U.S. patent number 3,912,228 [Application Number 05/475,012] was granted by the patent office on 1975-10-14 for integrated chain-wire rope mooring system.
This patent grant is currently assigned to Ocean Drilling & Exploration Company. Invention is credited to John L. Bell, Mark A. Childers, Carmon R. Costello, Terry Petty, Gude P. Rao.
United States Patent |
3,912,228 |
Petty , et al. |
October 14, 1975 |
Integrated chain-wire rope mooring system
Abstract
An integrated chain-wire rope mooring system is comprised of a
mooring line consisting of a chain attached to an anchor at one end
and permanently coupled to a wireline at the other end which is
wrapped around a drum. A windlass wildcat is positioned preferably
adjacent to the drum so that it can be driven and controlled in
unison with the drum. An interior sheave is positioned inside or in
the vicinity of the chain locker and in the path of the mooring
line between the wildcat and the drum. The sheave is sufficiently
below the drum to allow the wireline to maintain continuous contact
with the sheave such that an acceptable fleet angle is
maintained.
Inventors: |
Petty; Terry (New Orleans,
LA), Costello; Carmon R. (Kenner, LA), Bell; John L.
(Metairie, LA), Childers; Mark A. (New Orleans, LA), Rao;
Gude P. (New Orleans, LA) |
Assignee: |
Ocean Drilling & Exploration
Company (New Orleans, LA)
|
Family
ID: |
23885886 |
Appl.
No.: |
05/475,012 |
Filed: |
May 31, 1974 |
Current U.S.
Class: |
114/230.23;
242/388.9; 254/286; 226/118.4 |
Current CPC
Class: |
B63B
21/22 (20130101); B66D 1/72 (20130101) |
Current International
Class: |
B63B
21/00 (20060101); B66D 1/00 (20060101); B63B
21/22 (20060101); B66D 1/72 (20060101); B66D
001/72 () |
Field of
Search: |
;254/175.5,175.7,135R,136R,144,19R ;114/23R,235R,235A ;226/118R
;242/55.01,47.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Spar; Robert J.
Assistant Examiner: Noland; Kenneth
Attorney, Agent or Firm: Breston; Michael P.
Claims
What is claimed is:
1. An integrated mooring system for a floating structure, said
system comprising:
a mooring line including a wireline, a chain and a connector
coupling the wireline to the chain;
a drum for winding and unwinding the wireline, said drum being
mounted on a mooring tower which defines a chain locker;
a wildcat mounted on said structure for paying-out and paying-in
said mooring line from and into said chain locker;
an interior sheave mounted inside said tower and disposed at a
sufficient distance below said drum and in a position so as to
allow the wireline to continuously remain in engagement with the
sheave; and
power means adapted to rotate said drum and said wildcat
simultaneously or sequentially; and
said means being operable to stop the drum and continue rotation of
said wildcat to effect storage of said chain in said locker during
a pay-in of said mooring line.
2. An integrated mooring system mounted on a floating structure
having a chain locker, said system comprising:
a mooring line including a wireline, a chain and a connector
coupling the wireline to the chain;
a drum for winding and unwinding the wireline;
a wildcat mounted on said structure for paying-out and paying-in
said mooring line from and into said chain locker;
an interior sheave mounted at a sufficient distance below said drum
and in a position so as to allow the wireline to continuously
remain in engagement with the sheave; and
power means adapted to rotate said drum and said wildcat
simultaneously or sequentially, said means being operable to stop
the drum and continue rotation of said wildcat to effect storage of
said chain in said locker during a pay-in of said mooring line.
3. An integrated mooring system for mooring a structure floating on
a body of water, said system comprising:
a mooring line consisting of: a wireline, a chain, and a connector
coupling the wireline to the chain;
a drum rotatably mounted on said structure, a chain locker in said
structure for housing said chain;
a wildcat mounted on said structure for paying-in and paying-out
said mooring line;
a suitably disposed interior sheave adapted to remain in continuous
engagement with said wireline; and
power means adapted to rotate said drum and said wildcat
simultaneously or sequentially,
said power means being operable to stop said drum after winding
said wireline thereon and continue rotation of said wildcat to
effect storage of said chain in said chain locker during a pay-in
of said mooring line.
4. An integrated mooring system for mooring a structure floating on
a body of water, said system comprising:
a mooring line consisting of: a wireline, a chain, and a connector
coupling the wireline to the chain;
a drum rotatably mounted on said structure, a chain locker in said
structure for housing said chain;
a wildcat mounted on said structure for paying-in and paying-out
said mooring line; and
power means adapted for selectively powering said drum and said
wildcat simultaneously or sequentially,
said power means being operable to stop said drum after winding
said wireline thereon and continue rotation of said wildcat to
effect storage of said chain in said chain locker during a pay-in
of said mooring line.
Description
BACKGROUND OF THE INVENTION
With offshore drilling progressing to waters beyond the Continental
Shelf, there is an increasing need for improved mooring systems
that are especially adapted for deep waters beyond 300 meters.
While a chain has great mooring advantages, when it becomes too
long, it also can present certain disadvantages due to its
excessive weight: a very long chain requires a greatly reinforced
chain locker; because of the heavy weight of chain, a mooring line
exclusively of chain takes on too steep an angle near the water
surface, thereby imposing an inferior restoring force in the
horizontal direction.
It is an object of the present invention to provide a mooring line
which consists of a wire rope permanently coupled to a long chain
for use in an integrated chain-wire rope mooring system and
employing an interior sheave which is adapted to sequentially move
over its periphery in either direction a chain, a wireline, and a
connector therebetween. Accordingly the integrated mooring system
of this invention requires no making and breaking of the connection
between the wireline and the chain each time that the mooring line
is paid out or hauled in.
SUMMARY OF THE INVENTION
An integrated mooring system is provided having a mooring line
consisting of a chain and a wireline, permanently coupled to each
other by a connector device. The wireline is wound on a drum,
preferably, though not necessarily, positioned adjacent to and at
the same time elevation as a wildcat, so that both the drum and the
wildcat can be powered and controlled together. An interior sheave
is positioned in the path of the mooring line between the drum and
the wildcat. The sheave is preferably in or in the vicinity of the
chain locker and sufficiently below the drum so as to continuously
maintain contact with the wireline and maintain an acceptable fleet
angle. To pay out the mooring line, the drum remains stationary and
the wildcat is rotated until the chain has been completely run out
from its locker. The chain or wire rope then forms a loop around
the interior sheave, applying tension to the wireline which causes
the drum to start to rotate with the wildcat to unwind the
wireline. After all the chain is paid out, the wildcat acts only as
an unpowered fairlead sheave for the wire line, which is being paid
out from the wireline drum, passing around the lower or chain
locker sheave, over the wildcat, and thence overboard. The wireline
can then follow the chain's path over the components of the mooring
system.
The mooring line is retrieved by rotating the drum in an opposite
direction thereby winding the wireline on the drum until the
connector device is pulled just past the lower sheave. The drum is
then stopped and only the wildcat is rotated to retrieve the chain
which is allowed to pile up in the chain locker. For a brief period
of time, during which the connector between chain and wire has
passed over the wildcat but has not yet reached the position in
which it will remain while the wire has been retrieved to the
maximum extent and is stored on the drum, both the wireline winch
and the windlass wildcat are hauling in under power.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates the integrated chain-wire rope mooring system of
this invention with the chain piled up in the chain locker and the
leading end of the wireline and connector just past the outer
periphery of the sheave;
FIG. 2 is similar to FIG. 1, showing the chain after it has been
completely taken out from its locker, and the wireline drum has
begun paying out so that the connector has passed over the lower
sheave and over the windlass wildcat; and
FIG. 3 is similar to FIG. 2, but with the mooring line further
advanced, the connector now being outboard of the outer
fairlead.
Referring now to the drawings wherein the same numerals are used to
designate the same parts, the integrated mooring system 12 of this
invention is conveniently mounted on a suitable support, such as a
column or mooring tower 10. System 12 uses a mooring line 14 which
consists of a wireline 16, a chain 18, and a connector 20 for
permanently connecting the wireline to the chain. The connector can
be of the type as manufactured by Pusnes or Skagit Corporations or
others skilled in the design and manufacture of mooring
equipment.
Wireline 16 is wound on the cylindrical periphery of a spool or
drum 22 which is rotatably mounted about a shaft 24. Drum 22 is
mounted at an elevated position relative to a chain locker 26 in
which chain 18 is piled. An anchor windlass wildcat 28, preferably
positioned adjacent to drum 22, is rotatably mounted about a shaft
30. Wildcat 28 is followed by a fairleader 32 rotatably mounted
about a shaft 34 supported on an exterior bracket 35 extending from
tower 10 below wildcat 28.
In accordance with the gist of this invention, an interior
fairleading device such as a sheave 36 is located in, on top of, or
underneath locker 26 and is rotatably mounted about a shaft 38.
Sheave 36 has a circumferential periphery adapted to accept
sequentially chain 18, connector 20, and rope 16 in either
direction. It is essential to position sheave 36 sufficiently below
drum 22 to allow proper fleet angles between the sheave and drum
and at a distance from a vertical plane passing through shaft 24.
Any other arrangement will be acceptable as long as the wireline
continuously maintains contact with sheave 36 when all the chain is
out of the locker.
Thus the term "interior sheave" as used herein and in the claims
indicates an appropriately located sheave relative to the other
components of the mooring system 12, including chain locker 26,
drum 22, and wildcat 28. The appropriate location for sheave 36 may
include any position that enables the sheave to serve its intended
function between wildcat 28 and drum 22.
It is also desired to locate wireline drum 22 and wildcat 28
adjacent to one another so that they can be driven by a single
drive unit 40 and controlled by a control-transmission unit 42,
whereby shafts 24 and 30 can be driven simultaneously or
independently.
The operation of the novel integrated mooring system 12 of this
invention will now be described. When the mooring system is not in
use, chain 18 is piled up in chain locker 26 with its leading end
extending over wildcat 28 and under fairleader 32. The wireline is
wound on drum 22. In use, the leading end of the chain is attached
to an anchor or to any other object desired to be used in mooring.
Wildcat 28 is rotated clockwise (FIG. 2) until the entire chain is
taken out from chain locker 26. The chain then forms a bottom loop
around interior sheave 36. When that happens, both drum 22 and
wildcat 28 are made to rotate in a clockwise direction and in
synchronism, thereby causing wireline 16, chain 18 and connector 20
to move sequentially over the components of the mooring system
12.
In the position of the mooring line 14 shown in FIG. 3, the chain
is completely submerged in the body of water and the wireline
extends from tower 10 down to a desired depth. The wireline forms a
desired mooring angle 41 which is considerably smaller than a
comparable angle that would have been formed if only chain were
used in the mooring line. The smaller this mooring angle, the
greater will be the horizontal component of the required restoring
force imposed on the mooring system.
To retrieve the mooring line, the above described process is
repeated in reverse, that is, drum 22 and wildcat 28 are rotated
counterclockwise until connector 20 returns to the chain locker 26
and preferably past and above interior sheave 36 (FIG. 1). At that
point, drum 22 is stopped and only wildcat 28 is allowed to
continue to rotate until the chain piles up in chain locker 26 with
only the leading end of the chain remaining past fairleader 32.
The integrated mooring system of the present invention is
characterized by several advantages, chief among which are: there
is no need to make and break the connection between wireline 16 and
chain 18 each time that the mooring line 14 is paid out or hauled
in. The location of the interior sheave in the vicinity of the
chain locker allows for an orderly transition from chain to
wireline and vice versa. The entire mooring line can be controlled
by a single controltransmission unit.
Changes will readily suggest themselves to those skilled in the art
without departing from the scope of the attached claims:
* * * * *