Note: Descriptions are shown in the official language in which they were submitted.
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FABRICATING HELICAL FLOULINE BUNDLES
A fast and efficient method for installing small diameter
flowlines offshore is by means of reel, tensioner, and straightener
devices mounted on a floating vessel. However, this "pipe reel"
method becomes awkward if multiple lines must be laid simultaneously,
as is often the case for flowlines laid to, or originating at,
~eafloor wellheads. A typical flowline bundle to such a subsea well
consists of two production flowlines, one annulus accPss line, one
chemical inJection line, one hydraulic power line and one electrical
control cable. For such multiple lines it becomes necessary to
spool each line onto a separate reel, and then either (1) lay each
line separately off the floating vessel while carefully monitoring
each suspended span, or (2) bring the separate lines together and
wrap them with tape to form a "flowline bundle" which is then laid
into the water as a single entity.
Problems frequently are encountered with multiple flowlines or
flowline bundles as they are being laid or as they are being pulled-in
and connected, either to a subsea wellhead or other subsea structure,
or lnto a J-tube conduit on a fixed platform. Potential problems
include dynamic impActs between the lines during pipelaying if laid
separately. For a pull-in of a flowilne bundle to a subsea wellhead
or other subsea structure, potential problems include lateral
buckling of the smaller lines due to bending of the bundle, over-
stressing of some of the lines because of non-uniform sharing of the
tension and bending loads, and large torque required to orient the ~:
flowline terminal head before attaching to the wellhead. For a ~ :
flowline bundle pulled into a J-tube, potential problems include
increased pullforce due to composite-beam bending effect for pipes
that are tightly wrapped, differential stretching or buckling of the
smaller lines inside the curved portion of the J-tube, or formation
of buckled pipe "loops" at the mouth of the J-tube, for bundles that
are only loosely or partially wrapped. The present invention is
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dlrected toward overcoming these and other problems of the art as
wlll be apparent hereinafter.
In accordance with the invention this object i5
accomplished by twis~ing or branching a flowline assembly into a
permanent rope-like hellcal configuration, prior to laying ~he
flowline assembly offshore.
Thus, according to one aspect, the invention provides a
method for fabricatlng a hellcal flowllne as~embly, the method
comprlsing-
assembllng a flrst bundle of essentlally parallel flow-
llnes;
twisting the flowlines of the flrst bundle into an
es~entlally hellcal conflguratlon;
assembllng a second bundle of e~sentlally parallel
flowllnes;
attachlng the first bundle to the second bundle with
fluid-tight connections; and
twl~tlng the flowllnes of the second bundle into an
es~entlally hellcal conflguratlon.
Accordlng to another aspect, the lnvention provldes an
apparatus for fabrlcatlng a helical flowline assembly comprlslng:
mean~ for assembllng a flr~t bundle of essentlally
parallel flowlines;
means for twisting the flowlines of the first bundle
into an e~sentially helical configuratlon;
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means for a~sembling a second bundle of essentially
parallel flowllnes;
means for attaching the first bundle to the second
bundle with fluid-tight connections; and
means for twisting the flowlines of ~he second bundle
into an essientially helical configuration.
In one preferred embodiment, the method requires
assembling a first bundle of essentially parallel flowlines;
twistlng the first bundle into an essentially hellcal
configuratlon; assembling a second bundle of essentially parallel
flowllnes; attachlng the flrst (twisted) bundle to the second
~untwisted) bundle with fluid-tight connectlons; and twistlng the
second bundle into an essentlally hellcal configuratlon; etc. In
this preferred embodiment, the bundles are twlsted into a helix at
a point ad~acent to where the first and second bundles are
attached. The twi~ting is accompli~hed by rotating and
~0 translating either the first ~twi~ted) or second (untwisted)
bundle while translating but not rotating the other.
Alternatively, the second bundle, after attachment to the firs~
bundle, may be twlsted at an end oppo~ite to where the bundles are
attached. In another preferred embodlment, the method requires
assembllng a fir~t bundle of essentlally parallel flowlines;
twlstlng the flrst bundle lnto an essentlally hellcal
conflguratlon; assembling a eecond bundle of e~sentlally parallel
flowlines; twlstlng the second bundle lnto an essentlally helical
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configuration; and attaching the first (twisted) bundle to a
second (twisted) bundle with fluid-tlght connections; etc. In
thls embodiment the bundles may be twlsted from one or both ends.
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In all cases the bundles may be reeled onto a reel, which reel
may be onboard a vessel, and then may be laid offshore by unreeling
while moving the vessel forward along the flowline route. Alternately,
the helical flowline bundle may be assembled into one or more long
strings which may then be towed into place offshore by tow vessels.
In a highly preferred embodiment the parallel pipe strings to be
formed into a helical bundle are supported at intervals along the
lengths thereof by tu~blers which rotate the pipe strings during
helical twisting thereof, and the pipe strings are individually -
passed through orifices of a rotating twist head to produce the
helical configuration of the flowline bundle.
The invention will now be explained in more detail with reference -
to the accompanying drawings, in which:
Figure l shows a helical flowline bundle ~formed by twisting
multiple pipes and cables together into a helix.
Figure 2 discloses a flowline bundle being simultaneously
twisted and spooled onto a reel vessel.
Figures 3 and 4 disclose first and second embodiments of a pipe
spooling yard for fabricating and spooling helical pipe bundles.
Fi~ures S and 6 disclose third and fourth embodiments of a
layout of a pipe spooling yard.
Flgure 7 shows a double twist head arrangement for forming
helical bundles prior to being spooled onto a reel vessel.
Figures 8 and 9 disclose particulars of the arrangement and .
connections between a pipe twist head and a sequence of pipe tumblers
and intermediate bundle supports.
Figures lO and ll show mechanical details of a pipe twist head
apparatus including two designs of a pipe twist head disk.
Figures 12 and 13 show mechanical details of a pipe tumbler
30 apparatus including two designs of a pipe tumbler disk, ..
This invention relates to the twisting, braidin~, and/or
wrapping of a flowline bundle into a permanent rope-like helical
configuration, prior to laying the flowline bundle offshore,~ .
preferably by the reel method. Alternatively, the flowline may be
assembled onshore and towed into place offshore without placing it
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upon a reel. Throughout this disclosure, the terms "twisting",
"braiding", and ~pipe twist head," etc., have been given the special
meaning of rotating the several pipes around one another ~ithout
applying substantial torque to any of the pipes, as necessary to -
form the pipes into a permanent rope-like helix. Thus, a line drawn
along the top of each pipe in the bundle would remain at the top of
each pipe throughout the "twisting" process. The only residual
moment or torque left in the pipe bundle after forming this helix
would be that associated with the relatively small curvature of the
helix itself. This small torque, which incidentally, gives rise to
the forces holding the bundle together, are easily contained and
counteracted by tape wrapping means or other banding means applied
to the bundle at intervals, as described below.
A flowline bundle twisted or braided into a helix offers
several advantages over alternative configurations. Because of the
combined weight and stiffness, and the close proximity of the
various pipes, a helical bundle provides greater strength, integrity,
and protection for the various pipes in the bundle than is possible
if the lines are laid separately. This invention enables the
spooling and laying of an entire flowline bundle as a single pipeline
from a single reel, such as the large pipe reels on vsrious existing
vessels, Thus, the need for more than one reel, straightener,
tensioner, and span-monitoring device on the reel vessel is eliminated.
This invention also permits the handling, survey, repair, etc., of
the flowline bundle as a single pipeline instead of as several
separate lines, which is a significant operational advantage.
Composite beam behavior is virtually eliminated for a helical
flowline bundle. Thus, the stiffness of a helical bundle in bending
or twisting`is simply the sum of the stiffnesses of the individual
pipes, which is much smaller than that of a similarly sized composite
beam. Hence, the braided bundle minimizes the bending moments and
torques required to align the flowline terminal head with the
receptacle on a wellhead and minimizes J-tube pullforces. The
braided bundle also eliminates any problems with lateral buckling of
the smaller pipes due to either bending or thermal-pressure expansion,
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which can occur for a straight-pipe partially wrapped bundle confi-
guration. Thus, for example, the present invention eliminates
buck].ing problems for flowline bundles to be spooled onto a reel or
to be pulled through a J-tube. -
Referring now to the drawings, as shown in Figure 1 a helical
flowline bundle 1 is formed by twisting multiple pipes and cables
together into a helix. The bundle may comprise, for example, two
production flowlines 2 and 3, an annulus access line 4, an electrical
control cable 5, a chemical in~ection line 6 and a hydraulic power
line 7. When twisted helically together they comprise a flowline
bundle 1 which is stabilized from untwisting by wrappings 8 and 9 of
reinforced plastic tape or other strapping means. Experience has
shown that such wrapping or strapping of a helical bundle is strictly
required only at the two extreme ends of the bundle, but for safety
sake may also be employed at intermediate locations.
Several different methods are envisioned for forming pipes into
a helical flowline bundle for laying by the reel method, etc. as ~ :
illustrated in the figures of the drawings. One procedure, Figure
2, involves forming several pipes 10 into a helix 11 simultaneously
as the pipes are spooled onto a reel 12. For this procedure, a pipe
twisting head 13 i~ required, mounted near and aligned with the reel
12, optionally located on the stern of the reel vessel 14, which
applies the necessary tensions and rotations to the pipe~ 10 as they
are fed onto the reel 12. Pipe lengths are added to the free ends
15 of the pipe bundle 11 at a pipe ~oining area 16 ~ust beyond the
twlst head 13 from the reel 12. Where a fast-welding technique such
as the homopolar or flash-butt methods is available, or if mechanical
connections such as threaded pipe are used, then only short lengths
need be handled during the twisting and spooling process. However,
where manual welding is employed, the slower welding speed requires
thae the separate pipes of the bundle first be made up into long
strings, and then these entire pipe strings be rotated around each
other as the twisted pipe bundle is spooled onto the reel.
The rates of twisting and spooling must be carefully coordinated
to achieve a uniform helix with a proper pitch length. ~xperience
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has shown that the optimum pitch length of a helical flowline bundle
is 80-lO0 times the diameter of the largest pipe in the bundle. For
a longer pitch length the pipes are too loosely bound together and
tend to separate as they are bent onto the reel. For a shorter
pitch length the pipes become plas~ically bent in the process of
forming the helix, and so a straight uniform helix becomes impossible
to maintain.
Figure 3 Lllustrates a preferred procedure and layout of a pipe
spooling yard for assembling pipe into long strings 17, then forming
these pipe strings 17 into a helical bundle 11 as the bundle is
spooled onto a reel 12. This procedure involves the following
steps: (1) forming pipe into long strings 17 in shop 18 by welding
or other means, and placing these stringis onto storage rack 19; (2)
loading appropriate pipe strings 20 from storage rack 19 into pipe
string tumblers 21 and intermediate supports 22; (3) making tie-in
connections by welding or other means, at the pipe ~oining area 16,
between the pipe strings 20 and the free pipe ends 15 of the bundle
ll from reel 12 on vessel 14; (4) simultaneously rotating pipe
strings 20 by means of pipe tumblers 21, twisting pipe strings 20
into a helix by means of twist head 13, and spooling the resulting
helical bundle onto the reel 12, while adJusting feed and twist
rates as required to maintain a proper helix; (5) stopping the
twisting/spooling operations when the trailing end~ o the pipe
strings 20 reach the pipe ~oining area 16; (6) wrapping or banding
the bundle ll between the reel 12 and the twist head 13 to prevent
unraveling; and (7) repeating steps (1) through (6) until a sufficient
length of helical bundle 11 has been assembled and stored on the
reel 12 for a given offshore flowline applica~ion. The tumblers 21
are preferably designed to open at the top or ~iide to allow easy
loading of the pipe strings. The rotation speed of each pipe
tumbler 21 is synchronized with the twist head 13 to maintain the
pipe strings 20 straight and parallel during the twisting/spooling
operations. Back tension i8 maintained in the pipe strings primarily
by friction in the twist head, tumblers, and intermediate isupport
apparatus-
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Figure 4 illustrates another preferred procedure and layout of
a pipe spooling yard that is nearly identical to Figure 3, except
that the bundle twist head 13 is located onshore instead of on reel
vessel 14. Note in Figures 3 and 4 that a control cable or control -
umbilical 23 may be fed off a temporary storage reel 24 and assembled
together with the pipe strings 20 as part of the helical flowline
bundle 11.
A fourth procedure, shown in Figure 5, for forming pipes into a
helical bundle for laying by a reel vessel involves the following
steps: (1) fabricating pipe strings 17 in a shop 18 and storing on
racks 19; (2) loading appropriate pipe strings 20 from racks 19 into
bundle assembly/twist area 25, which comprises a series of supports
26 (preferably having rollers to allow free movement of the bundle);
(3) connecting pipe strings 20 at the pipe ~oining area 16 to pipe
15 ends emanating from the pipe bundle already on the reel 12; (4) `. :.
connecting other ends of pipe stringc 20 to a pipe twist head 27
located at the far end of the assembly/twist area 25; (5) twisting
pipe strings 20 on supports 26 into a specified helix by rotating
and applying ténsion to the pipe strings by means of the twist head
27 and winch 28; (6) taping or banding the pipe strings together at
the far end to prevent unraveling; (7) releasing plpe bundle 20 from
twist head 27 and from clamp 29 on reel vessel 14; (8) spooling pipe
bundle 20 onto reel 12 while maintaining sufficient back tension
with wlnch 28; and (9) clamping pipe bundle 20 in clamp 29 on reel
vessel 14 while leaving sufficient lengths of free pipe ends for
welding onto the next pipe strings. These steps (1) through (9) are .
repeated until a ~ufficient length of pipe bundle is stor~d on reel
12.
A fifth procedure for forming pipes into hellcal bundles for
30 laying by a reel vessel is indicated in Figures 6 and 7. This :
procedure involves first forming individual pipe strings into
helical bundle segments and then later Joining these helical strings
to pipe already on the reel and spooling these helical strings onto
the reel. The procedure involves: (1) fabricating pipe strings 17
in shop 18 and storing on racks 19, as before; (2) loading appropriate
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pipe strings 20 from racks 19 into a central bundle assembly/twist
area 30; (3) connecting pipe strings 20 to pipe twist heads 31 and
32 at each end of the assembly/twist area 30; (4) twisting pipe
strings 20 into a specified helix by rotating and applying tension
to the pipe strings by means of the two twist heads 31 and 32; (5)
taping or banding the pipe strings together at each end to prevent
unraveling; (6) releasing the helical pipe bundle segment 20a from
twist heads 31, 32, then placing this bundle segment 20a on pipe
bundle storage rack 33; and (7) repeating steps (1) through (6)
until a sufficient total length of twisted bundle segments for a
given offshore flowline application has been produced and stored on
rack 33. ~At a convenient later time these helical bundle segments
may be connected sequentlally at pipe ~oining area 16 and spooled
onto reel 12 of vessel 14. Finally, reel vessel 14 proceeds offshore
to lay this flowline bundle.
Figure 7 illustrates in more detail the apparatus for twisting
helical bundle segments from both ends. For this process two pipe
twist heads 31 and 32, driven by motors 34 and 35, are lacated at
each end of the bundle assembly/twist area 30, twist head 32 being
mounted on a stationary fixed support 36 and twist head 33 being
mounted on a trolley 37 with means 38 (e.g., a pneumatic cyllnder)
to apply tenslon to the pipe strings 20 as they are braided together.
The assembly/twist area 30 itself comprises a series of pipe supports
39a, 39b, etc., preferably having rollers to allow free movement of
the bundle during the twisting process. For any helical pipe
bundling process that involves twisting pipe strings from one or
both ends, as illustrated in Figures 5-7, in order to produce a
uniform helix additional friction reduction means (e.g., lubricants
or rollers) wlll have to be introduced between the various pipes of
the bundle prlor to and durlng the twisting operation.
Figures 8^13 disclose in more detail apparatus for twisting and
spooling flowllne bundles onto a pipe storsge reel, whlch apparatus
corre~ponds with the preferred procedure of Figures 3 and 4.
Referring to Figure 8, straight pipe strings 20 to be twisted are
passed through a series of pipe tumblers 21 which alternate with
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intermediate pipe supports 22, then through a special large disk
tumbler 40, and finally through a pipe twist head 13. Rotation of
the disk elements of each of these machines 21, 40, 13, causes the
parallel pipe strings 20 to rotate around one another as they move
toward the reel 12. As the pipe proceeds from the large disk
tumbler 40 through the twist head 13, the parallel pipe strings tend
to bow out at a point 41 and then focus together at a point 42 where
the helical bundle becomes fully formed, after which the helical
flowline bundle 11 translates but does not rotate until it reaches
the reel 12 upon which it is spooled. A variable speed motor 43 is
utllized to drlve the twist head 13, and, by turning a series of
drive shafts 44, the various pipe tumblers 40, 21, are turned in
synchronization with the pipe twist head 13. Alternatively, one or
more pipe tumblers 21, 40 may be powered by individual electric or :~
hydraulic motors, which are maintained in synchronous rotation with
the twist head 13 by an electronic control system or other means.
Figure 9 illustrates, for example, a scheme whereby three consecutive
pipe tumblers 21 are powered by a separate drive motor 45, through
worm gears (not shown) and drive shafts 44, which motor 45 is
synchronized with the twist head (not shown) by electronic controls
or other means. Figure S also illustrates an alternative type of
intermediate pipe support 22 in the form of a trough, snd coupling
means 46 between the drive shafts 44 and the tumblers 21.
Figures lOa and lOb illustrate mechanical details of a pipe
twist head Assembly. Pipe twist head 13 and drive motor 43, together
with speed control 47 and speed reduction gear box 48, are mounted
on a structural base 49, which preferably is anchored to a solid
foundation. Twist head 13 itself comprises a frame 50, twist head
disk 51, hold-down rollers 52, drive pinion 53, and drive bearings
54. Frame 50 comprises base plate 55, side members 56, end plates
57, and roller support plates 58, all welded together. Also shown
in Figures lOa, lOb, are drive shaft 44 and coupling 46. Figures lla
and llb show in greater detail two designs for a twist head disk 51,
wh~ch guides snd rotates the flowlines (not shown) as they are being
twisted into a helical bundle. In one design (Figure lla) the
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flowlines are guided through the inner cylindrical surfaces 59 of
two or more spherical bearings 60 which are embedded in the disk 51.
In a second design (Figure llb) the flowlines are guided through
orifices containing two or more rollers 61 whose shafts (not shown)
are embedded in the disk. The disks shown in Figures lla, llb, each
contain four orifices for twisting up to four flowlines. Other
twist head disk designs, having various numbers of orifices and/or
different pipe support features, are also possible. Also embedded
in the twist head disk 51 is gear 62 which meshes with gear 63 of
drive pinion 53, shown in Figure llc, to provide necessary slip-free
rotation of the disk 51.
Figures 12a and 12b illustrate mechanical details of a pipe
tumbler assembly. Pipe tumbler 21 consists of frame 64, tumbler
disk 65, hold~down rollers 66, drive pinion 67, and drive bearings
15 68. Frame 64 comprises base plate 69, side members 70, and end
plates 71, all welded together. Base plate 69 preferably is anchored
to a solid foundation and may contain screws 72 for leveling. Drive
pinion 67 may be coated with a high-friction surface (e.g~ rubber),
or meshing gears may be embedded in both drive pinion 67 and tumbler
disk 65, to provide necessary slip-free rotation of the disk 65.
Figures 13a and 13b depict in greater detail two designs for a
tumbler disk 65, which guides and rotates the parallel flowlines
(not shown) which eventually are twisted into a helix (see Figure
8). One tumbler disk (Figure 13a) has four orifices 73 to simul-
taneously rotate up to four flowlines, whereas the other disk(Figure 13b) has six orifices 73 which can rotate up to six flowlines.
Both disks 65 can be opened by removal of pieces 74, which are held
in place by recessed screws 75, to allow easy top- or side-loading
of the flowlines. Other tumbler disk designs, having various
numbers of orifices and/or different quick-opening features for
loading of the flowlines, are also possible.
The pitch length of the helix for the flowline bundles described
herein is preferably equal to or less than the minimal circumference
of a reel or J-tube to which the bundle will be bent, in order to
avoid problems with differential buckling or stretching of the
several pipes. Thus, for a helical bundle to be laid from the reel
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ship Apache, the normal pitch length is preferably equal to or less
than 160 feet, which is the circumfe-ence of the main reel. For any
flowline bundle twisting procedure in which the twisting process
must be halted, the bundle removed from the twisting apparatus, and -:
the process later started up again, and in particular for the
procedure of Figures 5 and 6, described above, a short length at the :~
end of each twisted pipe string is preferably specially twisted and ~-
temporarily banded into a tighter helix than normal. Once this pipe
string has been ~oined to the pipe already on the reel, the temporary
banding is preferably released, thus forming a uniform helix across
the entire pipe bundle including the sections of pipe containing the
Joints between the pipe strings.
The foregoing description of the invention is merely intended .
to be explanatory thereof, and various changes in the details of the
15 described method and apparatus may be made within the scope of the .
appended claims without departing from the spirit of the invention.
