flange

Abstract

A flange (1) for connecting to a complementary flange (1) is described, and wherein the flange (1) comprises: an annular connection face (1F) to abut against a complementary annular connection face (1F) of the complementary flange (1); a first body section (10) having a primary bolt circle (1P) comprising an annular arrangement of inclined openings (10_thru, 10_part) to receive a set of fasteners (10B) for connecting the flange (1) to the complementary flange (1); and a second body section (11) having a secondary bolt circle (1S) comprising an annular arrangement of openings (11) to receive a set of fasteners (11B) for connecting the flange (1) to an intermediate structure (3). A method of handling a cylindrical tower section (20A) equipped with such a flange (1) is also described.

Description

TECHNICAL FIELD

[0001] A flange for connecting to a complementary flange; and a method of handling a cylindrical tower segment equipped with such a flange are described. BACKGROUND

[0002] High towers such as wind turbine towers are often constructed by connecting tower segments together. For this purpose, each tower segment is equipped with a flange. A common flange shape is the "L-shaped flange" and a complementary L-shaped flange is connected together by fasteners such as bolts arranged in a bolt circle. The tower segments can be manufactured with L-shaped flanges with an inner bolt circle (i.e. the flange extends into the tower interior) or an outer bolt circle (i.e. the flange extends out from the tower).

[0003] Large wind turbines of the type currently being developed have very long rotor blades and therefore require higher towers. However, the limited load carrying capacity of the commonly used L-shaped flange connection imposes constraints on the tower structure.

[0004] The strength of the flange connection depends on various parameters such as the choice of steel, wall thickness, bolt diameter, number of bolts in the bolt circle, load path, etc. In order to increase the strength of the flange connection between tower segments, one approach can be to use a "T-shaped flange" instead, which has the shape of an inverted "T", with an inner flange extending into the tower interior and an outer flange extending out from the tower. The T-shaped flange can have twice the strength of the L-shaped flange, i.e. it can withstand twice the load that a comparable L-shaped flange can withstand. However, the main disadvantage of the T-shaped flange is that it requires access from the tower exterior as well as from the tower interior. Although the T-shaped flange is seen as a solution in some cases due to its greater load carrying capacity, the assembly of a multi-segment tower using T-shaped flanges and the service life maintenance is very expensive.

[0005] It is therefore an object of the present invention to provide an improved flange connection that overcomes the above-mentioned problems. SUMMARY

[0006] This object is achieved by the flange of claim 1 ; and by the method of handling a cylindrical tower segment equipped with such a flange of claim 13.

[0007] According to the invention, the flange is part of a structural component and is realized for connection to a complementary flange, which is part of another structural component. The flange of the invention comprises a substantially planar annular connection face, which is to abut against a complementary annular connection face of the complementary flange, a first body section with a primary bolt circle comprising an annular arrangement of alternating inclined openings to receive a first set of fasteners for connecting the flange to the complementary flange, and a second body section with at least a partial secondary bolt circle comprising an annular arrangement of openings for temporarily connecting the flange to an intermediate structure.

[0008] In the following, for the sake of simplicity, but not in any way limiting the invention, it can be assumed that the structural component is a tower segment, e.g. a wind turbine tower segment. In the following, the tower segment can also be referred to as "tower shell". The flange of the invention is "part of the structural component" when the structural component is connected. This is to be understood to mean that the structural component and its flange can be considered as a single entity. The structural component and its flange can be formed as a single body. Equally, the structural component and its flange can be manufactured separately and then joined, e.g. the flange can be welded to a steel tower shell, or the upright cylindrical portion of the flange can be embedded into the outer end of a concrete tower shell.

[0009] The primary bolt circle is to be understood as the circle along which the openings at the flange connection face open. The diameter of the primary bolt circle can be assumed to be similar to or equal to the average diameter of the tower segment or tower shell. The inclined openings extend from the flange connection face into the body of the flange. The advantage of the primary bolt circle is that the joint effectively moves "into" the tower shell, i.e. the force exerted by the tightened bolts is directed along an inclined path that intersects the average diameter of the tower shell. This means that the load is effectively transmitted from one tower shell much more to the next tower shell. In contrast, the vertical bolts of a conventional L-shaped flange are always at a distance from the average diameter of the tower shell, such that the load path is offset, resulting in a greater bending moment.

[0010] The openings of the secondary bolt circle can be assumed to be vertical in the regular sense, i.e. perpendicular to the connection face of the flange. The secondary bolt circle is exclusively provided for connection to an intermediate structure and overcomes the practical difficulties associated with using the primary bolt circle (with its inclined openings) for this purpose.

[0011] With its primary and secondary bolt circles, the flange of the invention effectively provides a structural strength comparable to that of a T-shaped flange, without sacrificing the main advantage of an L-shaped flange, i.e. the accessibility of the primary bolt circle from inside the tower.

[0012] In the context of the present invention, an "intermediate structure" can be understood as any device such as a holding structure used during transport of a tower segment, a lifting interface used during installation of a tower segment, etc. It can be assumed that the intermediate structure is not an element of the tower for which the tower segment is to become part of.

[0013] The terms "flange" and "complementary flange" are understood in the usual sense to mean substantially identical flanges, e.g. mirror images of each other, such that they can be connected together.

[0014] The flange of the present invention has the advantage that it combines two separate aspects, the combination of which results in a compact yet robust flange connection. In a first aspect, the flange connection is achieved by bolting two instances of the flange of the present invention together, wherein a set of fasteners is arranged in the oblique openings of the primary bolt circle. Due to the way the primary bolt circle is formed, this set of oblique fasteners is advantageously in close proximity to the tower segment body. In a second aspect, the tower segment can be relatively easily connected to an intermediate structure by fasteners extending through the secondary bolt circle.

[0015] According to the present invention, the method of handling a cylindrical tower segment equipped with such a flange comprises any one of: forming a temporary connection between the tower segment and a holding device by a plurality of fasteners inserted through the secondary bolt circle of the flange, and subsequently releasing the temporary connection by removing the fasteners from the secondary bolt circle; and / or forming a permanent connection between the tower segment and another tower segment by a plurality of fasteners inserted through the primary bolt circle of the flange and the primary bolt circle of a complementary flange of the other tower segment.

[0016] Particularly advantageous embodiments and features of the present invention are given by the dependent claims, as disclosed in the following description. Features of different claim categories can be suitably combined to give further embodiments not described here.

[0017] It can be assumed that the tower segment has a substantially cylindrical form, e.g. a straight cylinder. Likewise, the tower segment can have a truncated conical form, such that e.g. the diameter of its upper end is smaller than the diameter of its lower end. It can be assumed that the tower segment has a substantially circular cross-sectional shape.

[0018] The tower segment can be assumed to be "solid", i.e. to have a solid sidewall, e.g. made of steel or concrete, but the flange connection of the present invention is not limited to tower segments having a solid sidewall.

[0019] The flange of the present invention substantially comprises a first body segment incorporating the primary bolt circle and a second body segment incorporating (part of) the secondary bolt circle. As will be explained below, the flange of the present invention can be realized as a single-piece component or as a two-piece component.

[0020] In the following, it can be assumed that the flange has a general shape of an "L", i.e. the second body section of the flange is essentially a lip or collar extending into the interior space of the tower section.

[0021] The oblique openings of the main bolt circle are characterized by an oblique angle Θ subtended between their longitudinal axis and the surface normal of the flange connection face. In other words, the longitudinal axis of the main bolt circle openings is inclined with respect to the horizontal plane. In a preferred embodiment of the invention, this oblique angle Θ is between 15° and 25°.

[0022] In a particularly preferred embodiment of the invention, the main bolt distribution comprises an alternating arrangement of downwardly extending oblique openings and upwardly extending oblique openings. In a preferred embodiment of the invention, for the purpose of discussion the "upper" flange is used, the downwardly extending oblique openings extend through the flange to accommodate the shank of a fastener which extends into the complementary oblique opening of the lower flange, and the upwardly extending oblique openings extend partially into the flange from the contact face to accommodate the threaded end of a fastener which extends into the flange from the "lower" flange.

[0023] The downwardly extending oblique openings are through openings formed such that a fastener inserted through the flange extends into the oblique opening of the complementary flange. Thus, the downwardly extending oblique openings are "through holes" in that they extend all the way through the body of the flange.

[0024] The upwardly extending oblique openings are threaded openings formed to receive the threaded end of a fastener inserted into the flange via the oblique opening of the complementary flange. Thus, the upwardly extending oblique openings are "blind holes" in that they terminate at the body of the flange.

[0025] Thus, when viewed from the contact surface, the flange shows a ring of openings. Every other opening is an "exit" opening of an oblique through hole, while the other openings are "entry" openings of a relatively oblique blind hole. To form a flange connection, two flanges are arranged face-to-face such that each "exit" opening is aligned with its corresponding "entry" opening.

[0026] Since the flange of the present invention combines two types of bolt circles, namely a bolt circle with alternating inclined fasteners and a bolt circle known from the "L-flange", the flange of the present invention can be referred to as "X-L-flange" in the following. The "X-L-flange" has an advantageous high load carrying capacity, because of the alternating arrangement of the inclined bolts, and because the bolts cross each other along rings that coincide or at least very closely with the diameter of the tower shell. This results in a more efficient load path, such that the prying moment type that usually occurs in L-flange connections is substantially eliminated. The load carrying capacity of the flange of the present invention is comparable to that of a comparable "T-flange". However, unlike the "T-flange" of the prior art, the assembly of a tower using the "X-L-flange" of the present invention does not require access from the outside of the tower. This is because all fasteners or studs of the primary bolt circle can be inserted from the inside of the tower. This aspect is particularly important for the assembly of a tower at a location at sea or at a location where an external crane cannot be deployed to provide personnel access platforms.

[0027] While the primary purpose of the primary bolt circle is to allow the two flanges to be permanently bolted together, the secondary purpose of the secondary bolt circle is to allow the flanges to be temporarily connected to some intermediate structure. In a preferred embodiment of the present invention, the longitudinal axis of the openings of the secondary bolt circle is collinear with the surface normal of the flange connection face, i.e. the bolt holes extend vertically through the flange and are easily accessible.

[0028] The secondary bolt circle can be based on a complete ring, or on an arc segment of a ring. When based on a complete ring, the second body segment is similar in shape to an L-flange, extending horizontally from the first body segment towards the interior of the flange. When based on an arc segment of a circle, the second body segment can comprise angled segments, for example each segment subtending an angle of 30° from the midpoint of the flange, four such segments being evenly spaced around the inner circumference of the first body segment. Such an embodiment has the advantage of reducing material costs.

[0029] In a preferred embodiment of the present invention, the flange is manufactured as a single-piece component. In such an embodiment, a second benefit is provided by the second body segment, i.e. the lip or collar comprising the second bolt circle, of increased stiffness. This body segment or structural element helps to minimize ovalization during transport, i.e. it helps to reduce or eliminate the possibility of the flange deforming during storage or transport, which otherwise can cause the flange to take on a slightly oval form.

[0030] In an alternative preferred embodiment of the present invention, the flange is realized as a two-part flange, wherein the first body segment comprises the primary bolt circle, and the second body segment comprises the secondary bolt circle. Preferably, the second body segment is mounted to the first body segment by welding or by fasteners extending parallel to the flange connection face.

[0031] It is known from the prior art to design flanges of various tower housing diameters with specific bolt circle diameters (BCD). This simplifies the flange design and reduces the flange manufacturing costs, but leads to higher costs elsewhere, for example when an adapter is needed for a certain flange BCD to enable the flange to be connected to a transport fitting or lifting equipment. Since the flanges of the present invention can be realized as two-part components, it is relatively easy to provide a set of second body segments, each having a different BCD. In this way, the appropriate second body segment can be selected based on the BCD of the intermediate structure that will be used to handle the tower segment.

[0032] When two tower segments are connected together, the load is typically transmitted substantially vertically. Therefore, in a preferred embodiment of the present invention, the inner diameter of the annular flange connection face exceeds the diameter of the minor bolt circle. This can be achieved, for example, by machining a recess in the second body segment of the flange to limit the contact face between the flanges to the area between the upper and lower tower segment bodies. In other words, the thickness of the second body segment is reduced.

[0033] Another advantage of this preferred embodiment is that such a recess also helps to better define the flange contact face. Limiting the contact face to the area relevant for load transmission makes it easier to identify defects relevant for performance, such as gaps between the flange contact faces. Such gaps will impair the load transmission path. This preferred embodiment of the present invention allows such gaps to be quickly identified so that they can be remedied by shimming before the fasteners of the major bolt circle are tightened.

[0034] As mentioned above, a certain degree of ovalization can occur in the tower segments before the tower is assembled. In a preferred embodiment of the present invention, the flanges comprise alignment features formed adjacent to the inner diameter of the flange connection face and shaped to engage with counter-alignment features of a complementary flange. The weight of the upper tower segment in combination with the alignment features will be sufficient to correct any ovalization when one tower segment is lowered into position above another tower segment.

[0035] In a preferred embodiment of the present invention, the method of handling a tower segment during tower assembly comprises the step of inserting a guide pin through an opening of the minor bolt circle ring to align the flange of one tower segment with a complementary flange of another tower segment. BRIEF DESCRIPTION OF DRAWINGS

[0036] Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention.

[0037] Figures 1-5 An embodiment of the flange of the present invention is shown;

[0038] Figure 6 An embodiment of the flange of the invention is shown connected to an intermediate structure;

[0039] Fig. 7 and Fig. 8 show a tower comprising stacked tower segments connected according to the prior art. DETAILED DESCRIPTION

[0040] In the drawings, like reference numerals will generally refer to like objects throughout the drawings. Objects in the drawings are not necessarily to scale.

[0041] Figure 1 、 Figure 2 and Figure 3 An embodiment of the flange 1 of the invention is shown. The tower segment of the wind turbine can have an average diameter in the order of 6-8 m, and the flange 1 of the invention is dimensioned accordingly. Figure 1 An example of an embodiment of the flange 1 of the invention is shown (in cross section) connected to a functionally identical example of the flange 1. Each flange 1 has a first body segment 10 and a second body segment 11, the first body segment 10 incorporating a primary bolt circle 1P comprising an annular arrangement of oblique openings 10 thru, 10 part to receive a set of fasteners 10B for connecting the flange 1 to a complementary flange 1. The oblique openings 10 thru, 10 part of the primary bolt circle 1P are characterized by an oblique angle Θ subtended between its longitudinal axis 10A, 10A’ and the surface normal N of the flange connection face 1F. In Figure 1 In the embodiment shown, the center of the “exit” opening of the through-hole 10 thru and the center of the “entry” opening of the blind hole 10 part are points along the primary bolt circle 1P. This is more clearly seen in the perspective view given, which shows the alternating arrangement of through-hole “exit” openings 10 out and blind hole “entry” openings 10 in forming the primary bolt circle 1P. Figure 3 In the perspective view given, which shows the alternating arrangement of through-hole “exit” openings 10 out and blind hole “entry” openings 10 in forming the primary bolt circle 1P.

[0042] Figure 2 An embodiment of the flange 1 of the invention is shown as part of a tower segment 20A. The drawing indicates the diameter D_1P of the primary bolt circle 1P and the average diameter D_20 of the tower segment 20A.

[0043] Ideally, the primary bolt circle 1P has the same diameter D_1P as the average diameter D_20 of the tower shell 20A, i.e. the primary bolt circle 1P is in line with (i.e. coincides with) the mid-plane of the tower shell 20A (as Figure 3The main bolt circle 1 P can need to be slightly offset from the tower shell mid-plane (as shown in Fig. 1), for example to allow non-destructive testing of the weld between the flange 1 and the tower shell 20A (the weld joint between the flange and the tower shell is close to the outer end of the inclined through opening 10 thru). This offset between the main bolt circle 1 P and the tower shell mid-plane is preferably kept to a minimum in order to maintain the advantageous high load carrying capacity of the flange 1 of the present invention.

[0044] Each second body segment 11 incorporates a secondary bolt circle 1 S with openings 11 in an annular arrangement to receive a set of fasteners 1 IB for connecting the flange 1 to an intermediate structure (not shown). Figure 3 denotes the secondary bolt circle 1 S defined by the openings 11, and Figure 2 denotes the diameter D_1S of the secondary bolt circle 1 S. The area of the annular connection face 1 F is determined by the outer diameter D_1F_out and the inner diameter D_1F_in of the flange 1.

[0045] Figure 2 The structure shown in Fig. 1 can be one end of a tower section made of several stacked cylindrical elements. Both outer ends of the tower section terminate in an example of the flange 1 of the present invention. The joints between the cylindrical elements can be achieved using conventional L-shaped flanges or using the X-L-shaped flanges of the present invention.

[0046] As Figure 3 The flange has a connection face 1 F that will abut against the connection face of a complementary flange, as shown in Fig. 1. The figure also shows a possible variant, showing a recess 14 at the lower face of the flange 1. The inner diameter D_1F_in of the annular flange connection face 1 F thus exceeds the diameter D_1S of the secondary bolt circle 1 S. In this embodiment, the total area of the connection face 1 F is less than Figure 1 the connection face area of the embodiment shown in Fig. 1, but the load from the upper tower segment is still effectively transferred into the body of the lower tower segment. The recess 14 can facilitate easier connection to an intermediate device (not shown).

[0047] Figure 4A permanent flange connection 10_perm made by joining two instances of the inventive flange 1 is shown. The connection is "permanent" in the sense that it can withstand during the lifetime of the structure. Here, each flange 1 is formed with alignment features 15A shaped to engage with counter-alignment features 15B of a complementary flange 1. The alignment features 15A, 15B serve to correct any slight ovalization that can exist in the flanges when the tower segments are stacked. The drawing shows a fastener 10B extending through a through-hole 10_thru in the upper flange 1 and into a blind tapered opening 10_part of the lower flange 1. The drawing also shows another oppositely inclined fastener 10B extending through a through-hole 10_thru in the lower flange 1 and into a blind tapered opening 10_part of the upper flange 1.

[0048] Figure 5 Another embodiment of the inventive flange 1 is shown. Here, the flange 1 is implemented as a two-part flange with a first body segment 10 and a separate second body segment 11. The horizontal opening for the fastener is provided by a through-opening 12_thru in the second body segment and a partial or blind opening 12_part in the first body segment. The blind opening can have internal threads to receive the threaded end of a metal screw inserted through the second body segment. In this exemplary embodiment, the through-opening 12_thru, 12_part extends parallel to the flange connection face 1F. An alternative to this bolted joint can be to weld the second body segment 11 to the first body segment 10.

[0049] Figure 6 An embodiment of the inventive flange 1 in a temporary connection 11_temp to an intermediate structure is shown. Here, the flange 1 at the upper end 20A of the tower segment 2 is connected to a lifting fitting 31 of a crane 3 and the flange 1 at the lower end 20B of the tower segment 2 is connected to an upending tool 32 of another crane 3. The cranes 3 are controlled so that the tower segment 2 is "upended", i.e. moved from a horizontal storage orientation to a vertical installation orientation. The connections 11_temp are "temporary" in the sense that they will be disconnected again from the flanges 1. The flanges 1 at each end 20A, 20B of the tower segment 2 will be permanently connected to complementary flanges 1 at a later stage of the tower assembly process, as explained above by means of Figure 4 the drawings.

[0050] The tower segments are often handled in several stages between manufacturing and final installation, and therefore the secondary bolt circle 1S is used to connect the flanges at either end of the tower segment to cradles or brackets of a support structure, an anti-ovalization tool, an adapter of a transport vehicle, etc.

[0051] Figure 7 shows a tower 2 such as a wind turbine tower comprising tower segments 20 "stacked" on top of each other and connected in a prior art manner using L-shaped flanges LF. Fasteners are inserted into the inner bolt circles, the through holes LF H being shown in an enlarged portion in Figure 8. The offset between the bolt circle and the tower wall means that this type of connection is susceptible to excessive bending moments. As a result, the overall height of the tower 2 can be constrained by the load bearing limitations of the flanged connections. To overcome these constraints, alternative prior art structures use T-shaped flanges to connect the tower segments 20 with inner and outer bolt circles, but this solution is associated with significantly higher costs, as explained above.

[0052] Although the present application has been disclosed in the context of preferred embodiments and variations thereof, it will be understood that additional modifications and variations can be made thereto without departing from the scope of the application.

[0053] For the sake of clarity, it is to be understood that the use of "a" or "an" throughout the application does not exclude a plurality, and "comprising" does not exclude other steps or elements.

Claims

1. A flange (1) for connecting to a complementary flange, wherein the flange (1) is part of a tower segment, the tower segment having a circular cross-sectional shape, and wherein the flange (1) comprises: an annular connection surface (1F) which abuts against the complementary annular connection surface of the complementary flange; a first body section (10) having a primary bolt circle (1P) comprising an annular arrangement of angled openings (10_thru, 10_part) for receiving a first set of fasteners (10B) for connecting the flange (1) to the complementary flange; and a second body section (11) having a secondary bolt circle (1S) comprising an annular arrangement of openings (11_thru) for receiving a set of second fasteners (11B) for connecting the flange (1) to the retaining device (3), wherein the diameter (D_1P) of the main bolt circle (1P) is equal to the average diameter (D_20) of the tower sections, wherein the diameter (D_1P) of the primary bolt circle (1P) is greater than the diameter (D_1S) of the secondary bolt circle (1S), and wherein the primary bolt circle (1P) is the circle along which the inclined opening (10_thru, 10_part) at the annular connection surface (1F) extends, and wherein the secondary bolt circle (1S) is the circle along which the opening (11_thru) at the annular connection surface (1F) extends.

2. The flange according to claim 1, wherein The inclined opening (10_thru, 10_part) of the main bolt circle (1P) is characterized by an inclination angle (θ) subtended between a longitudinal axis (10A, 10A') of the inclined opening (10_thru, 10_part) and a surface normal (N) of the annular connection surface (1F).

3. The flange according to claim 2, wherein: The inclination angle (θ) of the inclined opening (10_thru, 10_part) of the main bolt circle (1P) is at least 10°.

4. The flange according to claim 2, wherein: The inclination angle (θ) of the inclined opening (10_thru, 10_part) of the main bolt circle (1P) is at most 30°.

5. The flange according to any one of claims 1 to 4, wherein: The main bolt circle (1P) comprises an alternating arrangement of inclined through-openings (10_thru) and inclined blind openings (10_part).

6. The flange according to any one of claims 1 to 4, wherein: An inclined through-opening (10_thru) extends through the flange (1) to accommodate a shank (10B_s) of a first fastener (10B), the shank of the first fastener extending into a complementary blind opening of the complementary flange.

7. The flange according to any one of claims 1 to 4, wherein: A blind opening (10_part) extends partially into the flange (1) to accommodate a threaded end (10B_t) of a first fastener (10B) extending into the flange (1) after passing through the inclined through-opening of the complementary flange.

8. The flange according to any one of claims 1 to 4, wherein: The longitudinal axis (11A) of the opening (11_thru) of the secondary bolt circle (1S) is collinear with the surface normal (N) of the annular connection surface (1F).

9. The flange according to any one of claims 1 to 4, wherein: The flange (1) is realized as a two-part flange having a first main body section (10) including the primary bolt circle (1P) and a separate second main body section (11) including the secondary bolt circle (1S).

10. The flange according to claim 9, wherein The second main body section (11) is mounted to the first main body section (10) by a third fastener, the third fastener extending through an opening (12_thru, 12_part) parallel to the annular connecting surface (1F).

11. A flange according to any one of claims 1 to 4, comprising an alignment feature (15A) shaped to engage with an opposing alignment feature (15B) of the complementary flange.

12. A method of manipulating a cylindrical tower section (20A) provided with a flange (1) according to any one of claims 1 to 11, the method comprising any of the following: - forming a temporary connection (11_temp) between the tower segment (20A, 20B) and the holding device (3) by means of a plurality of second fasteners (11B) inserted through openings (11_thru) of the secondary bolt circle (1S) of the flange (1), and subsequently releasing the temporary connection (11_temp) by removing the second fasteners (11B) from the secondary bolt circle (1S); - forming a permanent connection (10_perm) between the tower segment (20A) and the other tower segment (20B) by means of a plurality of first fasteners (10B) which are inserted through the main bolt circle (1P) of the flange (1) and openings in the complementary flange of the other tower segment (20B).

13. The method according to claim 12, wherein: The flange (1) is a two-part flange, and wherein, before the step of forming a temporary connection (11_temp), a step of selecting a second body segment (11) having a secondary bolt circle (1S) corresponding to the bolt circle of the retaining device (3) and mounting the selected second body segment (11) to the first body segment (10) of the two-part flange (1) is performed.

14. A wind turbine tower (2) comprising a plurality of cylindrical tower segments (20A, 20B) provided with a flange (1) according to any one of claims 1 to 11 and permanently connected by first fasteners (10B) inserted through inclined openings (10_thru, 10_part) in a main bolt circle (1P) of the flange (1).

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