tartary Strait during the
icing season.
- South of latitude 60oS.
4.6.3 A full
icing allowance is defined as an additional pressure of 1 kN/m2 (100
mm of ice) applied to all exposed horizontal or near horizontal surfaces
and 0,25 kN/m2 (25 mm of ice) applied to all exposed vertical
surfaces. The volumetric centre of the ice is to be taken as that
of an equivalent head of water. The density of the ice is assumed
to be 1000 kg/m3.
4.6.4 As a
minimum a half icing allowance is to be applied to vessels operating
in the winter seasonal areas as defined in the international Load
Line Convention.
4.6.5 A half
icing allowance is defined as an additional pressure of 0,5 kN/m2 (50
mm of ice) applied to all exposed horizontal or near horizontal surfaces
and 0,18 kN/m2 (18 mm of ice) applied to all exposed vertical
surfaces. The volumetric centre of the ice is to be taken as that
of an equivalent head of water. The density of the ice is assumed
to be 1000 kg/m3.
4.6.6 The
effects on stability of ice accretion are to be assessed in accordance
with the specified subdivision and stability standard.
4.7 Ice conditions
4.7.1 Charts and images for the current and recent ice conditions in all
areas of the world plus information on icebergs can be found from
the National Ice Centre on the world wide web at
-
http//www.natice.noaa.gov/.
Information is supplied by regular assessment and survey by
the naval ice centres patrols.
|