Note: Descriptions are shown in the official language in which they were submitted.
PORT~BL:E REEI. PIPI~:L.AYING APPi!~TUS i~ND ME~THOD
~2~37
BACKGROUND ~F T~IE INVENTION
The apparatus and method of this invention rela-tes
to a portable reel system. The system of this invention has
been specifically designed for installation and use on supply
boats, drillships, and any other vessel ~advantageously self-
propelled), having sufficient clear-deck area to accommodate
the combination of structural assemblies making up the reel
pipelaying system describea hereunder.
More particularly, the present invention rela-tes
to a reel pipelaying system mounted on the clear-deck area
1~) ,
to a ~ui~able carrier vessel (preferably self-prope]led) so
that the carrier vessel, for example, a supply boat, can be
used to lay pipelines to and from offshore drilling platforms
and/or storage tanks and/or terminal locations and/or sub-sea
well completion units. For convenience of description, and
since an operational system has been successfully m~unted on
a supply vessel, reference hereunder will sometimes be made
to a supply boat as one specific carrier vessel.
As used in the present descrip~ion, "supply boats"
are sometimes referred to in the offshore oil industry as
"supply vessels'l and/or "tug/supply vessels"; they are
characterized by a generally flat, continuous on-deck cargo-
carrying space between the superstructure and the stern and
are primarily used for carrying supplies, equipment, and
personnel between a shore base and an offshore platform or
rig. Supply boats generally have dimensions and cargo
capacities within the following ranges:
~`,.
~L2~ 3~
Length: 170 feet-225 feet
Gross Registered Tonnage (G.R.T.): ~50T-1300T
Con-tinuous On-Deck Cargo Space
Between Superstructure and Stern: 2300-4800 sq. ft.
On-Deck Cargo Capacity Between
Superstructure and Stern: 300-700T
Supply vessels as defined above and as generally
referred to in the present description are exemplified in
catalogs of the following representative suppliers of such
vessels:
1) Smit-Lloyd: 1977 Catalog of 16 pages, entitled
'IANYWHERE, ANYTIME, ANYHOW" with
picture of supply boat "Smit-Lloyd
104" on front cover;
2) Maersk: 1973 Catalog of 12 pages, entitled
"Maersk Supply Service/A.P. Moeller"
~nd describing three supply boat
types;
3) Offshore Supply Association, Ltd. tOSA):
1976 Catalog of 8 pages, entitled
"Actions Speak Louder Than Words",
and bearing legend on back cover:
"Printed in West Germany,
November 1976".
Another type of carrier vessel for which the reel
pipelaying system of this invention may be suitable is the so-
called "drill ship"; such vessel is generally a self-propelled
ship mounting a drilling tower or rig. The drilling tower may
be of the center-line type, in which drilling is done through
a well in the center of the ship; an alternative cons-truction
has the drilling rig cantilevered over the side of the vessel.
Examples of drill ships are shown in Howe, R.J., "The Evolution
of Offshore Mobile Drilling Units", Ocean Industry, 1966.
637
Drill ships of either type and having sufficient clear-deck.
space to mount the combination of elements.of the reel pipe-
laying system of this invention, may be advantageously used
to combine several offshore operations. Specifically, when
the drill ship has completed its hole into an oil reserve,
.the same ship can then lay pipe between the sub-sea well.
completion and collection point, such as-a storage tank.
Historically, the technique of laying undersea
fluid-carrying pipelines had its rudimentary beginnings in
~o England i.n the 1940's. In the summer of I944, 31' nominal bore
~teel tu~es, electxically flash-welded -together, were coiled
a~ound :Eloating drums.. One end of the pipe was fixecl to a
terminal poin-t; as the floa-ting drums were
towed across the English Channel, the pipe was pulled off
the drum. In this manner, pipeline connections were made
between the fuel supply depo-ts in England and distribution
points on the European continent to support ~he allied
inva~.ion of.Europe. ~See Blalr, ~.S., "Operation Plu-to:
The Hamel Skeel Pipelines", Transactions of -the Institute of
20 . Weld:ing, February 1946.)
~ The broad concept of reel pipelaying was also
disclosed in British Pa-tent No. 601,103 ~Ellis), issued
April 28, 1948, wherein it was suggested tha-t lengths of pipe
be joined together at the manu-facturing plant and coiled onto.
a drum, mounted on a barge or shi.p; the loaded barge would the~
6~3~
be moved to the desired marine location and the pipe unwound
from the drum b~ fixing one end of the pipe and towing the
barge away from the fixecl location.
While the concepts described in British Patent
601,103 and those actually used in Operation Plu-to were
adequate *or wartime purposes, no known fur-ther development
work or commercial use of the technique of laying pipe of~shore
from reels was carried out a~-ter World War II. After a hiatus
of about fifteen years, research into the reel pipelaying
I0 technique was renewed and was carried on by Gur-tler, ~Iebert
& Co., Inc., of New Orleans, Louisiana; by 1961,Gurtler, Hebert
had sufficiently advanced the reel pipelaying technique
to make it a commercially acceptable and viable
method of layiny pipe in the offshore petroleum industry,
able -to compete with the traditional stovepiping technique.
The first known commercial pipelaying reel barge, called the U-
303, was built by Aquatic Contractors and Engineers, Inc., a
subsidiary of Gurtler, ~Iebertl in 1961. The U-3Q3 u~ilized a
large vertical axis reel, permanently mounted on a barge and
having horizontally orien-ted flanges (generally referred to in the
trade as a l'horizontal reel")~ A combined straightener-level
winder was employed for spooling pipe onto the reel and for
straightening pipe as it was unspooled. The U-303 first laid pipe
commercially in September, 1961, in the Gulf o~ Mexico of~ the
coast of Louisiana and was used successfully during the 1960's to
~2~3~7
lay several million linear feet of pipe of up to 6" diame-ter.
The U-303 reel pipelayin~ barge is described in U.S Patent
3,237,43$ (Tesson) and U.S. Pa-tent 3,372j461 (Tesson), both
assigned to the assignee of the invention hereof.
The successor to ~he U-303, currently in use in
the Gulf of Mexico and known in the trade as the "Chickasaw",
also utilizes a large horizontal reel, permanently mounted to
the barge such that it is not readily movable from one carrier
vessel to another. Various aspects o~ "Chickasaw" are
described in the following U.S. Patents, all assigned to the
assignee o~ the invention hereof:
Sugasti, e-t al. No. 3,630,461
Gibson ~ No. 3,641,778
Mott, et al. No. 3,680,432
Key, et al. No. 3,712,100
Commercial reel pipelaying techniques require the
use of certain pipe handling equipment in addition to ~he
reel. ~mong such pipe handling equipment essential to any
commercial reel pipelaying system is a straightener
mechanism. This may take the form o~ a serîes o~ rollers or
tracks, or any other arrangement which imparts sufficient
reverse bending ~orce to the pipe to remove residual curvature
so that a~ter unspooling, the pipewill lay subs-tantially
637
straight on the sea bottom. No such pipe-conditioning
apparatus was used in Operation Pluto or contempla~ed by the
Ellis British Patent~
U.S. Patent 3~982,402 (Langl e~ al.) describes an
apparatus for laying pipe ~rom a ver~ical reel in which ~he
pipe conditioning apparatus is pivotable to adjust the
lift-off angle o the pipe relative to.the horizon~al (e.g.,
the deck of a ship~ as a ~unction o~ ~he wa~er depth in which
~he pipe is ~eing laid. This has dis~inct commercial
~dvantages, especially where the reel pipel~ying system is
incoxporated in~o a self-pr~pelled ship, such as ~ha-~ of ~he
pxesent inven~ion, capable of traveling to di~erent job
sites, hav.ing di~eren~ pipe size and/or lay depth rQ~uixe-
ments.
.. .... _ . .. .
~he design of the reel and the entire system of
this invention was dictated 1) by the desire to provide a
completely sel~-co~tained vertical reel pipelaying system
which can re~dily and economically be trans~erred from one
carrier vessel to another, and 2) b~ the require~ents.o
~U supply boats which are presently envisioned to be the
principal carrier vessels.
~L~2@3~7
3 Kno~n prior vertical reel systems have had a
re1a~ively hiyh center of gravity; using such known systems
on a supply boat could increase the overall ~G o~ ~he boat
to a poi-nt where.i~ exceeds the s~ability limi~s of the.
vessel.
CG of a reel is substantiall~ co-incident with
its rotational axis; ~hus, the larger ~he reel diameter .
at ~h~ ~langes, the higher will be its CG. The minimum
hub d:icuneter, howeverr is depenclent on the largest diameter
pipe to be spaoled (and vice versa); a reel designed,to
lS spool,up to 6" diameter pipe must have a larger hub radius
than o~e designed to spool a maximum of 4" diameter pipe.
.The reel pipelaying system of this invention,
including the reel, the straightener, ~he pipe guide and
theix r.espective support assemblies, was designed -to have a
low CG while maximizing the amount o~ pipe which can be
spooled ~or best commercial advantage~
SU~RY OF THE INVENTION
In essence, this invention comprises a portable
reel pipelaying system for laying a continuous length of pipe
on the sea bottom. ~ pipe-carrying reel is adapted to be
mounte~ to a sufficiently large clear deck area of a carrier
vessel. Means are provided for driving the reel in a first
direction for spooling pipe onto the reel and for exerting a
desired bra~ing action on the reel while unspooling pipe
from the reel in a second direction to maintain -the unspooled
pipe under desired tension. A straightener support assembly
is adapted to be mounted to the carrier vessel downstream of
the xeel in th~ d.~rection o:E pipe unspooling; pipe straighten-
ing m~,ans are mov~bly mounted to the straightener support
assembly; and straightener drive means are housed in the
straightener support assembly for driving the straightening
means in a.direction substantially parallel to the rotational
axis of the reel to level wind pipe being spooled onto the reel
and.to substantially straighten pipe being unspooled from the
reel. Finally, pipe guide means are adapted to be mounted
to the carrier vessel downstream of the straightener support
assembly in the direction of pipe unspooling and are movable
in a direction substantially parallel to the rotational axis
of the reel to guide pipe into the water as it is being
unspool.ed.
Mor~ specifically; this inven-tion comprises a
pro~able reel pipelaying system for laying a continuous length
of pipe on the sea botto~ from a supply boat or similar
carrier vessel. A pipe carrying reel, preferably having a
- hub diameter large enough to spool up to 6" O.D. pipe without
exceeding API ovality limitations is mounted to the deck of
the supply boat such that the a~is of rotation of the reel
lies in a plane substantially transverse to the longitudinal
a~is of the supply boat. ~rive means are provided for
driving the reel in a first direction toward the bow of the
supply boat for spooling pipe on the reel and for exertin~ a
desired braking action on the reel while unspooling pipe from
the reel in a second direction toward and over the stern of
the supply boat to maintain the unspooled pipe under desired
tension. A straightener support assembly movably mounts
p:ipe straightener rneans to the deck of the supply boat stern-
ward of the reel. Straightener drive means are housed in the
straightener support assembly for driving the straightening
means in a direction substan-tially parallel to the rotational
axis of the reel to level wind pipe being spooled onto the
reel toward the bow of the supply boat and to substantially
straighten pipe being unspooled from the reel. Finally,
pipe guide means are mounted to the deck of the carrier vessel
sternward of the straightener support assembly and are movable
across the deck of the supply boat in a direction substantially
parallel to the rotational axis of the reel to guide pipe into
the water after it has been unspooled and straightened over
the s-tern of the supply boat.
_9_
2~i3~
This inven-tion also comprises a method for laying a
substantially continuous length of pipe on the sea bottom
from a carrier vessel, in which a pipe carrying reel is
rotatably mounted on the carrier vessel, pipe straightener
means are mounted to the carrier vessel downstream of the
re~l in the direc-tion of unspooling for movement in a direction
substantially paral~el to the rota-tional axis of the reel, and
pipe guide means are mounted to the carrier vessel downstream
of the straightener means in the direction of pipe unspooling
.~Q for movement in a direction substantially parallel to the
rotational axis of~the reel; in essence the method comprises
the steps of rotating the reel in a direction to unspool the
pipe and maintaining a sbustantially constan-t dynamic braking .
force on the reel to maintain tension on ~he pipe as it is
unspooled.
More particularly, the method comprises the steps of
rotating the reel in a direction to unspool the pipe during a
lay operation; passing the pipe through -the straigh-tener means
after it is unspooled to impart a bending force on the pipe
sufficient to substantially straighten the pipe; passing the
pipe through the guide means after the pipe exits the
straightener means and before it enters the wateri moving
the straightener means and pipe guide means across the deck
of the supply boat in a direction substantially parallel to
the rotational axis of the reel to maintain the pipe path
--10--
æ2~
through the straightener and guide means in substantial
alignment with the departure point of the pipe from the reel;
and maintaining a substantially constant dynamic braking force
on the reel to maintain tension on the pipe as it is unspooled.
In accordance with one broad aspect, t~le invention
relates to a sel~-contained portable reel pipelaying system
for laying a continuous length of pipe on the sea bottom,
having a plurality of separate easily transportable component
packages mountable to and removable from a carrier vessel
including: a ~irst component package comprising a pipe-carrying
reel, reel support means for rotatably mounting said reel to a
sufficiently large clear-deck area of said carrier vessel,
and reel drive means mounted to said reel support means in
operative engagement with said reel; and a second component
package, comprising a straightener support assembly adapted to
be mounted to the carrier vessel downstream of the reel in the
direction of pipe unspooling, pipe straightener means movably
mounted to said straightener support assembly, and reel drive
power supply means and straightener drive and power supply
means housed in said straightener supply assembly, said reel
drive power supply means being adapted to be coupled to said
reel drive means for driving said reel in a first direction
for spooling pipe onto said reel and for exerting a desired
braking action on the reel while unspooling pipe ~rom the reel .
in a second direction to maintain the unspooled pipe under .
desired tension, and said straightener drive and power supply
means being adapted ~or driving said straightener means in a
direction substantially parallel to the rotational axis o~ said
reel to level wind pipe being spooled onto said reel and to
substantially straighten pipe being unspooled from the reel.
~ .
lI~$ ~ ,
i3~i9
In accordance with another aspectr the invention relates
to a method for laying a continuous length of pipe on the sea
bottom from a carrier vessel, in which a pipe carrying reel
is rotatably mounted on a carrier vessel, reel drive motor
means are coupled to the reel for driving the reel to spool up
pipe in a spooling mode and for providing a dynamic braking
force to the reel in an unspooling mode as plpe is unspooled
from the reel, pipe straightener means are mounted to the
carrier vessel downstream of the reel in the direction of
unspooling for movement in a direction substantially parallel
to the rotational axis of the reel, and pipe guide means are
mounted to the carrler vessel downstream of the straightener
means in the direction of pipe unspooling for movement in a
direction substant.ially parallel to the rotational axis of the
reel, said method comprising the steps o~: sensing changes in
tension on the pipe as it is being unspooled as a ~unction of
corresponding changes in torque on the reel drive motor means
in its dynamic braking mode; and automatically adjusting the
torque imparted to the reel by the reel drive motor means to
maintain a balance between the torque applied to the reel
by the reel drive motor means and the torque applied to the reel
drive motor means by the reel to thereby maintain a substantially
constant tension on the pipe in the unspooling mode.
``~ -llA-
sRIEF DESCRIPTION OF T~IE DRAWING
FIG. 1 shows a side elevation typical oE a carrier
vessel, such as a supply boat, mounting the pipelayinq reel
system of this invention;
FIG. 2 is a top plan view of the carqo dec]c area of
the supply boat of FIG. 1 mounting the pipelaying reel system
of this invention;
FIG. 3A is a plan view of the reel support structure;
FIG. 3B is an elevation (looking forward) of the reel support
structure; FIG. 3C is a starboard side elevation of the reel
1.0 support structure;
FIG. ~A is a starboard side elevation of the reel;
E'IG. 4B is a secti.on of the reel through A-A in FIG. 4A;
FIG. 5A is an elevation (looking forward) of the
straightener assembly, including the straigh-tener mechanism,
the car-t and the support platform; FIG. 5B is a starboard side
elevation of the straightener assembly; FIG. 5C is a plan view
of the straightener assembly;
E`IG. 6A is an elevation (looking forward) of the
traveling work platform mounted to -the straightener assembly;
FIG. 6B is a starboard side elevation of the traveling work
platform; FIG. 6C is a plan view of the trave~ing work platform;
FIG. 7A is an elevation (looking aft) of the pipe
guide assembly; FIG. 7B is a starboard side elevakion of the
pipe guide assembly; FIG. 7C is a plan view of the pipe guide
assembly;
~2~:)63~
FIG. 8 is a plan view of the s~raightener and pipe
guide assemblies linkage mechanism; and
FIG. 9 is a schematic drawing of the reel and
level winder/straightener drive system.
FIGS. 3-7 are taken from construc-tion layout drawings
and are drawn substantially to scale. Within each of these
figures, the component parts or elements are substantially
in proportion.
.0
-12~-
:~L2~31'7
DESCRIPTION OF THE PREFERRE~ EMsoDIMENT
General Arrangement (FIGS. 1-21
FIG. 1 is a side elevation of a typical supply boat
mounting the portable reel pipelaying system of this invention.
Such supply boats have a hull, generally designated 10, a
superstructure g~nerally designated 12 and a xelative]y flat~
unobstructed deck cargo area 14. The forward portion of the
supply boat (e.g., forward of frame FR-45~ carries the super-
structure 12 and has a relatively high freeboard. This forward
port.ion of the supply boat typically has little or no cargo-
ca.r~y.ing deck space; crew and passenger accommodations are
generally located in this forward portion of the vessel.
The rear portion of the supply boat (e.g., from
frame FR 45 to the stern o~ the vessel shown) has a generally
flat unobstructed deck area with a low freeboard design.
Typical deck cargos for such supply boats include bulky
equipment and supplies re~uired on offshore drilling platforms,
e.g., pipe, mud materials, etc. Another feature oEten found
on supply boats is a large stern roller 16 which facilitates
hauling large anchors (e.g., as part of semisubmersible
drilling rig anchoring systems) onto or off the supply boa-tls
cargo deck 14.
The apparatus of this invention comprises three
principal component sectio~s: a reel and its associated support
system, generally designated 20; a level winder/pipe straightener
assembly and its associated suppor-t system, genera11y designated ~0,
and used for level winding pipe on the reel and s-traigh-tening
pipe as it is unspooled from the reel,
~2~$~7
and a pipe guide assembly, and its associated support system,
generally designated 60, which g~ides the pipe into ~he water
after the pipe leaves the straightener assembly.
The reel assembly 20 comprises a reel 202 having a
hub 204, of a radius Rh, and a pair of encl flanges 206; the
hub 204 and fl~nges 206 are carried by a central shaft 208
which defines the ro~ational axis of the reel. The respective
ends of shaft 208 seat in bearings 210 and the entire assembly
is supported on a framework skid 212 through bracing members
214, 216. One or more ~e.g., three as shown) reel drive motor
assemblies 218, 220, and 222 are also supported an skid 212.
The skid 212, carrying reel 202 is shown secured to the cargo
deck 14 o~ a supply boat.
The level winder/straightener assembly 40 is shown
mounted to the supply boat cargo deck 14 aft of the reel assembly
20. The level winder/straightener asse~ly comprises a base
section 410 which advantageously houses the power supply
systems for the entire reel pipelaying assembly. A straightener
cart 450 rests on top of base 410 and is movable -therealong in
2Q a direction substantially parallel to the rotational axis of
the reel. ~ straightener mechanism 460 is pivotably mounted
to the straightener cart 450 and comprises a three-roll
straightener for removing curva-ture imparted to the pipe when
spooling same onto reel 202. A work platform 408 is mounted
to the straightener car-t 450 and is movable therewith. The
work platform 408 is mounted to the sternward side of the cart
450 to enable work (e.g., pipe welding, coatingr etc.) to be
done on the pipe as it comes Ollt of the straightener.
-14-
~2~ 7
The pipe guide assembly 60 is secured to the deck
aft of the straightener assembly and comprises a group of rollers
mounted to a traveling carriage 602 which, in turn, is mounted
on tracks for movement across the stern of the supply boat in
a direction substantially parallel to the rotational axis of
the reel.
In one embodiment, the straightener 460 and cart 450
are mechanically linked with the pipe guide carriage 602. By
this arrangement, the straightener and pipe guide assemblies
may be positively driven together to maintain the two in
substantial alignmen-t with each other and with the pipe entry~
exit point onto/of~ the reel.
FIGS. 1 and 2 show a continuous length of pipe P as it
comes off the reel 202, and thereafter passes through the
level winder/straightener assembly ~0 and through the pipe
guide assembly 60 before entering the water.
Details of the several component sections and their
operation are described below. Note that,for convenience, the
level winder/straightener assembly ~0 is sometimes referred to
only as the straightener asse~bly, although it is understood
that in the en~odiment described herc, it is con-templated that
assembly ~0 performs both level winding and straightening functions.
3~
Reel and Support ~ss~mbly 20 (FIGS. 3,4)
The pipe reel support assembly 23 is shown in detail
in FIGS. 3A-C~ The support assem~ly comprises a rectangular
base frame 230 having side members 231, end members 232, and
intermediate bracing members 233.
The reel bearings 210 rest on bearing plates 234.
Each of the bearing plates 234 in turn rests on the upper enas
- of support members 214, 216, 235, 236. Support members 21~
extend from one corner of the base frame 230 upward to the bottom
of pla-tes 234 (e.g., member 214a extends from the intersection
of members 231b, 232a to the underside of plate 234a) at a
vertical angle of about 45 ~15; for most cons-tructions, this
angle is preferably 45. Support members 216 extend from the
acljacent corner o the base frame 230 upward to the bot-tom of
plates 234 (e.cJ., member 216a extends from the intersection oE
members 232a and 231a to the underside of plate 234a) at the
same vertical angle as support members 214. A projection of
members 214, 216, and 232 into the plane of base frame 230
preferably defines an isosceles triangle having a vertex
angle (i.e., the angle between legs 214 and 216) of appro--
xi.mately 90. Support members 235 and 236 extend in
opposite dlrections from bearing plate 234 to side
frame members 231~ and 231a, respectively, such that projections
of support members 235a and 236a into the plane of the base frame
230 lie approximately parallel to end members 232.
-~6-
3~
The reel support structure 23 also mounts the reel
drive motor assembly or assemblies. In the embodiment shown here,
the reel 202 is driven by a group of three drive motors 218,
220, 222. The reel drive mo-tors 220 and 222 rest on motor
mount suppor-t pla-tes 237~ 238, respectively, fixed directly to
the base frame 230 (as shown in FIG. 3C) by any conventional
means. Motor mount support plate 239 is located at an elevated
posit-~on relative to the main base frame 230, in any conventional
manner, for example, by a tubular support framework, as shown
in FI~S. 3~-C. In the herein described embodimen-ts, the drive
motors are all mounted on the same (starboard) side of the reel
support assembly. ~lterna-tively, the motors could be mounted
on the port side, or in various combinations, on both sides of
~the support assembly.
Th~ reel itself is shown in FIGS. 4A and 4B. The
reel 202 has a hub 204 of a radius Rh and a pair of end flanges
206b, each having a flange radius Rf. In the preferred
embc>diment, the shaft comprises an axial pipe 251 extending
through the ent1re reel and protruding outwardly of flanges
206a, 206b. A pair of axially opposite shaEt members 252a, 252b
are fitted into the opposed end portions of pipe 251; shafts 252
have machined ends which seat in bearings 210. Pipe 251 and
shaft members Z52a, 252b, together effectively act as a unitary
shaft element, generally designated 208, with machined ends
which seat in the bearings 210.
-17-
37
A plurality of circumferential stiffening members
or rings 253 extend around the interior surface of hub 204
coaxial ~ith shaft 20~. Rings 253 are advantageously spaced
approximately axially e~uidistant from each other. A further
plurality of longitudinal stiffenlng members 254 an~ 255 extend
axially along the underside of hub 20~ at right angles to annular
members 253. Stiffening members 254 extend between adjacent
radial ribs 253 at the interior surface of hub 204; stiffeners 255
are corner members and are welded to rings 253, flanges 206, and
axia] pipe 251. This intèrior construction of the reel results
in a honeycomb shape under the plating of hub 204. Such con-
struction produces a reel with great streng~th, a quite desirable
~eature in pipe reel s~stems of the present invention. 'rhe
loncJitudinal stabilizing members 25~, 255 distribute the load
of multiple pipe wraps evenly on the reel. These members
permit the reel to accommodate large back tension forces which
may occur under certain conditions, such as when retrieving
pipe from the ocean floor.
Flanges 206 are beveled outwardly to de~ine an
angle ~ with a plane perpendicular to the reel axis. At least
one of the flanges incorporates a part of the reel drive sys-tem;
in the preferred embodiment, the starboard flange 206a has welded
thereto a circumferential outer plate 256 and a circum-ferential
inner plate 257. A plurality of matching throughholes are formed
in pla-tes 256 and 257; roller members 25~ are fixed to shafts
located in -the throughholes and secured, e.g., ~y cotter pins
or the like. S~ch rollers 258 are e~ually spaced around the cir-
cumference of flange 206a and mate with gears on the reel
drive mo~ors.
-18-
~22~i3~
The flanges 206 are -Eormed by a plurality of radial
ribs 259 extending from -the axial pipe 251 to the radially
outer ends of flanges 206. These radial ribs are preferably
equally spaced around the pipe 251 and,in the operative embodi-
ment, the arcuate spacing between adjacent ribs is approximately22.5~. A circumferential bracing member 260 is provided,
preferably co-radial with the hub 204. Preferably, plating
is provided on the inner surfaces of the flanges between the
flange ends and the hub surface to provide a uniform support
:l~ surace for end wraps of the pipe.
One or more openings 261 are formed in the hub 204,
preferably adjacent one of flanges 206. Such openings are
intended to receive an elbow member 262 of a size conforming to
the size of pipe to be spooled. If only one opening is used,
it should have a diameter slightly greater than the diameter
o the largest slze to be spooled; alternatively, a hole can be
cut in the reel hub or drum for each size pipe to be spooled,
each hole having a diameter slightly grea-ter than the diameter
of the plpe to be accommodated therein.
~19-
~22~3~
The radius of the reel should be large enouyh to
spool at least 4" diame-ter (nominal) and preferably 6"
diameter (nominal3 pipe withou-t exceeding maximum limits
for ovality as established by the American Petroleum Insti-
tute (API). Current API specifications re.quire that forsub-sea oil- or gas-carrying flow lines~ the pipe may not
be out of round by more than 2%; that is the difference
between two mutually orthogonal diameters at a given loca-
tion should be no greater than 2~.
-20-
~L2~3~
Level Winder/Straightener Assembly and Support Sys~ems
(F~GS. 5A-5C)
The plpe straightening or conditioning apparatus 40
comprises a straightener suppor-t platform 410, a movable
carriage or strai~htener cart 450 supported on and movable
across the top of platform 410, and a straightener 460 mounted
on and movable with cart 450.
The straiahtener su~ort ~latform 410 is essentiallv
a closed box-like structure with vertical side walls 412 and
vertical end walls 414. These side and end walls are composed
of panels some of which are advantageously welded and others
of wh:ich are bolted to the support platform frame; bolted panels
a~e removable to permit access to the interior of the support
platform ~10.
The exterior frame of the support platform 410 has a
substantially inverted trapezoidal configuration, i.e., top
frame members 416 are longer than parallel bottom frame memb-ers
418. Each of the trans~erse top frame members 416 comprises
a (preferably) C-shaped guide member or rai1, with which the
straightener cart 450 cooperates, for guidin~ the straightener
cart 450, and thus, the straightener assembly 460, across the
top of the support platform 410. Corresponding pairs of (pGrt
and starboard~ top and bottom end frame members 417 and 419 r
respectively, connect the exterior framework members 416 and 418.
A rail or guide member 420 is located approximately
intermediate the -top and bottom frame members 416b, 418b, res-
pectively. Intermediate rail 420 is supported at its respectiveends by angled f~ame members 422b and 424b, which ex-tend between
the extremities of the top and bottom (aft) frame members 416 b
3~ 1
and 418b. Corresponding angled frame members 422a and 424a
extend between the ends of top and bottom (fore) frame members
416a and 418a. Work platform 408, connected to the
strai~htener cart 450, is ~uided along the support platform 410
by quide rai] 420.
The intermediate guide rail 420 preferably comprises a
plurality of members so dimensioned that separate individual
members are bolted respectively to welded or bolted panels.
This permits the bolted panels to be removed with their associated il
portion of the intermediate guide rail; when the bolted panels
are in place, the structure acts effectively as a single guide
rai.l 420.
An operator's platEorm 423 and operating console 423a f
are preferably located on one or the other of the starboard and l
port side extensions of the platform 410, sùch extensions com- l
prising the area included within the extensions of top frame ;f
members 416 beyond the bottom frame members 418. The operator 7f
station contains the system controls for opera-ting the reel
and level wind/straightener mechanism; such operations will
be described in more detail below. 7
~11 of the hydraulic and electrical power supplies
required for operating the reel pipelaying system of this ;If
invention are located within the interior of the straightener l,
platform 410. This arrangement fur-ther enhances the portability 'f
of the entire s~stem and makes lt substanLially independent cf
-2~--
~.~2~3~3~
the power supply capacity of the carrier vessel. When installed
on board the carrler vessel, the hydraulic power supply con-
tained in the straightener platform 410 is connected by con-
ventional piping techniques ~o the reel drive motors 218, 220, 222.
A motor 425, advantageously of the hydraulic drlve
type, is mounted on a motor support 426 locatedr for example,
in the starboard extenslon portion of the straightener support
pla-tform 410. The motor 425 includes a shaft 427 on which are
mounted a pair of sprocket wheels 428. A pair of idler sprocket
wheels 429 are mounted on a shaEt 430 located on the por-t
e~t~nsion portion of the straightener support plat-form. The
shafts 427 and 430 are supported by pillow block bearings 431
on adjacent parallel bearing support beams 432. Chains 433
(e.g., 2" roller chain)are passed around the associated pairs
of sprocket wheels 428, 429; the respective ends of each of
chains433 are connected to the straightener cart 440. Operat~on
of motor 425 turns shaEt 427 and sprockets 428 which, -through
the chains 433, drive the straightener cart ~50 in translational
motion across the top of the straightener support platform 410.
A plurality of lifting shackles 441, advantageously four
in number (although only two can be seen in the drawing), are
located at strategic points on the top of the support platform 410.
A lifting cable and bar assembly may be readily attached to the
shackles 441 to lift, by means of a crane or the like, the entire
straightener assembly, including -the suppor-t platform 410, cart 450,
and straightener mechanism 460 on-to or off from the carrier
vessel deck as a single unit.
-23-
3~
The straightener cart 450 comprises a generally ope~
rectangular frame 451. A roller assembly 452 is located at
each of the four corners of said frame 451 for movably support-
ing the straightener ca,~t 450 on the straightener platform
S guide members 416. Each roller assembly 452 comprises a pair of
horizontal axis rollers 453, 454, which ride on the upper and
and lower flanges respectively, of a guide member 416; a vertical
axis roller 455 rides in the channel of a guide member 416. This
arrangement maintains the straightener cart secured to the
platform 410 to prevent movement of the cart in the vertical
and fore ancl aft directions relative to the platform while per-
mitting a~roll~d trans,verse movement of the cart along the
top of the platform 410.
A pair of pivot-mounting assemblies ~56 is welded,
or otherwise secured, to cart fra,me 451 for pivo-tably mountiny
the straightener assembly 460 to the straightener cart 450.
The straightener mechanism 460 includes a framework
(advantageously composed of tubular members) comprising upper
and lower fore and aft aligned members 461, 462, and relatively
vertically extending end members 463, 464. ~hese port and
starboard side frames are rigidly attached to each other by
upper and lower fore and aft transverse connecting members 465,
466 (also advanta~eously of tubular construction).
Relatively vertical frame members 463 extend above
the main frame and are connected at their top ends to a
transverse (e.~ tubular) bracing member 467, and to diagonal
bracing members 468. Additional intermediate bracing members 469,
470, and 471 may also be provided as shown (see, e.g., FIG. S~).
-2~-
37
The straightener mechanism itself comprises three
sets of rollers 472, 474, 476. The forward (or first) set of
straightener rolls comprises a pair of upper and lower rolls
472a, 472b; the rear (or third) set of rollers likewise com-
prises a pair of upper and lower rolls 476a, 476b.
Rolls 472 are rotatably mounted through bearing
assemblies to rigid brackets 477 which are secured (e.g., by
weldin~) to transverse bracing members 465. Similarly, rollers 476
are rotatably mounted to rigid brackets 478 which are similarly
.10 f:ixed to transverse bracing members 66.
A forward (or first) set of vertical axis guide
rollers 479 is fixed by brackets to frame members 463. A stern-
ward (or second) set of vertical axis guide rollers 481 is fixed
by bracke-ts to frame mèmbers 464. Roller sets 472, 479, and
roIler sets 476, 481, define the entry/exit portions of the pipe
path through the straightener 46 a .
~he intermediate (or second) roller 474 is adjustable
in a direction substantially perpendicular to the nominal
longitudinal axis of the pipe as it passes through the
straightener 460. Roller 474 is mounted by brackets to a box
frame 483; box frame 483 is so dimensioned to extend between
the support members 469 and 470, such that said support members
act as guide means to restrain the box frame 483, and thus
roller 474, against movement in the fore and aft direction while
permitting movement in the relatively vertical direction. A
-25-
~L2~ i3~7
positioning mechanism 484 (e.g., a Duff Nor-ton jacuator model 1820)
is mounted to a transverse support member 485, fixed between
frame members 461a and 461b. The positioning mechanism 484
provides for adjustment of roller 474 toward and away Erom the pipe.
S A pair of frame extension members 486 are located at
the lower forward end of straigh~ener 460. This frame extenSiQn
mounts a pair of rollers 487 on respective transverse members 488
similar to the mounting arrangement of rollers 472 and 476.
The function of these roller assemblies will be made clear below.
A pair of axially opposite tubular extensions 489
o transverse frame member 466b are provided on straightener
frame members 462; these ~xtensions 489 seat in pivot-mounting
assemblies 456 for pivotably supporting the stern portion of the
straightener 460 on cart 450. The forward end of straightener 460
is supported on cart 450 by substantially vertical support
members 490. The lower ends of support members 490 rest on
respective corner sections of the straightener cart 450, as shown.
The length of support members 490 may be adjusted to
thereby adjust an angle ~; this angle is called the "exit" or
"lay" angle and is the nominal angle at which the pipe enters
the-water. This angle is a function of such things as water
dep-th, tension on the pipe and the physical characteristics of
the pipe. For supply boat mounted systems, the lay angle ad-
vantageously is in the range of between about 10 and 25;
and preferably is in the range of about 15 20.
-26-
~2;2:~37
An upper block 491 is mounted to and hangs down
from transverse -top member 467; a lower b:Lock 492 is mounted
to and hangs downwardly from transverse frame member 465b.
These provide guide means for winch cables used during pipe
spooling and unspooling operations to pull the pipe end
aboard the carrier vessel or to lower the pipe end into the
water at the end of a layiny operation. A pair of forward
lifting pads 493 and a pair of rear lifting pads 494 are
Eixed respectively to transverse Erame members 467 and 466a
n to provide a connection point for lifting cables which may
be usecl to l:ift the straightener 460 oEf the support plat:Eorm
410. By connectiny cables to $he fron-t pair of lifti~g
pads 493, the straightener 460 may be pivoted about pivo-t
members 489, to thereby enable adjustment of the exit angle ~.
Alternative adjustment mechanisms may include hydraulic ~
cylinders loca$ed, e.g., in place of suppor-t members 490, etc.
-27-
~2~3~
Wor]c Platform (FIGS. 6A-6C)
The work platform 408 comprises a (tubular) horizontal
frame 508 which supports an open grid floor 509. A pair of
front vertical f~ame members 510 extend upwardly from the floor
frame 508 and are connected by a transverse bracing member 511
near their respective top portions. Additional bracincJ is
supplied by diagonal bracing members 512 which extend from the
rear corner of the floor frame 508 to the upper part of vertical
frame members 510.
A (preferably plate-like) member 514 extends forwardly
from each of vertical frame members 510. Members 514 mate with
ancl are sandwiched between corresponding pairs of members 457
loca-ted on the frame 451 of straightener cart 450. Members 514
and 457 are secured bY pins, bolts, etc. passinq throuqh
corresPo~dinq holes in the respective members 514 and 457.
A vertical axis roller 516 is secured by a roller
mounting assen~ly ~e.g., a pair of rigid brackets) to the
floor frame 508 at the junction thereof wi-th each of ver-tical
frame members 510. Rollers 516 ride in the channel of rail
or guide member 420.
2~ From the above, it will be seen that work platform 408
is secured to straightener cart 450 for transverse movement
therewith. I-t will also be seen that the work pla~form is
readily detachable from the rest of the straightener assembly
ta permit more compact storage of the straightener assembly 40
for shipping purposes.
~ lifting pad 520 is securely affixed ~e.~., by welding)
to each of dia~onal frame members 512 to allow the work platform 408
to be lifted by a ~rane (o~ other lifting means) away from the
rest oE the straight~ner assembly 40.
63~
Pipe Guide Assembly ~FIGS. 7A-7C)
The pipe guide assembly 60 comprises a roller
carriage 602 supported on a frame 610. The frame is advanta-
geously an open box-like frame having fore-and-af-t extending
end members 61] and longer transverse members 612; at least the
longer ~transverse~ members 612 are advantageously composed of
I-beams or T-beams. L-members 614 are secured (e.g., by welding)
to the upper faces of beams 612 to define an inverted V-shaped
track on each of beams 612.
The pipe guide carriage 602 is supported on and
is movable along frame members 612. The carriage 602 comprises
~ pair of fore-and-af-t extending side frames 618a, 618b mounting
V-yrooved upper guide wheels 620, 621, which mate with and ride
on respective tracks 614. Each of carriage frames 618 extends
over beams 612 to mount the axles for lower guide wheels 622, 623.
Lower ~uide wheels 622, 623 extend under the top face of beams
612 and cooperate therewith to inhibit upward vertical movement
of the stern roller carriage60~ and prevent the carriage from
rising off tracks 614.
~ transverse carriage member 624 rigidly connects
carriage side frame membexs 618a, 618b. A pair of pivot bracket
assemblies 626 are fixed to transverse carriaqe member 624 and
between them pivotably support a roller bed 628 for movement
about a pivot axis 629. The roller bed 628 mounts a pair of
horizontal axis pipe support rollers 630 at axially opposite
ends substantially radially equidistant from the pivot axis 629
of the bed 628.
-29-
~22~
A pair of ver-tical carriage members 632 are fixed
to and supported on transverse carriage member 624. Vertical
carri~ye frame rnembers 632 are further connected by upper and
lower transverse roller supports 63~. Roller supports 63
support a pair oE ver~ical axis rollers 636 in transverse
spaced-apart relation.
A further horizontal axis roller 638 is mounted on a
sternward extending roller frame support 639 above rollers 630.
Looking aft (see FIG. 7A) rollers 630, 636, and 638 define a
pipe passage window 6~0 through the pipe guide assembly 60.
Pipe being spooled onto the reel 202, or being unspooled there-
from, passes through the pipe guide assembly 60 and more par-
ticularly throu~h the window 640.
Xt :;s contemplated, in an alternative embodiment (not
shown), that rollers 630 could he replaced by a single roller
located at the pivo-t axis of bed 628, or a-t any other convenient
location on bed 6ZB; in -the latter case, the bed 620 preferably
is pivotable. The arrangement of a pair of pipe suppor-t rollers 630
on a pivotable bed 628 is particularly advantageous in that the
pipe passing through the window 640 will substantially always be
supported by two reaction points (rollers 630a, 630b) so that
the pipe will remain wi-thin its elas-tic range and overbend or
pipe buckling will be avoided as much as possible. Vertical axis
rollers 636 and upper horizontal axis roller 638 act as guides
to prevent the pipe from becoming substantially misaligned as it
leaves the pipe laying vessel.
Preferably the surfaces of rollers 630, 636, 638 are
made of or covered with material (advantageously an elastomer)
which is so~ter than the coating on the pipe; this preven-ts damages
to the pipe coating as pipe is paid out through the pipe
guide assembly.
-30-
~2~ 3~
Straightener - Pipe Guide ~inkage Mechanism
Under some conditions, the forces imparted by the
pipe itself may be sufficient to cause the pipe guide assembly
to move transversely substantially with movement of the
straightener assembly. Alternatively, and to ensure such
correspondence of movement between the pipe guide carriage hO2
and the straightener 460, the straightener cart 450 and the
.pipe guide carriage 602 are physically linked~
FIG. 8 shows the. linkage mechanism be-tween the
st.ra:ightener assembly 40, and most particularly the
.lO straightener cart 450, and the pipe guide carriage 602.
As part of such linkage mechanism, upper port and
starboard suppor-t assembly frame members 417 of straightener
assembly 40 mount sheaves (see FIG. 5). The rotational
axis of each of sheaves 437 is parallel to th.e long axis of
frame members 434, A pair of lower sheaves 438 are secured
to the bottom of frame members 419 parallel to top frame
mer~ers 434 and extending between bottom frame members 418.
Sheaves 438 are mounted at an angle to the vertical approxi-
mately the same as the angle which connecting members 422
make with the vertical.
i3~
Each of starboard and portside end frame
members 613 of pipe guide assembly 60 mount an upper
sheave 642 and a lower sheave 644 (see FIG. 7). A pair o~
cableways 646, advantageously comprising shor-t leny-ths of
pipe J are located at transverse opposite end portions of
frame member 612a. A linkage mechanism cable clamp 660
is fixed to the underside of and hangs downwardly from
transverse pipe guide carriage frame member 624. The cable
clamp assembly 660 advantageously comprises a pair of down-
wardly extending side members 662; a transverse plate 664
is E:ixed (e.y., by weld.ing) to the side members 662. A
removable plate 666 is boltable to transverse member 664.
Side members 662 have groves formed at their bottom por-
tions to allow passage therethrough of a cable 650. A
cable 650 is connected at one end to the (e.g , port side of)
straightener cart ~50; cable 650 is trained around (in
succession) sheaves 437b, 438b, 644b, and 642a, passes through
clamp 660 and then around sheaves 6~2b, sheave 6~4a, sheave 438a,
and sheave 437a; cable 650 is connected at its other end
`20 through a turnbuckle 654 to the (s-tarboard side of)
straightener cart ~50.
After the pipe guide carxiage 602 and the plpe
straightener 460 have been aligned with each other and the
linkage cable 650 has been pre-tensioned to the desired
amountr plates 666 and 664 are bolted together to tightly
--32-
~L2~;37
clamp cable 650 therebetween. By this linkage arrangement,
a positive dri.ving force is exerted on the pipe guide assembly
through the cables 650 and ~52 as the straightener cart
(and, thus, the straightener 450) are moved transversely
across the deck of the pipel.aying vessel in a direction
substantially parallel to the ro-tational axis of the reel 202.
3~-
-
~22~
Reel and Level Winder/Straightener Drive System (FIG. ~)
The operational embodiment o-f the invention described
herein incorporates an hydraulic drive arrangement. The
invention per se is not limited to the use of hydraulic drive;
however, it has been found that hydraulic motors are par-
ticularly suitable because of their high torque capability
at low speed. The reel drive mechanism also incorporates a
automatic tension control feature (described in more detail
below) which maintains a relatively constant tension on the
pipe, particularly during a lay operation, but which may be
utilized as well during retrieval operations.
The system for driving the reel 202 in a spooling
mode and for maintaining tension on the pipe (through the
reel) in an unspooling mode includes the drive motors 218,
220, 222. rrhese are preferably hydraulic motors (e.g.,
Hagglunds 3000 Psi 0-65 RPM Hydraulic motors) capable of two-
speed operation. The reel drive motors are connected in
parallel through fluid lines to variable volume hydraulic
pumps located in the straightener platform housing.
FIG. 9 shows a simplified schematic of ~he hydraulic
system used in the preferred embodiment of this invention for
driving the reel during a spooling operation, for braking the
reel during a pipe laying operation, and for driving the level
winder during spooling and~or laying operations. Hydraulic
pump 810 (e.g., Sunstrand PU25-2046 equipped with a pressure
compensator) is driven by, for example, a diesel engine ~12.
It should be noted that only one pump is required to operate
the system at its maximum rated capacity, speed, and torque.
-34-
2~36~ -
A second pump (not shown) may be provided as a backup. In
such case, the outputs of the main and back-up pumps are connected
in parallel so that the back-up pump can be brought "on~line"
in the event of failure of the main pump 810, with a minimum
of delay or adv~rse efect on the operation in progress.
Pump 810 is connected to -the reel drive motors 218,
220~ 222 through a pair of high pressure hydraulic fluid
conduits 816, 81B. The reel drive motors are connectecl in
parallel to conduits 816, 818 through respective shut-off valve
~roups 817, 819, 821; for convenience only motor 218 is shown
in FIG. 9.
A reservoir 814 provides storage volume for the
hydraulic fluid. During the spooling on operation, diesel
engine 812 drives pump-810 so that hydraulic fluid flows out
of the pump through supply conduit 816, through reel drive
motor 218, and through return conduit 818 back to the pump 81~.
Thus it will be seen that motor 21g is connected to pump 810
in a closed loop system. A branch line 820 supplies hydraulic
fluid to the level wind motor 425 through a directional control
valve 822 and a flow control valve 823 located on the operator's
control panel 423a. ~ return conduit 824 completes the fluid
flow circuit from the pump 810, through the level wind motor
motor 425 to the reservoir 814.
-35-
The reel drive motor 218 is provided with a hydraulic
brake 826 of the "fail-on" type. The brake is normally spriny-
biased into a locking position to prevent ro~ation of motor 218.
Hydraulic fluid supplied from the pump outpu-t through a
conduit 828 acts against the spring force to release the brake
and ~mlock the motor during normal operation.
Conduits 820 and 828 are connected in common to
a shuttle valve 830; this valve connects the brake and level wind
motor circuits to one of conduits 816 and 818 which is carrying
the h.ighest pressure hydraulic fluid supply. In the spoolin~
on mode, suppl~ conduit 816 carries fluid from pump 810 at a
hiyher pressure than return conduit 818; in the laying mode,
motor 218 provides the source of high pressure fluid throu~h
return conduit 818.
lS A torque control relief valve 832 is connected
between the return conduit 818 and the supply conduit 816
throuyh a check valve 834. Additional relief valves and/or
check valves may be added in parallel as needed to accommodate
the pxessure requirements of the system. A further relief
valve 836 is connected through a check valve 838 between the
supply conduit 816 and the return conduit 818. In the opera-
tive embadiment, relief valve 832 is adjustable up to a maximum
relief pressure of about 3800 psi; valve 836 is pre-set to open
at about 1000 psi.
-36-
37
A braking pressure control valve 8~0 located on
-the operator's console is connected to -the torque control relief
valve 832 to con-~rol -the pressure setting of the relief valve.
This in turn controls the torque provided by motor 218,
particularly in its dynamic braking mode during unspooling.
A multiscale gauge 842 is connected in the pressure relief
valve setting cir~uit; gauge 842 provides the operator wi~h
the system pressure and the amount o~ line pull (i.e., pipe
tension) with respect to the diameter of the wrap being made.
.lO ~ irst scale is calibrated for system pressure, a second scale
is calibrated for line pull at full drum ti.e.l tension on the
pipe when the drum is full), a third scale reads line tension
when the drum is at one-ha`lf capacity and a fourth scale reads
line tension when the drum is substantially empty.
A control valve 8~ located on the operator's console
].5
controls the flow of hydraulic fluid to the reel drive motor.
The control valve 844 is a three position valve; in the
first position, the motors will rotate the reel in the "reel
on" direction at maximum torque; in the second position, the
pump is stroked to xero volume and rotation of the reel is
stopped. In its third position, valve 844 reduces the
displacement of motor 218 by 50%i this increases the rate at
which the motors will rotate ~or a given amount o~ oil beiny
pumped but also reduces their torque capability for a given
pressure setting by 50~.
Flow control valve 823 interposed in flow line 820
controls the flow of fluid to level wind motor ~25 to thereby
control the speed a-t which motor 425 rotates.
-37- .
~2~
System Operation
In the spooling or reeling on mode, the control
valve 844 is moved to i~s first posi-~ion; the reel drive
motor 218 will therefore be driven by pump 810 a-t full torque.
The pump also supplies fluid under pressure to the level wind
motor 425 through directional control valve 822 and Elow control
valve 823. By controlling the volume of fluid supplied to the
level wind motor 425, by means of control valve 823,
the operator can control the movement of the level winder 450
as it traverses the carrier vessel deck in a direction sub-
lQ stAntially parallel to the rotational axis of the reel. The
operatox can thereby control the wrapping of the pipe onto
the reel.
When a full complement of pipe is spooled on the
reel, an operation which is usually and preferably carried
out at a shore base, the carrier -vessel (e.g., supply boat)
moves to the job site. There, the free end of the
pipe is secured to a fixed point, e.g.~ it may be welded
to the end of a previously laid pipe, or it may be connected
to a 10w terminal at a drilling rig, etc. Once the free
end of the pipe is secured, the carrier vessel moves off along
the lay path and the pipe is pulled off the reel and through
the straightener 460. The main engines of the carrier vessel
provide the forward thrust, against which the reel drive
motors work to maintain the pipe under tension as it is
unspooled.
-3~-
~;~2~63~
The adjustable roll ~7~ of the straightener 460 is
set to apply a predetermined amo~mt of re~erse bending force
and displacement to -the pipe as it passes through the straightener.
This bending force, coupled with the tension maintained on
the pipe, causes the pipe -to be straightened as it exits
the straightener assembly 40 and passes through the s~ern
roller assembly 60 into the wa-ter at the pre-set exit angle ~.
As pipe is unspooled, the reel and reel drive
motor 218 rotate in the opposite direction from the reeling-
lQ on modc. The amount of tension maintained on the pipe as it
comes o~E the reel is controlled by the dynamic braking a~tion
of motor 218 reacting against the forward -thrust o the vessel,
and specifically by the amount of torque applied by the motor
to the reel in the opposite direction to the direction of
unspooling rotation. The motor torque is in turn controlled
by the pressure setting of relief valve 832, as set by control
valve 840.
During the laying operation, the pump 810 is main-
tained in a pumping mode; however, the reel motor 218 is
driven by the reel as pipe is pulled oEf. The motor 218
therefore acts as a pump, b~ pumping high pressure hydraulic
fluid through return conduit 818, over the torque control
relief valve 832 and into supply conduit 816 through check
valve 83~. Relief valve 836 is provided to pre~ent the
pressure in supply conduit 816 from becoming too great
during the braking mode. Valve 836 is pre-set to release
-39-
3~7
at a desired pressure (e.g., 1000 psi) to thereby short circuit
the flow of ~lud between the supply conduit ~16 and return
conduit 818; valve 836 will close when the pressure in supply
conduit 816 decreases below its release point.
System pressure can be adjusted by removing one or
more reel drive motors from the operating circuit. This will
increase the pressure available to drive the remaining on-line
reel drive motors and the level winder motor. An alternative
method of adjusting system pressure is by moving control valve
from its f.irst to its third positions; this reduces the
displacement of the reel drive motors by 50% and increases the
pressure available to drive the level winder mo-tor during a
spooling operation. During a laying operation, this reduction
in displacement results in a decrease in line tension on the
pipe and is required where line tension is excessive even at
mini~um system pressu~e settings on relief vaIve 832.
In the laying mode, the closed loop dynamic braking
system maintains a constant tension on the pipe as it is
spooled off the reel. Such tension is adjustable, for example,
between 0 and 70,000 pounds in combination with laying speea,
which is adjustable, for example, between 0 and 10,000 ~eet
per hour. This enables the proper catenary to be maintained
on the pipe between its entry poin~ into the water and its
touchdown point on the ocean bottom. This is important to
avoid excessive bending of the pipe so that the radius o~
curvature of the catenary does not fall below the elastic
limit of the pipe~
-~0-
~3L2;~ 3~
During the laying operation, surface action of
the sea will result in back and/or down surging of the carrier
vessel. Such action tends to decrease the tension on the pipe,
resulting in changes to the pipe geometry ana particularly the
catenary. When the constant tension adjustment feature senses
a decrease in line pull, due to back or down surging, the
system automatically increases the pumping pressure ~n the motor
to increase the braking orce on -the drum and thereby increase
the tension on the pipe.
lq In order to achieve the automatic tension adjustment
to maintain a constant tension on the pipe, the pump 810 is
set for maximum pumping volume. The fluid pressure supplled
to the drive motor 218 by pump 810 through conduit 816 cannot
exceed the pressure setting of relief valve 836. This provides
a constant pressure supply to the input of the reel drive mQtorS
and the braking torque against which the reel acts. ~uring the
laying operation, the reel torque overcomes the driving force
of the fluid pressure in supply conduit 816. The drive motors
218, 220, 222 are rotated by -the driving force of the reel
against the dynamic braking force of the fluid supplied by
pump 810. The drive motors thus act as a pump in the manner
described above.
If during a laying operation, a back or do~n surge
occurs, the line tension, and thus the tor~ue exerted by the
reel on the drive motor, drops significantly, with a corres-
ponding drop in fluid pressure pumped by the motor. This
-41-
~2~
slack is taken up by the -fluid pressure supplied by pump 810
to incxease the torquin~ force exerted by the motor on the reel
in the opposite direction -to the torquing force exerted by the
reel on the motor. A proper balance of torquing forces will
therefore be maintained as line tensi:on c~anges due, for example,
to sea condition changes.
With the presen-t invention, pipe can be "overwound"
or "underwound" on the reel. T~at is, pipe can be spooled
onto the æeel ~rom the top ~in the overwound mode~ or from
the bottom ~n the underwound mode). ~hen unspooling from the
overwound configuration, the pipe describes an upwardly curving
parabola as shown in the drawing. When unspooling from the
underwound mode/ the pipe exits the reel from the hottom and
travels upwardly to the straightener mechanism 460. The pipe
will first contact rollers 4S7a and 487~ which, particularly in
the underwound mode, act as a curve uniformizer to impart a
uniform radius of curvature to the pipe in the opposite direction
to the spool impar-ted radius of curvature. The principle of
! operation of such a curve uniformizer is ]~nown; see, for example,
U.~. Patent 3,712,100, issued January 23, 1973 to I~ey et al.
The invention may be embodied in other specific forms
ithout departing from -the spirit or essential characteristics
thereof. The present embodiment is, therefore, I:o be
considered in all respectsas illustrative and not res-trictive,
the scope of the invention being indicated by the appended
claims rather than by the foregoing descrlption, and all
changes which come within the m~an:ing and range o~ e~uiva-
lency o~ the claims are, therefore, intended to be embraced therein.
\/'
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