GLASGOW COLLEGE OF NAUTICAL STUDIES

ICING ALLOWANCES

(Ref: 'LOAD LINE - Instructions for the Guidance of Surveyors' Pages 39-40; MCA 1999 London; The Stationary Office.)

The stability information book of any ship, which may trade in an area where ice may form should contain information that indicates the effect of the formation of ice on exposed hull, superstructures, houses, deck cargo etc. This must be calculated as either a full icing allowance or a half icing allowance.

Areas applicableThe full icing allowance should be applied:(a) North of 66º 30' N between the Norwegian coast and 10º W.(b) North of 63º N between 10º W and 28º W.(c) North of 45º N between 28º W and the North American coast.(d) North of the European, North American and Asian continents outside of the limits of

longitude in (a), (b) and (c).(e) The Sea of Okhotsk, Bering Sea and Gulf of Tartary.(f) South of 60º S.

The half icing allowance should be applied:(a) In the areas north of 61º N, between the Norwegian coast and 28º W, south of the

areas to which the full allowance applies. (b) Elsewhere in seasonal winter zones, as agreed by the MCA and owners.

The amount of the allowanceThe full allowance assumes:(a) That all exposed horizontal surfaces (decks, tops of houses and deck cargo) are

carrying an ice weight of 30 kg/m2.(b) That vertical surfaces are carrying a weight equivalent to 15 kg/m2 on the lateral area

on one side of the ship (hull, houses, and deck cargo) above the waterline.

The half icing allowance should be taken as one half of these values.

The centre of gravity of each area of ice formation has to be estimated in order that the moment about the keel of each part of ice weight can be calculated.

Ice on booms, stays, rails etc. should be allowed for as 5% of the weight on vertical surfaces, and the vertical moment of this ice allowed for as 10% of the moment due to formation on vertical surfaces.

ICING ALLOWANCES (MAR Rev 29/04/02) 1

EXAMPLEA ship displaces 31700 t and is loaded such that the solid KG is 9.12 m. KM is 9.46 m andtotal FSM's are estimated to be 2050 t-m at the worst anticipated stage of the voyage. The vessel is to enter an area where the full icing allowance applies.

Ship details are as follows:

Main deck 3100 m2 at Kg 16.2 m;2nd deck 60 m2 at Kg 18.6 m;3rd deck 42 m2 at Kg 21.0 m;Bridge deck 48 m2 at Kg 23.4 m;Monkey island 56 m2 at Kg 25.8 m;

Lateral exposed area above the waterline is 860 m2 at a Kg of 13.64 m.

Calculate the effective GM and displacement that will allow for icing.

ICING ALLOWANCES (MAR Rev 29/04/02) 2