CA1220637A - Portable reel pipelaying apparatus and method - Google Patents

Abstract

PORTABLE REEL PIPELAYING
APPARATUS AND METHOD
Abstract of the Disclosure The invention comprises a portable reel pipelaying system for laying a continuous length of pipe on the sea bottom.
A pipe-carrying reel is adapted to be mounted 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 braking 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 reel in the direction of pipe unspooling; pipe straightening means are movably 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 spooled onto the reel and to substantially straighten pipe being unspooled from the reel. 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 unspooled.

Description

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.

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 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 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.

~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.

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.

~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~.

~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.

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~-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

~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.

~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.

~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.

~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.

~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 ~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.

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.

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.

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 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 ~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.
\/'

Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. 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 pipe 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 carrier vessel downstream of the straightener means in the direction of pipe unspooling for movement in a direction substantially parallel to the rotational axis of the reel, said method comprising the steps of:
sensing changes in tension on the pipe as it is being unspooled as a function 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.

2. A method according to claim 1, wherein said reel drive motor means comprises one or more hydraulic motor means, the method comprising the further steps of:
providing a substantially constant external source of hydraulic fluid under pressure to the drive motor means in the unspooling mode; and regulating the output pressure of the drive motor means in its dynamic braking mode to thereby maintain a relatively constant output pressure from the drive motor means and a relatively constant tension on the pipe in the unspooling mode.

3. A method according to claim 2, further comprising the step of:
dumping excess hydraulic fluid from the drive motor system when the output pressure of the drive motor means in the dynamic braking mode exceeds a predetermined maximum pressure to thereby maintain the dynamic braking force of the drive motor means at or below a level which produces a maximum desired tension on the pipe in the unspooling mode.

4. A method according to claim 3, further comprising:
adding hydraulic fluid to the drive motor system when the output pressure of the drive motor means in the dynamic braking mode falls below a predetermined minimum pressure to thereby maintain the dynamic braking force of the drive motor means at or above the level which produces a minimum desired tension on the pipe on the unspooled mode.