CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable 
     REFERENCE TO A “MICROFICHE APPENDIX” 
     Not applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the placement of pipelines in a marine environment. More particularly, the present invention relates to an improved method and apparatus for laying a pipeline in a marine environment, wherein a specially configured pipeline laying ship provides a hull with a deck having a pair of reels independently rotatable during use, and wherein a pipeline fabricating “firing line” fabricates a pipeline that is then wound upon one of the selected reels. The pipeline “firing line” can be moved laterally in order to align with either of the reels as selected. Additionally, the pipeline can be payed out from either of the selected reels after it has been fabricated. A tower is provided for directing the pipeline from the reel through bend control and straightening stations and then to the seabed. 
     2. General Background of the Invention 
     For many years, pipelines have been fabricated at sea and lowered to the seabed at a desired location. For example, early patents to Tesson include U.S. Pat. Nos. 3,237,438 and 3,337,469 that are directed to a pipeline laying barge and method of operation. In the Tesson patents, the joints of pipe are welded on deck and then spooled or wound upon a reel. At a desired location, the pipeline is then placed on the seabed by unwinding the pipe from the reel and straightening it before it is lowered to the seabed. 
     A tilting tower has also been used to lower a pipeline to the seabed as the pipeline is being unwound from a reel. An example of such a titling tower and reel pipeline laying arrangement can be seen in the Uyeda U.S. Pat. No. 4,345,855 as an example. A similar arrangement is seen in the Springett U.S. Pat. No. 4,340,322. The Uyeda U.S. Pat. No. 4,345,855 and the Springett U.S. Pat. No. 4,430,322 are hereby incorporated herein by reference. Another method of laying a pipeline is through the use of a stinger. A stinger is simply an elongated boom structure that extends from usually one end of a hull or barge. The stinger supports the pipeline as it is being lowered to the seabed. Examples of the use of stingers can be seen us U.S. Pat. Nos. RE28,922, RE29,591 and 5,533,834. 
     Reel type pipeline laying systems are typically employed in deep water situations. While it is known to weld the pipeline joints on the deck of a vessel and wind them upon a reel (for example, see the above discussed Tesson patents), it is also known to weld the pipeline on shore and then wind it upon the reel before the ship leaves port. 
     The following table provides an exemplary listing of patents that are known to applicant and that relate to pipeline laying vessels and methods of operation: 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 MARINE PIPE LAYING PATENTS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 PAT. NO. 
                 TITLE 
                 INVENTOR 
               
               
                 3,237,438 
                 Pipe Line Laying Barge 
                 Tesson 
               
               
                 3,372,461 
                 Method of Laying Pipeline 
                 Tesson 
               
               
                 Re.28,922 
                 Column Stabilized Stinger 
                 Lloyd, III 
               
               
                 3,982,402 
                 Submarine Pipeline Laying Vessel 
                 Lang et al. 
               
               
                 Re.29,591 
                 Column Stabilized Stinger Transition 
                 Lloyd 
               
               
                   
                 Segment And Pipeline Supporting 
               
               
                   
                 Apparatus 
               
               
                 4,112,695 
                 Sea Sled For Entrenching Pipe 
                 Chang et al. 
               
               
                 4,165,571 
                 Sea Sled With Jet Pump For Under- 
                 Chang et al. 
               
               
                   
                 water Trenching And Slurry Removal 
               
               
                 4,218,158 
                 Pipe Handling Method And Apparatus 
                 Tesson 
               
               
                 4,230,421 
                 Self Propelled Dynamically Positioned 
                 Springett 
               
               
                   
                 Reel Pipe Laying Ship 
                 et al. 
               
               
                 4,260,287 
                 Portable Reel Pipelaying Method 
                 Uyeda et al. 
               
               
                 4,268,190 
                 Pipe Handling Method And Apparatus 
                 Tesson 
               
               
                 4,269,540 
                 Self Propelled Dynamically Positioned 
                 Uyeda et al. 
               
               
                   
                 Reel Pipe Laying Ship 
               
               
                 4,297,054 
                 Method of Laying Offshore Pipeline 
                 Yenzer et al. 
               
               
                   
                 From a Reel Carrying Vessel 
               
               
                 30,846 
                 Submarine Pipeline Laying Vessel 
                 Lang et al. 
               
               
                 4,340,322 
                 Self Propelled Dynamically Positioned 
                 Springett 
               
               
                   
                 Reel Pipe Laying Ship 
                 et al. 
               
               
                 4,345,855 
                 Self Propelled Dynamically Positioned 
                 Uyeda et al. 
               
               
                   
                 Reel Pipe Laying Ship 
               
               
                 4,486,123 
                 Underwater Pipe Laying Vessel 
                 Koch et al. 
               
               
                 4,687,376 
                 Multi-Reel Operational Lines Laying 
                 Recalde 
               
               
                   
                 Vessel 
               
               
                 4,721,411 
                 Multi-Reel Operational Lines Laying 
                 Recalde 
               
               
                   
                 Vessel 
               
               
                 4,723,874 
                 Multi-Reel Operational Lines Laying 
                 Recalde 
               
               
                   
                 Vessel 
               
               
                 4,765,776 
                 Convertible Barge 
                 Howson 
               
               
                 4,789,108 
                 Multi-Reel Operational Lines Laying 
                 Recalde 
               
               
                   
                 Vessel 
               
               
                 4,820,082 
                 Pipeline Laying System And Vessel 
                 Recalde 
               
               
                 4,917,540 
                 Pipeline Laying System And Vessel 
                 Recalde 
               
               
                   
                 With Pipeline Straightening And 
               
               
                   
                 Tensioning Device 
               
               
                 4,961,671 
                 Method of Converting a Pipeline Laying 
                 Recalde 
               
               
                   
                 Vessel From a Pivotal Ramp Type 
               
               
                   
                 To An Arcuate Type 
               
               
                 4,984,934 
                 Pipeline Laying System And Vessel 
                 Recalde 
               
               
                   
                 And Method of Spooling Lines 
               
               
                   
                 Onto The Vessel 
               
               
                 5,044,825 
                 Method And Installation For Laying 
                 Kaldenbach 
               
               
                   
                 a Pipeline 
               
               
                 5,413,434 
                 Method And Installation For Laying 
                 Stenfert 
               
               
                   
                 a Pipeline 
                 et al. 
               
               
                 5,527,134 
                 Pipelaying Vessel 
                 Recalde 
               
               
                 5,533,834 
                 Pipelay Stinger 
                 Recalde 
               
               
                 5,836,719 
                 Pipe Laying Vessel and Method 
                 Martin et al. 
               
               
                 5,971,666 
                 Pipe Laying Vessel 
                 Martin et al. 
               
               
                 5,975,802 
                 Pipeline Laying Apparatus 
                 Willis 
               
               
                 6,004,071 
                 Methods of Installing Elongate 
                 Broeder 
               
               
                   
                 Underwater Structures 
                 et al. 
               
               
                 PATENT 
                 TITLE 
                 ISSUED 
               
               
                 WO9525238A1 
                 Pipe Laying Vessel and Method 
                 Sept. 21, 1995 
               
               
                 WO9525237A1 
                 Pipe Laying Vessel and Method 
                 Sept. 21, 1995 
               
               
                 AU1898395A1 
                 Pipe Laying Vessel and Method 
                 Oct. 03, 1995 
               
               
                 AU1898295A1 
                 Pipe Laying Vessel and Method 
                 Oct. 03, 1995 
               
               
                 AU4088796A1 
                 Pipeline Laying 
                 Jul. 25, 1996 
               
               
                 AU676431B2 
                 Pipe Laying Vessel and Method 
                 Mar. 06, 1997 
               
               
                 AU681014B2 
                 Pipe Laying Vessel and Method 
                 Aug. 14, 1997 
               
               
                 AU696337B2 
                 Pipeline Laying 
                 Sept. 10, 1998 
               
               
                 BR9507088A 
                 Processo Para Assentar Uma 
                 Sept. 16, 1997 
               
               
                   
                 Tubulacao Submarina E Embarcacao 
               
               
                   
                 Para Ser Utilizada No 
               
               
                   
                 Assentamento De Uma Tubulacao 
               
               
                   
                 Submarina 
               
               
                 BR9507064A 
                 Processo Para Assentar Uma 
                 Oct. 14, 1997 
               
               
                   
                 Tabulacao Submarina E Embarcacao 
               
               
                   
                 Para Ser Utilizada No 
               
               
                   
                 AssentamentoDe Uma Tubulacao 
               
               
                   
                 Submarina 
               
               
                 BR9600055A 
                 Sistema De Colocacao De Tubos 
                 Jan. 21, 1998 
               
               
                   
                 Navio Conduzindo Um Sistema De 
               
               
                   
                 Colocacao De Tubos E Processo 
               
               
                   
                 Colocacao De Uma Tubulacao 
               
               
                   
                 De Um Navio 
               
               
                 GB2287518B 
                 Pipe Laying Vessel and Method 
                 Mar. 12, 1997 
               
               
                 GB2287518A 
                 Pipe Laying 
                 Sept. 20, 1995 
               
               
                 GB2296956B2 
                   
                 Mar. 10, 1999 
               
               
                 GB2296956B 
                 Pipeline 
                 Mar. 10, 1999 
               
               
                 GB2296956A1 
                   
                 Jul. 17, 1996 
               
               
                 GB2296956A 
                 Pipeline Laying with Bending 
                 Jul. 17, 1996 
               
               
                   
                 and Straightening 
               
               
                 GB2302157B 
                 Pipe Laying Vessel and Method 
                 Nov. 12, 1997 
               
               
                 GB2302157A 
                 Pipe Laying Vessel and Method 
                 Jan. 08, 1997 
               
               
                 GB9411702A0 
                   
                 Aug. 03, 1994 
               
               
                 GB9500664A0 
                   
                 Mar. 8, 1995 
               
               
                 GB9505344A 
                 Pipe Laying Vessel and Method 
                 May 03, 1995 
               
               
                 GB9600005A0 
                   
                 Mar. 06, 1996 
               
               
                 GB9600005A 
                 Pipeline Laying 
                 Mar. 06, 1996 
               
               
                 GB9619167A 
                 Pipe Laying Vessel and Method 
                 Oct. 23, 1996 
               
               
                 NO960135A0 
                 Roerlednings-leggesystem 
                 Jan. 11, 1996 
               
               
                 NO960135A 
                 Roerlednings-leggesystem 
                 Jul. 15, 1996 
               
               
                 NO963858A0 
                 Roerleggingsfartoey Og 
                 Sept. 13, 1996 
               
               
                   
                 Fremgangsmaate 
               
               
                 NO963858A 
                 Roerleggingsfartoey Og 
                 Nov. 11, 1996 
               
               
                   
                 Fremgangsmaate 
               
               
                 NO963857A0 
                 Roerleggingsfartoey Og 
                 Sept. 13, 1996 
               
               
                   
                 Fremgangsmaate 
               
               
                 NO963857A 
                 Roerleggingsfartoey Og 
                 Nov. 11, 1996 
               
               
                   
                 Fremgangsmaate 
               
               
                   
               
             
          
         
       
     
     GENERAL DISCUSSION OF THE PRESENT INVENTION 
     The present invention provides an improved pipeline laying vessel and its method of operation. The method employs a dynamically positioned barge or self-propelled dynamically positioned reel ship that has two independently rotatable reels or drums. The ship has a deck area that enables pipe joints to be welded together to form a pipeline. Joints of pipe are placed in a storage area on the deck of a vessel in suitable pipe racks. Welding stations near this storage area are arranged to receive multiple joints of pipe that have been internally cleaned and prepared for welding. Part of this preparation can include for example end bevels that are applied to the pipeline. 
     As pipeline fabrication proceeds, pipe joints are moved from the rack storage areas to the pipeline fabrication area, also referred to herein as the “firing line.” 
     This fabrication area or “firing line” can comprise essentially a set of rollers supporting the pipeline along the center line of the fabrication area. Welding equipment (manual or automatic) can be provided together with known weld preparation tools. 
     The incoming pipe joints are aligned with the pipeline being fabricated. The welded area between the pipe joints and the joints previously welded together can be adjusted as required. The pipe joints are progressively welded together to form a pipeline at multiple welding stations. The welds are tested and field joints are then coated at another work station located in the pipeline fabrication area. 
     When one or more joints of pipe have been welded together end-to-end on the firing line, a selected reel or drum is readied for storage of the assembled pipeline on provided reels or drums. In keeping with the present invention, two (2) reels or drums are provided. A selected length (eg. about forty feet) of pipeline is advanced at any time and wound upon the reel by plastic bending. The pipeline moves ahead in the pipeline fabrication area by the same distance (eg. 40 feet increments) through a back tensioning device. 
     The pipeline welding progresses until the selected drum or reel is filled with the pipeline that is being welded on the deck of the vessel. Each reel or drum can be between 30 and 50 feet in diameter, have a width of between about 10-20 feet, and store, eg. 30,000-50,000 feet of six inch pipe. 
     In order to arrange properly the pipeline on the selected reel drum during spooling, the firing line travels from one side of the ship to the other side in a coordinated back and forth direction to spool each wrap of the pipeline next to the previous wrap on the reel. 
     The firing line also travels from one side of the ship to the other side if it is to align with the second drum, so that the pipeline fabricated on the ship deck can be spooled on either one of the reels. In other words, the pipeline “firing line” moves laterally as it is being spooled upon a first reel. However, the entire firing line travels transversely on the ship&#39;s deck a larger distance in order to align with the second reel when the second reel is to be filled with pipeline. 
     When the ship undertakes pipe laying on the sea bottom, the pipeline that is stored on a selected reel leaves the drum in a direction tracking toward the top of the tilting tower. The titling tower can tilt in a position that varies such as for example between about 65 and 95 degrees from the deck plane. At the top of the tower, the pipeline bends through a bend controller downwardly toward the seabed. The tilting tower can also be provided with a device for straightening the pipeline, a tensioning device and a clamping device that can hold the pipeline and support the weight of the pipeline that extends downwardly toward the seabed. 
     It should be understood that the general concept of paying a wound pipeline from a reel to a tilting tower that has a bend controller, straightener, tensioner, and clamp mechanism is old and known in the art such as is shown in the above discussed Springett U.S. Pat. No. 4,340,322 and Uyeda U.S. Pat. No. 4,345,855 patents, each incorporated herein by reference. 
     With the improved arrangement of the present invention, the firing line and tower both move transversely in port to starboard and in starboard to port for two reasons. The firing line and tower move transversely in order to coordinate with the reel rotation, thus spooling the welded pipeline upon the reel or removing pipeline from the reel in an orderly fashion. Secondly, the firing line and tilting tower move transversely in order to align with either the first or the second drum as selected by the vessel operators. This larger transverse movement occurs when winding of the pipeline on the first reel is complete, and the winding of the pipeline on the second reel begins. 
     When leaving the bend controller, the pipeline passes through a straightening device that imposes a reversed plastic bending on the pipeline in order to straighten it. The straightened pipeline then passes through a vertical tensioner. The combined tension imposed on the pipeline by the tensioner and the drum back tension compensates for the suspended weight of the pipeline during its travel from the ship to the sea bottom. This tension is adjusted depending on the various pipe laying parameters such as pipeline characteristics (eg. diameter, wall thickness, coating, alloy, wet or dry lay) and water depth during lay operations. The proper tilting of the tower and the coordination of the tension with the ship as it moves along the pipeline route ensure that the stresses in the pipeline are maintained within predetermined predefined acceptable limits. 
     The area in between the last tensioner and the clamping mechanism or “hold off” clamp can be used to support the pipeline and install corrosion anodes and insulation coating when required on the pipeline joints that are welded in the pipeline fabrication area or “firing line,” or in the tower itself. A work station can be used to initiate the pipeline, lay down, and testing devices at the beginning and the end of the pipeline lay operations from either of the two reels. 
     The pipeline eventually leaves the ship after passing through the hold off clamp that has the ability to hold the pipeline suspended weight during lay down operations. 
     For pipelines that cannot be coiled on the reel drums, the tilting tower can be arranged to weld linepipe joints at one work station and to perform nondestructive testing and field joint coating at another work station. 
     The tension required to hold the weight of the suspended part of the pipeline being laid is being provided by the tensioner located on the tilting ramp and, when required, by the tension from an A &amp; R (abandonment and recovery) winch wire. This wire can be routed to the top end of the pipeline through a sheave located on top of the tower. In this case, collars are welded to the linepipe and are used to transfer the A &amp; R winch rope tension to the pipeline. 
     When an umbilical or flexible line installation is required, the ship can load this product in either a large capacity rotating basket located, for example, below deck, or on several smaller reels located on the ship deck, depending on the number of products, product length, and pipe characteristic, or on one or both of the main reels. 
     Such products can be laid on the sea bottom independently or simultaneously with the pipeline and attached as a “piggyback” to the pipeline in the work station located in the tower. The product can be conveyed out of the storage areas to a position next and parallel to the pipeline in the tower by a second bend controller. 
     When a smaller diameter pipeline is to be laid (for example 2 inch-6 inch) with the main pipeline and as a piggyback to the main pipeline, this smaller pipeline is preferably fabricated on shore and stored on reels located on the ship&#39;s deck. This smaller pipeline is conducted to the same position described above for umbilicals and flexible lines in the tower or work station. In this case, the small diameter pipeline is plastically bent and is straightened by another straightening device installed next to the one used for the main pipeline. 
     The present invention thus provides a method and apparatus for laying rigid pipelines, such as for example between 3 and 12 inches in diameter, on a sea bed and to lay, simultaneously or in sequence, long lengths of flexible products (umbilicals) and simultaneously limited lengths of small diameter (between about 2 inches and 6 inches) rigid pipelines. The system of the present invention thus provides a dynamically positioned ship of adequate length, width and depth. 
     The ship provides a deck that has multiple areas for storing pipeline lengths (linepipe or pipe joints). The deck provides an area for fabricating the pipeline from line pipe (firing line). A pair of storage reels are provided, preferably port and starboard reels. These reels or drums are powered separately from each other. Each drum or reel provides a back tension of, for example about 50 Te on the pipeline when it is used for pipe laying. 
     An area below deck can be provided to locate flexible products storage including for example a rotating basket. 
     An area on the deck is provided to locate multiple storage reels and their drives. 
     An opening on the deck is provided to load and unload flexible products into the below deck rotating basket. 
     An opening can be provided in the ship&#39;s hull (moon pool) located, for example, approximately amidship. 
     A tilting tower is provided that preferably tilts between about 65 and 90 degrees from the deck plane. 
     A pipeline hold off clamp is located at the bottom end of the tilting tower. A retractable enclosure can be located at the middle part of the tilting tower to protect a provided work area. 
     Multiple pipeline tensioning devices can be provided, one located on the ship deck and one or two located vertically on the upper part of the tilting tower. 
     A device can be provided for straightening the pipeline during laying. A pipeline guiding device can be provided to conduct the pipeline from the reel that is used for pipe laying to the bend controller and straightener located on the tower. 
     A flexible product and small diameter rigid pipeline guiding device can be provided for conducting such products from their storage area on or below deck to the entry of the straightener. 
     Multiple work stations, such as welding stations can be provided on the tower. 
     A winch can be located below deck for lowering the pipeline to the sea floor when pipe laying is completed. 
     Multiple retractable sheaves can be used in conjunction with the winch. 
     The present invention thus provides an improved pipeline laying ship and its method of operation. The improved reel ship apparatus of the present invention includes a dynamically positioned barge or self-propelled dynamically positioned ship having a deck. A pair of reels or drums are supported upon the deck, each reel or drum being powered and independently rotatable. The reels are preferably positioned port and starboard relative to one another. 
     A pipe joint storage area is provided on the deck that contains multiple joints of pipe. 
     One or more pipeline welding stations on the deck define a “firing line” that is positioned next to the reels. The pipeline welding stations are also positioned to join the joints of pipe together to form an elongated pipeline that can be wound upon a selected reel of said pair of reels. 
     After a selected reel has been filled with a pipeline, a tower is provided for guiding the elongated pipeline as it is unwound from the selected reel during the pipeline laying operation. The tower can include a bend controller, a straightener, a tensioner and a clamp mechanism. 
     The welding stations and tower are movably mounted upon the hull along a transverse path between port and starboard positions. This enables a pipeline to be welded and then wound upon either of the reels. Later, the pipeline can be unwound from either of the reels for launching to the sea bed via the tower. 
     The reels are preferably each supported to rotate about a generally horizontal axis. 
     The reels are preferably positioned generally parallel to one another and generally in between the pipeline welding stations on deck and the tower. 
     The present invention provides an improved method of laying a pipeline on a sea bed. The method first progressively joins joints of pipe (eg. 40 foot joints) together upon the deck of a vessel at a firing line to form a long pipeline. The vessel includes a pair of reels and a tower for launching the pipeline. The method includes winding the pipeline upon a selected reel of the pair of reels as the lengths pipe are joined (eg. welded) together at the firing line. 
     The method further includes the step of bending the pipeline to approximate the curvature of a reel before winding the pipeline upon the selected reel. With the present invention, one reel can be paying out a completed pipeline for placement on the seabed while the other reel is simultaneously being wound with a pipeline as it is being fabricated at the firing line. Two or more pipelines can be fabricated, reeled and then unwound for placement, and, if desired, joined together to make one very long pipeline. 
     After a selected reel is fully wound with a pipeline of selected length, the selected reel is moved along a path in which the pipeline is to be layed while unwinding the pipeline from the reel and simultaneously straightening the pipeline. 
     The method of the present invention provides that the reels are independently rotatable so that either reel can be wound with a pipeline independently of the other. 
     The method further includes the step of moving the firing line in a port to starboard direction that aligns the pipeline as it is being formed with a selected reel. 
     The method of the present invention also includes moving the tower in a port to starboard direction that aligns the tower with a selected reel during unwinding. 
     The reels preferably rotate about a generally horizontal axis and the method can further include the step of passing the straightened pipeline through a tensioner. 
     In the method of the present invention, the combined tension imposed on the pipeline by the tensioners and a drum back tension compensate for the suspended weight of the pipeline during its travel from the hull to the sea bed. 
     The method of the present invention further comprises the step of adjusting the tension on the pipeline depending upon pipeline laying parameters that include pipeline characteristics and water depth during pipe laying operation. 
     The method further includes providing a tower to guide the pipeline from a selected reel to the sea bed. The method further comprises the step of coordinating the tension applied by the tensioner as the ship moves along the pipeline route to insure that the stresses in the pipeline are maintained with an acceptable limit. 
     The method of the present invention further includes the step of using a hold off clamp to support the pipeline so that corrosion anodes and insulation coating can be applied thereto. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein: 
     FIG. 1 is an elevation view showing the preferred embodiment of the apparatus of the present invention and illustrating the method of the present invention; 
     FIG. 1A is another elevation of the preferred embodiment of the apparatus of the present invention showing the tower in a tilted orientation; 
     FIG. 2 is a plan view of the preferred embodiment of the apparatus of the present invention and showing the method of the present invention; 
     FIG. 3 is a fragmentary perspective view of the preferred embodiment of the apparatus of the present invention and illustrating the method of the present invention; 
     FIG. 4 is a fragmentary perspective view of the preferred embodiment of the apparatus of the present invention illustrating the method of the present invention; 
     FIG. 5 is a fragmentary view of the preferred embodiment of the apparatus of the present invention and illustrating the method of the present invention; 
     FIG. 6 is an enlarged fragmentary, plan view of the preferred embodiment of the apparatus of the present invention and illustrating the method of the present invention and illustrating the method of the present invention; 
     FIG. 7 is an elevation view showing an alternate embodiment of the apparatus of the present invention and illustrating an alternate method of the present invention; and 
     FIG. 8 is a plan view of the alternate embodiment of the apparatus of the present invention and illustrating the alternate method of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The attached drawing FIGS. 1 and 2 show a reel-type dynamically positioned barge or self-propelled dynamically positioned pipeline laying ship  10  that includes a hull  11  having bow  12  and stern  13  portions. A deck  14  supports a superstructure  15  that can include for example, accommodations for the crew, sleeping quarters, a galley, hospital, heliport, and the like. As pipeline fabrication proceeds, pipe joints are moved one by one from pipe rack storage areas  27 ,  28 ,  29  to the pipeline fabrication area, also referred to as the firing line  30 . 
     This fabrication area or “firing line”  30  can comprise essentially a set of rollers supporting the pipeline  20  along the center line of the fabrication area  30 . Welding equipment (manual or automatic) can be provided together with known weld preparation tools. The firing line  30  can be comprised of one or more welding stations. 
     Firing line  30  is an area of the deck that is a designated area for welding sections of pipe together to form a pipeline  20  that will be reeled upon a selected one of the drums or reels  16  or  17 . These drums or reels  16  and  17  are preferably independently driven and independently rotatable. 
     Incoming pipe joints are aligned with the pipeline being fabricated. The welded area between the pipe joints and the joints previously welded together can be adjusted as required. The pipe joints are progressively welded together at multiple welding stations to form a pipeline  20 . 
     In the stern area of the deck  14 , a plurality of pipe storage racks  27 ,  28 ,  29  can be provided such as those shown in FIG.  2 . Welding stations WS- 1 , WS- 2 , and WS- 3  are positioned near these storage areas  27 ,  28 ,  29  and arranged to receive multiple joints of pipe that have been internally cleaned and prepared for welding. Part of this preparation can include, for example, end bevels that are applied to the pipeline. The welds are tested and field joints are then coated at another work station located in the pipeline fabrication area or firing line  30 . 
     A trapezoidal through hull opening or moon pool  18  is provided amidships through which the pipeline  20  can be launched for placement on the seabed. A tilting tower  19  is supported by the hull  11  next to the moon pool  18 , as shown in FIGS. 1 and 2. The moon pool  18  is preferably positioned in front of reels  16 ,  17  and behind the tilting tower  19 . However, an alternative deck plan could position the tower  19  at stern  13 . The reels  16 ,  17  could then be positioned near the stern  13  and in front of the tilting tower  19 . 
     The tilting tower  19  includes a number of components including a bend controller  21 , pipe straightener  22 , tensioner  23 , hold-off clamp  24 , and a pair of welding stations at  25 ,  26 . 
     The double arrows  31  in FIG. 2 indicate schematically that the firing line  30  can be selectively shifted between port and starboard positions along a traverse path. In this fashion, the pipeline  20  that is being welded upon the firing line  30  can be spooled upon either of the reels  16  or  17 . The firing line  30  moves to port or to starboard in order to align with the selected reel  16  or  17 . 
     A bending shoe  33  and tensioner  34  can be used to bend and tension the pipeline after it is welded and as it is being spooled upon a selected one of the drums  16  or  17 . Each of these components (shoe  33  and tensioner  34 ) preferably move between port and starboard positions as indicated by arrows  31 . As welding is completed, a selected reel  16  or  17  is readied for storage. In keeping with the present invention, two (2) reels or drums  16 ,  17  are provided. About 40 feet of pipeline is advanced and wound upon the selected reel by plastic bending. The pipeline  20  moves ahead in the pipeline fabrication area by the same distance (eg. forty feet increments) through a back tensioning device. 
     When the ship  10  undertakes pipe laying on the sea bottom  35 , the pipeline  20  that is stored on a selected drum  16  or  17  leaves the drum  16  or  17  in a direction tracking toward the top of tilting tower  19 . At the top of the tower  19 , the pipeline  20  bends through a bend controller  21  downwardly toward the seabed  35 . The tilting tower  19  can be provided with bend controller device  21  for bending the pipeline, a straightener  22  for straightening the pipeline, a tensioner  23  and a clamping device  24  that can hold the pipeline  20  and support the weight of the pipeline  20  that extends downwardly toward the seabed  35 . When it is time to lay the pipeline  20 , the tilting tower  19  can move between port and starboard positions as indicated schematically by the double arrow  32  in FIG.  2 . The tilting tower  19  can align with a selected drum such as with the drum  17  in FIG. 2 as shown. The tilting tower  19  can tilt in a position that varies such as, for example, between about 65 and 90 degrees from deck plane  36 . 
     With the improved arrangement of the present invention, the firing line  30  and tower  19  both move transversely back and forth for two reasons. The firing line  30  and tower  19  move transversely in order to coordinate with the reel rotation, thus spooling the welded pipeline  20  upon the selected reel in an orderly fashion. Secondly, the firing line  30  and tilting tower  19  move transversely in order to align with either the first  16  or the second  17  reel as selected by the vessel operators. This larger transverse movement occurs when winding of the pipeline  29  one the first reel  16  is complete, and the winding of the pipeline on the second reel  17  begins. 
     When leaving the bend controller  21 , the pipeline  20  passes through straightening device  22  that imposes a reversed plastic bending on the pipeline  20  in order to straighten it. The straightened pipeline  20  then passes through vertical tensioner  23 . The reel back tension compensates for the suspended weight of the pipeline  20  during its travel from the ship hull  11  to the sea bottom  35 . This tension is adjusted depending on the various pipe laying parameters such as pipeline characteristics and water depth during lay operations. The proper tilting of the tower  19  and the coordination of the tension as the hull  11  moves along the pipeline route ensure that the stresses in the pipeline  20  are maintained within a predetermined, predefined acceptable limits. Hydraulic cylinder  37  can be used to tilt tower  19  (see FIGS.  1  and  1 A). 
     The welding station  25  in between the last tensioner  23  and the clamping mechanism or “hold off” clamp  24  can be used to support the pipeline  20  and install corrosion and insulation coating when required on the pipeline joints that are welded in the pipeline fabrication area  30  or “firing line,” or in the tower  19  itself. A welding station  25  or  26  can be used to install pipeline initiation, lay down, and testing devices at the beginning and the end of the pipeline lay operations from either of the two reels  16 ,  17 . 
     The pipeline  20  eventually leaves the ship hull  11  after passing through the hold off clamp  24  that has the ability to hold the pipeline suspended weight during lay down operations. For pipelines  20  that cannot be coiled on the reel drums,  16 ,  17  the titling tower  19  can be arranged to weld pipeline joints at one welding station  25  and to perform nondestructive testing and field joint coating at another welding station  26 . 
     The tension required to hold the weight of the suspended part of the pipeline  20  being placed is being provided by the tensioner  23  located on the tilting tower. Assistance can be provided by the tension from an A &amp; R winch wire to support the suspended weight of the pipeline  20 . A winch wire can be routed to the top end of the pipeline  20  through a sheave located on top of the tower  19 . In this case, collars are welded to the pipeline  20  and are used to transfer the A &amp; R winch rope tension to the pipeline  20 . 
     When an umbilical or flexible line installation is required, the ship  10  can load this product in either a large capacity rotating basket located for example below deck, or on one or both of the main reels  16 ,  17 , or on several smaller reels located on the ship deck  14 , depending on the number of products, product length and characteristics. 
     Such products can be placed to the sea bottom independently or simultaneously with the pipeline and attached as a “piggyback” to the pipeline in the work station located in the tower and the work station. The product is conducted out of the storage areas to a position next and parallel to the pipeline in the tower by a second bend controller. 
     When smaller diameter pipeline is to be placed (for example, 2 inch-6 inch) with the pipeline as a piggyback to the pipeline his smaller pipeline is preferably fabricated on shore and stored on reels located on the ship&#39;s deck  14 . This pipeline is conducted to the same position described above for umbilicals and flexible lines in the tower or work station. In this case, the small diameter pipeline is plastically bent around the system and second conduit and is straightened by another straightening  30  device installed next to the one used for the main pipeline. 
     The present invention thus provides a method and apparatus for laying rigid pipelines, such as for example between 3 and inches in diameter, on a sea bed and to lay, simultaneously or in sequence, long lengths of flexible products (umbilicals) and simultaneously limited lengths of small diameter (between about 2 inches and 6 inches) rigid pipelines. When a smaller diameter pipeline is to be laid (for example 2 inch-6 inch) with the pipeline as a piggyback to the pipeline this smaller pipeline is preferably fabricated on shore and stored on reels located on the ship&#39;s deck. This pipeline is conducted to the same position described above for umbilicals and flexible lines in the tower or work station. In this case, the small diameter pipeline is plastically bent around the system and second conduit and is straightened by another straightening device installed next to the one used for the main pipeline. 
     One feature of the present invention is that one drum  16  can be loaded with a pipeline  20  as it is being welded together as a first operation independent of pipe laying. The other drum (previously loaded with a pipeline) can be rotated to pay out the pipeline  20  independently of the other drum, and route it through the tilting tower  19  and its components  22 ,  23 ,  24 ,  25 ,  26  to the moon pool  18  and then downwardly to lay upon the seabed. The invention has unique features that include the laterally traversing firing line and the two independently driven drums, either of which can, independently of and/or simultaneously with the other, receive a welded pipeline to be spooled, or pay out a spooled pipeline to be placed on the seabed  35 . 
     FIGS. 7 and 8 show an alternate embodiment of the apparatus of the present invention designated generally by the numeral  10 A. In FIGS. 7 and 8, reel pipeline lay barge  10 A has a hull  11  that is similarly configured to the embodiment of FIGS. 1-6. However, the lay barge  10 A of FIGS. 7 and 8 provides a different positioning for the port and starboard drums  16 , 17 , the moon pool  18 , and the tilting tower  19 . In FIGS. 7 and 8, the reels or drums  16 , 17  are closer to the bow  12  of the hull  11 . The tilting tower  19  is positioned immediately aft drums  16 , 17 . Moon pool  18  is positioned aft tilting tower  19 . The tilting tower  19  is thus positioned in between the moon pool  18  and the pair of drums or reels  16 , 17 . 
     The tower  19  can be tilted using boom  38 . Boom  38  can be connected to any suitable support  40  on hull  11  using, for example, a pinned connection  39 . 
     A traveling member  42  can be slidably affixed to boom  38 . The traveling member  42  can, for example, be one or more hydraulic cylinders that can be expanded or retracted during use. The boom  38  provides openings for  43  that are preferably regularly spaced along the length of the boom  38 . Pins can be provided at end portions of the hydraulic cylinders for engaging the openings  43 . The pins are preferably remotely operable using pneumatic or electrical controllers. In this fashion, the pins  44  can be inserted into selected of the openings  43  as the hydraulic cylinders are expanded and then contracted. The traveling member  42  can be moved in a ratchet fashion along the length of the boom  38  to change the angular position of the titling tower  19  relative to deck  14 . The traveling member  42  can thus be pinned at pinned connection  41  to tilting tower  19 . 
     Alternatively, a rack and pinion gear arrangement can interface between boom  38  and traveling member  42 . 
     The following is a list of suitable parts and materials for the various elements of the preferred embodiment of the present invention. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 PARTS LIST 
               
             
          
           
               
                   
                 Part Number 
                 Description 
               
               
                   
                   
               
               
                   
                 10 
                 reel pipeline lay barge 
               
               
                   
                 10A 
                 reel pipeline lay barge 
               
               
                   
                 11 
                 hull 
               
               
                   
                 12 
                 bow 
               
               
                   
                 13 
                 stern 
               
               
                   
                 14 
                 deck 
               
               
                   
                 15 
                 superstructure 
               
               
                   
                 16 
                 port drum 
               
               
                   
                 17 
                 starboard drum 
               
               
                   
                 18 
                 moon pool 
               
               
                   
                 19 
                 tilting tower 
               
               
                   
                 20 
                 pipeline 
               
               
                   
                 21 
                 bend controller 
               
               
                   
                 22 
                 pipe straightener 
               
               
                   
                 23 
                 tensioner 
               
               
                   
                 24 
                 hold-off clamp 
               
               
                   
                 25 
                 welding station 
               
               
                   
                 26 
                 welding station 
               
               
                   
                 27 
                 pipe storage 
               
               
                   
                 28 
                 pipe storage 
               
               
                   
                 29 
                 pipe storage 
               
               
                   
                 30 
                 firing line 
               
               
                   
                 31 
                 arrow 
               
               
                   
                 32 
                 arrow 
               
               
                   
                 33 
                 bending shoe 
               
               
                   
                 34 
                 tensioner 
               
               
                   
                 35 
                 sea bottom 
               
               
                   
                 36 
                 deck plane 
               
               
                   
                 37 
                 hydraulic cylinder 
               
               
                   
                 38 
                 boom 
               
               
                   
                 39 
                 pinned connection 
               
               
                   
                 40 
                 support 
               
               
                   
                 41 
                 pinned connection 
               
               
                   
                 42 
                 traveling member 
               
               
                   
                 43 
                 opening 
               
               
                   
                 44 
                 pin 
               
               
                   
                 WS-1 
                 welding station 
               
               
                   
                 WS-2 
                 welding station 
               
               
                   
                 WS-3 
                 welding station 
               
               
                   
                   
               
             
          
         
       
     
     The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.
A pipeline laying ship and an improved method of laying a pipeline in a marine environment is disclosed. The pipeline laying ship is a dynamically positioned barge or self-propelled dynamically positioned vessel with a hull having a deck area that supports a pair of reels. The reels are independently rotatable, and are position to generally port and starboard relative to one another. A pipe joint storage area is provided for containing multiple joints of pipe. One or more pipeline welding stations are provided on the deck next to the reels, the pipeline welding stations being positioned to join the joints of pipe together to form an elongated pipeline that can be wound upon a selected reel of said pair of reels. A tower is provided for guiding the elongated pipeline as it is unwound from a selected reel, the tower including at least a bend controller, a straightener and a tensioner. The welding stations and tower are each transversely and movably mounted upon the hull between the port and starboard positions that enable a pipeline to be welded and then wound upon either of the reels and to be unwound from either of the reels for launching to the sea bed via the tower.