Marine reel lay method pipeline installation system and methods

Abstract

An improved system and method for laying on the seabed a pipeline and/or installing a subsea riser including one or more accessories are disclosed. In the system, a trolley rail for an auxiliary trolley is provided which includes a retractable trolley rail part supported by the tower via an associated mobile rail support assembly. Displacement of the retractable trolley rail part together with the auxiliary trolley when arranged on said retractable trolley rail part with respect to the tower is allowed, between an active position, wherein the auxiliary trolley is positioned to engage on an accessory in the firing line, and a retracted and non-operable position wherein a clear envelope about the firing line is created.

Claims

1. A marine reel lay method pipeline installation system for laying on the seabed a pipeline and/ or installing a subsea riser including one or more accessories, wherein the system comprises: one or more pipeline storage reels for storage of a pipeline to be laid; a pipeline launch tower, which is adapted to launch the pipeline in a firing line along said tower; a pipeline guide which is provided at an elevated position, which pipeline guide is adapted to guide the pipeline from a storage reel over the pipeline guide into the firing line; one or more tensioners, each tensioner comprising a tensioner frame and multiple tracks supported by said tensioner frame, the one or more tensioners being operable between an active pipelaying mode, wherein the firing line extends through the tensioner frame and between the tracks, so that the tracks are positioned to engage the pipeline and to support the pipeline in the firing line, and a retracted mode wherein a clear envelope is created about the firing line; a hang off device arranged in the lower part of the firing line, adapted to clamp and support the weight of the launched pipeline in the firing line; an abandonment and recovery (A&R) system comprising at least one A&R cable and associated A&R winch, and an A&R sheave arrangement with one or more sheaves provided at an upper position in the firing line, said one or more sheaves being supported by the pipeline launch tower, adapted to raise, lower and support the weight of the launched pipeline in the firing line; and an auxiliary trolley which is movable along a vertical trolley rail and which is adapted to engage on an accessory in the firing line in the retracted mode of the one or more tensioners, wherein the trolley rail comprises a retractable trolley rail part supported by the tower via an associated mobile rail support assembly, which is adapted to allow for displacement of the retractable trolley rail part together with the auxiliary trolley when arranged on said retractable trolley rail part with respect to the tower between an active position, wherein the auxiliary trolley is positioned to engage on an accessory in the firing line, and a retracted and non-operable position wherein a clear envelope about the firing line is created.

2. The system according to claim 1, wherein at least one tensioner frame comprises a first segment and a second segment, each including at least one of said tracks, wherein the first and second segment are each mounted pivotable about a respective first and second vertical segment pivot axis to the pipeline launch tower, the segments being pivotable between a pipelaying position in which the tracks are positioned to engage the pipeline; and an open retracted position, wherein the first and second segments are disconnected and separated, thereby creating a clear envelope about the firing line for passage of an accessory, wherein the trolley rail extends between the first and second vertical segment pivot axes.

3. The system according to claim 2, wherein the trolley rail further comprises a tensioner trolley rail part mounted on the tensioner.

4. The system according to claim 2, wherein the first and second segment are each mounted pivotable to a carrier which is displaceable along a tensioner rail which is mounted to the pipeline launch tower, extending parallel to the firing line, allowing the one or more tensioners to be translatable in the firing line, along the pipeline launch tower, and wherein a tensioner displacement drive is provided to support and translate the one or more tensioners along the pipeline launch tower.

5. The system according to claim 4, wherein the one or more tensioners are displaceable at least between an upper accessory handling position wherein the one or more tensioners have moved above a lower accessory position and a lower pipelaying position wherein the one or more tensioners at least partially overlap the accessory position.

6. The system according to claim 4, wherein the one or more tensioners are displaceable at least between a lower parking position wherein the one or more tensioners have moved below an end connector entry position and an upper pipelaying position wherein the one or more tensioners at least partially overlap the end connector entry position.

7. The system according to claim 5, wherein the upper pipelaying position and/or the upper accessory handling position overlap the active position of the retractable trolley rail part.

8. The system according to claim 1, wherein the trolley rail comprises a tower trolley rail part supported by the tower below the one or more tensioners, in the vicinity of and possibly until a position below the hang off device, such that the auxiliary trolley is movable to a position below the lowermost tensioner.

9. A marine reel lay method for laying on the seabed a pipeline including one or more accessories, wherein use is made of a pipeline installation system for laying on the seabed a pipeline and/ or installing a subsea riser including one or more accessories, wherein the system comprises: one or more pipeline storage reels for storage of pipeline to be laid; a pipeline launch tower, which is adapted to launch the pipeline in a firing line along said tower; a pipeline guide which is provided at an elevated position, which pipeline guide is adapted to guide the pipeline from a storage reel over the pipeline guide into the firing line; one or more tensioners, each tensioner comprising a tensioner frame and multiple tracks supported by said tensioner frame, the one or more tensioners being operable between an active pipelaying mode, wherein the firing line extends through the tensioner frame and between the tracks, so that the tracks are positioned to engage the pipeline and to support the pipeline in the firing line, and a retracted mode wherein a clear envelope is created about the firing line; a hang off device arranged in the lower part of the firing line, adapted to clamp and support the weight of the launched pipeline in the firing line; an abandonment and recovery (A&R) system comprising at least one A&R cable and associated A&R winch, and an A&R sheave arrangement with one or more sheaves provided at an upper position in the firing line, said one or more sheaves being supported by the pipeline launch tower, adapted to raise, lower and support the weight of the launched pipeline in the firing line; and an auxiliary trolley which is movable along a vertical trolley rail and which is adapted to engage on an accessory in the firing line in the retracted mode of the one or more tensioners, wherein the trolley rail comprises a retractable trolley rail part supported by the tower via an associated mobile rail support assembly, which is adapted to allow for displacement of the retractable trolley rail part together with the auxiliary trolley when arranged on said retractable trolley rail part with respect to the tower between an active position, wherein the auxiliary trolley is positioned to engage on an accessory in the firing line, and a retracted and non-operable position wherein a clear envelope about the firing line is created.

10. The method according to claim 9, further comprising the steps of: laying the pipeline with the one or more tensioners in the pipelaying mode and the retractable trolley rail part in the retracted and non-operable position; operating the one or more tensioners to the retracted mode; positioning the accessory in the firing line; connecting the accessory to the A&R system and possibly to the pipeline; displacing the retractable trolley rail part into the active position; engaging the accessory on the auxiliary trolley; and operating the A&R winch and thereby lowering the accessory and the pipeline by the A&R system, the accessory being engaged on the auxiliary trolley.

11. The method according to claim 10, for providing an accessory at the trailing end of a pipeline, further comprising the steps of: laying the pipeline with the one or more tensioners in the pipelaying mode and the retractable trolley rail part in the retracted and non-operable position; interrupting pipelaying by engaging the hang off device with the launched pipeline; transferring the weight of the launched pipeline to the hang off device; severing the pipeline above the hang off device; operating the one or more tensioners to the retracted mode; positioning the accessory in the firing line; connecting the accessory to the end of the launched pipeline supported by the hang off device and to the A&R system; displacing the retractable trolley rail part into the active position; engaging the accessory on the auxiliary trolley; releasing the hang off device from the launched pipeline; and operating the A&R winch and thereby lowering the accessory and the pipeline by the A&R system, the accessory being engaged on the auxiliary trolley.

12. The method according to claim 10, for laying on the seabed a pipeline with an end connector at the trailing end, further comprising the steps of: laying the pipeline with the one or more tensioners in the pipelaying mode and the retractable trolley rail part in the retracted and non-operable position; positioning the end connector in the firing line; interrupting pipelaying by engaging the hang off device with the launched pipeline; transferring the weight of the launched pipeline to the hang off device; operating the one or more tensioners to the retracted mode; connecting the end connector to the A&R system; displacing the retractable trolley rail part into the active position; engaging the accessory on the auxiliary trolley; releasing the hang off device from the launched pipeline; and operating the A&R winch and thereby lowering the end connector and the pipeline by the A&R system, the end connector being engaged on the auxiliary trolley.

13. The method according to claim 9, further comprising the step of connecting the auxiliary trolley to the A&R system, and connecting the accessory to the auxiliary trolley, thereby lowering the accessory and the pipeline by the A&R system, being supported by the auxiliary trolley.

14. The method according to claim 9, wherein use is made of a system wherein at least one tensioner frame comprises a first segment and a second segment, each including at least one of said tracks, wherein the first and second segment are each mounted pivotable about a respective first and second vertical segment pivot axis to the pipeline launch tower, the segments being pivotable between a pipelaying position in which the tracks are positioned to engage the pipeline; and an open retracted position, wherein the first and second segments are disconnected and separated, thereby creating a clear envelope about the firing line for passage of an accessory, wherein the trolley rail extends between the first and second vertical segment pivot axes, and wherein the first and second segment are each mounted pivotable to a carrier which is displaceable along a tensioner rail which is mounted to the pipeline launch tower, extending parallel to the firing line, allowing the one or more tensioners to be translatable in the firing line, along the pipeline launch tower, and wherein a tensioner displacement drive is provided to support and translate the one or more tensioners along the pipeline launch tower, the method comprising the steps of: providing the retractable trolley rail part in the retracted and non-operable position; providing the one or more tensioners in the pipelaying mode and in an upper pipelaying position wherein the one or more tensioners at least partially overlap an end connector entry position; laying the pipeline; operating the one or more tensioners to the retracted mode; translating the one or more tensioners to a lower parking position wherein the one or more tensioners have moved below the end connector entry position; displacing the retractable trolley rail part to the active position, wherein the auxiliary trolley is positioned to engage on the end connector in the firing line; and lowering the end connector.

15. The system according to claim 3, wherein the first and second segment are each mounted pivotable to a carrier which is displaceable along a tensioner rail which is mounted to the pipeline launch tower, extending parallel to the firing line, allowing the one or more tensioners to be translatable in the firing line, along the pipeline launch tower, and wherein a tensioner displacement drive is provided to support and translate the one or more tensioners along the pipeline launch tower.

16. The system according to claim 5, wherein the one or more tensioners are displaceable at least between a lower parking position wherein the one or more tensioners have moved below an end connector entry position and an upper pipelaying position wherein the one or more tensioners at least partially overlap the end connector entry position.

17. The system according to claim 6, wherein the upper pipelaying position and/or the upper accessory handling position overlap the active position of the retractable trolley rail part.

Description

(1) The invention can be further explained in relation to the drawings, in which:

(2) FIG. 1a is a side view of a marine reel lay method pipeline installation system according to the invention with the retractable trolley rail part in the retracted and non-operable position;

(3) FIG. 1b is a similar side view as shown in FIG. 1a, with the retractable trolley rail part in the active position;

(4) FIG. 2a is a side view of part of a marine reel lay method pipeline installation system according to the invention with the retractable trolley rail part in the active position;

(5) FIG. 2b is a similar side view as shown in FIG. 2a, with the retractable trolley rail part in the retracted and non-operable position;

(6) FIG. 2c is a rear view on the part of the marine reel lay method pipeline installation system of FIGS. 2a and 2b;

(7) FIG. 3a is a cross-sectional top view through a marine reel lay method pipeline installation system with the retractable trolley rail part in the active position;

(8) FIG. 3b is a similar cross-sectional view as shown in FIG. 3a, with the retractable trolley rail part in the retracted and non-operable position and with the tensioner frame in a retracted mode;

(9) FIG. 3c is a similar cross-sectional view as shown in FIGS. 3a and 3b, with the retractable trolley rail part in the active position and with the tensioner frame in a retracted mode;

(10) FIG. 4a is a cross-sectional top view of an embodiment of an auxiliary trolley;

(11) FIG. 4b is a cross-sectional side view of the auxiliary trolley of FIG. 4a;

(12) FIG. 5 is a perspective view of a marine reel lay method pipeline installation system according to the invention wherein the vertical trolley rail is supported by the pipeline launch tower and with the tensioner comprising a first and second segment in the retracted mode;

(13) FIG. 6a is a cross-sectional top view of a marine reel lay method pipeline installation system with the tensioner comprising a first and second segment in the retracted mode, and with an accessory therebetween;

(14) FIG. 6b is a similar cross-sectional top view of FIG. 6a, with an auxiliary trolley between a first and second segment of the tensioner in the retracted mode;

(15) FIG. 7 is a rear view onto a tensioner carrier;

(16) FIG. 8a is a cross-sectional top view through a tensioner in the active pipelaying mode of a marine reel lay method pipeline installation system;

(17) FIG. 8b is a similar view of that of FIG. 8a through a tensioner in the retracted mode and a centralizer in an active position;

(18) FIG. 8c is a similar view of that of FIGS. 8a and 8b through a centralizer and a hoist beam;

(19) FIG. 8d is a similar view of that of FIGS. 8a and 8b through a tensioner in the retracted mode and a centralizer in an open position.

(20) In FIGS. 1a and 1b side views of a marine reel lay method pipeline installation system 1 according to the invention are shown, for laying on the seabed a pipeline and/or installing a subsea riser (not shown), including one or more accessories such as the end fitting 2 visible in FIG. 1b. The system is here embodied as a vessel with a deck 3 in which a moonpool 4 is provided. Not shown are one or more pipeline storage reels for storage of pipeline to be laid.

(21) Adjacent the moonpool a pipeline launch tower 5 is provided, which is adapted to launch the pipeline in a firing line 8 along said tower, into the moonpool 4. The tower of the shown embodiment is pivoatable about pivot axis 5A. Via adjuster 6 the inclination of the tower 5 is adjustable.

(22) A pipeline guide 10, here embodied as a guide wheel, is provided at an elevated position, which pipeline guide is adapted to guide the pipeline from a storage reel over the pipeline guide into the firing line. In the shown embodiment, the not shown storage reel is provided at the left-hand side of the drawing, and the pipeline guide 10 guides the pipeline over a curved path from the left-hand side to the right-hand side into the firing line 8. Pipeline guide 10 is supported by the tower 5 via a guide frame 15. Via piston 15 the position of the pipeline guide 10 can be altered. In particular, the pipeline guide 10 can be displaced from a pipelaying position as visible in FIG. 1a, wherein the pipeline guide 10 is adjacent the firing line, and a retracted position as visible in FIG. 1b, wherein the pipeline guide 10 has moved away from the firing line 8, allowing the passage of an accessory, here end fitting 2, in the firing line 8.

(23) The guide frame 15 further supports a crane 12, which, as is visible in FIG. 1b, may be used to assist in positioning an accessory such as end fitting 2 into the firing line.

(24) The marine pipeline system 1 is furthermore provided with an abandonment and recovery (A&R) system 20 comprising at least one A&R cable 21 and associated A&R winch 22, and an A&R sheave arrangement with one or more sheaves provided at an upper position in the firing line, said one or more sheaves being supported by the pipeline launch tower 5, adapted to raise, lower and support the weight of the launched pipeline in the firing line 8. In the shown embodiment, an A&R sheave 23a is directly supported by the tower 5, and A&R sheave 23b is supported via a pivotable boom 24. The position of A&R sheave 23b is adjustable via the boom 24, e.g. to a position remote from the firing line as visible in FIG. 1a and a position adjacent the firing line 8 as visible in FIG. 1b.

(25) A hang off device 25 is arranged in the lower part of the firing line 8, here at the level of deck 3, which is adapted to clamp and support the weight of the launched pipeline in the firing line. The hang-off device 25 can be opened to allow the passage of an accessory, here through the moonpool 4.

(26) The shown marine pipeline installation system 1 comprises two tensioners 31, 36, each tensioner comprising a tensioner frame 31a, 36a and four tracks 31b, 36b, supported by said tensioner frame. Tensioners 31, 36 are operable between an active pipelaying mode as visible in FIG. 1a and a retracted mode as is visible in FIG. 1b, here via cylinders 32. In the active pipelaying mode the firing line extends through the tensioner frame and between the tracks, so that the tracks are positioned to engage the pipeline and to support the pipeline in the firing line 8. In the retracted mode a clear envelope is created about the firing line 8. Such a tensioner is further explained in relation to FIGS. 3a-3c.

(27) The tensioners 31, 36 are mounted to a carrier 38 which is displaceable along a tensioner rail 39 which is mounted to the pipeline launch tower 5, extending parallel to the firing line, allowing the tensioners to be translatable in the firing line 8, along the pipeline launch tower. Not visible is a tensioner displacement drive which is provided to support and translate the one or more tensioners along the pipeline launch tower. On the tensioner rail 39 a number of holes 39a is visible, used to fix the carrier 38 to the tensioner rail 39 in a position. The carrier 38 is shown in further detail in FIG. 7

(28) In the shown embodiment, the tensioners are displaceable to an upper accessory handling position wherein the one or more tensioners have moved above a lower accessory position. This position is not shown, but the tensioner rail 39 at the upper part of the tower is visible, where the tensioners are in the upper accessory handling position when a large accessory, e.g. a PLET, is provided at the lower part of the firing line between the hang off clamp 25 and the lowest tensioner 36.

(29) In FIG. 1a, the tensioners are shown in a pipelaying position, wherein the tensioners at least partially overlap the above-defined accessory position. In FIG. 1b, the tensioners are positioned in a lower parking position wherein the one or more tensioners have moved below an end connector entry position, where end connector 2 is in FIG. 1b. In the pipelaying position of FIG. 1a the tensioners partially overlap this end connector entry position.

(30) Below the upper tensioner 31, a centraliser 40 is provided to centralise the pipeline in the firing line. Centraliser 40 is mounted to the carrier 38 and thus translatable together with the tensioners 31, 36. The centralizer 40 is mounted movable between a horizontal operational position as visible in FIG. 1a, wherein the centralizer is in the firing line, and a non-operational vertical position as visible in FIG. 1b, wherein the firing line is cleared. Such a centralizer will further be elucidated in relation of FIGS. 8a-8d.

(31) Below the lower tensioner 36, in the shown embodiment a hoist beam 45 is provided, which is supported by the carrier 38 and thus translatable together with the tensioners 31, 36. This hoist beam may assist in positioning an accessory, such as a PLET, in a position below the lowermost tensioner 36.

(32) According to the present invention, an auxiliary trolley 50 is provided which is movable along a vertical trolley rail 55 and which is adapted to engage on an accessory 2 in the firing line 8 in the retracted mode of the one or more tensioners, as is visible in FIG. 1b. From this FIG. 1b, it is visible that the vertical trolley rail 55 extends to a position adjacent the A&R sheave arrangement, to the upper end of the tower 5. Also, it is visible that the trolley 50 has such dimensions that it is adjacent the retracted position of the pipeline guide 10. Hence, the auxiliary trolley 50 in the position of FIG. 1b overlaps the pipelaying position of the pipeline guide 10 of FIG. 1a. Details of the auxiliary trolley are explained in relation to FIGS. 4a and 4b.

(33) According to the invention, as shown in FIG. 1a, the trolley rail 55 comprises a retractable trolley rail part 55a supported by the tower 5 via an associated mobile rail support assembly, here comprising parallel bars 51a, 51b, part of a parallel bar linkage mechanism. The mobile rail support assembly is adapted to allow for displacement of the retractable trolley rail part 55a together with the auxiliary trolley 50 when arranged on said retractable trolley rail part 55a with respect to the tower 5 between an active position, wherein the auxiliary trolley is positioned to engage on an accessory in the firing line, as visible in FIG. 1b, and a retracted and non-operable position wherein a clear envelope about the firing line is created, as visible in FIG. 1a. A fixation device 52 is provided to fixate the auxiliary trolley 50 to the retractable trolley rail part 55a, in the retracted position thereof.

(34) In FIGS. 2a and 2b part of a marine reel lay method pipeline installation system 60 according to the invention is shown. A pipeline launch tower 65 is visible, pivotable about pivot axis 65A. In FIG. 2c it is visible that the tower comprises two parallel vertical stands 65b, 65c, interconnected by horizontal cross beams 65d, 65e.

(35) Onto the tower 65 a pipeline guide 70 is mounted via a guide frame 75. The position of the pipeline guide 70 can be changed via cylinder 75. A crane 72 is mounted to the pipeline guide 70.

(36) A retractable trolley rail part 61 is shown, here without an auxiliary trolley arranged on said retractable trolley rail part. The retractable trolley rail part 61 is supported by the tower 65 via an associated mobile rail support assembly, here comprising a frame 63 supporting the rails 61a, 61b (visible in FIG. 2c) and a parallel bar linkage. The parallel bar linkage is formed by parallel bars 62a, 62b, and 62a (not visible) and 62b, a connection bar 62c and the horizontal cross beam 65d.

(37) In the position of FIG. 2a, the retractable trolley rail part 61 is in an active position, wherein the auxiliary trolley (not shown) is in a position to engage on an accessory in a firing line 68. In the position of FIG. 2b, the retractable trolley rail part 61 is in a retracted and non-operable position wherein a clear envelope about the firing line is created.

(38) In FIGS. 3a-3c a tensioner 131, similar to tensioner 31 of FIGS. 1a and 1b, and auxiliary trolley 150, similar to auxiliary trolley 50 of FIGS. 1a and 1b, are shown in more detail.

(39) Part of a pipeline launch tower is shown in cross section, comprising parallel upright beams 105b, 105c, between which horizontal cross beams are provided. Cross beam 105d is visible.

(40) In FIG. 3a, auxiliary trolley 150 is visible which is movable along a vertical trolley rail and which is adapted to engage on an accessory in the firing line 108. The tensioner is not visible. The auxiliary trolley 150 is in FIG. 3a arranged on a retractable trolley rail part comprising parallel rails 155a and 155a. The retractable trolley rail part is supported by the tower, in particular cross beam 105d, via a frame 163 and a mobile rail support assembly, here a parallel bar linkage of which parallel bars 151a and 151a are visible. The retractable trolley rail part arranged on said retractable trolley rail part is in FIG. 3a in an active position, wherein the auxiliary trolley 150 is positioned to engage on an accessory in the firing line 108.

(41) In FIG. 3b, the retractable trolley rail part with rails 155a and 155a is in a retracted and non-operable position, wherein a clear envelope 109 about the firing line 108 is created. Tensioner 131 comprises a tensioner frame 131a and four tracks 131b supported by said tensioner frame 131a. The tensioner 131 is operable between an active pipelaying mode, not shown, wherein the firing line extends through the tensioner frame and between the tracks, so that the tracks are positioned to engage the pipeline and to support the pipeline in the firing line 108. In FIGS. 3b and 3c, the tensioner is shown in a retracted mode wherein a clear envelope 109 is created about the firing line 108.

(42) The tensioner frame 131a comprises a first segment 131a and a second segment 131a, here each including two of the four tracks 131b. The first and second segment are each mounted pivotable about a respective first vertical segment pivot axis 131A and second vertical segment pivot axis 131A via a carrier 138 to the the pipeline launch tower. The segments are pivotable between a pipelaying position, not shown, in which the tracks are positioned to engage the pipeline; and an open retracted position, visible in FIGS. 3b and 3c, wherein the first and second segments are disconnected and separated, thereby creating a clear envelope about the firing line for passage of an accessory. The carrier 138 is displaceable along a tensioner rail 139 which is mounted to the pipeline launch tower.

(43) The trolley rail comprises a carrier trolley rail part with rails 155b, 155b which are mounted on the carrier, between the first and second vertical segment pivot axes 131A and 131A. In FIG. 3b, these carrier trolley rail parts are clearly visible. The carrier trolley rail part with rails 155b, 155b of FIG. 3b is in line with the retractable trolley rail part with rails 155a and 155a in the active position of FIG. 1a, allowing the auxiliary trolley 150 to move from the retractable trolley rail part onto the carrier trolley rail part, as is visible in FIG. 3c, between the segments of the tensioner frame 131.

(44) In FIG. 3c, a centralizer 140 is visible between the carrier trolley rail part with rails 155b, 155b, similar to centralizer 40 shown in FIGS. 1a and 1b. Similar to the situation in FIG. 1b, the centralizer is mounted movable between a horizontal operational position wherein the centralizer is in the firing line, and a non-operational vertical position as visible in FIG. 3c (and FIG. 1b), wherein the firing line is cleared.

(45) In FIGS. 4a and 4b the auxiliary trolley 150 of FIGS. 3a-3c is shown in further detail. The auxiliary trolley 150 comprise two trolley parts 150 and 150, each part comprising an A&R cable guide 151a, 151b and a clamp part 152a, 152b. The trolley parts 150, 150 are movable along a horizontal guide 160, e.g. via shift cylinders. The auxiliary trolley 150 is movable along a vertical trolley rail via bogies 157. Alternatively, guide wheels may be provided. In FIG. 4b a pipe fitting piece 155 is clamped by clamp parts 152a, 152b, used to connect a pipe end to the auxiliary trolley 150. It is noted that a similar auxiliary trolley has been disclosed in WO2014/120004 of the same applicant.

(46) In FIGS. 5, 6a and 6b a marine reel lay method pipeline installation system 200 according to an aspect of the invention is shown, for laying on the seabed a pipeline and/or installing a subsea riser including one or more accessories. Here a large accessory 202 is visible. The system 200 is provided on a deck 203, e.g. of a vessel, furthermore comprising one or more pipeline storage reels for storage of pipeline to be laid (not visible). The system comprises a pipeline launch tower 205, which is adapted to launch the pipeline in a firing line 208 along said tower. A pipeline guide 210, here embodied as a semi-circular chute, is provided at an elevated position, here supported by an upper part of the tower 205, which pipeline guide is adapted to guide the pipeline from a storage reel over the pipeline guide into the firing line.

(47) Two tensioners 231, 236 are provided, each tensioner comprising a tensioner frame 231a, 236a and multiple tracks 231b, 236b supported by said tensioner frame. The tensioners are operable between an active pipelaying mode, not shown, wherein the firing line extends through the tensioner frame and between the tracks, so that the tracks are positioned to engage the pipeline and to support the pipeline in the firing line 208, and a retracted mode wherein a clear envelope is created about the firing line. In FIG. 5 the clear envelope is not visible as the accessory 202 is provided in the firing line.

(48) The marine reel lay method pipeline installation system 200 further comprises a hang off device 225 arranged in the lower part of the firing line, adapted to clamp and support the weight of the launched pipeline in the firing line. In addition, an abandonment and recovery (A&R) system 220 is provided comprising at least one A&R cable 221 and associated A&R winch (not visible), and an A&R sheave arrangement 223 with one or more sheaves provided at an upper position in the firing line, said one or more sheaves being supported by the pipeline launch tower, adapted to raise, lower and support the weight of the launched pipeline in the firing line.

(49) An auxiliary trolley 250 is provided which is movable along a vertical trolley rail 255 and which is adapted to engage on an accessory 202 in the firing line 208 in the retracted mode of the one or more tensioners, as visible in FIG. 5.

(50) Each of the tensioner frames 231a, 231b comprises a first segment and a second segment each including two of said tracks. In FIG. 6a, a first segment 231a and a second segment 231a are visible, each including two tracks 231b. The first and second segment 231a and 231a are each mounted pivotable about a respective first and second vertical segment pivot axes 231R and 231R to the pipeline launch tower 205. The segments are pivotable between a pipelaying position in which the tracks are positioned to engage the pipeline, not shown, and an open retracted position, wherein the first and second segments are disconnected and separated, thereby creating a clear envelope about the firing line for passage of an accessory, as visible in FIGS. 5, 6a and 6b. The trolley rail 255 extends between the first and second vertical segment pivot axes 231R and 231R. In FIGS. 5, 6a and 6b the vertical trolley rail 255 is supported by the pipeline launch tower 205. It is conceivable that also a retractable trolley rail part is provided. The auxiliary trolley is movable along the vertical trolley rail when the first and second segments of the tensioner frame are in the open retracted position.

(51) FIG. 7 is a rear view onto a tensioner carrier 38. The tensioner itself is not visible. The tensioner carrier 38 comprises pivot connections 81 allowing the segments of the tensioner frame to be pivotably connected to. As visible e.g. in FIG. 8a, the segments are pivotable via hydraulic cylinders, which are connected to the tensioner carrier via connections 82. The trolley rail, in particular carrier trolley rail part 55b, extending between the first and second vertical segment pivot axes at connection points 81 is also visible. Also a tensioner displacement drive 85, embodied similar to a jackup leg system, is visible. The carrier 38 is provided with a connection device 86 to fix the carrier 38 to one of the holes 39a on the tower to fix the tensioners in a certain position. A centralizer 40 is shown in the vertical position, pivoted away from the firing line, similar to the situation shown in FIG. 1b.

(52) In FIG. 8a is a cross-sectional top view through a tensioner 331 in the active pipelaying mode of a marine reel lay method pipeline installation system is shown. The tensioner 331 comprises a frame 331a and four tracks 331b, one of which in the shown situation does not engage a pipeline in the firing line 308. The tensioner frame 331a, according to an aspect of the invention, comprises two segments 331a and 331a as visible in FIG. 8b. The segments are mounted pivotable about a pivot axis 331R to a carrier 338, which is translatable along the tower 305. A carrier trolley rail part 355b extends between the first and second vertical segment pivot axes 331R.

(53) In FIGS. 8b and 8d, it is shown that further a centralizer 340 may be provided between the first and second vertical segment pivot axes 331R, and between the rails of the carrier trolley rail part 335b. In the clear area around the firing line 308 created by the opening of the segments of the tensioner, the centralizer 340 can be opened to the extent shown in FIG. 8d, allowing large pipelines and/or pipe sections and/or accessories such as end fittings to be centralized. Alternatively, it is possible to remove the centralizer from the firing line by pivoting it to a vertical position.

(54) In FIG. 8c, a cross section through a bottom part of the tower 305 is visible, where hoist beams 345 are provided, similar to hoist beams 45 in FIGS. 1a and 1b. In the shown embodiment, a further centralizer 340 is provided between the hoist beams.