GB1601730A - Method of spooling pipe or a reel - Google Patents

Description

(54) METHOD OF SPOOLING PIPE ON A REEL (71) We, SANTA FE INTERNA TIONAL CORPORATION, a corporation organised and existing under the laws of the State of California, of 505 South Main Street, Orange, California, 92668 United States of America, do hereby declare the invention. for which we pray that a patent may be granted to us, and the method by which it is to he performed, to be particularly described in and by the following statement: This invention relates to method of spooling pipe on a reel. More particularly, the invention is concerned with reel pipelaying methods and apparatus used primarily in laying pipe from a reel pipelaying vessel.

U.S. Patent No. 3,680,342, issued August 1, 1972, shows one such vessel, a barge having a reel with flanges located in horizontal planes and having a vertical axis of rotation (generally referred to in the trade as a 'horizontal reel" arrangement). U.S.

Patent No. 3,982.402 (Lang et al) describes a reel pipelaying vessel having a "vertical reel", i.e., vertical flanges and a horizontal axis of rotation.

In offshore pipelaying operations employing reel barges or ships of the type shown in the aforementioned patents, pipe is generally spooled onto the reel on the vessel at a shore base after short lengths of properly coated pipe are welded on shore at the base to form a continuous pipeline. The carrier vessel is then towed (or selfpropelled) to the job site where the pipe is laid between different points (e.g., between the drill site and a water- or shore-based storage point).

It is commercially important that as much pipe as possible (up to the maximum capability of the reel and carrier vessel) be spooled onto the vessel reel without damaging either the pipe or the coating which has been applied to the pipe to prevent or reduce the rate of corrosion when the pipe is laid on the occan floor. Spooling the maximum amount of pipe onto the reel at one time reduces the number of required trips of the reel pipelaying vessel between the shore bise and the job site in those cases where the job requires more pipe than can be carried on the vessel reel in a single trip.

This reduces the total job time and thus the net cost of the job.

Another factor to be considered in spooling pipe onto the reel is that damage to the pipe and/or coating be minimized. The pipeline owners and various regulatory bodies have set minimum standards for such factors as ovality of the pipe, continuity and thickness of the coating, etc. Improper spooling of pipe onto the reel can produce excessive stresses on the pipe which in turn results in excessive ovality and/or buckling of the pipe and/or substantial and unacceptable damage to the coating, causing unacceptable decrease in corrosion control of the pipeline in sea water.

Substantial damage to the coating is difficult to repair, although minor damage to the coating achieved by good spooling is reasonably easy to repair. Visual and/or electronic inspection of the pipe as it is unspooled and being laid will generally show up coating damage. If the pipe is not unacceptably damaged, it can then be repaired by locally (i.e., on the vessel) recoating the damaged portions during the lay operation. Generally, and when possible, repairs to non-major coating damage are made while the vessel continues to transit so that the recoating operation, including stripping of original coating in the damaged area and thereafter applying fresh coating, must be performed on a moving pipe after it comes off the reel and before it enters the water. This recoating is performed by suitably skilled personnel located on the vessel near the stern and often can be a dangerous operation.

A much more serious problem arises when unacceptable pipe damage is encountered in a given section of pipeline. In each such case, the vessel must be stopped and held in position while the unacceptably damaged pipeline section is cut out and the two remaining pipe ends rewelded; the new joint must then be properly coated. This is a complex, time-consuming and costly operation requiring highly skilled crew personnel, and may be hazardous. in certain sea conditions.

It is always difficult during the lay operation to locate excessive damage to the pipe itself, and particularly damage resulting in unacceptable ovality and/or buckling of the pipe beyond permitted customer and/or regulatory body limits, and which may cause serious difficulties after the pipe is laid on the sea bottom. Visual inspection prior to laying will be very seldom reveal such defects. Such damage is usually found after the pipe has been laid and a "gauge plate" is passed through the pipe between termination points.

Examination of the gauge plate after traverse through the pipe length will indicate whether or not a section of the pipe is too much out of round. However, this test will not pinpoint the damaged area itself; this must be done by diver inspection and/or the use of "tracer pigs". In such cases, once the damaged area has been located, it is necessary to pick up the pipe, cut out the damaged section, weld in a replacement section, and recoat the newly welded connection. This is a complicated, timeconsuming, and very costly process, requiring a skilled crew, and it may be hazardous in certain sea conditions. It sometimes even results in loss overboard of the laid pipe portion, which must then be retrieved, reconnected, and recoated; this presents major problems even more complex, timeconsuming, and costly to cope with.

It is an object of this invention to provide a pipe-spooling method which, when properly performed, substantially overcomes and minimizes the above described problems associated with reel-type pipelaying operations.

More particularly, it is an object of this invention to provide a pipe-spooling method which permits a maximum amount of pipe to be spooled onto a reel at one time.

Another particular object is to avoid or minimize, as much as possible, damaging the pipe and/or its coating as the pipeline is spooled onto the reel.

Reel pipelaying operations of the type described, for example, in the abovementioned U.S. patents, utilize certain pipe handling equipment in addition to the reel.

Such pipe handling equipment includes a level winder and a straightener which may be combined in a single unit. Such winder/ straightener advantageously comprises a series of reaction points, preferably a series of rollers or tracks (as in the above-cited U.S. patents), providing a suitable arrangement which imparts sufficient bending force to the pipe to remove residual curvature so that after unspooling, the pipe will lay substantially straight on the sea bottom. The level winder/straightener assembly is located in the pipe path between the loading/ unloading point and the pipe-carrying reel, ana is arranged to be movable in a direction substantially parallel to the rotational axis of the reel. Thus, in a "horizontal" reel system (for example, of the type described in the first above-mentioned U.S. patent), the level winder/straightener assembly is arranged to move vertically; whereas, in a "vertical" reel construction (of the type shown, for example, in the second abovementioned U.S. patent), the level winder/ straightener is arranged to move transversely across the deck of the carrier vessel.

The level winder portion of the level winder/straightener device, according to the present invention, controls the manner in which the pipe is wound onto the reel. The speed of the level winder is controlled by an operator through adjustments to the drive mechanism which drives the level winder in its movement essentially parallel to the rotational axis of the reel. This, in turn, controls the movement of the pipe across the reel hub during the winding or spooling process. level The level winder/straightener assembly may also advantageously include a tensioner (e.g., in the form of a roller or track cooperating with a straightener roll or track as shown, for example, in the aforementioned U.S. patents) for maintaining tension on the pipe as it is being laid.

A key feature of this invention is the manner in which pipe is spooled, as controlled by the movement of the level winder relative to the reel. The pipe is wound onto the reel in a helical fashion such that each layer of pipe is spooled in the same helical direction as the preceding layer. This technique is exactly the opposite of prior standard helical winding methods where the helix direction alternates with each alternating layer.

For convenience, the following terms will be employed with respect to the description of this invention: 1. A "turn" is that length of pipe wound through one complete revolution of the reel; 2. A "wrap" comprises a plurality of turns making up a layer of pipe wound on the reel across the full or substantially full width of the reel.

In accordance with the present invention, we provide a method of spooling pipe on a reel, primarily for use in off-shore pipe laying system, comprising the steps of: securing one end of a substantially continuous pipe line to said reel; maintaining the pipe under tension while rotating said reel at a relatively constant rotational speed X to spool said pipe thereon; and translating said pipe across said reel at speed Y while said reel is rotating at speed X for a major part of one complete revolution of the reel and at a speed substantially greater than Y for a minor part of one complete revolution of the reel to thereby wind pipe onto the reel in a helical pattern such that each succeeding wrap of pipe on the reel has substantially the same helical pattern as each preceding wrap, and wherein adjacent turns of the succeeding wrap cross over corresponding adjacent turns of the preceding wrap within an arcuate region substantially corresponding to the minor part of one complete revolution of the reel.

Further, in accordance with the present invention, we provide for use in conjunction with offshore pipeline laying apparatus comprising a pipe spooling reel and pipe conditioning means mounted to a surface carrier vessel, said pipe conditioning means including a combination pipe straightener and level winder, a method of spooling pipe onto the reel comprising the steps of: passing a continuous pipeline of discrete length through said pipe conditioning means and securing one end of said pipeline to the hub of the reel; thereafter maintaining the pipe under tension while rotating the reel about its rotational axis at a substantially constant rotational speed X to spool said pipe thereon; at the same time translating said level winder across the reel in a given direction substantially parallel to the rotational axis of the reel at a relatively constant speed Y to thereby spool a first wrap of pipe onto the reel in a helical pattern, the relationship of speeds X and Y being such that each turn of pipe in the first wrap lies substantially adjacent to each preceding turn: and thereafter winding a second wrap of pipe onto the reel by: translating the level winder in said given direction at said speed Y while said reel rotates at said speed X for a major part of one complete revolution of the reel; reversing the direction of translation of the level winder and at the same time increasing the speed of the level winder to a speed substantially greater than said speed Y for a minor part of one complete revolution of the reel to thereby cross the pipe of the second wrap over the pipe of the first wrap; and thereafter restoring the direction of translation of the level winder to the given direction while reducing the level winder speed to Y to thereby spool the next turn of pipe of the second wrap on and between adjacent turns of the first wrap, whereby the spooling pattern of the second wrap is substantially helical and in the same direction as the helical pattern of the first wrap.

The translational speed of the level winder and the pipe across the reel during said minor part of one complete revolutiion of the reel during such even-numbered wraps is preferably increased at said cross over portion to about 10-12 Y and in said direction A.

The arc lengths of the major part of one complete revolution of the reel and the minor part of one complete revolution vary somewhat as a ratioed percentage of the pipe size to the radius on the reel of the respective wrap; e.g., such arc lengths may vary from about 30 as a minimum arcuate distance for small diameter pipe (e.g., 2" OD nominal) to about 100" practical maximum for large diameter pipe up to about 24" OD (nominal).

Also in accordance with the present invention, we provide for use with an offshore pipelaying apparatus comprising a pipe spooling reel and pipe conditioning apparatus mounted to a surface carrier vessel, said pipe conditioning apparatus including a level winder, wherein pipe passes through the level winder before being spooled onto the reelb a method of spooling the pipe onto the reel, comprising the steps of: maintaining the pipe under tension while rotating the reel about its rotational axis at a substantially constant rotational speed X and while spooling pipe onto the reel; translating the level winder across the reel in a first direction substantially parallel to the rotational axis of the reel at a relatively constant speed Y while said reel is rotating at said speed X through a major portion of one complete revolution of the reel; thereafter reversing the translational direction of the level winder and substantially increasing the translation speed Y of the level winder for a minor portion of said one complete revolution of the reel to thereby cross the end of the turn of pipe currently being spooled over a turn of pipe of the immediately preceding spooled wrap; and thereafter restoring said level winder translation direction and reducing the level winder speed to substantially speed Y to thereby spool the next turn of pipe over and between adjacent turns of the immediately preceding spooled wrap, whereby the spooling pattern of each wrap is substantially helical and in the same direction.

Still further in accordance with the present invention, we provide a method of spooling pipe onto a reel, primarily for use in offshore pipelaying systems, comprising: (a) securing one end of a substantially continuous pipeline to said reel: (b) maintaining the pipe under tension while rotating said reel to spool said pipe thereon; (c) translating said pipe across the reel while spooling pipe onto the reel at a first given ratio of translation speed to spooling speed (V1) for a major part of each revolution of the reel; (d) translating said pipe across the reel while spooling pipe onto the reel at a second given ratio of translation speed to spooling speed (V2), (where V2 > V )for a minor part of each revolution of the reel so that each turn of a given wrap crosses over a corresponding turn of the immediately preceding wrap and seats in the interstice between adjacent successive turns of the.immediately preceding wrap; and (e) alternately repeating steps (c) and (d) so that succeeding turns of said given wrap are seated in succeeding interstices of said one wrap across substantially the full width of the hub to complete said.given wrap with substantially the same helical pattern as said one wrap.

Also in accordance with the present in invention we provide a method of spooling pipe on a reel. primarily for use in offshore pipelaying systems, comprising the steps of: (a) securing one end of substantially continuous pipeline to said reel: (b) maintaining the pipe under tension while rotating said reel to spool said pipe thereon; (c) translating said pipe across said reel hub in one direction at a first translation rate (Y) while spooling pipe onto the reel at a given rotational rate (X) for at least a major part of each revolution of the reel to complete one wrap of pipe on the reel: (d) bringing the pipe up and over the last turn of said one wrap to begin the first turn of the next wrap in the space between the adjacent end flange and said last turn of said one wrap.

(e) translating said pipe across said reel in the opposite direction at a second translation rate (Yl) while spooling pipe onto the reel at said given rotational rate (X) for a minor part of each revolution of the reel so that the pipe crosses the last turn of the one wrap at the interstice between the last and penultimate turns of said one wrap: (f) thereafter translating said pipe in said first direction at substantially said translation rate Y and rotational rate X for a major part of each revolution of the reel so that the second turn of said next wrap is seated in said interstice; and (g) alternately repeating steps (e) and (f) so that succeeding turns of said next wrap are seated in succeeding interstices of said one wrap across the full width of the hub to complete said next wrap with substantially the same helical pattern as said one wrap.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an illustrative plan view of a vertical reel pipelaying apparatus mounted on the deck of a carrier vessel; Figure 2 is an illustrative plan view on an enlarged scale of a small portion of two layers or wraps of pipe on the reel particularly showing the pipe cross over region with an even numbered wrap above an odd numbered wrap; and Figure 3 is a sectional view of a plurality of wraps of pipe taken along the line 3-3 of Figure 2.

Referring now to the drawings, Figure 1 shows a typical vertical reel-pipelaying apparatus on which the method of this invention may be used. Although the following details description is illustrated with a vertical reel arrangement, the same disclosed techniques of this method are equally applicable to horizontal reel arrangements in a manner which will be apparent to those skilled in the art in the light of the disclosure herein.

The apparatus shown comprises three principal component sections: a reel and its associated support system, generally designated 20; a level winder/pipe straightener assembly and its associated support system.

generally designated 40; and a stern roller assembly and its associated support system, generally designated 60. The level winder/ straightener assembly is used to guide pipe onto the reel 20 during a spooling operation and to track and straighten the pipe as it comes off the reel during a lay operation.

The (optional) stern roller assembly 60 guides the pipe into the water after it leaves the level winder/straightener assembly 40.

The component parts of the reel pipelaying apparatus are mounted on a carrier vessel.

generally designated 80; the carrier vessel may be a barge, as shown in the first above-mentioned U.S. patent or a selfpropelled vessel, such as a supply boat or specially designed reel pipelaying ship. as indicated in the second above-mentioned U.S. patent.

Figure 3 shows a portion of a reel flange 20a and hub 20b, along with a plurality of wraps, including odd-numbered wraps 21 and 24, and even-numbered wraps 22.

Figure 2 shows a portion of two wraps of pipe, an odd-numbered wrap 21 (pipe turn sections 21a-21d and an even-numbered wrap 22 (pipe turn sections 2'al'2b. Oddnumbered wrap 21 may be considered an inner wrap and even-numbered wrap 22 may be considered an outer wrap in relation to reel hub 20 and in relation to each other.

For purposes of illustration, it is immaterial whether inner wrap 21 is the first or innermost wrap lying directly on the reel hub or any subsequent intermediate odd-numbered wrap; it is only necessary to visualize that wrap 22 lies immediately on top of wrap 21.

It is a feature of this invention that the helix of each wrap of pipe runs in the same direction as the helix of the previous wrap.

Thus, the helix of wrap 22 runs in the same direction as the helix of wrap 21. This arrangement is wholly unlike normal prior spooling arrangements where the helix of each wrap runs in the opposite direction from the helix of the previous wrap.

For convenience, the inner wrap 21 may sometimes be referred to as the "first" wrap; and the outer wrap 22 may sometimes be referred to as the "second" wrap.

When pipe is properly wound onto the reel, each turn will lie next to the immediately preceding and succeeding turns; thus, turn 21b of the first wrap lies next to turns 21a and 21c with a minimum of space between each turn. It is preferably that the spacing between adjacent turns be as close together as possible to maximize the total number of turns in a wrap.

Except in the crossover region, designated 26 in Figure 2, a given turn of the second wrap (e.g., turn 22a) will lie over and between two adjacent turns of the first wrap (e.g.. 21a and 21b) on one side of the crossover region 26 and over and between turns 21b and 21c on other side of the crossover region 26. Like the first wrap, the adjacent turns of the second wrap (e.g., turns 22a and 22b lie as close to each other as possible. As will be seen in Figure 3, each turn of wrap 22 lies over and in the interstice between adjacent turns of wrap 21. Thus, turn 22a rests on the outer surfaces of turns 21a and 21b. In this manner, the weight of the pipe of turn 22a is distributed over two pipe surfaces, i.e., of turns 21a and 21b.

Distributing the pipe weight in this manner results in decreased stress on the pipe and substantially diminishes the chances of damaging both the pipe and its coating.

The only area in which the pipe weight is not distributed evenly over two turns of a previous wrap is in the crossover region 26.

It is in this region that one outer pipe turn (e.g., turn 22a) having completed almost one full revolution of the reel, crosses over one inner turn (e.g., turn 21b) and continues as the next outer turn (e.g., turn 22b) lying in the space between and resting on the surfaces of inner turns 21b and 21c.

It will be apparent to those skilled in the art that the immediately preceding description is applicable to all wraps, save the innermost wrap, in relation to the wrap immediately therebelow, when pipe is spooled onto a reel.

The technique of spooling pipe onto a reel includes coordinating the rotational movement of the reel with the translational movement of the level winder. Specifically, as the reel 20 is rotated about its rotational axis, shown at RA in Figure 1, the level winder 40 is moved transversely parallel to the reel rotational axis RA in a first direction, illustrated by arrow A in Figures 2 and 3. During the winding of the innermost wrap (wrap 21 in Figure 3), the level winder 40 is preferably moved in direction A at a relatively constant translational speed "Y", assuming also a constant rotational speed "X" of the reel 20. When the innermost wrap 21 has been completely wound on the reel hub 20b, the pipe must be brought up and over the last turn 21e to begin the next wrap 22.

Normally, at this point, the level winder 40 would be reversed and controlled to traverse the reel in opposite direction B, illustrated by arrow B in Figures 2 and 3, at a constant speed Y (again assuming a constant rotational speed X of the reel) to the opposite end of the reel hub 20b, thereby producing a second wrap having a helix running in the opposite direction from the helical pattern of the innermost wrap 21.

However, contrary to such practice, in the present invention the end of last innermost turn 21e is brought up and over turn 21e, e.g., within an arcuate distance of between about 30 and 100 , depending on various factors, including in particular pipe diameter, as noted above; this causes the pipe at the beginning of the next wrap to lie in the space between the reel flange 20a and turn 21e. Each succeeding turn of this next wrap (e.g., wrap 22) is then wound to lie in the space between adjacent turns of the preceding wrap, except in the crossover region 26 as particularly illustrated in Figure 2 and discussed herein.

As noted, crossover is accomplished within a minor arcuate part of one complete revolution of the reel, for example, in approximately 30 of arc (for, e.g., 2" O.D.

nominal pipe). This is done by substantially increasing the level winder speed through the crossover region; for example, during this approximately 30 arcuate movement of the reel, the level winder speed is increased approximately 10 to 12 times faster than during the remaining 330" of rotation of the reel. Thus, if the reel rotates at a predetermined rotational speed of "X" rpm (revolutions per minute) when spooling a given wrap of pipe, the level winder 40 will be operated at a given speed "Y" fpm in direction A in Figures 2 and 3 for approximately 330" of rotational movement of the reel 20 at said given speed X. During the above-discussed crossover period for alternate, even-numbered wraps in order to effect such crossover, the translational speed of level winder 40 is increased in the opposite direction B to approximately 10Y to 12Y while maintaining reel speed X; for odd-numbered wraps, a similar increase in translational speed is accomplished in the direction A. Upon completion of such crossover after about 30 of rotationa, the level winder speed is again reduced to speed Y in direction A for the next 330" of rotational motion of the reel at reel speed X. (The above discussion of arc lengths is subject to factors noted above, including, in particular, pipe diameter.) The above-discussed pipe spooling system is also preferably operated in accordance with the following factors: 1. Y = (d+s)X, wherein: Y = base translational speed, in feet per minute ("fpm") of the level winder 40 in direction of axis RA of reel 20.

d= the outside diameter ("O.D.") of the pipe being spooled on the reel, in feet; s= the space between adjacent "turns" of the pipe, in feet; and X = the angular rotational rate of the reel 20 in revolutions per minute ("rpm").

2. Z = (3600/Ar) Y, wherein: Z = the translational speed in fpm of the level winder 40 during and for effecting the described crossover of the pipe; and Arc = crossover arc of the reel (i.e., the angle of rotational displacement of the reel during accomplishing the described crossover).

3. For spooling on pipe, the velocity of the pipe in relation to the deck and peripherally with respect to the hub 20b of reel 20 (called "VP") is typically up to about 6,000 feet per hour (fph).

4. For reeling pipe off reel 20 and laying same, said pipe velocity "VP" is up to about 15,000 fph.

As noted above, the method and apparatus of this invention resides in spooling pipe onto a reel in such a way that each succeeding wrap has the same helix, so that adjacent turns of succeeding wraps are arranged to lie in the interstices between adjacent turns of the preceding wraps. This is accomplished by the crossover arrangement described above. In the crossover region 26, the bulk of the forces acting between, for example, turns 22a and 21b are substantially concentrated at a single point of tangency between the surfaces of the pipe turns 22a and 21b. This point of tangency is on a radius common to the sections of turns 22a and 21b in crossover region 26 defined by the intersection of planes perpendicular to the respective longitudinal axes of turns 22a and 21b. It is at this point that the greatest possibility of damage to the pipe and/or coating can occur.

By maintaining proper tension on the pipe during the spooling process, especially during crossover, the bulk of potential problems which can occur to the pipe and/or coating can be substantially avoided. For disclosure of an example of a suitable tensioner arrangement, see abovementioned U.S. Patent No. 3,680,342.

A key point, however, is that the potential problem area is restricted to a very small region of each individual pipe turn, as illustrated at 26 in Figure 2; by proper pipe handling techniques, according to the disclosure herein, damage to the pipe and/or coating can be substantially avoided or minimized, thereby achieving many advantages discussed above.

While a specific embodiment of the invention has been shown and described in detail, it will be understood that modifications may be effected without departing from the scope of the invention as defined in the

Claims (15)

claims. WHAT WE CLAIM IS:

1. A method of spooling pipe on a reel, primarily for use in off-shore pipe laying systems, comprising the steps of: securing one end of a substantially continuous pipe line to said reel; maintaining the pipe under tension while rotating said reel at a relatively constant rotational speed X to spool said pipe thereon; and translating said pipe across said reel at speed Y while said reel is rotating at speed X for a major part of one complete revolution of the reel and at a speed substantially greater than Y for a minor part of one complete revolution of the reel to thereby wind pipe onto the reel in a helical pattern such that each succeeding wrap of pipe on the reel has substantially the same helical pattern as each preceding wrap, and wherein adjacent turns of the succeeding wrap cross over corresponding adjacent turns of the preceding wrap within an arcuate region substantially corresponding to the minor part of one complete revolution of the reel.

2. A method according to claim 1, further comprising increasing the translational speed of the pipe across the reel to 10Y to 12Y during the minor part of one complete revolution of the reel while maintaining the rotational speed of the reel at said speed X.

3. A method according to claim 1, wherein the translational speed Y of the level winder during said major part of one complete revolution of the reel is aproximately equal to (d+s)X, where d = outside diameter of pipe being spooled on the reel, in feet, s = space between adjacent turns of pipe, in feet, X = angular rotational rate of the reel in revolutions per minute.

4. A method according to any one of claims 1 to 3, further comprising reversing the translational direction of level winder movement during said minor part of said one complete revolution when winding even-numbered wraps of pipe on the reel.

5. A method according to claim 4, wherein the translational speed Z of the level winder during crossover is approximately equal to (360"/Arc,)Y, where Arc = crossover arc of the reel.

6. A method according to any one of claims 1-5, wherein the minor part of one complete revolution of the reel covers an arcuate distance of between 30 and 100" and the major part of one complete revolution covers an arcuate distance of between 330" and 260".

7. For use in conjunction with offshore pipeline laying, apparatus comprising a pipe spooling reel and pipe conditioning means mounted to a surface carrier vessel, said pipe conditioning means including a combination pipe straightener and level winder, a method of spooling pipe onto the reel comprising the steps of: passing a continuous pipeline of discrete length through said pipe conditioning means and securing one end of said pipeline to the hub of the reel; thereafter maintaining the pipe under tension while rotating the reel about its rotational axis at a substantially constant rotational speed X to spool said pipe thereon, at the same time translating said level winder across the reel in a given direction substantially parallel to the rotational axis of the reel at a relatively constant speed Y to thereby spool a first wrap of pipe onto the reel in a helical pattern, the relationship of speeds X and Y being such that each turn of pipe in the first wrap lies substantially adjacent to each preceding turn and thereafter winding a second wr lp of pipe onto the reel by: translating the level winder in ;aid given direction at said speed Y while said reel rotates at said speed X for a major part of one complete revolution of the reel; reversing the direction of translation of the level winder and at the same time increasing the speed of the level winder to a speed substantially greater than said speed Y for a minor part of one complete revolution of the reel to thereby cross the pipe of the second wrap over the pipe of the first wrap; and thereafter restoring the direction of translation of the level winder to the given direction while reducing the level winder speed to Y to thereby spool the next turn of pipe of the second wrap on and between adjacent turns of the first wrap, whereby the spooling pattern of the second wrap is substantially helical and in the same direction as the helical pattern of the first wrap.

8. A method according to claim 7, further comprising increasing the translational speed of the pipe across the reel to 10Y to 12Y during the minor part of one complete revolution of the reel.

9. A method according to claim 7 or 8, wherein the minor part of one complete revolution of the reel covers an arcuate distance of between 30 and 100" and the major part of one complete revolution covers an arcuate distance of between 330" and 260".

10. For use with an offshore pipelaying apparatus comprising a pipe spooling reel and pipe conditioning apparatus mounted to a surface carrier vessel, said pipe conditioning apparatus including a level winder, wherein pipe passes through the level winder before being spooled onto the reel, a method of spooling the pipe onto the reel, comprising the steps of: maintaining the pipe under tension while rotating the reel about its rotational axis at a substantially constant rotational speed X and while spooling pipe onto the reel; translating the level winder across the reel in a first direction substantially parallel to the rotational axis of the reel at a relatively constant speed Y while said reel is rotating at said speed X through a major portion of one complete revolution of the reel; thereafter reversing the translational direction of the level winder and substantially increasing the translation speed Y of the level winder for a minor portion of said one complete revolution of the reel to thereby cross the end of the turn of pipe currently being spooled over a turn of pipe of the immediately preceding spooled wrap; and thereafter restoring said level winder translation direction and reducing the level winder speed to substantially speed Y to thereby spool the next turn of pipe over and between adjacent turns of the immediately preceding spooled wrap, whereby the spooling pattern of each wrap is substantially helical and in the same direction.

11. The method according to claim 10, wherein the translation speed of the level winder is increased to between 10Y to 12Y during said minor portion of one complete revolution of the reel, while maintaining the rotational speed of the reel at said speed X.

12. The method according to claim 10 or 11, wherein the level winder traverses the reel at speed Y during a period of arcuate travel of the reel of between 260 and 330" and the level winder thereafter traverses the reel at said increased speed during a period of between 100" and 30 of arcuate travel of the reel.

13. A method of spooling pipe onto a reel, primarily for use in offshore pipelaying systems, comprising: (a) securing one end of a substantially continuous pipeline to said reel; (b) mantaining the pipe under tension while rotating said reel to spool said pipe thereon.

(c) translating said pipe across the reel while spooling pipe onto the reel at a first given ratio of translation speed to spooling speed (V1) for a major part of each revolution of the reel; (d) translating said pipe across the reel while spooling pipe onto the reel at a second given ratio of translation speed to spooling speed (V2), (where V2 > V1) for a minor part of each revolution of the reel so that each turn of a given wrap crosses over a corresponding turn of the immediately preceding wrap and seats in the interstice between adjacent successive turns of the immediately preceding wrap; and (e) alternately repeating steps (c) and (d) so that succeeding turns of said given wrap are seated in succeeding interstices of said one wrap across substantially the full width of the hub to complete said given wrap with substantially the same helical pattern as said one wrap.

14. A method of spooling pipe on a reel, primarily for use in offshore pipelaying systems, comprising the steps of: (a) securing one end of substantially continuous pipeline to said reel; (b) maintaining the pipe under tension while rotating said reel to spool said pipe thereon; (c) translating said pipe across said reel hub in one direction at a first translation rate (Y) while spooling pipe onto the reel at a given rotational rate (X) for at least a major part of each revolution of the reel to complete one wrap of pipe on the reel; (d) bringing the pipe up and over the last turn of said one wrap to begin the first turn of the next wrap in the space between the adjacent end flange and said last turn of said one wrap; (e) translating said pipe across said reel in the opposite direction at a second translation rate (Yl) while spooling pipe onto the reel at said given rotational rate (X) for a minor part of each revolution of the reel so that the pipe crosses the last turn of the one wrap at the interstice between the last and penultimate turns of said one wrap.

(f) thereafter translating said pipe in said first direction at substantially said translation rate Y and rotational rate X for a major part of each revolution of the reel so that the second turn of said next wrap is seated in said interstice; and (g) alternately repeating steps (e) and (f) so that succeeding turns of said next wrap are seated in succeeding interstices of said one wrap across the full width of the hub to complete said next wrap with substantially the same helical pattern as said one wrap.

15. A method of spooling pipe on a reel, primarily for use in offshore pipe laying systems, substantially as hereinbefore described with reference to the accompanying drawings.