Floating marine platform with flange connections

Abstract

The invention relates to a floating marine platform comprising multiple columns that are interconnected with tubular members, wherein the floating marine platform comprises multiple flange connections in the tubular members, wherein at least one flange connection comprises a radial inwardly directed first mounting flange with a first annular engagement surface, a radial inwardly directed second mounting flange with a second annular engagement surface, and a seal ring that comprises a first annular seal surface that faces the first annular engagement surface, a second annular seal surface that faces the second annular engagement surface, wherein the seal ring tapers radially inwards along the first annular seal surface and the second seal surface, wherein mountings bias the first mounting flange and the second mounting flange against the seal ring.

Description

FLOATING MARINE PLATFORM WITH FLANGE CONNECTIONS

[0001] BACKGROUND

[0002] The invention relates to a floating marine platfomr comprising multiple columns that are interconnected with tubular members, wherein the floating marine platform comprises multiple flange connections in the tubular members or in a tubular transition between the floating marine platform and an offshore construction that is supported by the floating marine platform.

[0003] An example thereof is a floating marine platform that comprises a central column, multiple peripheral columns circumferentially around the central column, and outriggers extending radially from the central column that connect the peripheral columns with the central column, wherein the outriggers comprise a tubular member that is connected to the central column and the peripheral column via flange connections. The floating marine platform can for example be part of a floating wind turbine.

[0004] SUMMARY OF THE INVENTION

[0005] Traditionally, the flange connections comprise radially outwardly projecting flanges that are bolted together using an intermediate seal. The flanges and bolts are exposed to the sea water, making them vulnerable parts of the floating marine platform. Oxidation thereof may cause water ingress in the tubular member, which shortens the service life of the floating marine platform.

[0006] The parts of the floating marine platform are shipped to a large shipyard that is close to where the platform will be employed, for example an offshore wind farm site. The parts are manufactured at different locations and shipped in to be assembled by bolting the flanges together, wherein the manufacturing tolerances between the meeting parts are small to obtain a reliable flange connection.

[0007] It is an object of the present invention to provide a floating marine platform of the abovementioned type, having flange connections that are optimized for a long service life of the floating marine platform.

[0008] The invention provides a floating marine platform comprising multiple columns that are interconnected with tubular members, wherein the floating marine platform comprises multiple flange connections in the tubular members or in a tubular transition between the floating marine platform and an offshore construction that is supported by the floating marine platform, wherein at least one flange connection has a longitudinal central axis and comprisesa first circumferential wall with a first outer surface around the central axis and that merges into an radial inwardly directed first mounting flange with a first annular engagement surface and first flange mounting holes in the first mounting flange,a second circumferential wall with a second outer surface around the central axis and that merges into an radial inwardly directed second mounting flange with a second annular engagement surface and second flange mounting holes in the second mounting flange, anda seal ring between the first mounting flange and the second mounting flange,wherein the seal ring comprises a first annular seal surface that faces the first annular engagement surface, a second annular seal surface that faces the second annular engagement surface, and seal ring mounting holes in the seal ring, wherein the seal ring tapers radially inwards along the first annular seal surface and the second seal surface, wherein the first flange mounting holes, the second flange mounting holes and the seal ring mounting holes are aligned and mountings extend therethrough, wherein the mountings bias the first mounting flange and the second mounting flange against the seal ring.

[0009] The floating marine platform according to the invention has a flange connection in which a seal ring is enclosed between a first mounting flange and a second mounting flange that are radially inward directed, whereby the mounting flanges and the connecting mountings are located inside the tubular member to be formed. The seal ring tapers radially inwards along its first annular seal surface and second seal surface, and the mountings bias the first mounting flange and the second mounting flange against the seal ring. Therefore a highest sealing pressure may be present along the outer perimeter of the seal ring, so at the outside of the flange connection to ensure a watertight connection. This high sealing pressure is maintained on the long term by the bias in the first mounting flange and the second mounting flange. The tapering sealing ring may be manufactured under high tolerances, while the first mounting flange and the second mounting flange may be manufactured under less high tolerances to obtain the required reliable flange connection.

[0010] In an embodiment the seal ring comprises an ring outer surface that extends between the first annular seal surface and the second annular seal surface, wherein the ring outer surface projects radially or transverse to the central axis above the first outer surface and the second outer surface. This ensures that the highest sealing pressure is present along the outer perimeter of the seal even when small misalignments occur between the first mounting flange and the second mounting flange with respect to the seal ring.

[0011] In an alternative embodiment the seal ring comprises an ring outer surface that extends between the first annular seal surface and the second annular seal surface and that is flush with the first outer surface and the second outer surface, whereby a tubular member can be formed that is flush at the outside at the flange connection.

[0012] In an embodiment the first annular seal surface is straight in a longitudinal section of the flange connection. In the same way, the second annular seal surface may be straight in a longitudinal section of the flange connection. The sealing pressure on the seal ring may thereby gradually increase towards the outside of the tubular member that is formed.

[0013] In an embodiment the first annular seal surface is under a first seal surface angle with a reference plane that is perpendicular to the longitudinal central axis of the flange connection, wherein the first seal surface angle is 0,1 - 5 degrees.

[0014] In an embodiment the second annular seal surface is under a second seal surface angle with a reference plane that is perpendicular to the longitudinal central axis of the flange connection, wherein the second seal surface angle is 0,1 - 5 degrees.

[0015] In an embodiment the first seal surface angle is equal to the second seal surface angle.

[0016] In an embodiment the first annular engagement surface is under a first engagement surface angle with a reference plane that is perpendicular to the longitudinal central axis of the flange connection, wherein the first engagement surface angle is 0, 1 - 5 degrees. In this embodiment both first annular seal surface and the first annular engagement surface may radially inward run away from each other to form a gap to be closed by biassing the first mounting flange and the second mounting flange against the seal ring.

[0017] Alternatively, the first annular engagement surface extends in a reference plane that is perpendicular to the longitudinal central axis of the flange connection. The manufacturing with this first annular engagement surface may be less complex.

[0018] In an embodiment, the first mounting flange comprises a first annular groove that divides the first annular engagement surface in a first outer annular engagement surface and a first inner annular engagement surface. The first annular groove may ensure that the highest sealing pressure may be present along the outer perimeter of the seal ring despite local elastic deformations inside the first mounting flange under its bias.

[0019] In an embodiment the second annular engagement surface may be under a second engagement surface angle with a reference plane that is perpendicular to the longitudinal centralaxis of the flange connection, wherein the second engagement surface angle is 0,1 - 5 degrees. In this embodiment both second annular seal surface and the second annular engagement surface may radially inward run away from each other to form a gap to be closed by biassing the first mounting flange and the second mounting flange against the seal ring.

[0020] Alternatively, the second annular engagement surface extends in a reference plane that is perpendicular to the longitudinal central axis of the flange connection. The manufacturing with this second annular engagement surface may be less complex.

[0021] In an embodiment the second mounting flange comprises a second annular groove that divides the second annular engagement surface in a second outer annular engagement surface and a second inner annular engagement surface. The second annular groove may ensure that the highest sealing pressure may be present along the outer perimeter of the seal ring despite local elastic deformations inside the second mounting flange under its bias.

[0022] In an embodiment the seal ring comprises a seal projecting from the first annular seal surface towards the first mounting flange, or projecting from the second annular seal surface towards the second mounting flange.

[0023] In an embodiment the seal ring comprises a seal slot that is recessed from the first annular seal surface for insertion of a seal, or a seal slot that is recessed from the second annular seal surface for insertion of a seal.

[0024] In an embodiment the first circumferential wall, the first mounting flange, the second circumferential wall, the second mounting flange and the seal ring are made of steel.

[0025] In an embodiment the mountings comprise biased mounting bolts or biased threaded studs that extend through the aligned first flange mounting holes, second flange mounting holes and seal ring holes.

[0026] In an embodiment the floating marine platform comprises a central column, multiple peripheral columns circumferentially around the central column, and outriggers extending radially from the central column that connect the peripheral columns with the central column, wherein the outriggers comprise a tubular member that is connected to the central column and the peripheral column via the flange connections.

[0027] In an embodiment the floating marine platform comprises structural members spanning between each adjacent pair of peripheral columns, wherein the structural members are pre-tensioned.

[0028] The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings, in which:

[0031] Figure 1 is an isometric view of a floating marine platform that supports a wind turbine;

[0032] Figure 2 is an isometric view of the floating marine platform of figure 1 showing flange connections between its main parts:

[0033] Figure 3 is an isometric view of a longitudinal section of one flange connection as shown in figure 2 that is partially welded and before bolting together;

[0034] Figure 4 is a detailed view of the flange connection as shown in figure 3;

[0035] Figure 5 is an exploded view of the flange connection as shown figure 3;

[0036] Figure 6 is an isometric view of a seal ring of the flange connection as shown in figure 3;

[0037] Figure 7 is a detailed view of the flange connection of figure 3 fully welded and after bolting together; and

[0038] Figures 8-10 are cross sections of alternative seal rings of the flange connection as shown in figure 3.

[0039] DETAILED DESCRIPTION OF THE INVENTION

[0040] Figure 1 shows a floating marine platform 1 that supports in this example a wind turbine 300 to form a floating wind turbine 5. The wind turbine 300 has a vertical tower 301 and a nacelle 302 on top of the tower 301 having an internal generator that is driven by a wind turbine rotor 303. The wind turbine rotor 303 has a hub 304 that is connected to the generator, and in this example three blades 305 radiating from the hub 304. The wind turbine 300 is capable of producing more than 1 MW of electrical power, currently reaching about 10 to 15 MW. The bottom diameter of the tower 301 may be between 5 meter and 10 meter for a +10 MW wind turbine. The three blades 305 may be more than 100 meters long each. An example is the 12 MW Haliade X turbine from General Electrics. Other turbine designs, such as vertical axis wind turbines can also be supported by the floating marine platform 1.

[0041] Figure 2 shows the marine platform 1 without the wind turbine 300 and without gangways,railings and mounted utilities to locate and illustrate its flange connections between its main parts.

[0042] As shown in figure 2, the marine platform 1 comprises a central column 10 that is made of steel. The central column 10 has a vertical cylindrical upper circumferential wall section 11 that is closed off with a top wall 17 and that in this embodiment merges downwardly via a flared wall section or conically widening middle circumferential wall section 12 into a vertical cylindrical lower circumferential wall section 13 that is at the bottom closed off with a bottom wall 14 to define an internal chamber 16 to provide buoyancy. The central column 10 has at the upper circumferential wall section 11 a diameter that is approximately equal to the bottom diameter of the tower 301, and that increases in diameter towards the bottom or keel of the central column 10 via the conically widening middle circumferential wall section 12. Alternatively the central column 10 has a constant diameter over its entire height. The central column 10 may be provided with a non-shown footing below the base wall section 13 with a larger diameter that provides additional volume. When the footing is filled with air, it helps to support the weight of the wind turbine 300. When the footing is filled with water, it helps to provide stability to the floating wind turbine 5.

[0043] As shown in figure 2, the marine platform 1 comprises in this example three vertical cylindrical stabilizing or peripheral columns 30 that are made of steel. The peripheral columns 30 provide buoyancy and are disposed radially every 120 degrees around the central column 10. The peripheral columns 30 each comprise a vertical cylindrical circumferential wall 31 that is at the upper side closed off with a top wall 32 to form an internal chamber 34 that is open at the bottom side. The peripheral columns 30 comprise a horizontally extending skirt 33 around the bottom edge of the cylindrical circumferential wall 31.

[0044] The marine platform 1 comprises three outriggers 50 that extend radially between the central column 10 and the peripheral columns 30. The outriggers 50 are made of steel and are composed with an upper tubular member 51 and a lower tubular member 52 that extend in this example parallel to each other and that are interconnected with diagonal braces 53. Alternatively at least one of the upper tubular member 51 and the lower tubular member 52 may be diagonal to the other. Alternatively, the upper tubular member 51 and the lower tubular member 52 are solitary parts that are not interconnected with braces. The outriggers 50 comprise an upper outer outrigger mounting 54 and an upper inner outrigger mounting 55 at the ends of the upper tubular member 51, and a lower outer outrigger mounting 56 and a lower inner outrigger mounting 57 at the ends of the lower tubular member 52.

[0045] As shown in figure 2, the central column 10 comprises three upper central column mountings 20 and three lower central column mountings 25 for the outriggers 50. The upper central column mountings 20 each comprise a tubular section 21 that is welded against the upper circumferential wall section 11 , and that is aligned with the upper tubular member 51 of the mounted outrigger 50. The lower central column mountings 25 each comprise a tubular section 26 that is welded against the lower circumferential wall section 13, and that is aligned with the lower tubular member 52 of the mounted outrigger 50. Each upper inner outrigger mounting 55 and upper central column mounting 20 forms part of an upper inner flange connection 22. Each lower inner outrigger mounting 57 and lower central column mounting 25 forms part of a lower inner flange connection 27.

[0046] As shown in figure 2, the peripheral columns 30 each comprise an upper peripheral column mounting 35 and a lower peripheral column mounting 38. The upper peripheral column mounting 35 comprises a tubular section 36 that is welded against the upper side of the circumferential wall 31 , and that is aligned with the upper tubular member 51 of the outrigger 50. The lower peripheral column mounting 38 comprises a tubular section 39 that is welded against the lower side of the circumferential wall 31, and that is aligned with the lower tubular member 52 of the outrigger 50. Each upper outer outrigger mounting 54 and upper peripheral column mounting 35 fomrs part of an upper outer flange connection 37. Each lower outer outrigger mounting 56 and lower peripheral column mounting 38 forms part of a lower outer flange connection 40.

[0047] As shown in figure 2 the marine platform 1 comprises three pre-tensioned slender upper structural members or tendons 60 having the same length that interconnect the upper ends of the peripheral columns 30, and three pre-tensioned slender lower structural members or tendons 65 having the same length that interconnect the lower ends of the peripheral columns 30 at the skirts 33. The tendons 60, 65 are embodied as steel tubes. Due to the pre-tension in the tendons 60, 65 and the resulting compressive forces in the outriggers 50, the entire marine platform 1 needs to be const ructcd under tight tolerances to prevent eccentricities in the internal load transfer.

[0048] The central column 10 has a bottom diameter of up to 20 meters. The central column 10 and the peripheral columns 30 typically have a total height of 20-30 meters, in this example about 24 meters. The peripheral columns 30 have a diameter between 6-12 meters. The tendons 60, 65 each have a length of 60-90 meters, in this example about 73 meters.

[0049] The upper inner flange connections 22, the lower inner flange connections 27, the upper outer flange connections 37 and the lower outer outrigger flange connections 56 have identicalparts that are described hereafter for one upper outer flange connection 37 as shown in figures 3-7.

[0050] Figures 3-6 show the upper outer flange connection 37 before its final assembly. The upper outer flange connection 37 comprises the upper peripheral column mounting 35, the upper outer outrigger mounting 54 and a seal ring 110 in between.

[0051] The upper peripheral column mounting 35 is made of steel and comprises a first circumferential wall 70 having a first outer surface 71. The first circumferential wall 70 merges into an radial inwardly directed first mounting flange 75. The upper peripheral column mounting 35 comprises a first connecting wall 72 having the same cross section and diameter as the first circumferential wall 70. The first circumferential wall 70 is welded to the first connecting wall 72 by means of a first annular weld 73 or continues into the first connecting wall 72 to together form the tubular section 36 of the upper peripheral column mounting 35.

[0052] As shown in figure 3, the upper outer outrigger mounting 54 is made of steel and comprises a second circumferential wall 90 having a second outer surface 91. The second circumferential wall 90 merges into a radial inwardly directed second mounting flange 95. The upper outer outrigger mounting 54 comprises a second connecting wall 92 having the same cross section and diameter as the second circumferential wall 90. The second circumferential wall 90 is welded to the second connecting wall 92 by means of a second annular weld 93 or continues into the second connecting wall 92 to together form part of the upper tubular member 51 of the outrigger 50.

[0053] As shown in figure 3, the first connecting wall 72, the first circumferential wall 70, the first mounting flange 75, the second mounting flange 95, the second circumferential wall 90 and the second connecting wall 92 have a common straight central axis S. As shown in figures 4 and 5, The first mounting flange 75 comprises a first annular engagement surface 77 that comprises in this example a first outer annular engagement surface section 78 with a first radial width W1 and a first inner annular engagement surface section 79 with a second radial width W2 that are separated from each other by a first annular groove 81 in the first mounting flange 75 with a third radial width W3. The first outer annular engagement surface section 78 ends at the first outer surface 71 where it merges into the first outer surface 71 via a first circumferential comer edge 74. In this example the first circumferential comer edge 74 forms in the direction of the central axis S the outermost distal part of the first mounting flange 75. With respect to a notional reference plane transverses to the center line S, the first annular engagement surface 77, and thereby the first outer annular engagement surface section 78 and the first inner annular engagement surfacesection 79 make a first engagement surface angle A of 0,1 - 5 degrees, preferably 0,1 - 2 degrees. Alternatively, the first engagement surface angle A is 0 degrees whereby the first outer annular engagement surface section 78 and the first inner annular engagement surface section 79 extend orthogonal to the central axis S. The first mounting flange 75 comprises multiple longitudinal first flange mounting holes 76 that extend through it and that debouche in the first annular groove 81.

[0054] The second mounting flange 95 comprises a second annular engagement surface 97 that comprises in this example a second outer annular engagement surface section 98 with the first radial width W1 and a second inner annular engagement surface section 99 with the second radial width W2 that are separated from each other by a second annular groove 101 in the second mounting flange 95 with the third radial width W3. The second outer annular engagement surface section 98 ends at the second outer surface 91 where it merges into the second outer surface 91 via a second circumferential comer edge 94. In this example the second circumferential comer edge 94 forms in the direction of the central axis S the outermost distal part of the second mounting flange 95. With respect to a notional reference plane transverse to the center line S, the second annular engagement surface 97 and thereby the first outer annular engagement surface section 98 and the first inner annular engagement surface section 99 make a second engagement surface angle B of 0, 1 - 5 degrees, preferably 0,1 -2 degrees. Alternatively, the second engagement surface angle B is 0 degrees whereby the first outer annular engagement surface section 98 and the first inner annular engagement surface section 99 extend orthogonal to the central axis S. In this example the first engagement surface angle A is equal to the second engagement surface angle B. The second mounting flange 95 comprises multiple longitudinal second flange mounting holes 96 that extend through it and that debouche in the second annular groove 101.

[0055] As best shown in figures 5 and 6, the seal ring 110 that is made of steel with a minimum yield strength of 355 MPa or higher, and comprises a first annular seal surface 111, a second annular seal surface 115, a ring inner surface 120 and a ring outer surface 130. The first annular seal surface 111 merges via a first outer circumferential comer edge 112 into the ring outer surface 130. The first annular seal surface 111 merges via a first inner circumferential comer edge 113 into the ring inner surface 120. The second annular seal surface 115 merges via a second outer circumferential comer edge 116 into the ring outer surface 130. The second annular seal surface 115 merges via a second inner circumferential comer edge 117 into the ring inner surface 120.

[0056] With respect to a notional plane transverse to the center line S, which is in this example also the plane of symmetry of the seal ring 110, the first annular seal surface 111 is under a first seal surface angle C of 0, 1 - 5 degrees, preferably 0,1 - 2 degrees. In that same notional plane, thesecond annular seal surface 115 is under a second seal surface angle D of 0,1 - 5 degrees, preferably 0,1 - 2 degrees. In this example the first seal surface angle C is equal to the second seal surface angle D. The first annular seal surface 111 and the second annular seal surface 115 symmetrically taper as from the ring outer surface 130 to the ring inner surface 120. The seal ring 110 comprises multiple longitudinal seal ring mounting holes 135 that extend through it and that debouche in the first annular seal surface 111 and the second annular seal surface 115. The first flange mounting holes 76, the second flange mounting holes 96 and the seal ring mounting holes 135 correspond in their amount and can be aligned.

[0057] As shown in the detail of figure 7, the seal ring 110 has an outer diameter that is slightly larger than the outer diameter of the first circumferential wall 70 and the second circumferential wall 90, whereby the ring outer surface 130 projects radially or transverse to the central axis S above the first outer surface 71 and the second outer surface 91. In this manner it is ensured that the first circumferential comer edge 74 is located fully onto the first annular engagement surface 77, and that the second circumferential comer edge 94 is located fully onto the second annular engagement surface 97 despite small deviations along the circumference of these parts along the circumference of the seal ring 110. The first annular seal surface 111 and the second annular seal surface 115 therefore have an radial width W4 that is larger than the cumulative first radial width Wl, second radial width W2 and third radial width W3.

[0058] Alternatively, the seal ring 110 has the same outer diameter as the first circumferential wall 70 and the second circumferential wall 90, whereby the first outer surface 71, the second outer surface 91 and the ring outer surface 130 of the seal ring 110 are aligned and flush.

[0059] As shown in figure 7 the upper peripheral column mounting 35 comprises multiple mounting bolts 140 that extend through the aligned first flange mounting holes 76, second flange mounting holes 96 and seal ring mounting holes 135. The mounting bolts 140 comprise a bolt head 141 against the second mounting flange 95 and a nut 142 around a threaded end 142 of the mounting bolt 140 and against the first mounting flange 75. Before tightening the mounting bolts 140 only the first circumferential comer edge 74 of the first mounting flange 75 abuts the first annular seal surface 111 of the seal ring 110, and only the second circumferential comer edge 94 of the second mounting flange 95 abuts the second annular seal surface 115 of the seal ring 110. Due to the radial inwardly tapering shape of the seal ring 110 along the first annular seal surface 111 and the second annular seal surface 115, the annular gaps with the abutting first mounting flange 75 and second mounting flange 95 radial inwardly widen.

[0060] By initial tightening the mounting bolts 140, the first circumferential comer edge 74 and the second circumferential comer edge 94 ensure an airtight and watertight sealing off around the perimeters thereof. When the mounting bolts 140 are fully tightened, the first mounting flange 75 and the second mounting flange 95 are elastically bend and biased towards the seal ring 110 up until the first annular engagement surface 77 fully abuts the first annular seal surface 111, and the second annular engagement surface 97 fully abuts the second annular seal surface 115 of the seal ring 110. The first annular groove 81 and the second annular groove 101 ensure that the highest sealing pressure is present along the first circumferential corner edge 74 of the first mounting flange 75, and along the second circumferential comer edge 94 of the second mounting flange 95. The sealing pressure is the highest at the first circumferential comer edge 74 of the first mounting flange 76 and at the second circumferential comer edge 94 of the second mounting flange 95, so at the outer surface of the outrigger 50.

[0061] The upper outer flange connection 37 can be prefabricated at least in part to ensure the small dimensional tolerances of the sealing parts. The seal ring 110 can be prefabricated in its entirety and subsequently shipped to a remote assembly yard of the marine platform 1 close to the location where the offshore marine platform 1 of the floating wind turbine 5 will be brought offshore and anchored. The first circumferential wall 70 that merges into the first mounting flange 75 can be prefabricated and subsequently welded to the first connecting wall 92 on the remote assembly yard of the marine platform 1 to form the upper peripheral column mounting 35. Therefore, it is provided with a first circumferential welding bevel 80. The second circumferential wall 90 that merges into the second mounting flange 95 can be prefabricated and subsequently welded to the second connecting wall 92 on the remote assembly yard of the marine platform 1 to form upper peripheral column mounting 35. Therefore, is it is provided with a second circumferential welding bevel 100.

[0062] Figures 8-10 respectively show only the cross sections of a first alternative seal ring 210, a second alternative seal ring 310 and a third alternative seal ring 410 for the upper outer flange connection 37. The features that correspond with the seal ring 110 have been provided with the same reference numbers. Only the deviating features are discussed.

[0063] As shown in figure 8, the first alternative seal ring 210 has a first annular groove 211 having a radial width equal to the third radial width W3 that separates the first annular seal surface 111 into a first outer annular engagement surface section 212 with a radial width larger than or equal to the first radial width Wl, and a first inner annular engagement surface section 213 with a radial width equal to the second radial width W2. The first alternative seal ring 210 has a secondannular groove 215 having a radial width equal to the third radial width W3 that separates the second annular seal surface 11 into a second outer annular engagement surface section 216 with a radial width larger than or equal to the first radial width Wl, and a second inner annular engagement surface section 217 with a radial width equal to the second radial width W2. The seal ring mounting holes 135 debouche in the first annular groove 211 and the second annular groove 215.

[0064] As shown in figure 9, the second alternative seal ring 310 has a first annular seal confinement groove 312 in which a first flexible seal 313 is confined that projects from the first annular seal surface 111. The second alternative seal ring 310 has a second annular seal confinement groove 316 in which a second flexible seal 317 is confined that projects from the second annular seal surface 115. The first flexible seal 313 and the second flexible seal 317 are elastically impressed due to the engagement of the first mounting flange 75 and the second mounting flange 95 whereby a tight seal is formed between the meeting parts.

[0065] As shown in figure 10, the third alternative seal ring 410 has a first annular seal body 413 that projects from the first annular seal surface 111, and a second annular seal body 417 that projects from the second annular seal surface 115. The first annular seal body 413 and the second annular seal body 417 are integrally formed and are made of the same metal as the remainder of the seal ring 410. The first annular seal body 413 and the second annular seal body 417 are initially received in not shown annular grooves in the annular first annular engagement surface 77 and the annular second annular engagement surface 97, in which they are subsequently cold deformed and impressed due to the engagement of the first mounting flange 75 and the second mounting flange 95 whereby a tight seal is formed between the meeting parts.

[0066] It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the present invention.

Claims

1. CLAIMS1. Floating marine platform comprising multiple columns that are interconnected with tubular members, wherein the floating marine platform comprises multiple flange connections in the tubular members or in a tubular transition between the floating marine platform and an offshore construction that is supported by the floating marine platform, wherein at least one flange connection has a longitudinal central axis and comprisesa first circumferential wall with a first outer surface around the central axis and that merges into a radial inwardly directed first mounting flange with a first annular engagement surface and first flange mounting holes in the first mounting flange,a second circumferential wall with a second outer surface around the central axis and that merges into a radial inwardly directed second mounting flange with a second annular engagement surface and second flange mounting holes in the second mounting flange, anda seal ring between the first mounting flange and the second mounting flange,wherein the seal ring comprises a first annular seal surface that faces the first annular engagement surface, a second annular seal surface that faces the second annular engagement surface, and seal ring mounting holes in the seal ring, wherein the seal ring tapers radially inwards along the first annular seal surface and the second seal surface, wherein the first flange mounting holes, the second flange mounting holes and the seal ring mounting holes are aligned and mountings extend therethrough, wherein the mountings bias the first mounting flange and the second mounting flange against the seal ring.

2. Floating marine platform according to claim 1 , wherein the seal ring comprises a ring outer surface that extends between the first annular seal surface and the second annular seal surface, wherein the ring outer surface projects radially or transverse to the central axis above the first outer surface and the second outer surface.

3. Floating marine platfomr according to claim 1 , wherein the seal ring comprises a ring outer surface that extends between the first annular seal surface and the second annular seal surface and that is flush with the first outer surface and the second outer surface.

4. Floating marine platform according to any one of the preceding claims, wherein the first annular seal surface is straight in a longitudinal section of the flange connection.

5. Floating marine platform according to any one of the preceding claims, wherein the second annular seal surface is straight in a longitudinal section of the flange connection.

6. Floating marine platform according to any one of the preceding claims, wherein the first annular seal surface is under a first seal surface angle with a reference plane that is perpendicular to the longitudinal central axis of the flange connection, wherein the first seal surface angle is 0,1 - 5 degrees.

7. Floating marine platform according to any one of the preceding claims, wherein the second annular seal surface is under a second seal surface angle with a reference plane that is perpendicular to the longitudinal central axis of the flange connection, wherein the second seal surface angle is 0,1 - 5 degrees.

8. Floating marine platform according to claims 6 and 7, wherein the first seal surface angle is equal to the second seal surface angle.

9. Floating marine platform according to any one of the preceding claims, wherein the first annular engagement surface is under a first engagement surface angle with a reference plane that is perpendicular to the longitudinal central axis of the flange connection, wherein the first engagement surface angle is 0,1 - 5 degrees.

10. Floating marine platform according to any one of the claims 1-8, wherein the first annular engagement surface extends in a reference plane that is perpendicular to the longitudinal central axis of the flange connection.

11. Floating marine platform according to any one of the preceding claims, wherein the first mounting flange comprises a first annular groove that divides the first annular engagement surface in a first outer annular engagement surface and a first inner annular engagement surface.

12. Floating marine platform according to any one of the preceding claims, wherein the secondannular engagement surface is under a second engagement surface angle with a reference plane that is perpendicular to the longitudinal central axis of the flange connection, wherein the second engagement surface angle is 0,1 - 5 degrees.

13. Floating marine platform according to any one of the claims 1-11, wherein the second annular engagement surface extends in a reference plane that is perpendicular to the longitudinal central axis of the flange connection.

14. Floating marine platform according to any one of the preceding claims, wherein the second mounting flange comprises a second annular groove that divides the second annular engagement surface in a second outer annular engagement surface and a second inner annular engagement surface.

15. Floating marine platform according to any one of the preceding claims, wherein the seal ring comprises a seal projecting from the first annular seal surface towards the first mounting flange, or projecting from the second annular seal surface towards the second mounting flange.

16. Floating marine platform according to any one of the preceding claims, wherein the seal ring comprises a seal slot that is recessed from the first annular seal surface for insertion of a seal, or a seal slot that is recessed from the second annular seal surface for insertion of a seal.

17. Floating marine platform according to any one of the preceding claims, wherein the first circumferential wall, the first mounting flange, the second circumferential wall, the second mounting flange and the seal ring are made of steel.

18. Floating marine platform according to any one of the preceding claims, wherein the mountings comprise biased mounting bolts or biased threaded studs that extend through the aligned first flange mounting holes, second flange mounting holes and seal ring holes.

19. Floating marine platform according to any one of the preceding claims, wherein the floating marine platform comprises a central column, multiple peripheral columns circumferentially around the central column, and outriggers extending radially from the central column that connect the peripheral columns with the central column, wherein the outriggers comprise a tubular member that is connected to the central column and the peripheral column viathe flange connections.

20. Floating marine platform according to claim 19, wherein the floating marine platform comprises structural members spanning between each adjacent pair of peripheral columns, wherein the structural members are pre-tensioned.

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