US3595195A

US3595195A - Offshore vessel mooring system

Info

Publication number: US3595195A
Application number: US789028A
Authority: US
Inventors: Wouter H Van Eek; Johan De Groot; Simon F Westra
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1968-05-08
Filing date: 1968-12-31
Publication date: 1971-07-27
Anticipated expiration: 1988-07-27
Also published as: NL6806466A; GB1207935A; FR2008035A1

Abstract

An offshore vessel mooring system in which a one-point mooring buoy has attached thereto a mooring cable and floating hose which are maintained in an extended condition along the surface of the water by a floating propulsion unit attached to the free ends of the mooring cable and floating hose to thereby facilitate the mooring of a vessel.

Description

United States Patent Wouter H. Van Eek; Johan De Groot; Simon F. Westra. all of [72] Inventors Hague. Netherlands [2|] Appl. No. 789,028 [22] Filed Dec.3l, 1968 [45] Patented July 27, 197i [731 Assignee Shell Oil Company New York, N.Y. [32} Priority May 8, i968 33] Netherlands [3| 1 6806466 [54] OFFSHORE VESSEL MOORING SYSTEM 7 Claims,7 Drawing Figs. 4

[52] U.S.C| 114/230,

9/8 [51] Int. Cl B63!) 21/50 [50] Field ol'Search 9/8, 8 P; ll4/.5. .5 T. 230

[56} References Cited UNITED STATES PATENTS 3,321,923 5/1967 Smith etal ll5/l2X 3,466,680 9/1969 Schirtzinger l14/230X Primary ExaniinerMilton Buchler Assistant E.raminer-Gregory W. OConnor Attorneys-J. H. McCarthy and Theodore E. Bieber ABSTRACT: An offshore vessel mooring system in which a one-point mooring buoy has attached thereto a mooring cable and floating hose which are maintained in an extended condition along the surface of the water by a floating propulsion unit attached to the free ends of the mooring cable and floating hose to thereby facilitate the mooring of a vessel.

PATENTEUJULZIBII 3.595.195

'sum 1 BF 2 1 l l l A J I E INVENTORS WOUTER H. VAN EEK JOHAN DE GROOT SIMON WESTRA PATENTED .27 I8?! 3.595195 sum 2 or z FIG- 6 INVENTORS:

WOUTER H.VAN EEK JOHAN DE GROOT SIMON WESTRA OFFSHORE VESSEL MOORING SYSTEM BACKGROUND OF THE INVENTION The invention relates to a method for the self-mooring of a ship to a one-point mooring buoy for loading or unloading a medium toor from a ship and to a mooring system for use therewith.

One-point mooring buoys for loading or'unloading a mediwit to or from a ship are widely known and are being used in increasing numbers. Examples of known one-point mooring buoys of this type are described inter alia in the BritishPat. Nos. 977,45 l; l,03l,492 andl,0l7,894.

With these one-point mooring buoys the ship is fastened by its bow to the buoy by means of a mooring cable in such a manner that the ship is capableof swinging around the buoy with its bow invariably pointing towards the buoy. The onepoint mooring buoy is provided with a hose floating on the water, which hose is coupled to the ship after the latter has moored to the onepoint mooring buoy, whereupon a start is made with'the loading or unloading of the medium (a fluid or a gas) via the hose and the one-point mooring buoy. For the purpose of mooring the ship to the one-point mooring buoy and for connecting the floating hose to the ship, use is normally made of a mannedmooring launch. This has the drawback that amanned mooringlaunch must constantly be available to assist arriving ships in mooring and in connecting the floating hose with the ship.

SUMMARY OFTI-IE INVENTION It is the object of the invention to provide a method and a mooring system by means of which the ship can be moored and the floating hose can be connected to the ship without it being necessary to use manned a mooring launch. Since the mooring of the ship to the buoy will now no longer be dependent on the limiting wave conditions to which the mooring launch is subject, it will also be possible to moor when the waves are high so that less delay in loading and unloading can be expected.

. To this end the method according to the invention is characterized in that by means of a propulsion unit connected to a mooring cable and a floating hose of the one-point mooring buoy, the mooring cable and the floating hose are permanently maintained in stretched condition, that the mooring cable and the floating hose are subsequently picked up from on board an arriving ship, whereupon the mooring cable and the floating hose are connected to the ship and a start is finally made with the-loading or unloading of the ship.

The radial force on the mooring cable and the floating hose is advantageously exerted by the propulsion unit of a floating body which is connected to the mooring cable and the floating hose.

A mooring system for use with the above method and consisting of a one-point mooring buoy provided with a mooring cable and a floating hose is characterized according to the invention in that the mooring cable and the floating hose are connected to a floating body, which is provided with a propulsion unit in such a manner that by means thereof the mooring cable and the floating hose can be permanently maintained in a radially stretched condition when the propulsion unit is operating.

The invention also relates to a floating body for use with the above method and with the aforesaid mooring system, characterized in that it is of substantially circular cylindrical design and is provided with a propulsion unit consisting of a propeller and a driving motor.

DESCRIPTION OF THE DRAWINGS The invention will now be elucidated with reference to the drawings which represent an embodiment of the invention.

FIG. I is a top plan view of a mooring system according to the invention showing a ship engaged inpicking up the mooring cable;

FIG. 2 is a side view ofthe system shown in FIG. 1;

FIG. 3 is a top plan view of the mooring system according to the invention showing the ship moored to the one-point mooring buoy and engaged in picking up the floating hose;

FIG. 4 is a side view of the system shown in FIG. 3;

FIG. 5 is a top plan view of the mooring system according to the invention showing "the floating hose also coupled to the ship and medium being loaded or unloaded through the hose and the one-point mooring buoy;

FIG. 6 is a side view of a vertical cross section of a floating body with propulsion unit for use with the mooring system according to the invention; and

FIG. 7 is a top plan view of'ithe floating body taken on the section II-II in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, a one-point mooring buoy l of the conventional type provided with a turntable 2 with pipe swivel and supply and discharge lines (not shown) is anchored in the usual manner to the bottom 4 of the water by means of chains3. The one-point mooring buoy l is provided with two floating hoses 5 and 6 of the conventional type which float on the surface of the water 7. The ends of the hoses 5 and 6 are secured in the usual manner to the one-point mooring buoy l. The other ends of the hoses 5 and 6 are designated by the reference numerals 8 and 9. Fastened to the ends 8 and 9am hoisting cables 10 and II which converge at the point 12. At the point 12 the hoisting cables 10 and 11 are fastened to one end ofa steel bracing cable 13. The other end 14 of the cable 13 is connected with a floating body 16 via an elastic element such as a nylon cable 15.

The one-point mooring buoy I is also provided with a mooring cable 17 which is secured byv one end to the turntable 2 in the usual manner. Preferably, the mooring cable 17 is of the self-floating type. The other end 18 of the mooring cable 17 is connected to a bracing cable 19, which is connected to the floating body 16 in a manner which will be described hereinafter with reference to FIG. 6.

The floating body.l6'(see in particular FIGS. 6 and 7) is of substantially circular cylindrical design. The propulsion unit consists of a screw propeller 20 which is connected to a driving motor 22 via a shaft 21. The motor 22 is, for example, an internal combustion engine, for example, a diesel engine or a petrol engine. The liquid fuel for the motor 22 can be stored in a fuel reservoir 23. The motor 22 is located in an engine room 24. Connected to the motor 22 are an air suction line 25 and an exhaust line 26. For protection of the propeller 20 a protective frame or grating 27 is arranged around the propeller 20.

A filling line 28 leads to the fuel reservoir 23 via the engine room 24. Around the fuel reservoir 23 is arranged a ballast tank 29 which can be filled with ballast water. The engine room 24 is provided with a manhole which is closed by a cover 30. Above the engine room 24 is'a platform 31 which is surrounded by a railing 32. On the upper side of the body 16 a fender 33 is provided, which is made, for example, from a solid rubber.

Installed in the engine room 24 are ballast pumps 34 which are connected by means of

lines

35 and 36 to the water in which the body 16 floats and to the ballast reservoir 29, respectively. The pumps 34 are provided with an automatic control (not shown) in such a manner that if the quantity of fuel in the fuel reservoir 23 decreases more ballast water is pumped to the ballast reservoir 29, and conversely, if the quantity of fuel increases ballast water is pumped out of the ballast reservoir 29. The effect of this is that the draught of the body 16 is automatically maintained at a desired value under all conditions independently of the quantity of fuel in the fuel reservoir 23.

Extending vertically through the floating body 16 is a guide tube 37, the lower part of which protrudes relatively far underneath the body 16 andthe upper part of which protrudes relatively far above the body Fixedly secured to the lower part of the guide tube 37 is stabilizing weight 38, which serves to improve the stability of the floating body 16.

Rotatably secured to the upper part is a sheave 39; running over this sheave 39 is a cable 40 which is provided at one end with a weight 41 capable of moving freely through the guide tube 37. At least prior to mooring, the end 42 of the cable 40 is connected with the end 43 of the bracing cable 19. Located on one side of the floating body 16 is an eye or a similar member 44, to which the nylon cable is secured, the end 14 of which is connected with the bracing cable 13, at least prior to mooring as explained in the foregoing.

A light-beacon 45 is preferably present on the floating body 16.

The mode of operation of the invention will now be elucidated with reference to the Figures.

Let it be assumed that a ship 46 approaches the mooring system in order to moor thereto and to load or unload. The floating body 16, the driving motor 22 of which is constantly in operation so that the propeller invariably exerts a propulsive force on the floating body 16 ensures that the mooring cable 17 (via the cables 19 and 40), and the floating hoses 5 and 6 (via the cables 10, l1, l3 and 15) are always subject to a force which is radially directed with respect to the one-point mooring buoy 1. As a result of this both the mooring cable 17 and the floating hoses 5 and 6 are maintained in a radially stretched condition, as are, of course, the

appurtenant cables

19 and 40 and 10, 11, 13 and 15, respectively.

When the ship has reached the position indicated in the FIGS. 1 and 2, a grapple 48 is lowered from the ship 46 by means of a cable 47. The grapple 48 is hooked on to cable 19 (which at that moment is in the position shown by the solid line) and the grapple 48 is subsequently hauled into the ship 46 with the result that the cable 19 and the cable 40 are pulled, at least in part, into the ship 46, so that the

cables

19 and 40 occupy the position indicated by the dotted lines. In the position shown by the dotted lines the cable 40 has been removed from the guide tube 37 to such an extent that the counterweight 41 has moved to the uppermost part of the guide tube 37. The ends 42 and 43 of the

cables

40 and 19, respectively, are now disengaged from each other. The end 43 of the cable 19 is subsequently connected with one end 49 ofa cable 50 present on board the ship 46. The end 42 of the cable 40 is connected with the end 51 ofa second cable 52 present on board the ship 46.

The ship 46 is now shifted to the position shown in FIGS. 3 and 4 and made fast by means of a winch 53, the cable 52 being fastened to a winch 54.

Subsequently, a start is made with the second step of the mooring operation, namely the hauling in of the hoses 5 and 6 and the coupling thereof to the ship 46. To this end the grapple 48 is lowered for the second time from the ship 46 by means of the cable 47 in such a manner that the grapple 48 grasps the cable 13. At this moment the cable 13 and the cables 10 and 11 are in the position shown by the solid lines. The grapple 48 is subsequently hauled in so that the

cables

10, 11 and 13 are brought at least in part into the ship 46 and occupy the positions shown by dotted lines. The bracing cable 13 is then disengaged from the cables 10 and 11 and fastened to capstans 55. The ends 12 of the cables 10 and 11 are secured to a hoisting cable 58 which ends are subsequently suspended by means ofa hoisting

device

59 and 60 at the same height as the

lines

56 and 57 of the ship 46. After this the ends 8 and 9 of the hoses 6 and 5 are coupled to the lines 56 and/or 57, whereupon a start can be made with the loading or unloading of the ship 46 through the hoses 5 and 6 and the one-point mooring buoy 1.

After loading or unloading, the uncoupling of the ship 46 is in principle eflected by reversing the sequence of the above operations.

At times when no ship is moored to the mooring system the

propulsion unit

20, 21, 22 ofthe floating body 16 is constantly in operation as a result of which the mooring cable and the floating hoses can always be maintained in a radially stretched condition with respect to the one-point mooring buoy. Even at times when a ship is moored to the mooring system it is preferred to keep the

propulsion unit

20, 21, 22 of the floating body 16 constantly in operation.

It will be appreciated that whenever in the foregoing reference is made to cables, chains can equally well be used. Thus, the term cable should be interpreted in a broad sense. If desired, the floating body 16 may be of spindlelike design, the longitudinal axis pointing in a horizontal direction.

The propeller 20 is a traction propeller, i.e., it exerts a force which in the position shown is directed away from the onepoint mooring buoy 1.

it will be clear that instead of an internal combustion engine other motors, for example, an electric motor, may be used for the propulsion unit of the floating body 16. Further, as an alternative to a propeller propulsion device use can also be made of a propulsion unit operating with a water jet or an air jet.

The embodiment shows a one-point mooring buoy with two floating hoses. Use can of course also be made of one floating hose or of more than two floating hoses. The floating hoses or tubes can be made, for example, ofa flexible material such as rubber.

in the method described, a bracing cable is arranged between the free end of the floating hose and the floating body so that a force is exerted on the hose which keeps the hose in a stretched condition. Alternatively, however, the hose may be maintained in an at least more or less stretched condition by means of a continuous cable stretched between the floating body and the mooring buoy, the end of the floating hose being slidingly connected to this cable. As a result the hose retains its axial freedom of movement and great forces are prevented from acting on the hose, the life ofwhich is thereby prolonged.

We claim as our invention:

1. An offshore vessel mooring system for loading or unloading a fluid medium to or from said vessel, said system comprismg:

a one-point mooring buoy positioned on the surface of a body of water;

anchoring means attached to said buoy for maintaining said buoy at an offshore location;

mooring cable means having one end attached to said buoy;

floating hose means having one end operatively connected to said buoy;

a floating body operatively connected to the other ends of said mooring cable means and said floating hose means; and,

propulsion means carried by said floating body;

said propulsion means including a motor and being adapted to move said floating body away from said mooring buoy to thereby maintain said mooring cable means and said floating hose means in a permanently radially stretched condition along the surface of the body of water.

2. A mooring system as defined in claim 1 wherein said mooring cable means is operatively connected to said floating body by constant tension means prior to the engagement of said mooring means by a vessel, said constant tension means maintaining a constant tension on said mooring cable means independent of said propulsion means.

3. An offshore vessel mooring system for loading or unloading a fluid medium to or from said vessel, said system comprising:

a one-point mooring buoy positioned on the surface of a body of water;

mooring cable means having one end attached to said buoy;

floating hose means having one end operatively connected to said buoy;

a floating body operatively connected to the other ends of said mooring cable means and said floating hose means;

propulsion means carried by said floating body;

said propulsion means being adapted to move said floating body away from said mooring buoy to thereby maintain said mooring cable means and said floating hose means in a permanently radially stretched condition along the surface of the body of water;

said mooring cable means being operatively connected to said floating body by constant tension means prior to the engagement of said mooring means by a vessel, said constant tension means maintaining a constant tension on said mooring cable means independent of said propulsion means; and said constant tension means comprising a weight attached to said other end of sad mooring cable means and pulley means carried by said floating body and adapted to engage said mooring cable means. 4. A mooring system as defined in claim 3 including vertically extending tube means carried by said floating body for 6 guiding said weight.

5. A mooring system as defined in claim 4 wherein said pulley means is carried by the upper end of said tube means.

6. A mooring system as defined in claim 5 wherein said propulsion means comprise an internal combustion engine and a screw propeller.

7. A mooring system as defined in claim 6 including:

ballast chamber means carried by said floating body; and,

pump means in communication with said ballast chamber means and said body of water to vary the amount of ballast water in said ballast chamber means.

Claims

1. An offshore vessel mooring system for loading or unloading a fluid medium to or from said vessel, said system comprising: a one-point mooring buoy positioned on the surface of a body of water; anchoring means attached to said buoy for maintaining said buoy at an offshore location; mooring cable means having one end attached to said buoy; floating hose means having one end operatively connected to said buoy; a floating body operatively connected to the other ends of said mooring cable means and said floating hose means; and, propulsion means carried by said floating body; said propulsion means including a motor and being adapted to move said floating body away from said mooring buoy to thereby maintain said mooring cable means and said floating hose means in a permanently radially stretched condition along the surface of the body of water.

3. An offshore vessel mooring system for loading or unloading a fluid medium to or from said vessel, said system comprising: a one-point mooring buoy positioned on the surface of a body of water; anchoring means attached to said buoy for maintaining said buoy at an offshore location; mooring cable means having one end attached to said buoy; floating hose means having one end operatively connected to said buoy; a floating body operatively connected to the other ends of said mooring cable means and said floating hose means; propulsion means carried by said floating body; said propulsion means being adapted to move said floating body away from said mooring buoy to thereby maintain said mooring cable means and said floating hose means in a permanently radially stretched condition along the surface of the body of water; said mooring cable means being operatively connected to said floating body by constant tension means prior to the engagement of said mooring means by a vessel, said constant tension means maintaining a constant tension on said mooring cable means independent of said propulsion means; and said constant tension means comprising a weight attached to said other end of sad mooring cable means and pulley means carried by said floating body and adapted to engage said mooring cable means.

4. A mooring system as defined in claim 3 including vertically extending tube means carried by said floating body for guiding said weight.

7. A mooring system as defined in claim 6 including: ballast chamber means carried by said floating body; and, pump means in communication with said ballast chamber means and said body of water to vary the amount of ballast water in said ballast chamber means.