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Title:
A SYSTEM FOR PROTECTING A LEADING EDGE ON A WIND TURBINE ROTOR BLADE, A VACUUM SHEET FOR USE IN THE SYSTEM AND A METHOD FOR, IN SITU, PROTECTING A PART OF A LEADING EDGE OF A WIND TURBINE ROTOR BLADE
Document Type and Number:
WIPO Patent Application WO/2019/186220
Kind Code:
A1
Abstract:
The invention relates to a system for protecting a leading edge on a wind turbine rotor blade, a vacuum sheet for use in the system and a method for, in situ, protecting a part of a leading edge of a wind turbine rotor blade. The system comprises a protective cover sheet to be arranged on a part of a leading edge of a wind turbine rotor blade. The protective cover sheet has a pressure-sensitive adhesive material for adhesively bonding the protective coversheet to the part of the rotor blade. The system further comprises a vacuum sheet having a textured bottom surface and a sealing element arranged at a peripheral circumference and suitable for being connected to a vacuum pump and for being arranged to the protective cover sheet in a full covering and overlapping manner where the sealing element engages the surface of the rotor blade. The protective cover sheet is hereby arranged in a sealed chamber between the rotor blade and the vacuum sheet, and the vacuum system creates a vacuum inside the sealed chamber which forces the textured bottom surface against the protective cover sheet, which activated the pressure-sensitive adhesive material.

Inventors:
BØRSTING, Kristian (Nørregårdsparken 118, 6705 Andrup, DK)
Application Number:
IB2018/000309
Publication Date:
October 03, 2019
Filing Date:
March 27, 2018
Export Citation:
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Assignee:
POLYTECH A/S (Industrivej 37, 6740 Bramming, DK)
International Classes:
F03D1/06; B29C65/48; F01D5/28
Domestic Patent References:
WO2015132700A12015-09-11
WO2014170232A12014-10-23
Foreign References:
US5439635A1995-08-08
US20110169190A12011-07-14
EP3098438A12016-11-30
EP3218597A12017-09-20
Attorney, Agent or Firm:
HOFFMANN DRAGSTED A/S (Rådhuspladsen 16, Copenhagen V, DK-1550, DK)
Download PDF:
Claims:
CLAIMS

1. A system (10) for, in situ, protecting a part of a leading edge of a wind turbine rotor blade (30), said system (10) comprising: a protective cover sheet (12) adapted to be placed and affixed by adhesion on said part of said leading edge,

said protective cover sheet (12) having a top surface, a bottom surface for facing said part of said leading edge, and a number of peripheral side edges, preferably four side edges, a pressure-sensitive adhesive material (14), adapted for adhesively fixing said bottom surface of said protective cover sheet (12) to said part of said leading edge, a vacuum sheet (16) adapted for being affixed on top of said protective cover sheet (12) in a full covering and overlapping manner,

said vacuum sheet (16) having a top surface and a bottom surface for facing said protective cover sheet (12), said bottom surface having a textured surface pattern (20), a number of peripheral side edges, preferably four side edges, and a sealing element (18) arranged at a peripheral circumference of said bottom surface and adapted for overlapping said protective cover sheet (12) and engaging said surface of said rotor blade (30) in a sealingly manner, hereby adapted for arranging said protective cover sheet (12) in a sealed chamber between said surface of said rotor blade (30) and said vacuum sheet (16), said vacuum sheet (16) at said top surface having an opening (22) for connecting a vacuum system, and a vacuum system adapted for being connected to said opening (22) for creating a negative pressure inside said sealed chamber for activating said pressure- sensitive adhesive material (14).

2. A system (10) according to claim 1 , wherein said protective cover sheet (12) being made of a polymer material, such as a polyether based polyurethane, being elongated in a longitudinal direction, and having a central cover sheet section extending in the longitudinal direction and two peripheral cover sheet sections extending in the longitu dinal direction at either side of said central cover sheet section, respectively, said cen- tral cover sheet section having a minimum thickness of at least 1 millimeter, and each peripheral cover sheet section having a thickness decreasing from a maximum thick ness of at least 1 millimeter to a minimum thickness of less than approximately 1/2 mil limeter.

3. A system (10) according to any of claims 1-2, wherein said bottom surface of said vacuum sheet (16) having a textured surface pattern (20) defining a number of airflow channels (40) in connection with said opening (22).

4. A system (10) according to claim 3, wherein said textured surface pattern (20) hav ing a plurality of projections being individually spaced.

5. A system (10) according to claim 3, wherein said textured surface pattern (20) being corrugated.

6. A system (10) according to any of claims 1-5, wherein said sealing element (18) having an adhesive tape for adhesively connecting said vacuum sheet (16) to said ro tor blade (30).

7. A system (10) according to any of claims 1-6, wherein said vacuum system having a vacuum pump (24) and a hose (26).

8. A vacuum sheet (16) for use in the system (10) according to any of claims 1-7, said vacuum sheet (16) having a top surface, a bottom surface, and a number of peripheral side edges, preferably four side edges, and a sealing element (14) arranged at a peripheral circumference of said bottom surface, said top surface having an opening (22) for connecting a vacuum system, and said bottom surface having a textured surface pattern (20) defining a number of air-flow channels (40) in connection with said open ing (22).

9. A vacuum sheet (16) according to claim 8, wherein said textured surface pattern (20) having a plurality of projections being individually spaced.

10. A vacuum sheet (16) according to claim 8, wherein said textured surface pattern (20) being corrugated.

11. A method for, in situ, protecting a part of a leading edge of a wind turbine rotor blade (30), said method comprising:

- providing said wind turbine rotor blade (30) having said leading edge,

- providing a protective cover sheet (12) for covering said part of said leading edge, said protective cover sheet (12) having:

a top cover surface, a bottom cover surface opposite said top cover sur face for facing said part of said leading edge, and a number of peripheral side edges, preferably four side edges defining a first circumference,

- providing a pressure-sensitive adhesive material (14) for bonding said protec tive cover sheet (12) to said part of said leading edge,

- providing a vacuum sheet (16) adapted for being affixed to said top surface of said protective cover sheet (12) in a full covering and overlapping manner, said vacuum sheet (16) having a top surface and a bottom surface for facing said pro tective cover sheet (2), a number of peripheral side edges, preferably four side edges defining a second circumference, said vacuum sheet (16) further having an opening (22) constituting an outlet for connecting a vacuum system,

- providing a sealing element (18) arranged for sealing said vacuum sheet (16) at the second circumference against said part of the leading edge, and

- providing a vacuum system adapted for being connected to said opening (22) of the vacuum sheet (16), said method further comprising:

- arranging said protective cover sheet (12), covering said part of said leading edge,

- arranging said vacuum sheet (16) to said top surface of said protective cover sheet (12), said peripheral side edges of said vacuum sheet (16) overlapping said peripheral side edges of said protective cover sheet (12), said sealing ele- ment (18) engaging said rotor blade surface and establishing a fluid tight cham ber between said rotor blade surface and said vacuum sheet (16), - attaching said vacuum system to said opening (22) in said vacuum sheet (16) and creating a negative pressure inside said chamber of approximately -0.5 to -1 bar, preferably approximately -1 bar, and

- after activation of said pressure-sensitive adhesive material (14), said vacuum sheet (16) being removed from said rotor blade surface, leaving said protective cover (12) adhesively fixed to said rotor blade surface.

Description:
A SYSTEM FOR PROTECTING A LEADING EDGE ON A WIND TURBINE ROTOR BLADE, A VACUUM SHEET FOR USE IN THE SYSTEM AND A METHOD FOR, IN SITU, PROTECTING A PART OF A LEADING EDGE OF A WIND TURBINE ROTOR BLADE

The present invention relates to a system for protecting a leading edge on a wind turbine rotor blade, a vacuum sheet for use in the system and a method for, in situ, protecting a part of a leading edge of a wind turbine rotor blade.

Generally, a wind turbine includes a wind turbine foundation, a tower erected on the foundation, a nacelle and a rotor hub mounted on top of the tower. The rotor hub comprises a number of rotor blades. The nacelle comprises a generator being connected via a gearbox to the rotor hub. The rotor blades transform wind energy into a mechanical rotational torque of the rotor hub being coupled to the gearbox. The gearbox increases the low rotational speed of the rotor hub for the generator to enable the rotational me chanical energy to be efficiently converted to electrical energy which is supplied to a utility grid.

Wind turbines are often operated in extreme environmental conditions where the wind turbine blades are vulnerable to erosion, lightning strike and icing.

Erosion to the edge has the possibility of causing physical damage to the blade and may cause the wind turbine to shut down for extended periods of time.

Especially the leading edges of the rotating blades are particularly subject to erosion and subsequent wear. Especially the newer long wind turbine blades have been found to cause problems, since the relative speed between the air and the blade surface is high.

Wind turbine blades located in severe environments, such as offshore and desert envi ronments, may also be subject to leading edge wear or erosion, further resulting in frac tures from high velocity impact with objects such as rain, hail, seawater, sand, animals or other particulates. Such damage may increase operational maintenance and replace ment costs, decrease electric power generation during associated maintenance out ages, and decrease the expected life spans of the blades. In recent years much effort has been made by wind turbine manufacturers to enhance the robustness of wind turbine blades so that they are able to operate effectively in the environment in order to avoid damage to the blade and the cost associated with turbine down-time during blade repair or replacement.

In some of the known wind turbines, coatings are applied on the leading edges of the rotor blades to inhibit erosion. Such coatings, however, provide only limited protection, and over time, the leading edges may still erode. Therefore, there is an increasing need for a coating that can be retrofitted on older wind turbine blade having beginning corro- sion.

The applicant company has been producing and developing protective covers for wind turbine blades and has been involved in improving protective covers, disclosed in among others EP3218597, which is incorporated in the present disclosure by refer ence, and relating to an improved pre-formed protective cover made of a polyurethane material prepared from a polyol, butanediol, and an isocyanate, the preformed protec- tive cover being adapted to be attached along at least a part of a longitudinal edge of the wind turbine blade by adhesion of an inside of the preformed protective cover to a surface of the longitudinal edge of the wind turbine blade.

A known process for repairing a corroded surface on a rotor blade is raising a basket with personnel up to the rotor blade or lowering the personal via a rope and then after a preparation of the blade directly applying an adhesive onto the rotor blade surface. After applying the adhesive, a protective cover is arranged over the corroded surface area and manually by the personal and with the hands applying a pressure onto the cover for binding of the cover onto the rotor blade surface.

This process is dangerous, complicated and requires developed worker skills for cor rect fixation of the protective cover onto the rotor blade surface. Further, the quality and uniformity of the finished work leaves a requirement for improvement.

Other known processes for repairing a corroded surface on a rotor blade is to dismount the entire rotor blade and repair the rotor blade on the ground, or if the rotor blade is of an offshore wind turbine, the blade has to be transported into shore before repairing. These processes are time consuming and costly in work labour. It is an object of the present invention to provide a system, a vacuum sheet and a method for protecting a part of a leading edge of a wind turbine rotor blade that is safely and effective executed.

The above object and advantages, together with numerous other objects and advantages which will be evident from the description of the present invention, are ac- cording to a first aspect of the present invention obtained by:

A system for, in situ, protecting a part of a leading edge of a wind turbine rotor blade, the system comprising: a protective cover sheet adapted to be placed and affixed by adhesion on the part of the leading edge,

the protective cover sheet having a top cover surface, a bottom cover sur- face for facing the part of the leading edge, and a number of peripheral side edges, preferably four side edges, a pressure-sensitive adhesive material, adapted for adhesively fixing the cover bottom surface of the protective cover sheet to the part of the leading edge, a vacuum sheet adapted for being affixed on top of the protective cover sheet in a full covering and overlapping manner,

the vacuum sheet having a top surface and a bottom surface for facing the protective cover sheet, the bottom surface having a textured surface pattern, a number of peripheral side edges, preferably four side edges, and a sealing element arranged at a peripheral circumference of the bottom surface and adapted for overlapping the protective cover sheet and engaging the rotor blade surface in a sealingly manner, hereby adapted for arranging the protective cover sheet in a sealed chamber between the surface of the rotor blade and the vacuum sheet, the vacuum sheet at the top surface having an opening for connecting a vacuum system, and a vacuum system adapted for being connected to the opening for creating a negative pressure inside the sealed chamber for activating the pressure-sensi- tive adhesive material.

The system for protecting a part of a leading edge of a wind turbine rotor blade is de- scribed in relation to a traditional horizontal axis wind turbine having three rotor blades. However, the protective cover sheet could also be attached to the leading edge on a rotor of another type of wind turbine, e.g. a vertical axis wind turbine such as a“Dar- rieus” or a“Helix”, and to both wind turbines onshore or offshore. The protective cover may also be attached to a different part of the rotor blade than the leading edge, and may be attached to the rotor blade in situ or in an alternative embodiment be attached to the rotor blade on ground surface.

The pressure-sensitive adhesive material is in a preferred embodiment pre-mounted onto the bottom surface of the protective cover sheet; however, the protective cover sheet and the pressure-sensitive adhesive material may be separate elements suitable for being assembled on site.

The bottom surface of the vacuum sheet is in a preferred embodiment having a tex- tured surface pattern, for in an enhanced mounting process letting air escape from the sealed chamber between the vacuum sheet and the surface of the rotor blade by the use of a vacuum system.

The protective cover sheet and the vacuum sheet is in a preferred embodiment de- scribed as having a top surface, a bottom surface and four side edges. The protective cover sheet and the vacuum sheet may be arranged having a number of edges, e.g. be found or having a different number of side edges e.g. 2, 3, 5, 6 or more.

According to a further embodiment of the first aspect, the protective cover sheet is made of a polymer material, such as a polyether based polyurethane, is elongated in a longitudinal direction and has a central cover sheet section extending in the longitudinal direction and two peripheral cover sheet sections extending in the longitudinal di- rection at either side of the central cover sheet section, respectively, the central cover sheet section having a minimum thickness of at least 1 millimeter, and each peripheral cover sheet section having a thickness decreasing from a maximum thickness of at least 1 millimeter to a minimum thickness of less than 1/2 millimeter. The particular form of the peripheral cover sections provides for a good transition from the central cover section of the preformed protective cover to the surface of the rotor blade. A good transition without edges is of great importance in order to avoid that the wind will destroy the materials. A sealing material (sealer) may be applied in a possible groove between an edge of the peripheral cover sections and the surface of the rotor blade in order to even further improve the transition.

The maximum thickness of each peripheral cover section may correspond to the mini mum thickness of the central cover section. The minimum thickness of the central cover section may be at least 2 millimetres, preferably at least 3 millimetres, more preferred at least 4 millimetres, and most preferred approximately 5 millimetres.

The thickness of the central cover section may be at least substantially constant from side to side of the central cover section.

According to a further embodiment of the first aspect, the bottom surface of the vac uum sheet has a textured surface pattern defining a number of airflow channels in con nection with the opening.

According to a further embodiment of the first aspect, the textured surface pattern has a plurality of projections being individually spaced.

The textured surface pattern of the bottom surface defines a plurality of air-flow chan nels between the vacuum sheet and the protective cover sheet when the vacuum sheet is mounted to the protective cover sheet, and a plurality of projections arranged between the air-flow channels for abutting the top surface of the protective cover sheet. Air which is trapped between the vacuum sheet and the protective cover sheet may thus easily escape out of the opening arranged in the vacuum sheet when the vacuum system is connected to the opening.

Further, the vacuum sheet is in a preferred embodiment pre-mounted with the sealing element at the peripheral circumference; however, the sealing element and the vac uum sheet may be separate elements suitable for being bonded in site. When the protective cover sheet is arranged on the rotor blade and the vacuum sheet with the connected vacuum system is arranged to the rotor blade and the protective cover sheet, the protective cover sheet is sealed in a chamber defined by the space between the vacuum sheet and the rotor blade surface. The vacuum system escapes all or near all air from the sealed space and creates a vacuum inside the chamber.

The vacuum inside the sealed chamber creates an equal force acting in a direction to- wards the rotor blade and forces the plurality of abutting surfaces against the top surface of the protective cover sheet, activating the pressure-sensitive adhesive material. According to a further embodiment of the first aspect, the textured surface pattern is corrugated.

The textured surface of the vacuum sheet may have a variety of patterns. The function of the textured surface pattern is to establish a plurality of air-flow channels between the vacuum sheet and the protective cover sheet when being mounted, and for arrang ing a plurality of projections at the bottom surface of the vacuum sheet for acting a force against the protective coversheet, hereby activating the pressure-sensitive adhesive material. A person skilled in the art may thus advise a variety of surface patterns suitable for the above.

According to a further embodiment of the first aspect, the sealing element has an ad hesive tape for adhesively connecting the vacuum sheet to the rotor blade.

In a preferred embodiment, the sealing element, which is arranged at a peripheral cir- cumference on the bottom surface of the vacuum sheet, is an adhesive tape such as a double-sided self-adhesive tape. In an alternative embodiment, the sealing may be a silicone or similar synthetic compound or in a further alternative a static cling tape.

According to a further embodiment of the first aspect, the vacuum system has a vac- uum pump and a hose.

The vacuum system is preferable a vacuum pump being connected to the vacuum sheet via a hose. A vacuum pump can be manufactured smaller than an air pressure pump and is hereby more easily transported. Further, having a vacuum pump instead of an air pressure pump requires a far smaller sealing element of the vacuum sheet, as the created vacuum“sucks” the vacuum sheet towards the rotor blade. In an alternative embodiment, the vacuum system may be an air pressure system, creating a positive air pressure in the sealed chamber between the rotor blade and a sealing sheet similar to the vacuum sheet. The skilled person will thus advise a suitable seal- ing element at the circumferential peripheral edge of the sealing sheet to establish a sealing suitable to withstand the positive air pressure.

According to a second aspect of the present invention, the above objects and ad vantages are obtained by:

a vacuum sheet having a top surface, a bottom surface and a number of periph eral side edges, preferably four side edges, and a sealing element arranged at a pe ripheral circumference of the bottom surface, the top surface having an opening for connecting a vacuum system, and the bottom surface having a textured surface pat tern defining a number of air-flow channels in connection with the opening.

According to a further embodiment of the second aspect, the textured surface pattern has a plurality of projections being individually spaced.

According to a further embodiment of the second aspect, the textured surface pattern is corrugated.

According to a third aspect of the present invention, the above objects and advantages are obtained by: A method for, in situ, protecting a part of a leading edge of a wind turbine rotor blade, said method comprising:

- providing the wind turbine rotor blade having the leading edge, - providing a protective cover sheet for covering the part of the leading edge, the protective cover sheet having:

a top cover surface, a bottom cover surface opposite said top cover sur face for facing the part of the leading edge, and a number of peripheral side edges, preferably four side edges defining a first circumference, - providing a pressure-sensitive adhesive material for bonding the protective cover sheet to said part of the leading edge,

- providing a vacuum sheet adapted for being affixed to the top surface of the protective cover sheet in a full covering and overlapping manner, the vacuum sheet having a top surface and a bottom surface for facing the protective cover sheet, a number of peripheral side edges, preferably four side edges defining a second circumference, the vacuum sheet further having an opening constituting an outlet for connecting a vacuum system,

- providing a sealing element arranged for sealing the vacuum sheet at the sec ond circumference against the part of the leading edge,

- providing a vacuum system adapted for being connected to the opening of the vacuum sheet, the method further comprising:

- arranging the protective cover sheet covering the part of the leading edge,

- arranging the vacuum sheet to the top cover surface of the protective cover sheet, the peripheral side edges of the vacuum sheet overlapping the peripheral side edges of the protective cover sheet, the sealing element engaging the rotor blade surface and establishing a fluid-tight chamber between the rotor blade surface and the vacuum sheet,

- attaching the vacuum system to the opening in the vacuum sheet and creating a negative pressure inside the chamber of approximately -0.5 to -1 bar, prefera bly approximately -1 bar, and

- after activation of the pressure-sensitive adhesive material, the vacuum sheet being removed from the rotor blade surface, leaving the protective cover adhe sively fixed to the rotor blade surface.

The part of a leading edge of a wind turbine rotor blade to which the protective cover sheet is to be attached is typically prepared before mounting, e.g. by removing any corroded or damaged surface material with a grinder or other suitable tool. Also rotor blades intended for an aftermarket may be refurnished with a protective cover.

Further, the protective cover sheet is preferable pre-mounted with the pressure-sensi- tive adhesive material, but may in an alternative embodiment be bonded in site. This aspect also applies to the sealing element, which in a preferred embodiment is pre formed with the sealing element.

The pressure-sensitive material may in an alternative embodiment be applied to the protective cover sheet on-site before the protective cover sheet (including the pres sure-sensitive material) is arranged on the rotor blade, or the pressure-sensitive mate rial may first be arranged on the rotor blade and the protective cover sheet may sec ondly be arranged to the pressure-sensitive adhesive material.

In a preferred embodiment where the protective cover sheet having the pressure-sen sitive adhesive material is placed on the leading edge of the rotor blade, the vacuum sheet is arranged to the protective cover sheet in an overlapping manner, hereby the peripheral edges of the vacuum sheet overlapping the peripheral edges of the protective cover sheet.

The sealing element of the vacuum sheet is attached to the rotor blade in a close prox imity to the peripheral edges of the protective cover sheet, and the vacuum system is connected to the opening of the vacuum sheet and activated.

After activating the vacuum system, a negative pressure is established inside the sealed chamber between the vacuum sheet and the rotor blade, preferably at a pre ferred negative pressure of approximately -1 bar. This results in a pressure of approximately 1 bar acting on the top surface of the protective cover sheet in a direction to wards the rotor blade, and activates the pressure-sensitive adhesive material.

The invention will now be explained in more detail below by means of examples of em bodiments with reference to the very schematic drawing, in which:

Fig. 1 shows a perspective view of a wind turbine and a protective cover. Fig. 2 shows a perspective view of the system for protecting a part of a leading edge of a wind turbine rotor blade.

Fig. 3 shows a perspective view of a part of a leading edge of a wind turbine rotor blade and the protective cover sheet having pressure-sensitive adhesive material.

Fig. 4 shows a perspective view of a part of a leading edge of a wind turbine rotor blade, the protective cover sheet, and the pressure-sensitive adhesive material.

Fig. 5 shows a perspective view of a part of a leading edge of a wind turbine rotor blade, the protective cover sheet, and the vacuum sheet.

Fig. 6 shows a perspective view of a part of a leading edge of a wind turbine rotor blade, the protective cover sheet, and the vacuum sheet being affixed to the rotor blade.

Fig. 7 shows a perspective view of a part of a leading edge of a wind turbine rotor blade, the protective cover sheet, and the vacuum sheet being affixed to the rotor blade and connected to a vacuum pump.

Fig. 8 shows a perspective view of a part of a leading edge of a wind turbine rotor blade, the protective cover sheet, and the vacuum sheet being affixed to the rotor blade and vacuum activated.

Fig. 9A shows a cross-sectional view of the rotor blade, the protective cover sheet, and the vacuum sheet exposed to vacuum pressure.

Fig. 9B shows a blow-up of the cross-section in fig. 9A.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully con vey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. Like elements will, thus, not be described in detail with re spect to the description of each figure.

Fig. 1 shows a perspective view of a wind turbine 28 and a protective cover 12. The wind turbine is illustrated having a tower 36 erected on a tower foundation (not shown), a nacelle 34, and a rotor hub 32. The rotor hub 32 is illustrated having three rotor blades 30, and the leading edge of one of the rotor 30 blades is illustrated with a protective cover sheet 12 being affixed in the direction of the arrows.

Fig. 2 shows a perspective view of the system 10, protecting a part of a leading edge of a wind turbine rotor blade 30. The system 10 is illustrated having a protective cover sheet 12 having a top surface and a bottom surface for facing the rotor blade 30. The bottom surface of the protective cover sheet 14 is illustrated having a layer of adhesive material which according to the invention is arranged as a pressure-sensitive adhesive material.

The system is further illustrated with a vacuum sheet 16 having a top surface and a bottom surface for facing the protective cover sheet 12 and an opening 22 for connect- ing a vacuum system, which is illustrated as a vacuum pump 24 having a hose 26. The bottom surface of the vacuum sheet is illustrated having a textured surface pattern de fining a plurality of air-flow channels being in fluid connection with the opening 22. The bottom surface of the vacuum sheet 16 is illustrated having a sealing element 18 for sealing against the surface of the rotor blade 30 in a proximity of the peripheral edges of the protective cover sheet 12.

Fig. 3 shows a perspective view of a part of a leading edge of a wind turbine rotor blade 30 and the protective cover sheet 12 having pressure-sensitive adhesive mate rial 14. The protective cover sheet 12 is illustrated in a direction of arrangement as in dicated by the arrows and is illustrated being pre-formed with the pressure-sensitive adhesive material 14.

Fig. 4 shows a perspective view of a part of a leading edge of a wind turbine rotor blade 30, the protective cover sheet 12, and the pressure-sensitive adhesive material 14. The wind turbine rotor blade 30 and the protective cover sheet 12 are illustrated similar to fig. 3. However, the pressure-sensitive material 14 and the protective cover sheet 12 are illustrated as separate elements. The pressure-sensitive material 14 and the protective cover sheet 12 are mounted in the direction of the arrows. Fig. 5 shows a perspective view of a part of a leading edge of a wind turbine rotor blade 30, the protective cover sheet 12, and the vacuum sheet 16. The cover sheet 12 having the pressure-sensitive adhesive material 14 is arranged on the surface of the wind turbine rotor blade 30, and the vacuum sheet 16 is illustrated in a mounting direc tion as indicated by the arrows. The vacuum sheet is connected to a hose 26 of the vacuum system. From the figure, it is obvious that the textured surface pattern 20 of the vacuum sheet 16 will cover the protective cover sheet 12 when being mounted, and the sealing element 18 of the vacuum sheet 16 will engage the surface of the wind turbine rotor blade 30.

Fig. 6 shows a perspective view of a part of a leading edge of a wind turbine rotor blade 30, the protective cover sheet 12, and the vacuum sheet 16 being affixed to the wind turbine rotor blade 30. The protective cover sheet 12 is arranged on the wind tur- bine rotor blade 30, and the vacuum sheet 16 is arranged on the protective cover sheet 12 with the sealing element 18 engaging the surface of the wind turbine rotor blade 30. The hose 26 is connected to the opening 22 of the vacuum sheet 16 and may at the other end be attached to a vacuum system (not shown) Fig. 7 shows a perspective view of a part of a leading edge of a wind turbine rotor blade 30, the protective cover sheet 12, and the vacuum sheet 16 being affixed to the rotor blade 30 and connected to a vacuum pump 24. Figure 7 illustrates a perspective cross-section of the system 10 being arranged to the wind turbine rotor blade 30. Fig. 8 shows a perspective view of a part of a leading edge of a wind turbine rotor blade 30, the protective cover sheet 12 and the vacuum sheet 16 being affixed to the rotor blade 30 and a vacuum activated. As illustrated in the figure, the protective cover sheet 12 and the vacuum sheet 16 are arranged on the wind turbine rotor blade and via the hose 26 being connected to a vacuum system (not shown). The vacuum sys- tern“sucks” air 26 out of the sealed chamber between the vacuum sheet 16 and the wind turbine rotor blade 30, creating a vacuum within the chamber which results in a vacuum pressure 38 acting on the protective cover sheet 12.

Fig. 9A shows a cross-sectional view of the rotor blade 30, where the protective cover sheet 12 and the vacuum sheet 16 are exposed to vacuum pressure 38. From figure 9A, the arrangement of the wind turbine rotor blade 30, the protective cover sheet 12, and the vacuum sheet 16 is apparent. The vacuum pressure 38, as a result of the vac uum inside the sealed chamber, is illustrated across the top surface of the vacuum sheet, hereby illustrating an evenly distributed vacuum pressure 38 acting towards the protective cover sheet. Figure 9A clearly illustrates the sealing element 18 of the vac- uum sheet 16 engaging the surface of the wind turbine rotor blade 30.

Fig. 9B shows a blow-up of the cross-section in fig. 9A. From figure 9B it is apparent that the vacuum sheet 16 is having air-flow channels 40 and projections between the channel, which projections are in abutment with the top surface of the protective cover sheet 12. Upon activation of the vacuum system, the vacuum pressure 38 will act on the protective cover sheet 12 in contact points where the projections of the vacuum sheet 16 abut the protective cover sheet 16. A large number of projections in the tex tures surface pattern 20 will result in an evenly distributed force applied to the top sur face of the protective cover sheet 12.

In all of the drawings, the protective cover sheet 12 and the vacuum sheet 16 are illus trated having a curved shape. This should not be interpreted limiting in any way. Both the protective cover sheet and the vacuum sheet may be arranged as plane sheets. Further, the vacuum sheet is preferably flexible and may be made from a polyolefin material such as polyethylene or other similar material.

In the following is given a list of reference signs that are used in the detailed descrip tion of the invention and the drawings referred to in the detailed description of the in- vention.

REFERENCES

10. The system

12. Protective cover sheet

14. pressure-sensitive adhesive material

16. Vacuum sheet

18. Sealing element

20. Textured surface

22. Opening

24. Vacuum pump

26. Hose

28. Wind turbine

30. Rotor blade

32. Rotor hub

34. Nacelle

36. Suction air

38. Vacuum pressure

40. Air-flow channel