EP2806086A1

EP2806086A1 - Flange assembly for a tower segment

Info

Publication number: EP2806086A1
Application number: EP13168756.8A
Authority: EP
Inventors: Soeren Oestergaard Mathiasen
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2013-05-22
Filing date: 2013-05-22
Publication date: 2014-11-26
Also published as: CN104179633A; US20150068150A1

Abstract

The present invention concerns a flange assembly (8) for a tower segment (2). The flange assembly comprises a number of flange portions (8a, 8b, 8a', 8b') each with a first interface (14) to the tower segment (2) and a second interface (16a, 16b, 16a', 16b') to connect to another flange portion (8a, 8b, 8a', 8b'). The invention also concerns a production method (Z) for a flange (100).

Description

The present invention concerns a flange assembly for a tower segment. It also concerns a method of construction of such a flange assembly. In particular, the tower segment is realized as a tower segment of a wind turbine tower.
Wind turbines comprise a tower and a nacelle placed on top of that tower, whereby the nacelle is equipped with a rotor which rotates due to the impact of wind. In the nacelle, the rotational movement of the rotor is used to generate electric power.
In order to increase power output of wind turbines the nacelles of the wind turbines are positioned at ever increasing heights. This implies that rotors with longer rotor blades can be installed which then means a higher output of electric energy. Currently, heights of about 80 metres are quite usual, especially in offshore areas. Because of that, the towers which hold the nacelles need to be constructed stable enough to carry both the weights and to withstand the forces that increase substantially with the increase of height. Such forces are for instance vibration forces but also forces due to the movement of the tower in the wind.
Generally, there are two types of towers available today, namely concrete towers and metal tower, i.e. steel towers. Both constructions have in common that they are often not constructed in one piece but rather based on tubular tower sections which are placed on top of each other to build up the entire height of the tower. It is therefore necessary to interconnect these tower sections firmly, for instance by bolting them together along inner or outer flanges at either tubular ends of the tower sections. Such flanges thus project perpendicularly to the axial extension of the tubular tower sections, either into the shape of the tube of the tower sections or out of that shape to the outside of the tube.
Such flanges, in particular in the case of steel towers, are often produced separately and then firmly connected to the tubular parts of the tower sections, for instance by bolting them together.
With the ever-increasing heights of wind turbine towers, the construction of flanges has become a problem: Increasing heights also imply that the diameter of the tower sections, in particular of the lower tower sections, becomes larger and larger as well. For instance, diameters of up to 6,5 metres at the bottom tower section can currently be found. About the same diameters have to be realized for the flanges of such bottom tower sections. The enormous size of such flanges poses problems both during production - as only few facilities can produce such large flanges - and during transport and assembly on site. This leads to an increase in both effort and cost.
It is thus the object of the present invention to provide a solution of how to supply flanges, in particular such large flanges, easier and/or with less consumption of resources.
This object is met by the flange assembly according to claim 1 and by the method according to claim 13.
According to the invention, a flange assembly as mentioned in the introductory paragraph comprises a number of flange portions each with a first interface to the tower segment and a second interface to connect to another flange portion.
Such flange assembly is thus used for the construction of a flange, be it an inner flange or an outer flange, of a tower segment, preferably of a wind turbine tower. Such tower segment preferably comprises a metal structure, such as steel, and the flange assembly preferably comprises the same material as the tower segment. That means if the tower segment primarily comprises metal, the flange assembly is also preferably made of metal, most preferred from the same metal or metal alloy as the metal tower segment. Metal is particularly preferred for both the tower segment and the flange as the connection between the flange (portion) and the tower segment is easier to accomplish and also because currently, concrete towers sections are often produced with the flange as an integral part.
The flange assembly may comprise a single flange portion. In such case, at least one more flange portion is needed to establish a flange. The first interface of each flange portion serves to be connected to the tower segment. This can for instance be accomplished by welding and/or bolting (in the case of a metal tower segment and metal flange portion).
In essence, the invention is based on two principles, namely that of division and that of connection: In order to reduce the size of the produced and/or transported flange assembly overall, use is made of a flange that is divided into a plurality of flange portions. However, it has been found out by the inventor that to use several flange portions which are separately connected to a tower segment is not enough: the construction would be too instable to withhold the forces and tensions inflicted on the tower, at least the tower of a wind turbine which has to endure even more forces than a tower which serves a less mechanical function such as for instance a lighthouse.
Therefore, a flange portion of the flange assembly is equipped with a second interface to interconnect with an adjacent flange portion along the (inner or outer) circumference of the tower. Such interface can be characterized as a contact region of the flange portion which is equipped to get into a firm and stable mechanical contact with the adjacent flange portion. Such equipment of the contact region can also be accomplished upon assembly of the flange portions to become a flange. For instance, the flange portions may be welded together and/or interconnected by a filling material. However, welding is surprisingly not essentially necessary, but rather only constitutes one possibility of connection of flange portions.
It is to be understood that the second interface is located at an end region of the flange portion along its principal extension. This principal extension describes a part of a circle along the (inner or outer) circumference of the tower section. In fact, each flange portion therefore has two such end regions which are most preferably both equipped with a second interface (preferably, but not necessarily of the same shape and/or according to the same connection mechanism). This way one flange portion can be connected at either end region to an adjacent flange portion. In the case where the assembly comprises a number of flange portions which are semi-circular, i.e. constitute exactly one half of a circle, a first flange portion can be connected to a second flange portion of the same size in order to make up a complete flange. That implies that the two flange portions are connected at both their end regions to each other. In case one single flange portion describes less than a half circle, more flange portions (given the flange portions all have the same sizes) are connected so that each flange portion is in contact with two different adjacent flange portions at either end regions.
Preferably, the second interface comprises some dedicated connection element such as a protruding element which fits into a receiving element of the second interface of an adjacent flange portion. More examples will be given below.
The inventor has thus surprisingly found out that although to divide a flange into several portions which are separately connected via their first interfaces to a tower section means a substantial reduction of strength at the junction between two tower sections, it is possible to overcome this weakening by interconnecting the flange portions so that they function together virtually like a flange made of one piece. Therefore, he has provided a solution to the problem of increasing sizes of flanges whilst maintaining sufficient stability at the same time.
The above-mentioned method of construction of a flange assembly for a tower segment - namely for connection to a corresponding flange assembly of another tower segment - comprises the step of providing a flange portion and equipping it with a first interface to the tower segment and with a second interface to connect to a further flange portion.
Further, the invention also concerns a flange for a tower segment comprising a flange assembly according to the invention, the flange portions of which are interconnected. That means that each of the flange portion is at least connected to one other adjacent flange portion as indicated above.
Thus, the invention also concerns a method of construction of a flange for a tower segment comprising the steps of

providing a flange assembly comprising a plurality of flange portions each with a first interface to the tower segment and a second interface to connect to another flange portion,
interconnecting the flange portions via their second interfaces to form the flange.

Furthermore, the invention concerns a tower segment, in particular of a tower of a wind turbine, comprising a flange according to the invention and thus also a method of construction of a tower segment, in particular of a tower of a wind turbine, comprising the steps of

providing a flange constructed using the method according to the invention,
connecting the flange to the tower segment via the first interfaces.

Lastly, the invention also concerns a tower, in particular a tower of a wind turbine, comprising at least one tower segment according to the invention, and a method of constructing a tower, in particular a tower of a wind turbine, whereby a number of tower segments are interconnected, at least one tower segment of which is produced according to a method according to the invention.
Particularly advantageous embodiments and features of the invention are given by the dependent claims, as revealed in the following description. Features of different claim categories may be combined as appropriate to give further embodiments not described herein.
As indicated above, a flange assembly according to the invention may comprise a single flange portion of the above-described kind. In order to be able to produce a flange out of a flange assembly, it is however necessary that the flange assembly comprises a plurality of flange portions each interconnectable with at least another flange portion via their second interfaces. Most preferred the number of flange portions is chosen such that a complete flange can be produced by interconnceting them via their second interfaces. For instance if each of the flange portions describes a third of a circle, three of the above-described flange portions are preferably included in the package or set, i.e. are part of the flange assembly.
It is thereby preferred to use as few flange portions as possible because interconnecting the flange portions is also time-consuming. Thus it is most preferred that exactly two flange portions are in the flange assembly, i.e. the set of flange portions which make a flange when interconnected. In case tower segments become even bigger and/or if the transport facilities at hand are considerably small, it may however also be suitable to use smaller and thus more flange portions instead of only two, for instance three or four flange portions to make a flange when interconnected. According to a first variant, complementary second interfaces of interconnectable flange portions are realized to interconnect by means of form fit. That implies that the shape of one second interface of one flange portion fits to the shape of a second interface of an adjacent flange portion in such way that they engage. For that purpose, the contact regions of the second interfaces of the two adjacent flange portions comprise more than one single flat surface. Rather both contact surfaces of the two second interfaces must be curved and/or comprise angles and be realized and located such that they correspond in shape to be fitted into/onto each other. The two contact surfaces are thus designed as complementary connection surfaces.
According to a second variant, which can be used as an alternative or as an add-on, the second interfaces of interconnectable flange portions are realized to interconnect by means of force closure and/or by means of welding.
That second variant implies that not (only) form fit is used as a connection priciple between two adjacent flange portions but an even firmer connects in which forces and/or tensions are directly and reliably transferred from one flange portion into the adjacent next one.
Welding has the advantage that the two flange portions are permanently joined such that they form one integral element. However, contrary to what one might believe, welding is only preferred in special applications of the inventions rather than as a rule. It has been found out by the inventor that such welding may introduce additional stress into the flange. That means that welding is only an option, but not an overall necessity.
Force closure is a less permanent solution with a comparable effect concerning stability of the interconnection. Thereby, it is preferred that a number of fasteners such as bolts is used for the connection. For that purpose, both adjacent flange portions comprise through-openings through which the fasteners can be led before tightening. These trough-openings must be complementary in shape and position. Such solution is particularly preferred because through openings exist in flanges anyway and serve the purpose of interconncting adjacent flanges of two adjacent tower sections. Thus, the through-openings of the flange portions in the region of the second interfaces can be used at the same time to connect flange portions.
In particular, it is preferred that a second interface of at least one flange portion comprises a protruding element which protrudes from an end of that flange portion with respect to a circumference of the tower segment. This means that the end of the flange portion is extended by the protruding element, at least (and preferably) partially. Such protruding element can then be used to (at least partially) establish the second interface of the flange portion. This provides for instance for a considerably easy form fit effect. This is particularly so with a first flange portion the second interface of which comprising a first protruding element which protrudes from the end of the first flange portion at a first level and with the second interface of an adjacent flange portion comprising a second protruding element which protrudes from the end of that adjacent flange portion at a second level. Both can then be aligned and interconnected such that the first and second protruding elements are positioned one above the other when the two flange portions are connectedly aligned at a substantially same level along the circumference of the tower segment. In other words: One (upper) protruding element of one flange portion lies above another (lower) protruding element of an adjacent flange portion whilst the two flange portions are essentially aligned along the same level with respect to their designated position relative to the tower segment.
It is further preferred that the second interface of a first flange portion comprises a tooth which corresponds in shape and position with an inlet opening of a second interface of an adjacent flange portion to interconnect with the inlet opening. Such tooth can thus be form fitted into the inlet opening. It is most preferably directed at an angle other than 0° or 180° to the principal extension of the flange portions. This way the connection between the tooth and the inlet opening can compensate and/or transfer forces or tensions directed from one flange portion towards the adjacent flange portion.
It is possible to realize the invention using a number of differently sized and/or shaped or otherwise differently configured flange portions. That may for instance be useful in such cases in which the tower section which is to be equipped with a flange comprises an opening in its shell which opening opens towards an adjacent tower section. Then, it may be that not a complete circle can be realized as a flange. However, it is highly preferred that a plurality of flange portions, most preferred the complete amount of flange portions, of the flange assembly has the same shape and size. This means that one standard flange portion can be used for each flange so that production (and also transport) becomes easier, less time-consuming and thus also cheaper.
Although flanges have been described throughout this description as simply circular, it may be noted that other shapes of flanges along the circumference of a tower section may also be realized, this certainly depending on the respective shape of the tower section. Thus, in particular oval tower sections and flanges can be realized. Even tower sections (and thus flanges) may be used with angled cross sections.
Other objects and features of the present invention will become apparent from the following detailed descriptions considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention. They are not necessarily drawn to scale.

Fig. 1 shows a wind turbine according to the prior art,
Fig. 2 shows a prior art tower section connection,
Fig. 3 shows a top view of a first embodiment of a flange and a flange arrangement according to the invention,
Fig. 4 shows a section view along a section line IV - IV of Fig. 3,
Fig. 5 shows a section view along a section line B - B of Fig. 3,
Fig. 6 shows a section view along a section line VI - VI of Fig. 3 of a second embodiment of a flange and a flange arrangement according to the invention,
Fig. 7 shows a section view along a section line B - B of Fig. 3 of the same second embodiment,
Fig. 8 shows a schematic block diagram of embodiments of the methods according to the invention.

Fig. 1 shows a wind turbine 4 of a usual construction. A nacelle 6 is supported by a tower 5. The tower 5 is made by stacking tower sections 2 one on top of the other to reach the desired height. As the diagram indicates, the tower 5 is usually widest at the bottom and tapers gradually towards the nacelle 6. The tower sections 2 are therefore also tapered accordingly. Adjacent tower sections 2 must be firmly secured to each other. To this end, a tower section 2 will have an interior and/or an exterior flange at its upper and/or lower edges (depending on its position in the tower), to match the flange(s) of one or two adjacent tower sections.
Fig. 2 shows a prior art connection arrangement for the sections 2 of a wind turbine tower 5. Here, the problems with the prior art constructions are illustrated using two different flange realisations, although it is usual to use the same realisation for both tower sections 2.
The upper part of the diagram shows an upper tower section 2 with a shell 20 welded to an upper flange 100', leaving a raised weld seam 23. The lower part of the diagram shows a lower tower section 2 with a shell 20 welded to a lower flange 100', also, leaving a raised weld seam 23. Both the upper and the lower flange 100' are equipped with corresponding through-openings 10 one of which each is indicated in the diagram. These through-openings 10 are supplied all along the circumference of both tower sections 2, in order to permit bolts 3 to be inserted through them. These bolts 3 are firmly tightened by nuts 30 at either side, with washers 31 adjacent to the nuts. In addition, between the upper washer 31 and the upper flange 100', there is a strengthening element 70, also equipped with a complementary through-opening to permit the bolt 3 to pass through it. By tightening the nuts 30 at both ends of the bolt 3, the two flanges 100' are firmly pressed together and connected by force closure.
According to the prior art, such flanges 100' as shown in Fig. 2 are made of one piece. According to the invention, this is changed. Figs 3 to 7 thus show two embodiments of a flange 100 and of a flange assembly 8. Thereby, Fig. 3, although referring to the first embodiment, is used as a reference for Figs 6 and 7 as well, although it becomes clear from these latter section views that the second embodiment is different with some respects - thus the different elements are marked by a "'" in the respective reference signs in Figs. 6 and 7. Still, for the purpose of referring to the section points, Fig. 3 fully suffices.
Referring to Fig. 3, the flange assembly 8 comprises two semi-circular flange portions 8a, 8b which are interconnected at two interface regions 16. In this interconnected state they thus form a flange 100. It is also shown that the flange portions 8a, 8b in the interface regions 16 comprise a number of through-openings 10 such as the ones shown in Fig. 2. As will be shown with reference to Figs. 4 to 7, these through-openings 10 are part of the connection between the two flange portions 8a, 8b.
Figs. 4 and 5 show two section views of this first embodiment of Fig. 3.
Both flange portions 8a, 8b - Fig. 5 shows the first flange portion 8a - comprise an essentially square (along the perpendicular extension to the main extension ME of the flange portions 8a, 8b) main body 12 and an upper connection part 24. The surface 14 of the upper connection part 24 facing away from the main body 12 serves as a first interface 14 for welding to a tower section - cf. Fig. 2. In the interface region 16 each of the flange portions 8a, 8b comprises a second interface 16a, 16b. These two second interfaces 16a, 16b are complementary in shape and position: The second interface 16a of the first flange portion 8a comprises a protruding element 22a (protruding from the end surface 18a of the first flange portion 8a towards the end surface 18c of the second flange portion 8b) which fits exactly under a corresponding protruding element 22b (protruding from the end surface 18c of the second flange portion 8b towards the end surface 18a of the first flange portion 8a). Along an inner surface 18b, the two protruding elements 22b, 22a are placed on top of each other. They are thus form fitted. To further enhance the connection of the two flange portions 8a, 8b bolts 3 (not shown) are inserted into the through-openings 10 so that a bolt passing through both flange portions 8a, 8b in the interface region 16 will automatically interconnect the two flange portions 8a, 8b by additional force closure. Additionally, a filling material, in particular an adhesive and/or a sealing filling material can be introduced along the contact surfaces 18a, 18b, 18c of the interface region 16. This can serve as a sealing material but also add more strength to the overall connection.
Figs. 6 and 7 show a second embodiment of the invention in two section views. As most of the features in these figures are the same as in the preceding two figures, only the additional elements will be described:

A first flange portion 8a' and a second flange portion 8b' make up the flange assembly 8' and indeed (cf. Fig. 3) the complete flange 100. The difference with the first embodiment lies in the geometric approach of the two second interfaces 16a', 16b'. Namely, the protruding element 22a' of the first flange portion 8a' comprises a tooth 26 projecting from the connection surface 18b upwards. Correspondingly, the protruding element 22b' comprises an inlet opening 28 into which the tooth 26 fits. This combination of tooth 26 and inlet opening 28 adds more strength to the overall connection of the two flange portions. 8a', 8b'.

Referring now to Fig. 8, this shows schematic block diagrams of embodiments of all mentioned methods Z, Y, X, R according to the invention.
Firstly referring to the method Z of construction of a flange assembly 8, 8' according to the invention. This comprises a first step W of providing a flange portion 8a, 8a' and a second step V of equipping that flange portion 8a, 8a' with a first interface 14 to a tower segment and with a second interface 16a, 16a' to connect to a further flange portion 8b, 8b'.
In order to further construct a flange 100 according to method Y that method Y comprises a step U in which a plurality of such flange portions 8a, 8b, 8a', 8b' is provided and interconnected via their second interfaces 16a, 16b, 16a', 16b' to form the flange 100.
A tower segment 2 is constructed according to the method X which after the provision of the flange 100 by method Y further comprises a step T of connecting the flange 100 to the tower segment 2 via the first interfaces 14.
Lastly, a tower 5 can be constructed using method R which further comprises step S whereby a number of tower segments 2 are interconnected, at least one tower segment 2 of which has been produced according to the last-mentioned method X.
Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.
For the sake of clarity, it is to be understood that the use of 'a' or 'an' throughout this application does not exclude a plurality, and 'comprising' does not exclude other steps or elements.

Claims

Flange assembly (8) for a tower segment (2), the flange assembly comprising a number of flange portions (8a, 8b, 8a', 8b') each with a first interface (14) to the tower segment (2) and a second interface (16a, 16b, 16a', 16b') to connect to another flange portion (8a, 8b, 8a', 8b').
Flange assembly according to claim 1, comprising a plurality of flange portions (8a, 8b, 8a', 8b') each interconnectable with at least another flange portion (8a, 8b, 8a', 8b') via their second interfaces (16a, 16b, 16a', 16b').
Flange assembly according to claim 2, whereby complementary second interfaces (16a, 16b, 16a', 16b') of interconnectable flange portions (8a, 8b, 8a', 8b') are realized to interconnect by means of form fit.
Flange assembly according to claim 2 or 3, whereby the second interfaces (16a, 16b, 16a', 16b') of interconnectable flange portions (8a, 8b, 8a', 8b') are realized to interconnect by means of force closure, preferably by a number of fasteners (3), and/or by means of welding.
Flange assembly according to any one of the preceding claims, whereby a second interface (16a, 16b, 16a', 16b') of at least one flange portion comprises a protruding element (22a, 22b, 22a', 22b') which protrudes from an end of that flange portion (16a, 16b, 16a', 16b') with respect to a circumference of the tower segment (2).
Flange assembly according to claim 5, comprising a first flange portion (8a, 8a') the second interface (16a, 16a') of which comprising a first protruding element (22a, 22a') which protrudes from the end of the first flange portion (8a, 8a') at a first level and whereby the second interface (16b, 16b') of an adjacent flange portion (8b, 8b') comprises a second protruding element (22b, 22b') which protrudes from the end of that adjacent flange portion (8b, 8b') at a second level in such way that the first and second protruding elements (22a, 22a', 22b, 22b') are positioned one above the other when the two flange portions (8a, 8b, 8a', 8b')are connectedly aligned at a substantially same level along the circumference of the tower segment (2).
Flange assembly according to any one of claims 2 to 6, whereby the second interface (16a') of a first flange portion (8a') comprises a tooth (26) which corresponds in shape and position with an inlet opening (28) of a second interface (16b') of an adjacent flange portion (8b') to interconnect with the inlet opening (28).
Flange assembly according to any one of claims 2 to 6, whereby a plurality of flange portions (8a, 8b, 8a', 8b') has the same shape and size.
Flange (100) for a tower segment (2) comprising a flange assembly (8) according to any one of claims 2 to 8, the flange portions of which are interconnected.
Tower segment (2), in particular of a tower (5) of a wind turbine (4), comprising a flange (100) according to claim 9.
Tower (5), in particular tower of a wind turbine (4), comprising at least one tower segment (2) according to claim 10.
Method (Z) of construction of a flange assembly (8) for a tower segment (2), comprising the step of providing (W) a flange portion (8a, 8a') and equipping (V) it with a first interface (14) to the tower segment (2) and with a second interface (16a, 16a') to connect to a further flange portion (8b, 8b').
Method (Y) of construction of a flange (100) for a tower segment (2) comprising the steps of
- providing (Z) a flange assembly (8) comprising a plurality of flange portions (8a, 8b, 8a', 8b') each with a first interface (14) to the tower segment (2) and a second interface (16a, 16b, 16a', 16b') to connect to another flange portion (8a, 8b, 8a', 8b'),

- interconnecting (U) the flange portions (8a, 8b, 8a', 8b') via their second interfaces (16a, 16b, 16a', 16b') to form the flange (100).
Method (X) of construction of a tower segment (2), in particular of a tower (5) of a wind turbine (4), comprising the steps of
- providing (Y) a flange (100) constructed using the method according to claim 13,

- connecting (T) the flange (100) to the tower segment (2) via the first interfaces (14).
Method (R) of constructing a tower (5), in particular a tower of a wind turbine (4), whereby a number of tower segments (2) are interconnected, at least one tower segment (2) of which is produced according to a method (X) according to claim 14.