Oy Wartsila Ab

Eero Makinen

Torsten Heideman

Bengt Johansson

Arno Keinonen

Stefan Gordin

A floating semisubmersible off-shore drilling platform or the like comprises an upper working level portion and a lower pontoon portion. When the platform is transported from one place to another, it floats on the pontoon portion, but when it is working as a stationary unit in open water, it is submerged deeper, so that the pontoon portion is at a considerable distance below the water surface and the working level portion is at a considerable distance above the water surface. The platform is adapted to withstand ice pressure from ice occurring in the ambient water by giving the pontoon portion of the platform a form particularly advantageous in ice conditions. When ice occurs, the platform is lifted to such a position, that its pontoon portion comes to float at the water surface level.

Floating drilling platform

A vessel, in particular a ferry, intended for use in ice-filled waters, is provided with a propeller guard having the form of a rigid grid construction and being arranged to enclose one or several propellers acting in the front part of said vessel and/or below the keel line of said vessel. The width of the guard at its upper edge at the hull of the vessel is at least substantially equal to the greatest width of the guard. At its front end, the guard has an oblique front edge which, in a longitudinal section, is at least to its major part, inclined relative to a horizontal plane at the most 50.degree., preferably at the most 45.degree..

Propeller guard

In an ice-breaking ship, having sufficient power and being generally designed for efficient ice-breaking, the breaking of the ice is made more effective by changing the zone of ice crushing and shearing which occurs at the stem during normal ice-breaking of level ice, to a zone where the breaking occurs due to bending. This is obtained by forming the front portion of the ship so that at least within the area where the stem contacts and breaks level ice, the basically wedge-formed stem is truncated to form a relatively broad runner-like portion being inclined forwards in a relatively small angle to the water line plane of the ship. The width of the runner-like portion is determined in conformity with the general ice-breaking ability of the ship, whereby the driving power (P) of the ship, in kW, and the maximum beam (B) of the ship at its design water line, in meters, forms the basis for calculating, in meters, the width (W) of the runner-like portion by means of the formula:

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Espoo, Finland

Eero Makinen