US3315630A

US3315630A - Mooring arrangement for ships

Info

Publication number: US3315630A
Application number: US481543A
Authority: US
Inventors: Hopkins Kenneth William
Original assignee: BP Shipping Ltd
Current assignee: BP Shipping Ltd
Priority date: 1964-09-07
Filing date: 1965-08-23
Publication date: 1967-04-25
Anticipated expiration: 1984-04-25
Also published as: DE1456246A1; NL6511466A; GB1046676A; BE669295A

Description

A ril 25; 1967 Filed Aug. 25, 1965 2 Sheets-Sheet l INVENTOR KENNETH W|LL|AM HOPKINS MORGAN, FINNEGAN, DURHAM 8 P\NE ATTORNEYS A ril 25, 1967 Filed Aug. .25, 1965 K. w. HOPKIN 5 3,315,630

MOORING ARRANGEMENT FOR SHIPS,

2 Sheets-Sheet 2 INVENTOR KENNETH WILLIAM HOPKINS BY MORGAN, FINNEGAN, DURHAM 81 PINE ATTORNEYS United States Patent 3,315,630 MOORING ARRANGEMENT FOR SHIPS Kenneth William Hopkins, Long Ditton, Surrey, England, assignor to BP Tanker Company Limited, London,

England, a corporation of England Filed Aug. 23, 1965, Ser. No. 481,543 Claims priority, application Great Britain, Sept. 7, 1964,

Claims. (Cl. 114-230) This invention relates to a mooring arrangement for ships and in particular to single point mooring for ships, especially tank ships.

With the advent of so-called super. tankers, tank ships of 50,000 d.w.t. and above, it is becoming increasingly difiicult to find harbours which have sufiicient depth to allow such ships to berth.

To overcome this difficulty it has been proposed to moor such ships to buoys anchored in deep water and to transfer the liquid cargo via the buoys. In the case of a single point mooring the ship is moored to a single buoy, usually by ropes or cables which extend from the bow of the ship to the buoy, the ship being allowed to rotate 360 around the buoy at will, according to, for example, tide and wind.

In the past considerable difliculty has sometimes been experienced in selecting the correct length for the mooring line or lines between the buoy and the bow of the ship. A long rope (150-300 ft.) has the advantage that it possessed considerable elasticity thus enabling the energy caused by small movements of the ship to be absorbed by the rope without putting any undue strain on it. On the other hand the long rope has a disadvantage in that it enables the ship to gain considerable momentum if a sudden change in wind or current should occur and cause the ship to move towards-the buoy, thus perhaps causing damage to the buoy and/or the ship. Alternatively the ship, when moored on the long rope, may ride past the buoy and, gathering momentum all the time, go to the end of its travel whereupon considerable strain will be placed on the mooring ropes (and also the buoy) to arrest the ships movement.

On the other hand if a short rope (30-60 ft.) is used the ship cannot build up much momentum even if there is a sudden change in wind or current as is the case with the long rope but unfortunately the short rope possesses but little elasticity, so small movements of the ship can put considerable strain on the mooring line. Another disadvantage is that the point of mooring of the single rope on the bow of the ship will be considerably above the buoy and so, due to the steep angle of the line, there may be snatching of the rope when the movement of the buoy and the ship are not in harmony.

It is an object of this invention to reduce the dis-advantages of 'both the long and the short ropes.

According to the invention a single point mooring comprises two mooring lines each of which is attached to the same end of a link-line the other end of which is attached to a mooring member which is rotatable about a vertical axis and supported by a buoy anchored to the sea bed, the dimensions of the mooring lines being such that when a ship is moored to the buoy, the mooring lines may be connected to the ship at points substantially abaft the bow, one line to the port side and the other to the starboard side. The single point mooring may also have at least one warping line for warping a ship up to the buoy in order that it may be moored.

Conveniently the two mooring lines are attached to the link-line by means of a link-member having a plurality of attachment points. Preferably all the warping lines are also attached to the link member.

The link-member preferably comprises a collar rotatably mounted upon an axle, the link-line being attached to one end of the axle and the mooring lines being attached to the collar. The link-line is conveniently attached to the mooring member by means of a rotatable coupling which permits the link-line to twist upon its axis.

Where the single point mooring comprises a single warping line this may be attached to the link-members axle at the opposite end to the link-line.

The invention also includes the combination of a ship moored to a single point mooring as described above in which one mooring line is attached to the ship at a point substantially abaft the bow of the port side and the other mooring line is attached to the ship at a point substantially abaft the bow on the starboard side; preferably 'both lines are attached to points abaft the forecastle.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of a ship moored to a single point mooring according to the invention, and

FIG. 2 is a plan view of a link-member comprised in the mooring shown in FIG. 1.

The single point mooring shown in FIGURE 1 comprises a buoy 2 which supports a mooring member 5 which is rotatable about a vertical axis. The mooring member 5 terminates in a hook 6 to which one end of a link-line 3 is attached by means of a shackle 4. The mooring member 5 includes a swivel which allows the link-line to twist upon its axis. The other end of the link-line 3 is connected to two mooring lines, 9 and 10 by means of a link-member 8. A warping line 17 is also connected to the'link-member 8.

The link-member 8, shown in greater detail in FIGURE 2, comprises an axle 20 (having attachment points 22 and 23' at opposite ends) and a collar 24 (having attachment points 25 and 26) rotatably mounted thereon. The linkmember 8 is shackled to the link-line 3 by the shackle 7 at the attachment point 22, to the warping line 17 by the shackle 18 at the attachment 23 and to the mooring lines 9 and 10 by means of the

shackles

11 and 12 at the

attachment points

26 and 25. When the mooring is in the use, the pull in the mooring lines 9 and 10 is taken by the thrust block 21 which is welded onto the axle 20; the collar 24 is prevented from falling off the other end of the link-member (when there is no load) by

stops

27 and 28.

A ship may be moored onto the single point mooring shown in FIGURE 1 by the following procedure. The ship steams into the vicinity of the buoy and the warping line 17 is picked up and attached to a capstan 19 in the bows. The ship is then warped towards the buoy until the mooring lines 9 and 10 can be picked up, passed through fairleads 15 and 16, and attached to capstans 13 and 14 which are situated abaft the torecastle on the starboard and port sides of the ship respectively. When the mooring lines have been adjusted the warping line may be slackened.

While the ship is being warped towards the buoy as described above the warping line 17 may twist under the strain. The rotatable collar 24 and axle 20 comprised in the link-member 8 permit this twist to be transmitted to link-line 3 without tangling the other lines; the swivel in the mooring member 5 permits the link-line 3 to twist freely as described.

When a ship 1, moored as shown in FIGURE 1, tends to move away from the buoy 2 there are long lengths of mooring lines to be stretched and thereby absorb the energy.

If the direction of wind and tide changes slowly the ship will move round the buoy, this motion being permitted by the rotation of the mooring member 5 about its vertical axis, so that the ship always tends to move away 3 from the buoy and this motion is prevented as described above.

On the other hand a sudden large change in the direction of wind 'and/or tide may cause the ship 1 to move towards the buoy 2 so that the mooring lines 9 and 10 go slack. As can be seen from FIGURE 1 the ship has only a small distance (compared with the length of the mooring lines) to travel before it collides with the buoy. This means that the ship will be able to build up only a small momentum before collision. Similarly there will be only a relatively small amount of energy to be absorbed if the ship misses the buoy and fetches up at the end of the mooring line in a new angular position.

The warping line 17 may be slackened to avoid unnecessary strain being placed thereon. It is, however, desirable to so adjust the warping line that the link-member 8 does not fall under the ship when the mooring cables slacken.

The motion of a moo-red ship is such that the mooring lines may chafe against the bows and this may cause undesirable wear. To guard against this possibility the appropriate portions of the mooring ropes may be replaced by wire cables or chains.

To provide cargo transference for a tank ship a pipe line is conveniently laid under the sea and thence up to a terminal on the buoy. The terminal conveniently comprises a swivel arrangement through which the pipe line may be connected to the tank ship. The swivel may be rotated by the mooring member 5 so that the connection between the ship and the buoy moves round the buoy with the ship.

I claim:

1. In a single point mooring which comprises a buoy floating on or near the surface of the sea and a buoy anchoring system which anchors said buoy to the sea bed, sai-d. buoy including a buoyancy chamber and a mooring member external to said buoyancy chamber, said mooring member being rotatable about a vertical axis, the combination of: two mooring lines, a link-line, and a link-member comprising a collar and an axle, the collar being rotatably mounted upon the axle, the two mooring lines being attached to the collar, and the link-line being attached at one end to one end of the axle and the other end of the link-line being attached to the mooring member; the dimensions of the mooring lines being such that, when a ship is moored, the mooring lines may be connected to the ship substantially abaft the bow, one line to the port side and the other to the starboard side.

2. A single point mooring according to claim 1 which comprises a single warping line attached to the link members axle at the opposite end to the link-line.

3. A single point mooring according to claim 2, in which the link-line is attached to the mooring member by means of a rotatable coupling which permits the link-line to twist upon its axis.

'4. The combination of a ship moored to a single point mooring as defined in claim 1, in which one mooring line is attached to the ship at a point substantially abaft the bow on the port side and the other mooring line is attached to the ship at a point substantially abaft of the bow on the starboard side.

5. A combination as claimed in claim 4, in which the mooring lines are attached ab'aft the forecastle.

OTHER REFERENCES Morris Weeks, In: The Complete Boating Encyclopedia, page 540 relied on.

MILTON BUCHLER, Primary Examiner.

T. M. BLIX, Assistant Examiner.

Claims

1. IN A SINGLE POINT MOORING WHICH COMPRISES A BUOY FLOATING ON OR NEAR THE SURFACE OF THE SEA AND A BUOY ANCHORING SYSTEM WHICH ANCHORS SAID BUOY TO THE SEA BED, SAID BUOY INCLUDING A BUOYANCY CHAMBER AND A MOORING MEMBER EXTERNAL TO SAID BUOYANCY CHAMBER, SAID MOORING MEMBER BEING ROTATABLE ABOUT A VERTICAL AXIS, THE COMBINATION OF: TWO MOORING LINES, A LINK-LINE, AND A LINK-MEMBER COMPRISING A COLLAR AND AN AXLE, THE COLLAR BEING ROTATABLY MOUNTED UPON THE AXLE, THE TWO MOORING LINES BEING ATTACHED TO THE COLLAR, AND THE LINK-LINE BEING ATTACHED AT ONE END TO ONE END OF THE AXLE AND THE OTHER END OF THE LINK-LINE BEING ATTACHED TO THE MOORING MEMBER; THE DIMENSIONS OF THE MOORING LINES BEING SUCH THAT, WHEN A SHIP IS MOORED, THE MOORING LINES MAY BE CONNECTED TO THE SHIP SUBSTANTIALLY ABAFT THE BOW, ONE LINE TO THE PORT SIDE AND THEOTHER TO THE STARBOARD SIDE.