U.S. patent application number 12/626062 was filed with the patent office on 2010-05-27 for wind power plant and a method for assembling the same.
This patent application is currently assigned to VESTAS WIND SYSTEMS A/S. Invention is credited to Jonas Kristensen.
Application Number | 20100126079 12/626062 |
Document ID | / |
Family ID | 41323397 |
Filed Date | 2010-05-27 |
United States Patent
Application |
20100126079 |
Kind Code |
A1 |
Kristensen; Jonas |
May 27, 2010 |
WIND POWER PLANT AND A METHOD FOR ASSEMBLING THE SAME
Abstract
A wind power plant includes a tower, the tower including at
least one tower section provided with at least one flange and
forming at least part of the wall of the tower. The power plant
further includes an element provided with at least one flange and
adapted to be installed adjacent the tower section. The tower
section and the element have abutting flanges, the flanges being
releasably interconnected by sets of bolts and nuts. At least one
surface associated with each set of bolt and nut and facing away
from the flanges is provided with a plurality of recesses for
receiving projections of a tightening device. A method of joining a
tower section and an adjacent element is also disclosed.
Inventors: |
Kristensen; Jonas; (Skjern,
DK) |
Correspondence
Address: |
WOOD, HERRON & EVANS, LLP
2700 CAREW TOWER, 441 VINE STREET
CINCINNATI
OH
45202
US
|
Assignee: |
VESTAS WIND SYSTEMS A/S
Randers SV
DK
|
Family ID: |
41323397 |
Appl. No.: |
12/626062 |
Filed: |
November 25, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61118680 |
Dec 1, 2008 |
|
|
|
Current U.S.
Class: |
52/40 ; 52/292;
52/651.01; 52/705; 52/745.17 |
Current CPC
Class: |
E02D 27/42 20130101;
E02D 27/425 20130101; F03D 80/00 20160501; F05B 2240/912 20130101;
B25B 13/02 20130101; B25B 13/485 20130101; Y02E 10/728 20130101;
F03D 13/22 20160501; E04H 12/085 20130101; F16B 23/0069
20130101 |
Class at
Publication: |
52/40 ; 52/705;
52/651.01; 52/292; 52/745.17 |
International
Class: |
E04H 12/00 20060101
E04H012/00; E04B 1/38 20060101 E04B001/38; E02D 27/00 20060101
E02D027/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 27, 2008 |
DK |
PA 2008 01671 |
Claims
1. A wind power plant comprising a tower, said tower comprising at
least one tower section provided with at least one flange and
forming at least part of the wall of the tower, said power plant
further comprising an element provided with at least one flange and
adapted to be installed adjacent said tower section, wherein said
tower section and said element have abutting flanges, said flanges
being releasably interconnected by sets of bolts and nuts, wherein
at least one surface associated with each set of bolt and nut and
facing away from said flanges is provided with a plurality of
recesses for receiving projections of a tightening device.
2. A wind power plant according to claim 1, wherein said element is
a tower section.
3. A wind power plant according to claim 1, wherein said element is
a tower foundation.
4. A wind power plant according to claim 1, wherein said element is
a nacelle of the wind power plant.
5. A wind power plant according to claim 1, wherein said nuts are
provided with said recesses.
6. A wind power plant according to claim 1, wherein said bolts each
have a bolt head provided with said recesses.
7. A wind power plant according to claim 1, wherein at least one of
said sets of bolts and nuts comprises a stud bolt and two nuts,
said two nuts each provided with said recesses.
8. A wind power plant according to claim 1, wherein each bolt
further comprises an at least partially threaded shaft, said bolt
being arranged such that its shaft is parallel to the longitudinal
axis of the tower, and wherein the distance between a wall of the
tower facing said flange and an outer periphery of the shaft is
less than 70 mm, more preferred less than 60 mm and most preferred
less than 50 mm.
9. A wind power plant according to claim 1, wherein each bolt is
arranged such that a head thereof is orientated downwards.
10. A wind power plant according to claim 1, wherein said recesses
are provided with such depth that projections of a tightening
device are fully insertable into said recesses.
11. A wind power plant according to claim 1, wherein the recesses
are provided with such width that the inner lateral surfaces of the
recesses abut outer lateral surfaces of projections of a tightening
device when said projections are inserted into said recesses.
12. A wind power plant according to claim 1, wherein the recesses
are cylindrical blind bores arranged parallel to each other.
13. A method for joining a tower section to an adjacent element of
a wind power plant comprising: arranging the tower section and the
element such that a flange of tower section is brought into contact
with a flange of the element, aligning holes arranged in the flange
of the tower section with holes arranged in the flange of the
element, interconnecting the flanges by sets of bolts and nuts, the
bolts being arranged and extending through at least some of the
aligned holes, and tightening each set of bolt and nut with a
tightening device having projections adapted to engage recesses
provided in at least one surface associated with said set and
facing away from the flanges.
14. A method according to claim 13, further comprising the step of
arranging each bolt such that a head thereof is oriented downwards.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims prior under 35 U.S.C. .sctn. 119(a)
to DK Application No. PA 2008 01671, filed Nov, 27, 2008. This
application also claims the benefit of U.S. Provisional Application
No. 61/118,680, filed Dec. 1, 2008. Each of these applications is
incorporated by reference herein in its entirety.
TECHNICAL FIELD
[0002] The present invention generally relates to a wind power
plant and a method for assembling a wind power plant.
BACKGROUND
[0003] Towers for wind power plants may be constructed from, for
example, steel lattice frameworks, concrete, steel tubes or
composite materials. Currently, the towers are predominantly made
of a number of tubular steel sections mounted on top of each other
and interconnected by using bolted flange joints. The method of
connecting objects by means of bolted flange joints has long been
known in the art and the method is universally employed.
[0004] The flanges are usually provided with a plurality of
through-holes uniformly distributed along the flanges. This
arrangement allows for a large number of bolts and corresponding
nuts to be used.
[0005] One way to assemble sections of a wind turbine tower by
using bolts and nuts is disclosed in US patent application
US2006000185.
[0006] However, ever larger and heavier towers are being
continuously developed as this is a fairly simple way to increase
power output of the wind power plant by taking advantage of the
higher wind speed, and thus higher energy content, at higher
altitude. As a consequence, the wind loads on the tower have
increased significantly and the strength requirements of the wind
tower components in general and their flange joints in particular
will also increase. Consequently, the required number of bolts and
corresponding nuts has also increased significantly. However, this
is in conflict with the constant goal of reducing the weight of the
tower, the material consumption, the work required to install the
wind power plant and thus the total cost.
SUMMARY
[0007] In view of the above, one embodiment in accordance with
aspects of the invention renders possible the use of an increased
number of nuts and bolts in order to interconnect a flange of a
tower section with a flange of an adjacent element.
[0008] Another embodiment in accordance with aspects of the
invention decreases the size of the flanges of both the tower
sections as well as the adjacent element, thereby achieving
material savings.
[0009] In yet another embodiment, the structural strength of the
tower as a whole is increased.
[0010] A further embodiment in accordance with aspects of the
invention provides a method for assembling a tower, the tower being
part of the wind power plant.
[0011] Embodiments in accordance with aspects of the invention
relate to a wind power plant comprising a tower, the tower
comprising at least one tower section provided with at least one
flange and forming at least part of the wall of the tower, the
power plant further comprising an element provided with at least
one flange and adapted to be installed adjacent the tower section,
wherein the tower section and the element have abutting flanges,
the flanges being releasably interconnected by sets of bolts and
nuts, wherein at least one surface associated with each set of bolt
and nut and facing away from the flanges is provided with a
plurality of recesses for receiving projections of a tightening
device.
[0012] By providing a surface of each bolt or nut facing away from
the flanges with a plurality of recesses and consequently enabling
it to receive projections of the tightening device, a torque may be
applied by means of the tightening device without engaging the
external lateral surfaces of the bolt or the nut. Instead, the
interface surface for transmitting the torque to the bolt or the
nut is the surface provided with a plurality of recesses. As a
consequence, less space is required in order to tighten individual
sets of bolts and nuts.
[0013] This means that sets of bolts and nuts may be positioned
closer to the tower wall since less space around the nut is
required for tightening the bolt. Accordingly, the flange width can
be reduced, thereby reducing the material consumption, production
costs and also the weight of the tower.
[0014] Furthermore, the individual sets of bolts and nuts may be
positioned closer to each other, ensuring that an increased number
of bolts and nuts may be installed along the circumference of the
flanges. The increased number in combination with the closer
positioning of the bolts and nuts relative the tower wall may
increase structural stability of the tower.
[0015] The element adapted to be installed adjacent the tower
section can be another tower section, a tower foundation, a nacelle
or some other component of the wind power plant. Accordingly, the
sets of bolts and nuts can be arranged in any interconnection
between the main structural parts of a wind power plant, which
structural parts are interconnected by flange joints.
[0016] The nuts can be provided with the recesses, whereby the
bolts as such can be standardized and readily available bolts.
[0017] The bolts can each have a bolt head provided with the
recesses. Such bolt can either be used with a standardized, readily
available nut or together with a nut provided with recesses.
[0018] At least one of the sets of bolts and nuts can comprise a
stud bolt and two nuts, the two nuts each provided with the
recesses. A stud bolt is known as a shaft being threaded along its
full length or along a portion of its two ends. The stud bolt can
be a standardized and readily available stud bolt.
[0019] Each bolt can further comprise an at least partially
threaded shaft, the bolt being arranged such that its shaft is
parallel to the longitudinal axis of the tower, and wherein the
distance between a wall of the tower facing the flange and an outer
periphery of the shaft is less than 70 mm, more preferred less than
60 mm and most preferred less than 50 mm.
[0020] It is to be understood that the distance to the tower wall
depends on the size of the nut and the bolt head. Since the torque
required to tension the bolt and nut can be applied by a tightening
device without engaging the lateral sides of the bolt head or the
nut, the bolt head or the nut can be arranged directly adjacent the
tower wall. Accordingly the flange width can be reduced while
maintaining the structural stability of the tower.
[0021] Each bolt can be arranged such that a head thereof is
orientated downwards. The technician installing the wind tower may
thus perform his tasks in an optimal working position. This also
facilitates the connecting of the bolt with the corresponding nut,
since threading of the nut on the shaft of the bolt may be visually
controlled.
[0022] The recesses can be provided with such depth that
projections of a tightening device are fully insertable into the
recesses. In this way, the contact of the bolt or nut surface
provided with recesses and the surface of the tightening device
from which the projections extend is ensured. The friction between
these two surfaces may provide additional grip while the bolt and
nut are being tightened.
[0023] The recesses can be provided with such width that the inner
lateral surfaces of the recesses abut outer lateral surfaces of
projections of a tightening device when the projections are
inserted into the recesses. In this way, a close fit of the
tightening device and the bolt or nut is achieved while the bolt
and nut are being tightened. This may contribute to an improved
torque transfer from the tightening device to the bolt or nut.
[0024] The recesses can be cylindrical blind bores arranged
parallel to each other. In this way, a simplified manufacturing
process of the bolts or nuts, using relatively simple tools may be
achieved. This may reduce the overall production costs. It is to be
understood that recesses with the same function can be arranged as
through-holes.
[0025] According to another aspect, embodiments in accordance with
aspects of the invention relate to a method for joining a tower
section to an adjacent element of a wind power plant comprising:
arranging the tower section and the element such that a flange of
the tower section is brought into contact with a flange of the
element, aligning holes arranged in the flange of the tower section
with holes arranged in the flange of the element, interconnecting
the flanges by sets of bolts and nuts, the bolts extending through
at least some of the aligned holes, and tightening each set of bolt
and nut with a tightening device having projections adapted to
engage recesses provided in at least one surface associated with
the set and facing away from the flanges.
[0026] The method allows, as has been discussed above in view of
the wind power plant, sets of bolts and nuts to be positioned
closer to the tower wall. This may make it possible to reduce the
width of the flange, thereby reducing the material consumption and
the total weight of the tower.
[0027] Furthermore, the inventive method may make it possible to
install an increased number of sets of bolts and nuts along the
circumference of the flange, thereby increasing the structural
stability of the tower.
[0028] The method can further comprise the step of arranging each
bolt such that a head thereof is oriented downwards. The technician
installing the tower may thus perform his tasks (e.g. tightening
the sets of bolts and nuts) in an optimal working position. This
also facilitates the connecting of the bolt with the corresponding
nut, since threading of the nut on the shaft of the bolt may be
visually controlled.
[0029] Other objectives, features and advantages of the present
invention will appear from the following detailed disclosure, from
the attached claims as well as from the drawings.
[0030] Generally, all terms used in the claims are to be
interpreted according to their ordinary meaning in the technical
field, unless explicitly defined otherwise herein. All references
to "a/an/the [element, device, component, means, step, etc]" are to
be interpreted openly as referring to at least one instance of the
element, device, component, means, step, etc., unless explicitly
stated otherwise. The steps of any method disclosed herein do not
have to be performed in the exact order disclosed, unless
explicitly stated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The above, as well as additional objects, features and
advantages of the present invention, will be better understood
through the following illustrative and non-limiting detailed
description of preferred embodiments of the present invention, with
reference to the appended drawings, where the same reference
numerals will be used for similar elements.
[0032] FIG. 1 is a schematic view of a wind power plant;
[0033] FIG. 2 is a cross-sectional view of a flange joint between
two adjacent sections of the tower without any bolts and nuts;
[0034] FIG. 3 is a cross-sectional view of a flange joint between
two adjacent sections of the tower with a plurality of sets of
bolts and nuts;
[0035] FIG. 4 shows a first embodiment of a set of a bolt and a
nut;
[0036] FIG. 5 shows a second embodiment of a set of a bolt and nut;
and
[0037] FIG. 6 shows one embodiment of a tightening device.
DETAILED DESCRIPTION
[0038] FIG. 1 is a schematic view of a wind power plant 1 with a
nacelle 3 supported by a tower 2. The purpose of the tower 2 is to
support the weight of a nacelle 3 that is arranged on top of the
tower 2. Further, it serves to position rotor blades 4 to a
suitable operational height.
[0039] Modern towers comprise a plurality of tubular tower sections
5, which may be manufactured in 20-30 meter long segments and
subsequently mounted on top of each other to provide the tower with
a sufficient height. Typically, the tower sections are made of
steel. The shape of the individual tower sections are normally
either straight cylindrical or frusto-conical.
[0040] FIG. 2 is a vertical cross-sectional view of a portion of an
upper 8 and a lower 9 tower section with corresponding flanges 6,
7.
[0041] Each tower section 8, 9 normally comprises a flange
positioned at each end of the tower section. A first flange 6 is
attached to the upper tower section 8 and a second flange 7 is
attached to the lower tower section 9. In the disclosed embodiment
each flange 6, 7 runs along the entire circumference of the
associated tower section 8, 9. It is to be understood that the
flanges may also be divided into a number of flange sections which
together form a circumferential continuous or non-continuous
flange.
[0042] For practical reasons, each flange 6, 7 is normally mounted
as a separate part to the individual tower section by using a
suitable joining technique, for example welding.
[0043] The first flange 6 has a substantially L-shaped
cross-section with a first leg 10 extending horizontally towards
the interior of the tower, thus forming a substantially
perpendicular angle with the longitudinal axis LA of the tower
sections 8 and 9, and a second leg 11 attached to the upper tower
section 8 by means of a welding seam 50 at the lower edge 12 of the
upper tower section 8.
[0044] Analogously, the second flange 7 also has a substantially
L-shaped cross-section with a first leg 13 extending horizontally
towards the interior of the tower, thus forming a substantially
perpendicular angle with the longitudinal axis LA of the tower
sections 8, 9, and a second leg 14 attached to the lower tower
section 9 by means of a welding seam 50 at the upper edge 15 of the
lower tower section 9.
[0045] The inwards extending horizontal first legs 10, 13 of the
first and second flanges 6, 7 are in direct contact with each
other.
[0046] Each flange 6, 7 is provided along its circumferential
extension with a number of through-holes 16. The through-holes 16
may be circumferentially equally spaced from one another or
arranged in groups. The through-holes 16 of the first flange 6 are
aligned with the through-holes of the second flange 7.
[0047] The flanges 6, 7 are used as flat support surfaces when the
two adjacent, upper 8 and lower 9, tower sections are to be
interconnected.
[0048] Now turning to FIG. 3 a portion of the upper and lower tower
sections 8, 9 with the corresponding flanges 6, 7 are shown in an
interconnected state.
[0049] As it may be seen, the flanges 6, 7 are interconnected by
means of a plurality of sets 18 of bolts 19 and nuts 20 engaging
the through-holes 16. The bolts can be provided with washers (not
shown).
[0050] Typically, each bolt 19 is arranged such that a bolt head 25
thereof, when installed, is orientated downwards. However, upwards
orientated bolt heads 25 are also conceivable. Typically,
standardized and readily available bolts are used. The bolt 19 can
be threaded along the full length of its shaft 26 or, as shown, be
threaded only along its free end.
[0051] As can be seen in FIGS. 3 and 4, each nut 20 has an internal
thread which engages the threaded section of the bolt shaft 26. The
nut 20 according to the shown embodiment has circular
cross-section, although it is to be understood that other
cross-sectional shapes are equally possible. This also applies to
the bolt head 25.
[0052] The surface 22 of the nut 20 facing away from the bolt head
25 and flange is provided with a plurality of recesses 21 extending
in the longitudinal direction of the shaft 26. In the disclosed
embodiment the recesses 21 are shaped as cylindrical blind bores
and arranged parallel to one another and circumferentially
uniformly distributed. Still it is to be understood that any
pattern and geometry can be used. Also, it is to be understood that
the recesses can be arranged as through-holes. Typically, there are
6-12 recesses 21 per nut 20, depending on the size of the nut.
[0053] Although not shown, it is to be understood that generally
the bolt head 25 as such can be provided with recesses
corresponding to the recesses of the nut.
[0054] Now turning to FIG. 5, as an alternative to a threaded bolt
and a nut provided with the recesses, the bolt can be a so called
stud bolt 19', i.e., a shaft 26' provided with threads, either
along its full length or along its two free ends. Such stud bolt
19' is used together with two nuts 20', each having the above
disclosed recesses 21.
[0055] FIG. 6 shows one embodiment of a tightening device 27. The
tightening device 27 typically comprises an engagement head 30
having a plurality of circumferentially distributed projections 28.
The distribution pattern as well as the size and geometry of the
projections 28 correspond to those of the recesses 21 of the nut
20. A dedicated tightening device 27 may be made available for each
nut size.
[0056] The tightening device 27 may, as shown in FIG. 6, include a
handle 31 adapted to operate in conjunction with the engagement
head 30. The handle 31 can be a fixed handle, an interchangeable
handle or even a ratchet wrench.
[0057] Referring back to FIGS. 2 and 3, when joining the two tower
sections 8, 9 by the flange joint, the two tower sections are
arranged on top of each other with the two opposing flanges 6, 7
lying flat against each other so that their corresponding
through-holes 16 are aligned. A bolt 19 is arranged in each
through-hole 16 thus formed and a nut 20 is threaded onto the free
end of the bolt 19. Then the engagement head 30 of the tightening
device 27 is arranged to the nut 20 with the projections 28
inserted to the recesses 21. Finally, the bolt 19 is tensioned by
applying a sufficient torque to the nut 20. This procedure is
repeated throughout the flange joint.
[0058] By allowing play between the bottom surface of the recess 21
and the front surface of the projection 28, i.e., the depth of the
recesses is exceeding the length of the projections, the
projections 28 of the tightening device 27 are fully insertable
into the recesses 21. This means that the contact between the nut
surface 22 provided with recesses 21 and the surface of the
tightening device 27 from which the projections 28 extend is
ensured. Consequently, the friction between the inner lateral
surfaces of the recesses and the outer lateral surfaces of the
projections provide additional grip while the nut 20 is being
tightened.
[0059] By providing recesses 21 with such width that their inner
lateral surfaces abut the outer lateral surfaces of the projections
28, a close fit of the tightening device 27 and the nut 20 is
achieved while the nut 20 is being tightened. This may contribute
to an improved torque transfer from the tightening device 27 to the
nut 20.
[0060] By the design of the recesses 21 and the projections 28, the
tightening device 27 can engage the nut 20 and tighten it on the
bolt 19 without engaging the lateral surfaces of the nut 20. As a
consequence, less space is required in order to tighten individual
nuts 20.
[0061] By the tightening device 27 engaging the nut 20 in the
longitudinal direction of the bolt 19 without any circumferential
outer engagement, a larger number of sets 18 of bolts 19 and nuts
20 can be used allowing a higher structural strength of the tower.
Also, the width of the flanges can be reduced since the sets 18 of
bolts 19 and nuts 20 can be arranged closer to the longitudinal
wall of the tower section, allowing a reduced weight and material
consumption and thus a cheaper tower design.
[0062] The above disclosed design of the flange joint is known as a
L-flange joint. Although the flanges are disclosed as being
directed towards the interior of the tower, they can within the
scope of the invention be directed outwards from the interior of
the tower. Also, the inventive concept is equally applicable to a
T-flange joint (not shown) wherein each flange has a T-shaped
cross-section with a first leg extending horizontally into the
interior of the tower and a second leg extending horizontally to
the exterior of the tower, wherein both legs are provided with
through-holes to receive sets of bolts and nuts.
[0063] The above disclosed flange joint has been described with
regard to two adjacent, upper and lower, tower sections that are to
be interconnected. However, the disclosed flange joint is also
conceivable with regard to other elements of the wind power plant,
such as between a tower section and a part of a tower foundation or
between the nacelle and an upper most tower section. In case the
sets of bolts and nuts are used between the nacelle and the
uppermost tower section, the bolts are preferably arranged to
extend through a yaw system, which yaw system allows the nacelle to
turn in view of the tower. The flange joint is also applicable
while connecting other elements such as transition pieces to the
tower sections.
[0064] The invention has mainly been described above with reference
to a few embodiments. However, as is readily appreciated by a
person skilled in the art, other embodiments than the ones
disclosed above are equally possible.
* * * * *