US3678873A

US3678873A - Method and apparatus for cutting ice

Info

Publication number: US3678873A
Application number: US77483A
Authority: US
Inventors: John D Bennett
Original assignee: Sun Oil Co
Current assignee: Sunoco Inc
Priority date: 1970-10-02
Filing date: 1970-10-02
Publication date: 1972-07-25
Anticipated expiration: 1989-07-25
Also published as: CA942591A

Abstract

Removing ice encroaching an offshore platform from an ice floe or ice located in the path of a vessel, by making a pair of cuts in the ice parallel to the direction of travel of the vessel or ice floe, with each cut angled from vertical so that the crosssectional area of the bottom surface of the ice being removed is larger or smaller than the cross-sectional area of the top surface of the ice being removed. The ice section being removed is then broken from the remaining ice mass by forward movement of the vessel or pressure of the ice floe against the offshore platform. An additional cut can be made between and parallel to the pair of parallel cuts, to make two ice sections in order to facilitate forcing of the severed ice aside to a point beneath or on top of the ice mass when the ice sections are broken from the remaining ice mass. These cuts can be made with mechanical saws or high pressure nozzles utilizing high pressure fluids.

Description

United States Patent Bennett 1 July 25,1972

[54] METHOD AND APPARATUS FOR CUTTING ICE [72] Inventor: John D. Bennett, Denton, Tex.

[73] Assignee: Sun Oil Company, Dallas, Tex.

[22] Filed: Oct. 2, 1970 [21] Appl. No.1 77,483

Primary Examiner-Trygve M. Blix Attorney-George L. Church, Donald R. Johnson, Wilmer E. McCorquodale, Jr. and John E. Holder S 7] ABSTRACT Removing ice encroaching an offshore platform from an ice floe or ice located in the path of a vessel, by making a pair of cuts in the ice parallel to the direction of travel of the vessel or ice floe, with each cut angled from vertical so that the crosssectional area of the bottom surface of the ice being removed is larger or smaller than the cross-sectional area of the top surface of the ice being removed. The ice section being removed is then broken from the remaining ice mass by forward movement of the vessel or pressure of the ice iloe against the offshore platform. An additional cut can be made between and parallel to the pair of parallel cuts, to make two ice sections in order to facilitate forcing of the severed ice aside to a point beneath or on top of the ice mass when the ice sections are broken from the remaining ice mass. These cuts can be made with mechanical saws or high pressure nozzles utilizing high pressure fluids.

l0 Chins, 5 Drawing Figures Patented July 25, 1972 DIRECTIONAL CONTROLS .25.

\ gg FIG. 4

D|SCHARGE FROM VESSEL'S HEAT FIG 2 5 f EXCHANGER WATER INTAKE 0N UNDERSIDE OF VESSEL 2o 20 +7- W/-' '7 P-F t Fri? E; Z: FIG. 3B

\ INVENTOR 46 FIG. 3A

v JOHN 0. BENNETT ATTORNEY METHOD AND APPARATUS FOR CUTTING ICE BACKGROUND OF THE INVENTION This invention deals with the problems caused by ice floating in frigid waters such as in the Arctic Islands area. Currently there is high interest in exploring for and developing natural resources in such areas. In the search for and development of petroleum from offshore areas, platforms have been used which are supported on the floor of a body of water by rigid upright members. Such platforms if located in the Arctic Islands area would be exposed to ice floes which float freely in the water and may be of such a size and propelled at such a speed that the platform would be subjected to damage or destruction from the severe pressures. Additionally, the specially equipped SS Manhattan recently made a voyage through the Northwest Passage to determine if a vessel could be used,

for transportation of hydrocarbons from the Arctic regions and encountered difi'iculty in penetrating the ice. Other vessels will be attempting to serve both the offshore drilling structures and storage facilities in these areas, and must be able to penetrate through ice floes in order to reach these locations.

The Arctic Ocean adjacent the North Slope area of Alaska is characterized by its shallow depth and gradual slope to deep water. Air temperatures usually range from -40 F. to +50 F. The water is very uniform in temperature, from +28 F. to +30 F., and very saline except in the lagoons opposite the rivers. Winds are predominantly from the East I to 15 mph, with a maximum of 50 to 60 knots, however, waves are not usually more than 5 feet high. In the months of November through April, large masses of ice are in continuous movement by the effects of wind in the Arctic Ocean. Ice fields measuring thousands of feet in diameter are propelled in many directions by the winds and are generally unaffected by the minor currents present in the Arctic Ocean.

The main ice form in the Arctic Ocean is the ice sheet, which is generally uniform and 6 to 10 feet in thickness. Another form of ice encountered is rafted ice, which is the term used to describe the overlapping of ice sheets as one sheet rides up over another sheet resulting in an ice floe made up of two or more distinct layers. In open locations, the rafting does not generally take place between sheets of more than one or two feet in thickness, since thick sheets cannot withstand the deflection necessary for one sheet to ride over the other. Rafted ice has a much smaller surface area than that of the more prevalent ice sheets, and is not as strong because of poor bonding between its layers.

Other forms of ice in the Arctic Ocean are the icebergs and pressure ridges. Icebergs do not occur, except in waters over 120 feet deep. Since these icebergs can be several square miles in area and can be up to 160 feet thick, in those areas where icebergs may be encountered, an above water-surface platform would not appear to be feasible. Pressure ridges occur when two sheets of ice impinge upon each other. Crushing occurs and the ice is broken and piles up above and below the general ice level. Pressure ridges may be encountered which are some I50 feet thick. These ridges should also be avoided.

Thus, it can be seen that offshore platforms located in shallow water will encounter ice sheets from 6 to 10 feet thick when located in the Arctic Ocean, and occasionally rafted or sheet ice up to feet thick. Generally speaking then, an offshore platform should be able to routinely withstand at least 15 foot thick ice sheets having diameters of several thousand feet, being moved by winds of 15 miles per hour. This ice has a shear strength of 60 psi and a crushing strength of 300 psi.

Regarding ice which a vessel will encounter while attempting to service drilling platforms located in the Arctic Ocean as well as storage facilities located in such areas as Cook Inlet and Prudhoe Bay, it is presumed that ice would not be encountered beyond the same l0 or 15 foot thick sections. It is therefore an object of the present invention to provide a method and apparatus for aiding marine structures to penetrate and withstand ice floes.

SUMMARY OF THE INVENTION With these and other objects in view, the present invention contemplates cutting ice located in frigid waters with mechanical saws or high pressure nozzles emitting a cutting fluid. The nozzles or saws can be mounted on the prow of a ship in such a manner that cuts would be made in the direction of movement of the vessel or on a marine structure. Two outside cuts would be made at angles from the vertical so that the upper surface of the ice section located between the cuts would be smaller or larger than the bottom surface of such ice sections. A vertical cut can also be made between the two angle cuts thereby dividing the ice sections into two parts. The ice sections are then broken from the larger ice mass by the force of the forward moving vessel or pressure of the ice against the marine structure. The shape of the ice section and the pressure exerted thereon forces the ice sections above or below the remaining ice mass. A complete understanding of this invention may be had by reference to the following detailed description, when read in conjunction with the accompanying drawings illustrating embodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a cross-sectional view through a body of water containing floating ice and a vessel having high pressure nozzles;

FIG. 2 is a diagram assembly drawing depicting a nozzle system for cutting ice;

FIG. 3A is a cross-sectional view of a body of ice illustrating the angular cut of the ice by the nozzles attached to the vessel;

FIG. 3B is a cross-sectional view of a body of ice showing the location of sections which have been cut from the body of ice; and

FIG. 4 is a cross-sectional view through a body of water having floating ice therein and an offshore platform equipped with high pressure nozzles and mechanical saws.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. I of the drawings a vessel I2 is located in the body of water 42 which has ice mass 20 also floating therein. Located at the prow of the vessel 12 are nozzles 14 connected to the vessel I2 by conduits 16. Liquid exiting nozzles 14 impinges the ice mass 20 thereby cutting the ice because of the high pressure impact of the fluid. The vessel I2 is propelled forward by propeller I8 and by the direction of the fluid exiting nozzle 14. As herein depicted, an ice section 22 has been broken from the ice mass 20 because of the force of the forward movement of the vessel I2. This action will be amplified further in a discussion of FIGS. 3A and 3B.

In FIG. 2 there is illustrated the nozzle assembly. This consists of the nozzles I4 having control valves 24 associated therewith connected to directional controls 28. The conduit 16 connects the nozzles 14 to a pump 26, which pumps water from water intake 30 located at the underside of a vessel and heat exchanger discharge 32 from the vessel propulsion system. The directional controls 28 allow selective opening and closing of each nozzle which can be used to control the directional movement of the vessel. A typical control valve 24 could be a simple valve having a single flow channel element therein, which when rotated, moves such flow channel into or out of alignment with the conduit I6, thereby stopping flow to the related nozzle 14. As shown in FIG. 2, these valves are in a closed position. These valves can be actuated by hydraulic or electrical lines 58 connected with directional controls 28. Directional controls 28 can be manually operated with pushpull handles which directly act on hydraulic lines, or by closing contacts to complete electric circuits for supplying power to solenoids which operate to open and close the valves 24. Thus the pump 26 in combination with the nozzles 14 provides a method for directional control at the prow of the boat because of the force of the high velocity water stream exiting selected nozzle 14. The temperature of the fluid exiting nozzles 14 will be somewhat in excess of the temperature entering through water intake 30 located on the under side of the vessel, due to the heat contained in the water coming from heat exchanger discharge 32. This additional temperature aids in the cutting action of the fluid exiting nozzles 14.

FIG. 3A illustrates the cutting action of the nozzles on the ice mass 20. The two outside nozzles are arranged so that exiting fluids impinge on the ice at an angle to generate cuts along angular surfaces such as at 44. The middle nozzle 14 is arranged so as to make a cut 46 in a substantially vertical plane. Thus the nozzles 14 cut the ice mass to create ice sections 22 which, as seen in cross-section approximately define trapezoids. The shape of the cut ice section facilitates vertical movement of said ice section so as to substantially eliminate crushing of the ice in the path of the vessel. This effect minimizes horsepower requirements necessary to remove the ice from the path of the vessel. As the vessel 12 moves forward, the ice sections 22 are easily broken from the remainder of the ice mass because of the mechanical advantage in using the ice section as a lever arm. As these ice sections 22 are forced downward by the weight of vessel 12 they can easily slide under the ice mass 20 as shown in FIG. 38. Movement of the ice sections 22 underneath the ice mass 20 efiectively removes the ice from the newly created sea lane which tends to retard refreezing of such sea lane and therefore allows freer movement of vessels therethrough. For vessels having prows which act like plows and therefore lift the ice to break a section from the ice mass 20 rather than to ride up on it and force it downward, the two outside nozzles would have to be angled inwardly to create ice sections 22 having larger top surfaces than bottom surfaces. This facilitates upward movement of the ice sections 22 under the influence ofthe plow.

FIG. 4 illustrates an offshore platform in waters 42 having free floating ice mass 20 located therein. The platform 34 supports typical equipment such as drilling rig 36, crane 38 and machinery and storage housing 50. Also located on the platform are nozzles 14 and mechanical saws 40. These nozzles 14 and/or mechanical saws 40 can be arranged singly or in groups of three as used with the vessel 12 in FIG. 1 and 3A and 3B. Mechanical saws 40 are depicted as chain saws; however, other types of saws may be equally serviceable. Nozzles 14 and/or the mechanical saws 40 may be arranged on a track to facilitate movement for inter-positioning between the platform substructure 52, and the encroaching ice mass 20. Alternatively, a series of nozzles 14 may be arrayed around a periphery of the platform 34 and selectively used. In order to generate water stream pressures of 2 to 3 thousand pounds per square inch, each cut should be made by a single nozzle 14 and a high pressure pump 26 would be necessary. It is however contemplated that a series of nozzles 14 can be used for a single cut. The nozzles 14 should be located as close to the ice mass 20 as practical. Sensors can be employed to determine height of the ice mass to adjust the height of nozzles 14 relative to the upper surface of the ice mass 20. If the nozzle 14 is located a substantial distance from the ice mass 20, the stream of water exiting the nozzle tends to dissipate, and thereby lose cutting strength or be distorted by the wind. When the nozzle 14 is placed closer to the ice mass 20, the profile of the water stream is improved and thus the cutting power is improved. As the ice mass 20 moves past the nozzles 14 and/or mechanical saws 40, it collides with substructure 52 of the offshore platform 34, whereupon, the cut sections are broken from the remaining ice mass 20. At this point, because of the shape of the cut sections, these sections tend to move under the ice mass 20 if the outside nozzles are directed outwardly. The ice sections will tend to move above the ice mass 20 if the outside nozzles are directly inwardly. If only a single cut is made, a substructure 52 would simply shear through the ice mass 20. If a substructure 52 has a large cross section, a single cut may not be satisfactory as the substructure 52 would have to crush the oncoming ice mass 20 by the force of the ice mass 20 against the substructure 52.

Because of the movement of the vessel 12 in FIGS. 1 and 3A and 3B, the noules 14 should be connected to the vessel 12 in such a manner as to allow upward and downward movement depending on the height of the me being cut and movement of the vessel 12. This will prevent damage to the nozzles 14 and afford greater cutting efficiency because of the nearness of the nozzles 14 to the ice mass 20.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. Method of removing ice located in the path of a vessel, wherein the ice being removed is part of a larger ice mass, comprising the steps of: making a plurality of cuts in the ice. the cuts having parallel longitudinal axes and where at least two of the cuts are angled from vertical in opposite directions to define ice sections having unequal top and bottom surface areas; breaking the ice sections located between the cuts from the ice mass, and forcing the ice sections to the side of the vessel.

2. The method of claim 1 wherein the cuts are made with high pressure fluid.

3. In a method of breaking ice from an ice mass in the path of a vessel where the forward movement of the vessel breaks a path in the ice mass, the improvement comprising: directing a high velocity liquid against the ice mass for cutting the ice mass in a generally vertical plane prior to contacting the ice mass with the vessel.

4. Method of removing ice from an ice mass comprising: directing high pressure nozzles emitting a cutting fluid against the ice mass to make a plurality of generally vertical cuts in the ice mass and thereby define ice sections in the ice mass; breaking the ice sections from the ice mass; and forcing the ice sections to the side of the original position of the ice section.

5. The method of claim 4 wherein the plurality of cuts includes a pair of outside cuts which are angled from a vertical plane to define ice sections having unequal top and bottom surfaces and a single substantially vertical cut between the pair of outside cuts.

6. Apparatus for removing ice from a large ice mass located in the path of a vessel comprising: noule means attached to the prow of the vessel and extending in front of the vessel. including a plurality of nozzles of which there is at least one pair of nozzles arranged so that an extension of the longitudinal axes of the pair of nozzles intersect above the nozzles; and means for supplying a cutting fluid under pressure to said nozzles.

7. The apparatus of claim 6 wherein the nozzles are inclined toward the vessel to aid in propulsion of the vessel and including means connected to said nozzle means for controlling the direction of travel of the vessel.

8. The apparatus of claim 6 wherein the nozzle means includes a nozzle located between said pair of nozzles which is positioned in a substantially vertical plane.

9. Apparatus for cutting an ice floe encroaching an offshore platform having at least one support member, comprising: nozzle means directed downwardly towards the ice floe and attached to the platform support member; and means for supplying a liquid under pressure to said nozzle means.

10. The apparatus of claim 9 wherein the nozzle means includes a pair of noules arranged so that an extension of the longitudinal axis of the pair of nozzles intersect and are at right angles to the direction of movement of the ice floe.

* k f l l

Claims

1. Method of removing ice located in the path of a vessel, wherein the ice being removed is part of a larger ice mass, comprising the steps of: making a plurality of cuts in the ice, the cuts having parallel longitudinal axes and where at least two of the cuts are angled from vertical in opposite directions to define ice sections having unequal top and bottom surface areas; breaking the ice sections located between the cuts from the ice mass, and forcing the ice sections to the side of the vessel.

2. The method of claim 1 wherein the cuts are made with high pressure fluid.

6. Apparatus for removing ice from a large ice mass located in the path of a vessel comprising: nozzle means attached to the prow of the vessel and extending in front of the vessel, including a plurality of nozzles of which there is at least one pair of nozzles arranged so that an extension of the longitudinal axes of the pair of nozzles intersect above the nozzles; and means for supplying a cutting fluid under pressure to said nozzles.

10. The apparatus of claim 9 wherein the nozzle means includes a pair of nozzles arranged so that an extension of the longitudinal axis of the pair of nozzles intersect and are at right angles to the direction of movement of the ice floe.