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The expertise of used wind energy converters

1. Purchase and installation of Used wind energy converters A manual for potential investors AUTHORS NORBERT SCHULZ PETER DIERKEN PUBLISHED 1 ISSUE AUGUST 2005 PUBLISHER BALTIC WIND ENERGY ASSOCIATION M V ROSTOCK THIS PROJECT IS SUPPORTED BY THE EUROPEAN UNION AND INTERREG IIIB IMPRINT RESPONSIBLE PUBLISHED PUBLISHER FOTO LAYOUT S lt H 1 NORBERT SCHULZ PETER DIERKEN 1 ISSUE AUGUST 2005 BALTIC WIND ENERGY ASSOCIATION M V ROSTOCK GERMANY TOM MAERCKER BE DEUTEN DE CLIMATE DESIGNERS ROSTOCK Foreword The study on hand is one output of the InterregIIIb project Wind energy in the BSR which has united 29 partners in wind energy related co operations from 2003 on As much as the project itself the study intents to contribute to a further stimulation of the European wind energy market Despite of it should be read as a document written by German authors as a lot of the practical hints and information have been gained by Norbert Schulz and Peter Dierken during many years of work within the German wind energy branch The heterogeneity of the wind energy market has to be considered as well many types of wind energy converters WEC produced by various manufacturers exist a study as this one will be only able to take the most commo
2. 8 What kind of documentation is required for a WEC expertise 2 2 2 22 2 9 What are the prerequisites for the expertise Of a WEC cccssccccscssscscssssscesscscesecssscesecscscesessseceeneseseeees 10 Before climbing the WEC notes on safety During the The expertise of rotorblades different options F rtherexpert Work apes 13 What do the different expertises 14 The written expertise how should it look like ccccccssssesssssssescsssesessesessssessusesseseeesseseeseseesesseessseeees 17 What can an expertise achieve What not be achieved by an expertise ccccsscccsscssssscssssssesscscscecscsneseusseseseseveseseseseseseasecesesanenteees 18 What else can be measured xs steven atest disses dass 19 The expertise Of used wind energy CONVerterS ceccececeseseseseeeeeescseecescseseeescessceeeesetseeeetesaenenesesieeeeetess 20 Evaluation of assembled operative 21 Evaluation of assembled non operative WECS ccccsssceeseesessssesesssssssesssssesssssssesesssseeseassss
3. Operating from a man basket pulled by the main crane a rope same length as above and crane loop are attached to the blade end The rear edges have to be protected with a spe cial edge protection The crane loop has to be attached to the waiting crane hook of the auxiliary crane The loop at the blade root will be thrown over the hook of the main crane from nacelle direction after the man basket has been set down Both cranes tighten slightly to unload the boltings Loosen the nuts and adjust the cranes in a way that the blade is hanging on the blade flange Only then the nuts can be re moved The blade is slewed away from the nacelle Now the cranes are lowering the blade while keeping it constantly in horizontal position to avoid that it slips out of the loops Both cranes have to be coordinated in a way that the crane ropes hang perpendicularly all the time The bearing surface of the blade root should be lined with tarpaulin or carpet The blade tip should be propped with pallets or something similar at the well known points For some types for transport devices it is recommendable to disassemble them even by now Afterwards the rotor is turned further until the next blade has reached horizontal position Proceed further as described above until all three blades are stored safely on the ground Usually the hub remains attached to the shaft of the drive train during the disassembly of the nacelle But in case it shall be disassem
4. Are there more than one construction variants of this wind energy converter Which fixing point fits for the plant to be disassembled Are there single heavy components to be disassembled and craned separately and prior to reduce the weight of the nacelle and to keep the balance Have for instance the tower cable bolts and tools been stored in the nacelle and thus been part of the balance Are there special devices such as stay bolts to be screwed in with eyebolts or crane lugs to be assembled required for fixing Do components block the way inside the nacelle and have to be disassembled prior to the craning or protected by special devices Has the nacelle lid to be removed for fixing the crane load attachment rigging Tower The different tower types require very different ways of disassembling Apart from the main question what tower has to be taken apart the following general questions have to be solved What fixing devices are required How are these fixing devices to be assembled tightening torques of the bolts etc Are there special crossbeams for the crane needed Are there footing at grade areas on the territory next to the wind energy converter where the tower segments can be stored intermediately Are there possibilities to provide the transport vehicles in the required order next to the wind energy converter for loading Are there assembly components that has to be loosened prior to the disass
5. THE INDIVIDUAL COMPONENTS OF THE WEC Rotation angle controlled pick up procedure With this procedure the bolt is tightened up to a certain pick up and turned around for a pre determined angle afterwards by this the appropriate preload force is brought on For this a preloading up to the overelastic range is possible When preloading into the overe lastic range small hardly noticeable distortions occur The bolt remains fully elastic For this procedure the friction inside the thread and below the bearing surfaces has to be kept low as well to keep the bolt twist as low as possible Yieldstress controlled pick up procedure With this procedure the entire elastic limit of the bolt will be used During the procedure the ratio of pick up torque and pick up angle of rotation are measured continuously the process will be finished as soon as this ratio is reduced The thread and the bearing surfa ces have to be lubricated well during this procedure too The preload force can also be applied via elongating pulling into the length twist free stretching the bolt until the ela stic limit has been reached The friction is not relevant for this procedure All pick up procedures are subject to certain scatterings when the preload force is app lied These scatterings result from friction and or the elastic limit To consider this scatte ring appropriately a so called tightening factor has to be integrated even into the calcu lation o
6. The bearing surface of the bla de root should be lined with carpets or tarpaulin the blade root has to be propped with pallets or something similar at the well known spots For some transport devices it is re commendable to disassemble the blades even by now Proceed with the two other blades correspondingly Screw the hub tightly towards the transport device and seal it at the openings of the blade bearing the front holes etc with tarpaulins Disassembly of single blades This way of disassembly can only be executed with wind turbines that have an appropria tely designed drive train and correspondingly strong locking devices for the rotor The two cranes have to be installed in a way that the main crane is able to reach the blade root and the auxiliary crane the blade tip of the blade in assembly position An auxiliary drive should be assembled to the drive train if necessary This auxiliary dri ve is designed to turn the rotor after the disassembly of the first and the second blade sa fely into the right position to disassemble the next blade DISASSEMBLY AND TRANSPORT OF USED WIND ENERGY CONVERTERS One tightening crane loop is put around the blade root of the blade to be disassembled starting from the nacelle On this loop again a rope has to be fixed minimum double length of the hub height to protect the blades moves from the ground Turn and lock the rotor in a way that the blade to be disassembled 15 adjusted horizontally
7. control cabinets transformers hub and blades Sanitation Main crane As a rough empirical formula the following can be estimated The lifting capacity of the crane has to be twenty times as high as the heaviest component to be carried This means that for a nacelle that weighs about 20 tons a crane with a lifting capacity of about 400 tons has to be taken into consideration This value might vary depending on the crane ty pe and hub height Auxiliary crane The auxiliary crane is needed for putting down the tower segments and the rotor on the ground or for disassembling the rotorblades Such a crane will be available at the site any way if the main crane is not able to transfer the counter weights The auxiliary crane has to be able to carry at least half of the weight of the heaviest tower segment The hook height depends on the task it has to fulfil In some cases auxiliary drives are required for the disassembly of single blades to reloca te the rotor With other turbine types only the rotorblade showing downwards will be dis assembled with a special device the nacelle will be brought down together with the two remaining blades General course of disassembly Preparation of the wind energy converter In advance of the disassembly some preparations have to be made Areas which are hea vily polluted with hydraulic oil and bearing grease have to be cleaned in some of the plants so far that an operation of heavy devices will be
8. draulic or an electric motor a gearbox and a drive pinion For the gear reduction of the large differences in rotational speed between drive and yaw system a multi stage epicyclic gear is the best option The coaxial arrangement of the in put and output shaft allows a very compact construction The electric or hydraulic drive unit serves as the parking brake too An additional spring loaded brake is located behind the electric drive engine on a second shaft It is ventilated during the yawing process In general no wearing of the brake oc curs because of this second function as a parking brake With hydraulic drives the braking effect is reached by switching off the hydraulic pump The drive shaft of the pinion is eccentric towards the fixation flange of the yaw drive This allows an adjustment of the tooth flange clearance between pinion and the toothing of the yaw bearing For this in many cases the entire drive can be turned within its bea ring The adjustment is done with the help of the bolt pattern At some variants the drive can be moved sidewards by turning the eccentric ring The boreholes for the fixation bolts are designed appropriately large then The entire drive is attached to the main frame via a screw flange The adjustment of the tooth flank clearance does effects considerably the lifetime and the wearing of the toothing so that the manufacturer information about the tooth flank clea rance should be followed absolutely
9. thunders torm and high wind speeds can be dangerous to life Please note Every WEC has further turbine specific safety regulations Make the necessary inquiries BEFORE CLIMBING THE TURBINE normally the operating manual or service manu al contains such information Please pay particular attention to the safety instructions for clim bing the nacelle or hub Any work at the turbine s electric and electronic installation must only be performed by qualified service personnel EXPERTISES During the expertise In either case a qualified service engineer should accompany the expertise preferably a technician of the team who was in charge of the surveyed turbine His tasks are depen ding on the scope of the required expertise Answering the questions or giving explanations to the questions of the expert The operation of turbine control and locks The disassembly of the covers cover of the fast shaft between gearbox and generator or opening the inspection hatch of the gearbox Inspecting the tightening torques of the screw joints The expertise of rotorblades different options Roping from the blade The expertise of rotorblades can be performed in different ways Some specialists are ro ping from the blade downwards along the blade and work in direct contact with the surfa ce Although this seems to be a relatively simple way not everybody would prefer that Pulling down the blades in the basket Pulling d
10. at the outside depending on the arrangement of the yaw drives If the wind direction changes the wind energy converter will be newly adjusted via this too things In general the yaw bearing is slightly preloaded If treated appropriately the fourpoint bearing is only exposed to the operation related we ar that should remain within the limits Particular attention should be drawn to a proper lubrication Due to longer standstill periods compression spots and corrosion at the bea ring runways might occur as the lubricant between bearing runway and rolling element is pressed away For this reason it is important that the yaw bearing is moved in regular interval with a motor or manually this ensures that the relevant contact spots between runway and rolling element are provided with fresh lubricant The toothing yaw bearing pinion has to be lubricated properly as well to prevent early wear through pitting at the toothing of the yaw bearing Pitting is form of material fa tigue at the tooth flanks pitting like cavities at the surface It might result into the release of tooth flank items if the compression that effects on the teeth exceeds a certain limit The reason for this material fatigue is a permanent loading and unloading of the tooth flanks but only problematic if these pitting grow further or the number increases during unmodified operation In general pitting occurs at the toothing of the yaw bearing as the toothing o
11. at wind speeds that exceed the shutdown limit In case one of the two problems occurs the control system of the WEC has to record this as an error and report it so that repair work can be started immediately Sensor for rotational speed monitoring With this sensor critical overspeed can be recognized If such an overspeed occurs the rotor will be braked and brought into a safe operation mode again A monitoring of the ro tational speed is needed for a controlled braking and the recognition of WEC shutdowns too Sensor for temperature monitoring To record the temperature of the components which heat up during operation temperature sensors assembled in appropriate positions are necessary The most important things are the temperature control at gearbox and generator as a heating can cause a damage of the components here even faster than with others see chapter gearbox as well High tem peratures at the generator might damage the insulation and possibly cause a short circuit In addition the lubrication grease inside the generator bearing might get liquefied and run out of the bearings THE INDIVIDUAL COMPONENTS OF THE WEC Documentation The documentation papers of the WEC are an indispensable basis for the professional in stallation commissioning operation maintenance and if necessary repair of the turbine Because of this you should really pay attention that the following documents are availa ble and complete when buy
12. carried out in the same way The fixing devices have to be fixed at the upper flange and hooked into the crane hook of the main crane At the separation spot towards the next segment all connections such as ladders climbing protection cables etc have to be removed Now the crane operator loads the crane hook with a load as high as the dead weight of the tower segment Afterwards the bolts are loosened until the segment is hanging several millimetres above the flange Only after this the bolts must be removed Please note Take extreme care when removing the bolts moves of the hanging tower seg ment might cause injuries Lower the segment until it hangs directly above the ground Now the fixing devices of the lower flange have to be assembled and hooked to the auxiliary crane Both cranes bring the tower segment into horizontal position As far as the tower segment will not simply be stored temporarily on the ground the transport devices have to be attached in this posi tion Repeat this procedure with the other tower segments When lifting the lowest segment consider that there are control cabinets or pedestals inside which are loaded for transport at the end of the disassembly Please note A tubular tower without its nacelle on top should not remain standing as a whole in case the weather conditions get worse At certain wind speeds hunting aerodynamic chords occur at the backside of the tower The aerodynamic forces
13. com plete assembly of the gearbox high repair costs and a loss of yield The sensors for gearbox monitoring should be inspected for proper operation Defect sen sors have to be exchanged where necessary The oil level can be checked via the gauge glass All oil filters that are necessary for the gearbox coarse and fine mesh filter should be exchanged as well as the gearbox oil Gearbox oils must never be mixed If an oil exchan ge shall be carried out the gearbox has to be flushed with the new oil completely several times Consult the gearbox manufacturer and the oil manufacturer under any circumstan ces if the oil type shall be modified THE INDIVIDUAL COMPONENTS OF THE WEC Rotorbrake The rotorbrake is divided into two systems an aerodynamic and a mechanical brake that operate independent from each other Aerodynamic brake The aerodynamic brake shall decelerate the rotor until a complete stop At pitch control led and ActiveStall controlled wind energy converters it consists of the entire blade The blade will be turned by 90 towards the leading flag like position and thus creates a very high drag Depending on the design of the control system the rotorblades can be operated independent from each other or as a unit thus triggering the braking procedure Mechanical brake At plants with three independent single blade pitches the mechanical brake has been de signed as a parking brake As every blade pitch is able
14. energy converters Progression and explanatory power of a used WEC expertise depend on the condition of the WEC to be purchased The optimum would be the inspection by a surveyor when the turbine is assembled and ready for operation Only at this point operation faults can be detected If the WEC subjected to expertise is assembled but not ready for operation or even dismantled the expert can only give limited statements on the situation But even for this case certain recommendations can be given Detailed information about the individual components to be inspected can be referenced in the chapters about the individual components of the WEC However the reading of this passages does not replace the knowledge you and a surveyor get from own inspections Evaluation of assembled operative WECs In the ideal case the purchaser is offered an assembled operating wind energy converter The plant can be inspected measured and dimensioned while in operation In the course of disassembly further spots will be accessible that can normally not be reached In addi tion a supervision of the dismantling can identify damages that have occurred due to in EXPERTISES appropriate work and may have been not detected otherwise An inspection of the entire documentation is the minimum work a purchaser should do A status oriented inspection will provide the best foundation for the purchaser to evaluate the efforts to be expected until the plant is re c
15. installation of the transformer station Under certain condition a small transformer station has to be built next to the tower bot tom for the medium voltage transformers and switching devices For this local norms ha ve to be followed Standard components available at specialist suppliers can be used for the transformer station Special attention has to be drawn to the cable entry into the transformer station and into the tower these openings have to be waterproof and inaccessible for animals to avoid in undations or scuff mark from rats etc The installation of the tower Concrete tower Concrete towers have to be either cast with a timbering that comes along upwards or as sembled of pre manufactured segments which are pre tensioned with steel ropes laid along the tower wall and bonded at the connection points Lattice tower Lattice towers are pre assembled on the ground and then depending on their height erec ted with a crane completely or segment by segment Conical tower As during the disassembly the processes are the same of every tower segment with this tower type The fixing devices have to be attached to the top flange and to the lowest flan ge and hooked to the cranes Both cranes lift the tower from the transport vehicle toge THE RE INSTALLATION OF THE WIND ENERGY CONVERTER ther The transport devices are disassembled after the segment is hanging directly above the ground Both cranes bring the tower segment i
16. like a bullet out of the connection Other disad vantages of hot dip galvanized bolts are the larger undersize during fabrication these bolts are smaller than others before the zinc layer is applied and the gliding behaviour of the zinc layer during the bolt tightening which is determined to be bad In case of doubt black bolts should be taken for the high strength boltings for bolts with strength class 12 9 there is not alternative for this The corrosion protection is done by applying a co lour varnish THE INDIVIDUAL COMPONENTS OF THE WEC Rubber bearings Rubber bearings are supposed to absorb vibrations and shocks In general they are used at the following components Gearbox Generator Control cabinet which are installed inside the nacelle Control cabinets inside the hub for pitch and ActiveStall controlled plants Hydraulic aggregate The rubber elements at gearbox and generator are often adapted to their specific geome tries and stresses With the other components standard elements can be used Apart from the stress caused by component vibration the rubber is subject to the normal maturing processes caused by heat oxygen and sunlight If rubber elements are damaged porous or with torn off metal rubber connections the standard items can be replaced comparatively fast and cheap and independent from the manufacturer For the rubber bea rings of generator and gearbox the geometry should be considered as we
17. of magnetic bases at the spot used and marked for the first measurement In doing so the comparability can be ensured in terms of recorded values in comparison to previously measured data Checking the tightening torques Calibrated torque spanners have to be used for checking the tightening torques The value to be checked should not range in the full scale points of the tools Oil analysis Oil analysis is carried out by external laboratories The laboratories sell together with the analysis complete sampling sets with special sample containers EXPERTISES Gear inspection by means of an endoscope The gear toothing and gear bearings that are not visible through the inspection holes are checked by means of flexible endoscopes Apart from the conventional endoscopes with optics lamp and adaptor for a miniature camera currently digital systems are more fre quently used the images of which can be easily integrated into the reports What do the different expertises cover Expertise after commissioning The purchaser of a wind energy converter arranges for the inspection of the following Assembly faults Completeness of the wind energy converter Compliance with type testing used components components features WEC opera tion labelling Compliance with building permission requirements Operatibility of all components Compliance with safety regulations guidelines Generally the expertise is carried out either direct
18. parts which can be easily obtained by any customer Even the number of teeth can be easily identified by simply counting the teeth Before purchasing a used turbine always clarify whether the manufacturer is ready to cooperate EXPERTISES The written expertise how should it look like The written expertise that the surveyor hands out to you after compiling the expertise should contain at least the following items Type and serial number of the wind energy converter Location and wind farm ID Date of on site inspection Names of the persons attending the expertise Weather conditions under which the expertise took place Previous operating hours and total yield of the wind turbine Description of the inspection task and its scope Result of the inspection where applicable with picture documentation The written expertise must be handed out to the customer as hard copy bearing the signa ture of the expert If more than one expert have been involved in the inspection all indivi dual reports are integrated into the documentation and signed by the expert being in char ge for the entire expertise What can an expertise achieve An expertise specifies already existing faults from which arise corresponding repairs or guarantee claims If the manufacturer is not inclined to accept these claims even if it is a guarantee claim he will arrange for a counter expertise The documented errors can relate to the engineering electrical
19. penetration and inclusion of hydrogen in metal As hydrogen is the lightest and smallest element it can escape from metal as diffusion comparatively easy Some of the hydrogen is included in the metal during this process and thus extended The result is an embrittlement of the metal at this spot were the hydrogen has been absorbed into the lattice Even after the hydrogen escaped from the metal again a failure in the lattice remains which saps the structure durably By and by the metal embrittles that strong that a breaking occurs This effect resembles the material fatigue process very much Vi KINDLY SUPPORTED BY THE CITY OF ROSTOCK WITH FUNDS OF THE EU INTERREGIIIB PROJECT WIND ENERGY IN THE BSR
20. purchase a second hand wind energy converter It is the main objective to outline the extent of technical inspections for used wind energy converters and to reveal possible risks and consequences This includes the technical con dition of WEC components and also the documentation performed maintenance work possible repairs the assembly amp disassembly and the transport of the WEC Further aspects are life expectancy estimations of individual components and the entire plant a possible plant optimization and the investigation of regional conditions Naturally the present study can not cover all problematic issues as the individual plants can widely differ in terms of construction and technology Therefore we have focused on aspects with a certain universality Differentiations are made were it seemed generally sensible for instance plants with a rigid rotor blade hub connection so called stall tur bines require different considerations than pitch turbines that are able to adjust their ro tor blades according to the aerodynamic requirements For whom is the study designed This study addresses persons who intend to purchase or re install a used wind energy plant on a new site We will point out possible problems and describe solutions that ena ble new owners to operate their new old wind energy plant successfully and profitably The study serves in the preparation phase of a project with used wind energy plants it di
21. resulting from this periodic fore and backward trailing at the downwind side can initiate extreme vibrations which might lead to a destruction of the entire building Thus the nacelle should either remain on top of the tower or at least the top segment should be dismantled No anchoring of the tower will not be suffi cient Ask the manufacturer for information about the proceeding under any circumstances when dealing with this topic Disassembly of the transformer With older plants the medium voltage transformer and switchgears are located inside smaller transformer stations next to the tower bottom These component groups can be disassembled easily and loaded for transportation with a crane Disassembly foundation The foundations of conical towers are large plates sometimes additionally buttressed with pilings in softer grounds The connection between tower and foundation is ensured either by a short tower segment cast into the concrete or by a steel flange on top of the foundation and tension rods that are several metres long and reach deeply into the founda tion In addition there are one or more layers of concrete reinforcement with a total length of several hundred metres DISASSEMBLY AND TRANSPORT OF USED WIND ENERGY CONVERTERS In general foundations cannot be moved to another construction site If the building regu lations or the contracts require to remove the socket and the residuals of the transformer station this is m
22. swinging will be accelerated instead of absorbed The co ordination among the team members who stand far away from each other has do be done perfectly preferably by an experienced member who is standing near the crane operator The tow bar of the service vehicles may be used for holding the ropes Lowering the rotor The rotor will be lowered until the blade directing downwards hangs shortly above the ground The hook of the auxiliary crane is attached to the additional loop Now the main crane lowers the rotor while the auxiliary crane keeps the blade tip on a constant level of height Both cranes have to be co ordinated in a way that both crane ro pes hang perpendicularly all the time The teams standing at the two remaining free blade ends have to protect the rotor further against swinging The hub is put down with the flange on the table of the transport device and protected temporarily with some bolts Disassembly of the rotorblades Two blades will be propped with pedestals devices pallets or similar near the blade tip at the spots intended for this The third blade is hinged with loops around the blade root into the hooks of the main crane and at the relevant spot of the blade end edge protec tion into the hook of the auxiliary crane Both cranes tighten slightly to release the bolting Loosen the nuts and adjust the crane so that the blade hangs at the blade flange Only then the nuts can be removed and the blade slewed away
23. the nacelle against a twisting of the yaw bearing an tilting of the nacelle would make the lorry turn over inevitably The nacelle should be protected against water and dirt as well to prevent the electronics and the mechanical components from getting damaged The sensitive control cabinets that cannot be heated during transport and provision at the construction site have to protected against moisture with thick tarpaulins Hub If the hub cannot be transported connected to the nacelle it has to be loaded attached to an own supporting frame In both cases the hub has to be protected against moisture and dirt as well The best way to do this is to cover the hub entirely and including all cases with tarpaulins Special protection is needed for the electronic components and the blade bearings where rainwater might get into the runways Towers In general mass and dimensions of the tower segments of conical steel towers are desi gned regarding their transportability and craneability during the development and design period The segments are designed in a way that one transport vehicle is needed for every component If the segments are covered during the transport this reduces the cleaning effort prior to the re installation of the wind turbine Dismantled lattice towers can be transported easier due to their much smaller volume the amount of needed vehicles depends on the permitted total weight Take care that the corrosion protection of
24. the single profiles remains undamaged during loading and trans port Additional remarks The control cabinets of the tower bottom and the transformer station and the transformers itself have to be transported in closed up lorries A complete covering of the cabinets with tarpaulins is recommended All dismantled platforms measuring masts hatch covers or tower doors and all additional items have also to be loaded into one lorry The re installation of the wind energy converter The descriptions in the following chapter are based on the assumption that the majority of the required tools and information for a re installation are available If the project de veloper organised the disassembly by himself he has own experiences with the topic The installation of a wind energy converter purchased in disassembled condition should be based on the experiences and devices of the company that carried out the disassembly In addition it can be assumed that the medium voltage cable has already been wired up to the connection point Required information for the installation In addition to the information and general conditions that were described in chapter Di sassembly of wind energy converters the following has to be considered for the installa tion of the plant Working drawings have to be available for all newly manufactured components and items All newly manufactured items and buildings have to correspon
25. they vary only in the way of pitch control and actuating of the blades For easier reference both versions are referred to as pitch systems in the following description Pitch systems may be either provided with electric or hydraulic pitch control Both sy stems have generally similar designs They consist of the following components Drive motor Gear and or hydraulic cylinder with mechanic actuating system One or more switchboards Uninterrupted power supply UPS for electric systems and or hydraulic accumulator for hydraulic systems Steel frame for fastening the individual components optional Electric pitch The rotorblades of turbines with electric pitch systems are adjusted by the toothing bet ween pinion and blade bearing Always check the wear of the pinion if the material fati gue is too high this may impair the toothing which causes enhanced wear and tear at the toothing A further component of the pitch control is the transmission gear multi level planetary gear and the drive engine with the control unit Hydraulic pitch For hydraulic pitch systems the clearance of the movable components must be regularly checked where applicable the clearance must be re adjusted In addition the entire hy draulic system must be checked for leakages The hydraulic accumulator must be inspec ted for a possible pressure decline The vibration adsorbing elements made of rubber must be replaced at regular intervals Un
26. to shut down the plant by itself this is called a redundant braking system If no single blade pitch exists the mechanical brake is designed to brake the rotor as well Brake system of stall plants At stall blades that are rigidly screwed with the rotorhub the aerodynamic rotorbrake consists of a movable tip brake that moves 90 towards the leaning direction if the bra king function has been triggered The drag created by this is high enough to decelerate the rotor to low rotational speed On this low rotational speed level the mechanical rotorbrake is used It brakes the wind energy converter until complete shutdown Even with stall controlled wind energy converters aerodynamic and mechanical brake form a redundant system in case of emergency the rotor should be braked to shutdown with the mechanical brake The aerodynamic brake is designed fail safe This means If no hydraulic pressure is put on when the WEC is started or it trails during production operation the aerodynamic bra ke deceleration by appropriate turning of the rotorblades remains active or gets active via a spring and centrifugal force the WEC passes on into a fail safe operation mode The construction of the mechanical rotorbrake The mechanical rotorbrake is a disc brake It is located depending on the wind energy converter on the slow shaft within the flux in front of the gearbox and or on the fast shaft within the flux behind the gearbox Either activ
27. wind energy converter have special peculiarities With prototypes or series that were multiply changed during re designs or where components from different manufacturers were assembled larger deviations between documentation and construction might occur In case these information cannot be obtained it should be clarified whether there is a ser vice company that has experiences with this design If no transport and assembly devices are available they can be designed newly by expe rienced design engineering offices and manufactured by mechanics Organisational matters Regarding the working steps required for the installation and disassembly the differences between smaller and larger wind energy converters are quite small But in most cases the larger plants are younger and thus have a higher technological standard They are docu mented more detailed and much better and have special solutions for the installation and disassembly of the construction Not all assembly work can be carried out by every team member Blastings of concrete towers must only be carried out by specialised companies La vish blocks and safety measures are necessary The disconnection of the transformer from the grid has to be executed by a trained technician who has a medium voltage switching authorisation For the disconnection of the transformer and all other work at the medium voltage si ded ground cables the medium voltage cables of the wind energy co
28. Especially regarding the wind energy converters that have already been operated for many years on a site with frequent changes of the wind di rection this aspect is very important to avoid that existing pitting cannot progress too much Brakes in the yaw system In addition to the brakes of the yaw drives there is a second braking system for yawing It may consists of several active disc brakes that are spaced regularly along the yaw bearing Permanent braking system Alternatively a permanent braking system can be used For this variant several construc tions exist depending on the manufacturer These brakes decelerate the yawing of the WEC to avoid strong vibrations which might be dangerous for the wind energy converter In addition these brakes are able to lock the yaw system in case it shall not be activated when the wind direction changes during WEC standstill during maintenance and service work etc Cooling system High temperatures occur within the gearbox and the generator during the operation of the wind energy converter they require a cooling of these components Gearbox cooling The cooling of the gearbox is done with gearbox oil which again is cooled by a heat ex changer As with the gearbox the temperature of the bearing is monitored by appropriate sensors Generator cooling Depending on manufacturer and design the generator can be cooled with air or water With a water cooling the cooling circuit of th
29. Maintenance specification including all maintenance and service reports Logbook with all the service team calls In addition it may be required to view the documentation related to type testing or the in spection and experience reports of converter components or replaced parts If for instan ce the rotorblades of the turbine have already been replaced the newly installed rotorbla des must be included in the type testing If this is not the case it is mandatory to perform a subsequent certification of this component related to the specified wind energy conver ter This procedure must be documented in a corresponding certification report However not compulsory but very helpful may be documentation from previous experti ses They may give information about the operation breakdown of the service department responsible for the WEC and the work quality of the on site service team This documentation and the service reports of the employees provide the following infor mation to the expert How much time did it take to eliminate the damages Was the service rendered by the manufacturer or by external companies Were all damages eliminated After own inspection of the repairs With which capability was the work done A long period of time between reporting the damage and its elimination may be an indica tion that the service team was not capable Certain damages for instance a low oil level inside the gearboxes or insufficient
30. ON SYSE e aa a 54 e E E E E E RSG I eG MAS 55 Disassembly and transport of used wind energy 2 58 Disassembly Of wind energy CONVELTELS 61 Transport of uSed wind energy Converters serren a a a a aia EA O ES 73 The re installation of the wind energy 22 Required information for the installation General course Of the ASSEMDIY cscccssssssscsssssssssssssssssssssssesscscesasacacecasscsseasacasesauasasesavacssavauaseeesavaseses GIOSS APY ae Sled cele ee 81 ABOUT THIS STUDY About this study For the classic wind energy countries which already look back to a long tradition of wind energy converter installation the issue of second hand wind energy converters or used wind energy converters has become more and more important over the past years Due to the lack of new sites available in countries like Germany and Denmark smaller wind energy converters WEC are more and more replaced by converters with a consi derably higher rated output However the dismantled plants have very often a residual li fe expectancy of more than ten years thus offering a good opportu
31. Reports of all service and maintenance work Reports of all oil analyses Operating manual of the turbine Electrical circuit diagrams Hydraulic diagrams Kinematic data of the drive train Operating instructions and test log of the crane installation Operating instructions and test log of the climbing protection Operating instructions and test log of the passenger lift where applicable All expertises and inspection records Repair reports The individual components of the WEC General remarks A wind energy converter consists of many different components mechanical and electri cal that are designed selected and assembled for an optimal interaction The result of this interaction is based on years of development by experienced engineers Therefore a non conforming assembly even of unimportant components can lead to consequential da mages of other much more important components It is therefore recommended to exercise reasonable care not only at the time of the first assembly but also at the time of the WEC re assembly in order not to delay the commis sioning and avoid future damages The same applies naturally also for future maintenance and repair work The following chapters are focused on the individual components of a wind energy con verter It is intended to give a deeper insight into its design thus enabling a competent and professional handling of each individual component At first some general remarks sho
32. ade bearings in the main bearings in the yaw bearing and the gene rator bearings Gear oil in the main gear Gear oil in the pitch and yaw gearbox Supplies Hydraulic oil The set up of a wind energy converter The figure on the interior of the cover page shows the general set up of a wind energy converter Naturally the implementation of this structure by individual manufacturers may widely differ However there are some statements that generally apply The figure shows the most important major components which can be found at almost all wind ener gy converters Rotorblades Hub Blade adjusting system for pitch and ActiveStall turbines Rotor shaft Main bearing Main frame Nacelle cover Gear with clamping set Coupling Generator Rotor break Azimuth system yaw bearing gear breaks Cooling system Switchboards Tower Foundation If you intend to purchase a second hand gearless wind energy converter currently only turbines made by Enercon can be recommended These turbines are provided with rotor and generator one shaft and run with equal rotation speed Enercon wind energy converters are not only gearless but also pitch controlled and have variable rotational speed i e the angle at which the wind is hitting the blade can be adjusted by a pivoted blade and a corresponding setting of the rotor speed according to the respective operating situation The generator is designed as a ring gener
33. ain frame at several spots via vibration damping elements At the outside the GFP is covered with a gel coat layer that protects it against UV radiation and humidity The interior is usually covered with a layer of painting The interfaces of the GFP cover should be sealed because of its hygroscopic quality as humidity might get into the laminate at these spots which would damage the material Scorings of the GFP cover that can for instance be caused during transport or assembly can be repaired relatively easy Nacelles made of sheet steel Instead of the GFP cover steel sheets can be used They have to be protected against cor rosion in the usual way Possible damages of the layers have to be repaired according to the colour specification details are specified in the maintenance manual of the plant For some energy converters a part of the nacelle is formed by the main frame The nacelle interlock To open and close the nacelle without problems hinges and possibly existing interlocking systems have to be inspected regularly In case the interlock does not work without pro blems the hatch might get open at high wind speed and get damaged Worst case would be that the nacelle hatch or even the nacelle cover is torn down Tower 3 types of tower are used for the installation of wind energy converters Segmented conical steel towers screwed via flange connections Lattice tower Ferroconcrete tower The disadvantage of concr
34. al of the residuals to a disposal company or a scrap dealer has to be carried out by the WEC owner Second hand component market As a principle everything can be sold second hand that can be taken away from the con struction site without destroying it The problem is to find a purchaser and until he has been found to store the components so that they do not lose their market value and do not cause storage costs higher than the price to be achieved How to find potential purchasers for single used components Some component manufacturers buy their own products back and offer them by them selves after an overhaul The same applies for repair companies Especially blades gearboxes generators and drive technology can be used again after an overhaul carried out by an expert Service companies from the wind energy branch might be interested in special compo nents to keep them in stock as spare parts Single manufacturers keep reference lists of all installation sites of turbines of the sa me type These lists can be useful to determine owners of the same type of wind turbi ne that might be interested in these components There are several second hand turbine markets to be found in the internet Material disposal incurring costs or cost free With a disposal of the following materials not only transport costs have to be paid but al so the disposal itself Concrete scrap from foundation and transformer station from th
35. ase While installing and re assembling a WEC the bearings must be re lubricated The re lubrication is carried out via the lubrica ting nipples Lubricating nipples are small cups that can be filled by a grease gun with grease The further lubrication of the rotor bearing should be carried out in compliance with the maintenance intervals details can be referenced in the chapter Documenta in the first line also in the maintenance and service manual for your wind energy converter Some wind energy converters are provided with an automatic re lubrication In this case it is sufficient to provide an adequate amount of grease for re lubrication purposes This work forms also an integral part of the maintenance specified and described in the respec tive manuals Anew mounting of the rotor bearing requires full compliance with the assembly instruc tions of the manufacturer If the shaft is fitted tightly into the rotor bearing press fit the inner bearing ring must be warmed The material extension allows an assembly without damaging the seat of the bearing The rotor shaft The rotor shaft connects the hub with the gear respectively for gearless turbines with the generator Rotor shafts are mostly made of heat treated steel in individual cases ma terials like spheroidal cast iron EN GJS 400 18U LT or cast steel are used Under adequate operating conditions of the wind energy converter the rotor shaft is only sub
36. ational speed control it determines how strong the WEC has been braked within a certain period of ti me Generator coupling The generator coupling has to compensate the axis and shaft angle displacement between gearbox output and generator input shaft If the displacement is too high the stress of the flexible components becomes too high and the coupling tends to fail earlier Thus it is possible to inspect the axis and shaft angle displacement misalignment during the as sembly of gearbox and or generator and to correct it if necessary via the adjustable gene rator feet In most of the cases the generator coupling is assembled together with the brake disc at the gearbox side Some plants are provided with an additional safety coupling located at THE INDIVIDUAL COMPONENTS OF THE WEC the generator side between coupling and generator shaft mostly designed as slip clutch It serves to limit the maximum torque In wind energy converters different forms of generator couplings are used multiple disc clutch steel lamellas plastic lamellas curved tooth gear coupling CENTALINK CENTAFLEX Multiple disc clutch Multiple disc clutches have one or more flexible lamellas at both ends that allow a radial and angular misalignment of the connected shafts In case of plastic lamellas mostly fi bre plastic bonding one lamella is used at every side If the lamellas consists of metal there are several thin lamellas on every sid
37. ator with several pole pairs The elec trical energy of these turbines is fed to the grid by a frequency converter Control and operation of wind energy converters The operation and control of a wind energy converter is performed by a computer equip ped with corresponding software The basis forms the recording of current operating and environmental conditions wind direction wind speed outside temperature etc For this purpose the WEC is equipped with an anemometer for measuring the wind speed on the roof of the nacelle On the basis of the measuring results the measuring and control software activates the different operating conditions e g Starting the WEC as soon as the switch in wind speed is achieved Switching off the WEC as soon as the maximum operating wind speed is exceeded Pitch control in relation to the respective wind speed Initiating an emergency stop in case of damage Yawing at changes of the wind direction There are different concepts for the control and operation of wind energy converters Stall controlled wind energy converters ActiveStall controlled wind energy converters Pitch controlled wind energy converters Wind energy converters with constant rotational speed Wind energy converters with variable rotational speed THE INDIVIDUAL COMPONENTS OF THE WEC Stall controlled wind energy converters At stall controlled wind energy converters the rotor blades are rigdly connected with t
38. bled as well and no particular devices have been provided the hub is hooked to the main crane with a loop that has been thrown through two blade flange openings An additional loop is located at the opposite end it is thrown through the front hole and the third opening of the blade flange All loops are pro tected against sharp edges The maximum load of the fixing the devices must not be ex ceeded The crane operator loads the crane hook with a load that corresponds with the dead weight of the hub with all fixed equipment The boltings of the shaft flange and the hub are released for several millimetres Afterwards the hub will be pulled away with the help of the thread inside the shaft flan ges intended for this or other technical devices Move the hub away from the nacelle slew it sideward and lower it with the crane until the hub is located directly above the ground The lower still unused loop is attached to the hook of the auxiliary crane now Bring the hub into an upright position so that it can be driven together with the shaft flan ge over the transport devices and put down there by both cranes together Loading the blades The loading procedure for the blades depends mainly from the construction of the trans port devices If possible the transport devices of the blade tips and the blade roots should be assembled to the blades when they are still stored on the ground With a twisted hin ging of the loops the blades are cau
39. breaking of the rotorblade rear edges or blade tips will occur Special attention has to be turned to the suspension of the entire rotor and the fixation of the sheets and the crane loop of the auxiliary crane at the blade tip during disassembly of the rotorblades together with the hubs i e as star or the loops for single blade disassemblies Blade of wind energy converters are despite of their huge dimensions and high weight some blade types weigh more than 10 tons aerodynamically very sensitive components that might make unpredictable aggressive moves even at lower gusts In addition their edges and surfaces can be damaged very easily Therefore rotorblades should be treated with maximum care DISASSEMBLY AND TRANSPORT OF USED WIND ENERGY CONVERTERS Nacelle The nacelle has to hang horizontally at the crane hook otherwise problems might occur when positioning it above the fixation holes to put it on the transport devices Therefore special spots have been determined where the nacelle has to be fixed this ensures that every involved fixing device carries about the same load and that the nacelle balance is located directly below the crane hook Different from work in the manufacturing hall and the installation there is hardly an opportunity to equilibrate the nacelle while disassem bling the plant The following questions have to be answered prior to the disassembly Where are the fixing points of the nacelle located
40. ccurs due to permanent loading and unloading of the tooth flanks In ca se the tolerable compression of the gearing teeth is exceeded items dissolve out of the tooth flanks After a certain amount of overruns pittings occur Tooth flank fatigue is only problematic if these pitting gets worse during unmodified operation oeizure The so called Seizure occurs if the lubrication film between the tooth flanks is interrup ted and metallic surfaces ream directly against each other This can lead to momentary lo cal welding of the tooth flanks Stripe shaped roughened ribbons occur mostly pronoun ced at the tooth bottom and tooth head Due to a temperature rise during too high sliding speed with simultaneous compression the so called warm seizure occurs If the com pression is too high while the sliding speed is low cold seizure occurs One of the main reasons for the seizure is the use of unsuitable lubricants However this can be almost avoided by careful maintenance and lubrication of the gearbox If one of the above mentioned damages occurs an expert should be consulted regarding the remaining life time of the component Options of bearing inspection A careful inspection of the bearing should be carried out as well as far as this is possible with the appropriate method and the condition monitoring system Consider a bearing damage that draws attention to itself only during further operation results often into
41. come possible at all Crane time costs money Therefore the following preparation work should be finished prior to the beginning of the crane work Providing and mounting the needed fixing devices inside the nacelle or inside the hub Disassembly of disturbing component groups Disassembly of the tower cables in case the generator will not be used to turn the ro tor Saving the control cabinets onboard crane loose items or devices Removing all oil leakages inside the nacelle Cleaning the hub interior from all grease and oil films Setting a temporary power supply fort he control and the drive engines of the wind energy converter Disassembly of the entire rotor as one unit With this variant the rotor will be disassembled as a star i e with blades that are still assembled to the hub Both cranes and the transport devices of the hub have to be arranged in a way that all three blades can be reached by the cranes from any side after the rotor has been laid on the ground The rotor has to be brought into V position one blade directing downwards the two other blades towards upper right and left and to be locked DISASSEMBLY AND TRANSPORT OF USED WIND ENERGY CONVERTERS The staff standing inside a man basket has to fix the ropes at the end of all three blades minimum length 2 5times longer than hub height A crane slope should be attached to the blade that directs downwards in addition The sensitive rear edges of the bla
42. d in a way that even at changing wind speeds an optimal performance can be achieved If the turbines are provided with variable rotation speed their generator or rotor speed can be adjusted in a way that the generator can be operated in its optimal characteristic curve at all times For pitch controlled wind energy converters with variable rotation speed 2 operating mo des are distinguished 1 the fractional load range 2 achieving the rated output Part load operational range In the so called fractional load range the wind energy converters are operated with less than the maximum output rated output This is provided through controlling the output via the generator speed THE INDIVIDUAL COMPONENTS OF THE WEC The pitch is adjusted in a way that the drive engine generates the highest possible drive torque Achieving the rated output When the WEC achieves the so called rated output during operation the performance li mit is provided by a corresponding adjusting of the rotor blades and speed control if ap plicable in order to maintain the output level and prevent damaging the WEC For pitch controlled turbines the fore edge of the rotor blade is turned towards the wind Turbines with variable speed are provided with a generator which is connected with the grid by a frequency converter This reduces the feedback between WEC and grid to the largest possible extent For wind energy converters with blade adjustment 2 conc
43. d releasing of the teeth happens gradually and more teeth lay within the gearing area at the same time Because of this the helical teeth are more suita ble for higher rotational speeds and can be stressed harder than straight toothed wheels of the same size In addition the smoother operation reduces the noise level of the gearbox The disadvantage additional axial forces occur due to the helical toothing at the toothed wheels they have to be absorbed by the bearings and shafts THE INDIVIDUAL COMPONENTS OF THE WEC Cables and wires that lead into the hub have to be wired coaxially towards the rotor through gearbox and rotor shaft in any case All required connections rotational feedth rough of the hydraulic oil slip ring runner for electric cables are located at the backsi de of the gearbox The coaxially positioned axes and shafts inside the gearbox are hol low At this gearbox the sensor for rotational speed control of the slow shaft can be in stalled comparatively easy High temperatures occur during the operation of the wind energy converter they are mo nitored with special sensors In case the oil temperature exceeds a certain limit the oil looses gradually his lubrication characteristics It matures fast and looses its viscosity For wind energy converters that are operated in colder regions an appropriate operation temperature is extraordinarily important In case the WEC has longer standstill periods at very low tempe
44. d wind energy converters are provided with 2 rotation speeds the speed is changed by a pole switching in the generator The second speed the smaller of the two is switched in to achieve an optimal performance at lower wind speeds and thus achieving the best possible energy yield ActiveStall controlled wind energy converters For ActiveStall controlled wind energy converters the connection between rotor blade and hub is no longer rigid the rotor blades can be rotated alongside their longitudinal axis This mobility of the blades allows a better balancing of larger variations of the wind speed than for stall controlled turbines If the performances of the WEC must be limited due to high wind speeds the fore edge of the rotor blade must be turned from the wind This provides a wider angle of incidence at the rotor blade and the stall is appropriately controlled ActiveStall turbines are also ope rating with continuous rotation speed If the upper performance limit the so called rated output of the WEC is achieved the tur bine control ensures that even at rising wind speeds the output is kept on a permanent le vel This can also be achieved by changing the pitch A output limit of this kind is neces sarily required as the WEC may be damaged by high loads Pitch controlled wind energy converters with variable rotation speed Pitch controlled WECs are able to change their pitch and thus the position of the rotorbla de towards the win
45. d with the type certifi cate of the wind energy converter regarding material dimensions and manufacturing Without valid permission no other designs of the foundation tower and blades must be used The characteristic values of the ground have to keep within the limits defined by the type test which has to be verified by a soil expertise The construction site must be accessible for all vehicles The construction site must be prepared to carry the loads of transport vehicles and cra THE RE INSTALLATION OF THE WIND ENERGY CONVERTER nes by solidifying and covering with gravel High solid galvanized bolts must not be re used Only new ones must be used which were ordered as sets which means that the bolts were delivered with washers and nuts Never mix different charges Torques are needed for all component joints with boltings The sources for these infor mation are mainly the manufacturer possibly the manuals inspection reports or exper tises of the plant as well Pick up regulations for the boltings of tower hub blades and nacelle have to followed necessarily For this the bolts have to be fastened in the right order the torque levels during the different phases have to be considered as well as the lubrication status of the threads Ask the manufacturer for the provisional torques during the assembly too Thus for instance the tower bolts are only tightened up to the required torque after the installa tion of the WEC A pr
46. des have to be equipped with a special edge protection The blades of the wind energy converter have to be pitched so far that the rear edge shows sideward or the perfect position towards the front Otherwise it won t be possible to put down the entire rotor as the rear blade edges reach much further then the bearing surface of the hub All hydraulic and electric components and all items that might cause a hooking of the hanging rotor with the nacelle cover have to be loosened For this two loops are put around the blade roots of the rotorblades that show upwards and hinged into the crane hooks There are turbine types where the hub is equipped with a special device for hinging the crane harness The crane operator loads the crane hook with a load as high as the dead weight of the ent ire rotor The boltings of shaft flange and hub are loosened for several millimetres Afterwards the hub is cautiously pulled away using the threads inside the shaft flange intended for that or other technical devices generally the shaft step is 30 to 60 mm long By then the ro tor is hanging freely at the crane hook The work of the ground team dealing with the three ropes at the blade ends requires expe rience it has to adjust the rotor and protect against swinging The ropes of the swinging component must be pulled only as long as the fixation end moves backwards If you still pull after reversing the motion energy will be given into the system the
47. e bearing into the gear This allows to completely omit the rotor shaft Similar to the 3 point bearing the bending moments in the gear im ply an adverse effect Due to the relatively high bending moments this type of bearing can only be implemented for smaller turbines Bearings of used wind energy converters To determine the condition of a used wind energy converter the condition of the bearings must be subject to an extensive inspection in order to perform a possible replacement prior to re assembly or during maintenance The dismantling and assembly of a rotor bla de requires a complete dismantling of the power train on the slow shaft This procedure is much easier to perform in a workshop or prior to installing the machine house on the to wer than at a completely installed WEC Inspection of the bearing condition of used WECs The condition of the bearings can be either checked by visual inspection or condition mo nitoring The condition monitoring allows an inspection of the assembled bearing and can be performed during operation of the wind energy converter It specifies approaching or occurring damages and wear As the condition monitoring requires an exact knowledge of technical and geometrical data of the bearing and therefore much experience it should only be performed by professional engineering staff THE INDIVIDUAL COMPONENTS OF THE WEC Lubrication of the rotor bearing In general rotor bearings are lubricated with gre
48. e generator is placed on adjustable generator feet more or less flexible regarding level and height The rubber of these feet is wearless apart from maturing Fur ther information about the rubber feet you get in chapter Rubber feet The generator is either equipped with air or water cooling Further information can be found in the chapter Cooling system Synchronous generators Synchronous generators are used for pitch controlled WEC with variable rotational speed They are connected to the grid via a static converter It prevents that occurring po THE INDIVIDUAL COMPONENTS OF THE WEC wer fluctuations are directly transmitted to the grid Synchronous generators are provided with a better coefficient of efficiency than asyn chronous generators On the other side losses of up to 5 percent occur while the current is converted to grid frequency Asynchronous generators In general asynchronous generators with two different pole pair figures are used with stall controlled wind energy converters This allows to equip the generator with two diffe rent power levels and to operate the wind energy converter at two rotational speed levels The rotational speeds of the generator amount to 1500 min 4 pole pairs for high capaci ty ranges and 1000 min 6 pole pair for low capacity ranges Asynchronous generators are cheap sturdy and need little maintenance They allow an easy synchronisation with the grid Its coefficient of
49. e may be the risk of a sudden short circuit because of the resins ageing process with possibly high consequential costs Therefore it is recommended to check the insulation condition at re gular intervals Rotor imbalance By measuring the accelerations in the nacelle aerodynamic imbalances and mass imba lances at the rotor can be determined If these problems occur the loads resulting from the vibrations of the turbine head and affecting the entire turbine including foundation may be higher than assumed in the component calculations That may cause premature fa tigue of materials which also impairs the life expectancy of the wind energy converter so called fatigue failures may occur If they are recognized in time imbalances can be generally eliminated with compensating material or by removing loose residual resin from the blades Blade angle If the blade angles of the blades do not coincide so called aerodynamic imbalances may occur see also rotor imbalance In most cases aerodynamic imbalances can be elimina ted by correcting the blade angles Bending and torsion moments at tower shafts and blades By means of strain gauges transmission units like slip rings or radio paths and data logs the actual load of the major components can be determined If meteorological data after the installation of the turbine is measured over a longer peri od estimations can be made whether the loads affecting the turbine over the years
50. e of the clutch Lamella clutches operate wearless and noiseless The maintenance efforts are low it has only to be inspected for mechanical damages Curved tooth gear coupling Curved tooth gear couplings are shaft connections with a positive transmission of forces The curved tooth gear principle allows edge compression at the toothing with radial and angular shifting Because of this the clutches work nearly wearless The positive effects of the rigid toothing allow a transmission of high torques and high rotational speeds With curved tooth gear couplings it has to be checked regularly whether the toothings are lubricated sufficiently during operation this is only the case if a certain radial and an gular shifting exists that allows the relative motion between the teeth Design related curved tooth gear couplings are operated with more noise than lamella couplings as they have less vibration damping characteristics Curved tooth gear cou plings are characterized by a relatively compact construction CENTALINK coupling The CENTALINK coupling is a simple highly elastic and connecting coupling easy to assemble and with rubber like bushings The coupling allows a compensation of large axial radial and angular shiftings The CENTALINK coupling 15 a torsion rigid zero backlash coupling that work noiseless CENTAFLEX coupling The CENTAFLEX coupling is a simple rubber coupling that work maintenance free and quiet It is set up
51. e or passive brakes are used here Passive brakes are so called fail safe brakes i e they can only be opened if hydraulic pressure is put on The required brake torque is adjusted by regulating the hydraulic pres sure it depends on the operation situation of the wind energy converter In an emergency situation the brake is operated with maximum brake torque In other situations the brake torque is kept as low as possible to minimize the stress on the WEC and the components to the lowest possible extent Inspection of the brakes Carry out a functional test of the mechanical brake In addition the brake linings have to be inspected the brake lining must be designed with a prescribed minimum thickness If this is not the case the linings have to be exchanged Some brake types are equipped with an abrasion sensor here it has to be inspected if the display corresponds with the real status of the lining During the braking procedure brake disc and brake linings are exposed to high tempera tures that are an additional stress of the material It has to be ensured that no deeper score marks are on the brake linings that as well as an increased impact of the disc result into an uneven and enhanced abrasion of the brake linings In addition attention has to be paid to possible discolouration of the brake disc as they might result from a malfunction of the brake The braking procedure of the wind energy converter is monitored via rot
52. e tower Glass fibre reinforced plastics from the blades hub cover nacelle cover insulation matting Electronic scrap such as control cabinets light fitting computers and monitors Valuable materials These residuals could be sold with a good profit The prices that can be achieved depend on the fluctuations in the exchange of metal stocks and can differ a lot within shortest pe riods of time In any case offers from several dealers should be inquired Valuable and available to a greater extent in wind energy converters are steel scrap from the tower and the machine components as well as copper from the cables In 2004 about 100 Euros were paid per ton of steel for cable copper about 2000 Euros per ton Transport of used wind energy converters Restrictions in connection with the transport Apart from the above mentioned general transport conditions within the direct environ ment of the wind turbine bearing capacity of the access roads and bridges minimum headroom etc there are various restrictions for the heavy goods vehicle traffic that might influence planning and costs Weekend ban on driving Special regulations during holiday seasons Bans on driving in the daytime DISASSEMBLY AND TRANSPORT OF USED WIND ENERGY CONVERTERS Roads closed for heavy goods vehicle traffic Special roads for very wide transports Required escort vehicles Queue times at customs when crossing national borders Truckage companie
53. e water can be connected to the heat ex changer for the gearbox oil The water again is cooled by a heat exchanger with outside air An air cooled generator uses outside air for cooling The airflow needed for this is produ ced by a fan located on the generator axis The cooling system should be inspected regularly the intervals are defined in the main tenance manual of the WEC Although the movable components of the cooling system pumps fans etc are not exposed to excessive stress they should be inspected regularly Possible faults of the cooling system are recorded by the temperature sensors To ignore these error messages or nonconformity reports might cause severe and expensive dama ges THE INDIVIDUAL COMPONENTS OF THE WEC Nacelle The nacelle is the cover of the wind energy converter towards outside It can be opened and is accessible via one or more hatches The opening of the nacelle is mostly done by the hydraulic system As no rainwater must get into the closed nacelle when the nacelle is closed the air exchange with the outside is exclusively done via the fan or openings in the nacelle wall They allow a heat exchange and reduce the formation of condensate Nacelles made of GFP Usually nacelles are made of glass fibre reinforced plastics GFP The GFP cover is reinforced by a steel frame This steel frame consists of galvanized square and pipe outli nes that are laminated with GFP The nacelle is connected with the m
54. efficiency is lower than those of syn chronous generators The generator level or the rotational speed the generator is working with depends on the wind speed The values for switching from one generator level into the other are set by the manufacturer They can be examined in the control system of the wind energy conver ter and adjusted there As a permanent alternation between the two generator levels due to frequently changing wind speed should be avoided the switching values are taken as standard values a real switching over takes place only after not just the value itself but also a preset tolerance zone has been exceeded Unlike other components the mechanical stress of the generator remains low During in spections of this component particular attention should be drawn to the bearings and their lubrication If the maintenances were carried out correctly a proper functioning of the be aring over the entire life time of the wind energy converter can be expected The maintenance effort is limited to a regular lubrication of the bearing regarding the intervals please consider the maintenance manual that can be done via grease nipples in the easiest cases Double fed asynchronous generators Double fed asynchronous generators are able to modify the rotational speed during opera tion within a certain tolerance zone Thus performance fluctuations can be compensated and structure loads can be reduced Double fed asynchronous generat
55. embly or that has to be removed Is the personal safety system inside the tower operating during the disassembly too Dangerous aspects The aspect that can be hardly judged during the assembly work is the weather The best conditions calm 20 C and a cloudy sky occur quite seldom on wind turbine sites Wind speeds and wind directions forecasted for the day of disassembly are influenced by local daily curves thunderstorms rain fronts geographical peculiarities of the region and va rious other things A particularly critical point during the disassembly has arrived when the rotor has to be loosened and put down The long blades cannot always be kept safely by the ground team In case the rotor or single blades start to swing back and forth due to the wind a collision with the nacelle the tower or the crane jib might occur easily The crew is very much in danger while preparing to put the blades down at the transport devices An horizontally swinging rotor with a dead weight of 30 tons cannot be stopped by a human being With older wind energy converters the manufacturer information on weights and centres of gravity edited in the documentation are not in accordance with reality The crane ope rator supported by the assembly team should slowly grope his way towards the real va lues with every component to be carried by the crane The measured weights and the de termined working steps have to be documented for the later installation
56. engineering control engi neering corrosion protection and building technology A detected fault may have the usual causes for instance assembly or operating faults but can also arise from design shortcomings In this case the owner of the wind farm will be enabled through the exper tise to require a permanent solution of the problems from the manufacturer or other speci alized companies In addition expertises throw light upon the quality of the wind energy farm an aspect which is primarily interesting for insurance agencies But also manufac turers attach increasing importance to expertises They regard expertises not only as an annoying element causing work but rather as a source from which many information is given about the product manufactured by them What can not be achieved by an expertise An expertise can never determine all faults The expert can only identify obvious errors a complete detection of all faults would require the entire disassembly of the WEC Ho wever that goes beyond the economic acceptable limit The same applies to some other inspections for instance X ray of all welding seams In some place an insight can be given of otherwise invisible parts for instance by remo ving the shaft casing or other covered components Nevertheless there will be always areas that can not be inspected without comprehensive work or expensive technical equipment Furthermore in some cases pollutions may obstruct the vi
57. epts are distinguished 1 single blade adjustment 2 uniform adjustment of all three rotor blades The single blade adjustment allows an independent adjustment of each individual blade For the second concept the blades are adjusted together by the same angle each With the single blade adjustment blades can be operated as redundant brake system see chapter Rotor brake The second concept requires a sufficiently dimensioned mechani cal rotor brake Rotorblades The rotorblades of a wind energy converter are the most significant components in terms of the energy transformation of wind energy into mechanical rotation energy Naturally this component has a considerable influence on the mechanical behaviour and the life ex pectancy of the entire wind energy converter Therefore nature and structural condition of the rotorblades will considerable influence the yield and thus the economic success of your wind energy project Function The rotor blades cover two tasks 1 They transform wind energy into mechanical rotation energy 2 They are designed as aerodynamic brake Its specific structure and function depends on the control and regulation principle of the wind energy converter Material Rotorblades are made of GFP Glass Fibre reinforced Plastics GFP or Carbon Fibre reinforced Plastics CFP The shaft between blade tip and rotorblade which can be found in stalled turbines is mostly made of CFK for blades with blade t
58. essesesseenes 21 Evaluation of dismantled ccccscsseseesescsesesescsssescsessscscsescscscscssscscscssssscasecssscssesscseecacesenscesesenases 21 The Set Up Of A WIN energy sssini itai apia anaiai iaeaea a 25 Control and operation of wind energy 25 Pitch controlled wind energy converters with variable rotation speed 27 ROLONDIAGGS ae eee ee 28 ROOM alee ea 31 Pitch and ActiveStall SySteMS c ccccccssesesesssescsesesssesessscscscscscscscscscscscscssscecesesscscssssscssasesesasacececssasenenasas 32 bearing re 33 PROLOMDGANING oss Av sees 33 TMM OLON SNM A R 35 ASH 36 Reichs utes as 38 Generator 40 42 Main frame Yaw system Yaw bearing Yaw dive ONG 2 ses 46 Cooling SYSTOM ede 47 48 48 BOMINGS dads els e dA naw ies 50 Rubber Dealings 53 SGNS
59. ete tower is that they generally cannot be used again see chap ter Disassembly of wind energy converters Lattice and conical steel towers can be di sassembled into segments and re installed on the new site Conical steel tower Depending on its length and diameter the conical steel tower is divided into two or more segments that are screwed via a flange connection Another flange connection attaches the tower to the foundation and the nacelle to the tower Platforms which are needed for the assembly of the flange connections are assembled between the segments Later they serve as the prescribed rest places for the mechanics The climb through hatches in the platforms are covered by lids The hatch lids have to be closed after every passing as falling items and or tools during maintenance work at the wind energy converter are stopped by the next platform below A ladder is assembled at the tower wall for climbings into the nacelle It is equipped with an additional safety rope or runner system for personal safety The control cabinet at the tower bottom contains the operation unit of the wind energy converter The current and control cables run along the tower wall up to the control cabi net inside the nacelle Before reaching the nacelle they form a long hanging loop This loop provides the clearance for several possible turns of the nacelle around the tower axis and into one direction twisting This twisting is monitored by a
60. extended by the following inspections Random sampling of tightening torques of screw joints at the major components bla de blade bearing hub shaft gear generator main frame azimuth system tower foundation Measuring the continuity of the lightning protection and the ground electrode EXPERTISES Status oriented survey It is common knowledge that insurers have a vital interest in contracting wind energy converters with a low damage potential After the bitter years at the beginning of this century the emergency brake was pulled and a surveillance systems was included in the insurance contracts that is aimed at an early damage detection The reason If a component failure can be detected at an early stage immediately introdu ced repair measures can considerably limit the extent of the failure including time amp fi nancial expenses In the ideal case the teams fulfil their tasks in just one day if it is a warm long summer day with low wind speeds and well negotiated crane fares In contrast to that a sudden breakdown at high wind speeds in autumn may take weeks to eliminate the failure and can cause high expenses including the loss of earnings due to the stand still The recurring inspections are regularly arranged the time intervals are graded according to the performance Wind energy converters less than 300 kW every 4 years Wind energy converters with 300 kW up to less than 1500 kW every 2 years Wind energ
61. f the bolting This tightening factor is lower with yield stress controlled or rota tion angle controlled tightening than with torque controlled tightening Some of the boltings are exposed to very strong dynamic stress Because of the vibrating operating force bolts of purely elastically preloaded boltings can get loose gradually Thus the thightening torques of torque controlled preloaded bolts that use up to 90 of their elastic limit for pick up have to be inspected regularly about the detailed mainte nance intervals please consult the maintenance and service manual of the WEC With elastic limit preloaded bolts preload up to the overelastic range the preload force can not be increased further as this only results in a further plastic deformation of the materi al Which pick up procedure shall be used During the assembly of the wind energy converter attention should be paid to which tigh tening procedure was recommended by the manufacturer for every single bolting In case single or all bolts of one connection have to be exchanged the strength class of the bolts has to be considered in addition Yieldstrength controlled preloaded bolts must not be used again for a re installation of the wind energy converter all bolts have to be replaced by new ones here With torque controlled preloaded boltings at least the highly dynamically stressed force transmitting bolts have to be exchanged due to material fatigue Important fo
62. f the pinion consists of harder material And a component with a much smaller number of teeth is overrun more often during the toothing procedure and thus experiences larger stress In case there is a main wind direction at the new installation site of the wind energy converter it should be examined whether the yaw bearing could be installed turned for 90 around the axis of revolution In this case the other areas of the bearing runways will be stressed more In most cases this should be possible because of the rotation symmetry Take care that the possible assembly or disassembly boreholes remain accessible Because of the very large reduction ratio between pinion and yaw bearing the yaw speed is extremely low THE INDIVIDUAL COMPONENTS OF THE WEC The contact pattern of the toothing The contact pattern provides information how the teeth engage with each other It can be found in those area of the tooth flank where the tooth flank contact and the transmission of forces take place Its structure tells a lot about the quality of the toothing Too large de viations from the ideal contact pattern cause an uneven transmission behaviour that redu ces the lifetime of the toothing and increases the noise Because of this the contact pat tern of the toothing should be examined over the entire periphery of the yaw bearing Yaw drive Azimuth drive In most cases two or more drives are used for the yaw system The drives consist of a hy
63. flow pas sing the rotordiameter is considered here V ee From this formula it can be seen that the wind speed has the largest influence on the po wer of the wind energy converter Thus the site become the most relevant factor Material fatigue Material fatigue describes the maturing process of a material caused by environmental in fluences such as mechanical load temperature or a corrosive medium see chapter Cor rosion During the lifetime of the relevant component fatigue might cause a failure in serviceability or even a total failure Because of this the life time of critical components is evaluated calculated and even tested in advance to estimate its durability Pitch In this context the word pitch refers to a changeability of the rotor blade stall Due to this the airflow effects on the blade profile even at higher wind speeds Pitting Pitting is a very common form of tooth flank fatigue a material fatigue caused by perma nent loading and unloading of the tooth flanks If the bearable compression of the enga ging teeth is exceeded particles will be released from the tooth flanks After a correspon dingly high number of overruns pitting like cavities occur Relative motions Examining two bodies that move with different speed these bodies have speed towards each other that results from the difference of their absolute speeds as they are to be exa mined from the outside Stall Blade stall occur
64. force can be applied to the bolts with various pick up procedures see guide line VDI 2230 1 with a torque wrench torque controlled tightening 2 rotation angle controlled pick up procedure 3 yieldstress controlled pick up procedure Torque controlled tightening This procedure is the most frequently used The bolts are brought to the prescribed pick up with a certain preload force both data can be found in the maintenance and service manual of the WEC When turning the bolt friction forces occur at the thread and below the bolt head They have to be taken into consideration when adjusting the required pick up torque otherwi se the connection might not get preloaded sufficiently or the bolt might get overstretched In every case the transmission of forces and torques would get obstructed and the durabi lity of the bolting would decrease In addition the bolt is twisted a lot if too high friction occurs during the torque controlled procedure This additional stress has to be absorbed by the material of the bolt For this reason the threads and bearing surfaces of the bolt head and bolt nut have to be lubricated with an appropriate lubricant Lubricants based on molybdenum disulfide MoS2 plum bago and Teflon PTFE reach extraordinary low friction coefficients During torque con trolled tightening the bolt is usually tightened up to 90 of its yield strength i e the ma terial does still remain within the elastic range
65. g constructions where mounting facilities holders and steps can be assembled with comparatively low effort The disadvantage is that they cannot be manufactured in every desired form THE INDIVIDUAL COMPONENTS OF THE WEC Maintenance Main frames are not exposed to further wear then those resulting from material fatigue as long as there is an appropriate corrosion protection Nevertheless the critical spots should be examined for cracks and damages corrosion within the regular maintenance intervals detailed information on that you find in the maintenance manual Corrosion protection The corrosion protection can be carried out differently depending on the original material and the size of the main frame Welding constructions up to certain size can be galvani zed which is a very good and lasting corrosion protection For possible later welds the corrosion protection has to be removed The machined spots have to be protected against corrosion again afterwards If zinc spray is used it should be additionally varnished If the melded main frame is too large for a galvanizing zinc coating bath a multi layer colour system can be put on as corrosion protection If damages from assembly work or something similar have to be repaired the relevant colour specification has to be consi dered Surfaces where the power transmitting component rotor bearing gearbox is fixed with bolt connections have to be metallically bare before the assemb
66. hat means if no hydraulic pressure is availa ble at the start of the WEC or the hydraulic pressure declines during operation the aero dynamic brake rotorblade brake remains activated by the spring and the centrifugal for ce That provides a fail safe operation and prevents damage from the WEC Important issues to be taken into consideration for a used WEC the surface condition of the rotorblades A damaged rotorblade surface reduces not only the energy yield it may also lead to an additional material damage weakening the whole structure For instance the fibre plastic composite under the gelcoat layer may be impaired by UV radiation or intruding water Deeper damages can occur due to the notch effect of locally increased tensions which may lead to a premature fatigue Unfortunately these damages are relatively hard to iden tify in case of doubt always call in a surveyor Special attention should be taken to the following damages pores holes cracks on bonding surfaces dissoluting Vortex generators loose lightning protection Pores and holes up to a certain size can be relatively simple filled with suitable surfacer Cracks on bonding surfaces should be eliminated with the kind of resin epoxy or polye ster the rotorblades are made of If the dissoluting Vortex generators are undamaged the may be re affixed to the rotor blade Otherwise they must be replaced by new generators in order to achieve optimal flow condi
67. he hub The aerodynamic profile of the blades is designed in a way that the performance is limited by blade stall A performance optimisation can only be achieved to a certain ex tent via long holes in the blade flanges of the hub the angle of incidence can be re adju sted In order to achieve a performance optimisation the rotor blade can be equipped with stall strips or Vortex generators see glossary To avoid damaging of the Vortex generators the disassembly transport and installation of the rotor or blades must be performed with reasonable care Even light damages can im pair its positive effect See also explanations in the glossary Damaged Vortex generators can be easily removed as they were subsequently affixed to the rotor blade If you require new Vortex generators make sure to inquire the former operator of the blade manufactu rer for the respective supplier For turbines of this type the performance of the WEC is limited if the wind speeds at the turbine reach 13 to 15 m s If the 10 minute average value ranges around or beyond 25 m s the wind energy converter is switched off via the blade tip breaks to avoid overload The rotation speed of stall controlled turbines is equal and is specified by the mains fre quency the pole pair number of the generator see also chapter Generator and the rotor blades The gear transmission is adjusted on the basis of this specification All in all most of the stall controlle
68. he cables form a loop that provides clearance for several turns of the nacelle in the same direction The ladder is equipped with an additional safety rope Concrete tower As concrete towers have to be built newly on every new wind turbine site no former de tails about their consistency functionality and maintenance are given here Where appro priate concrete towers could be replaced by conical steel towers in case conical steel to wers are available for the same WEC type Boltings Numerous boltings of different sizes are used at wind energy converters they connect and fix the single components Boltings allow a relatively simple assembly and disassem bly of the components that consist of different materials very often At flange connections between the force transmitting components comparatively many bolts can be used even for one single connection Some of the bolting of wind energy converters have to transmit very high forces and tor ques Because of this exclusively high strength bolts are used The most usual strength class is 10 9 sometimes strength class 8 8 is used for smaller boltings Bolts with strength class 12 9 are used in exceptional cases only To enable them to transmit forces and torques the bolts have to be tightened up to a cer tain preload force This preload force will already be taken into consideration when the boltings are designed i e during the planning and development period The preload
69. ing the WEC Operation manual of the WEC and the control system Service and maintenance manual Assembly instruction for hall assembly and installation with the corresponding re cords Commissioning instruction with commissioning records Circuit diagrams Type test Technical drawings Operation manual of the WEC and control system Here the operation of the wind energy converter is explained in detail Absolutely essen tial are information about the turbine safety the operation of the plan in general and in certain emergency situations and a detailed description of the control software Nowa days many plants can be monitored from the distance Take care that you get not only the necessary technical requirements for such a remote control software where appropriate with special devices but also the corresponding operation manuals Service and maintenance manual The maintenance manual should describe in detail which maintenances have to be carried out at what time and which working steps have to be executed at every single maintenan ce after all the assigned mechanics have to execute the service and maintenance work based on this documents In most cases a record pattern or check list belongs to this ma nual it lists all necessary working steps and has to be ticked off by the responsible me chanic After filling it in he files this records in the WEC file which enables to recall without problems when which work
70. interrupted power supply hydraulic accumulator The uninterrupted power supply and the hydraulic accumulator are designed to provide a so called emergency operation in case of grid failure or errors of the turbine During emergency operation the rotorblades can be turned to the flag position even without grid supply and the rotor is decelerated In doing so a safe operation mode is provided For this reason the UPS and or hydraulic accumulator are of great significance for the wind energy converter Their breakdown can lead to overspeed and in worst case scena rios to the destruction of the WEC Therefore both components must be regularly main tained and checked for their functioning If batteries are used for the stand by power sup ply they should be replaced after one year Before the wind energy converter is dismantled the entire pitch system should be chek ked for its proper functioning Possible non conformities should be eliminated without delay or at least documented in detail At least during maintenance the non conformities of the wind energy converter should be eliminated in order not to delay the commissio ning The set blade pitch adjusted by the pitch control is measured via a sensor Before com missioning the blade pitch must be adjusted in compliance with the manufacturer s speci fication in order to ensure an optimal operation of the wind energy converter THE INDIVIDUAL COMPONENTS OF THE WEC Blade bearing S
71. ip brake because this material is best suitable to stand high loads Plastic composite is hygroscopic i e it is able to absorb moisture from the environment and is sensitive to ultraviolet radiation Therefore the outer surface of the rotorblades is applied with a UV protection layer so called gelcoat Pitch and stall turbines Depending on the measurement and control principle provided on your WEC two cate gories of wind energy converters can be distinguished 1 turbines with blade adjustment pitch active stall 2 turbines without blade adjustment stall The blade adjustment of pitch and active stall turbines used both for the energy produc tion and the brake system The brake effect derives from the rotor blade rotation by 90 Differences between pitch and active stall blades are mainly referring to the aerodynamic profile Brake procedures by tip mechanism Rotor blades for stall turbines are provided with a tip mechanism which must be activa ted to introduce the brake procedure In general this mechanism consists of a spring a tu be with a nut drilled by 90 a sleigh gliding inside it and a hydraulic cylinder The tip head is disengaged by the spring while turning the tip head by 90 The hydraulic cylin der located in the blade root and connected by a steel rope with the tip head is designed to recover the tip head THE INDIVIDUAL COMPONENTS OF THE WEC The tip mechanism is designed fail safe T
72. is hollow that allows to lead the piping hydraulics and electric ca bles from the gearing to the hub The dismantling of a rotor bearing in the course of a service call or re installation should include the inspection of the bearing seats If the wind energy converter operated appro priately no wear or tear can be expected at the bearing seats The gearbox The gearbox of the wind energy converters is one of the most important components of the WEC and requires special care Usually the operating time of Second hand WECs is elapsed to at least 50 so that the risk of a gear damage or failure increases continuously Due to the fact that such a failure or even the repair may cause considerable costs the profitability of the wind energy project can be significantly impaired Therefore even in the event of smaller failures considerations should be made whether a replacement of the gear would be sensible in the course of the re installation Combined planetary and spur gear units are used in most of the wind energy converters Here the planetary level is located at the gear entrance whereas the outlet is provided with two spur levels The advantage of the planetary level is that a very high transmission is achieved with only one level Depending on the year of manufacturing of the gearbox the toothed wheels gear straight ly or helically towards each other Modern wheels with helical toothing enable a smoother operation as the gearing an
73. ith ropes The blade bolts are threaded into the boreholes of the blade bearing the nuts are tightened temporarily with a torque that remains below the final value The loops edge protection and guide ropes have to be retrieved using a man basket Afterwards the rotor can be turned further until the next blade flange has reached the re quired position Then the blades are preassembled to the hub as described above The boltings of the blade pins with the blade bearings are only brought to the final torque when the wind energy converter can be operated via the control system GLOSSARY Glossary ActiveStall With ActiveStall plants the blade stall can be controlled actively For this the rotor bla des is assembled mobile to the rotorhub The angle of incidence is adjusted via a pitch mechanism according to the wind speed Meanwhile the front edge of the rotorblade is turned out of the wind so that the angle of incidence increases Wind power The power of the wind derives from the kinetic energy of the moved air masses The cine tic energy is proporational towards the air mass that flows along the rotor s area of circle and proportional towards the square of the wind speed 1 m v The airmass is determined by the volume and the density of the air p V The volume is determined by the rotor s area of circle and the way covered by the air mass As the power is considered as energy or work per time unit the volume
74. ject it can be dif ficult to get all required information and tools for various reasons Some of the older plant types face the problem that the manufacturer disappeared from the market due to insolvency or sale In case of insolvency documents as manuals in structions and devices might get lost within the liquidation turmoil If you are lucky the essential documents could be found via the insolvency administrator responsible for the sale of the assets and for archiving documents If the manufacturer was integrated into another company it depends mainly on the new owner how he deals with the needs and requests of former customers As the service for small turbines is not very profitable this field is often neglected the devices are rotten the documents cannot be found If the manufacturer is not assigned with the disassembly and assembly it is absolutely possible that he refuses any co operation For several plants installed in the 1990s only carelessly kept documentation exists The assemblies were managed by team members who s expert knowledge had never been re corded In such a case it is essential to hire experienced persons that were involved into the installations DISASSEMBLY AND TRANSPORT OF USED WIND ENERGY CONVERTERS If the required information can be obtained it should be checked for safety reasons whe ther they fit with the purchased wind energy converter Is the information valid for this version in general or does this
75. ject to the load caused by the rotor so that apart from normal material fatigue no wear and tear should occur A possibly problematic case Under certain conditions it may occur that the rotor shaft may distort towards the gear entrance shaft Such a distortion may either lead to a seizing of the joint or result in a large i e too large clearance If such a condition has occurred for the relevant WEC it should have been documented by the maintenance personnel or must be documented in the course of an expertise Always make sure that while mounting the rotor shaft to the gear the contact surfaces between rotor shaft and entrance hub of the gear are grease and oil free Only then the transmission of the drive torque is ensured In addition it reduces the risk of distortion see previous passage It must be ensured that the shrink disc can be tightened smooth ly The thread and the head bearing area of the rotor shaft must be sufficiently lubricated see chapter Screw connections in order to ensure that the shrink disc can safely transmit the drive torque If the friction below the head surface areas and the thread is too high the clamping torque of the screws will be achieved but the shrink disc is not sufficiently tightened The transmitted torque of the shrink disc depends on the pre load of the screws and is additionally reduced by the transmission of bending moments 3 point bearing The inner rotor shaft
76. lar intensity of vibrations from a bearing or an equal gearing is also known than even a statement can be made whether the compo nent shows a an appearing damage The measurements are carried out during the opera tion of the turbine the wind speed should be sufficient to achieve the fractional load ran ge For the vibration diagnosis the complete cinematic data from the main bearing the gear and the generator are required Gear drawing Number of teeth of the toothing Data of all bearings Speed range of the wind energy converter Interference frequencies of all secondary installations e g azimuth drives hydraulic units etc The interference frequencies are required to evaluate individual unexpected signals and frequencies An azimuth drive which suddenly starts operating during the measurements sends an initial strong impulse when the engine brake has been opened In addition the whole frequency range consisting of drive engine and gear levels must be taken into con sideration Afterwards the yaw drive again generating a strong impulse puts on abruptly the engine brake located behind the drive engine These effects must be known to provide a correct evaluation of results as they are reflected in the measurement Some manufacturers still claim that the number of teeth of the equal gearing and the type denominations of the bearings are confidential insider knowledge However these com ponents are only purchased
77. ll as the spring stiffness and spring characteristic If these information cannot be taken clearly from the delivered documentation only the manufacturer is able to provide the required spare part Sensor system There are several different sensors at the wind energy converter that monitor the opera tion and the environmental conditions The most important ones are Anemometer to measure the wind speed Wind flag to measure the wind direction Sensors to measure the electric capacity the rotational speed the temperature at seve ral different spots the gearbox the generator and the outside temperature Sensor to measure the hydraulic pressure Acceleration absorber to investigate the moves of the nacelle Anemometer and Wind speed measuring device In most cases cup anemometers are used as anemometers in some cases it can be ultraso nic anemometers as well The wind speed measuring device is usually the classical wind flag combined with an ultrasonic anemometer or sometimes an ultrasonic sensor The proper operation of both sensors is regularly tested by the control system as these measuring values are of enormous importance If the wind flag fails the plant cannot re act on changes of the wind direction The yaw system is not activated the blades remain in an angle of incidence and thus unintentionally high loads occur If the anemometer fails overload and worst case destruction of the wind energy conver ter might happen
78. lubrication of the toothing of blade bearings and yaw bearings can if tolerated over a long period lead to so called initial damages A prompt ly operating service of the manufacturer is normally regarded as a guarantor for a WEC with a low damage potential EXPERTISES What are the prerequisites for the expertise of a WEC The turbine must be accessible The access must be neither blocked nor swampy Larger animals on the site in particular bulls must be removed before the expert starts his work Any person who intends to climb a wind energy converter must obtain a complete set of protective equipment Generally it consists of the following parts Harness please note the instruction for fastening the harness Climbing protection normally a guide rail runner or rope runner Safety rope with pipe hook Safety helmet Sturdy footwear Very often the experts dispose of their own equipment in case of doubt inquire the infor mation beforehand Before climbing the WEC notes on safety Emergency switch In compliance with the valid safety regulations every WEC is equipped with one or more emergency switches which are marked with the corresponding symbols They are desi gned to immediately switch off the WEC in emergency cases by interrupting the power supply Please find out where is are the emergency switch es before you climb the turbine Fire protection equipment Depending on the national fire p
79. ly after commissioning or after appr 500 operating hours The earlier point of time has the advantage that major assembly faults can be identified and eliminated by the service team thus avoiding damage to the installation An expertise after some days of operation can also reveal nonconformities of the turbine that arise from the motion of the components galling of cables bearing damages leaka ges in the hydraulic system etc The expertise after commissioning is only designed as visual inspection of the transfor mer station the foundation the safety installations tower nacelle and hub An inspection of the rotorblades from a lift platform is not compulsory the visual inspection of the bla de roots and the evaluation of blade noise during turbine operation are sufficient The ex pert should have the opportunity to receive an acoustic impression of the operating turbi ne inside the nacelle Furthermore the sensor operation must be checked The expertise should contain the denominations manufacturers and serial numbers of the major components read out by the expert at the corresponding parts Expertise prior to expiry of guarantee period In order to ensure the guarantee claims towards the manufacturer the owner of the WEC arranges for an expertise that results in a residual work to be done In some cases it may lead to an extension of the guarantee period for replaced components The extent of inspections is similar to the firs
80. ly is started During transport or maintenance these surfaces should get an easily removable corrosion protec tion as well It is possible that the seatings of the rotor bearing and the gearbox were treated with a zinc silicate layer This layer is supposed to increase the coefficient of friction see chap ter boltings for this too it must not be removed Main frames of cast material are generally protected against corrosion with a colour lay er system Damages of the colour layers can easily be repaired considering the relevant colour specification Larger wind energy converters may have a two piece main frame The generator and pos sible control cabinets inside the nacelle are mostly located on the so called generator fra me which is connected to the main frame via boltings In such cases the main frame and the generator frame may consist of casting or as a welding construction Yaw system The yaw system of the WEC consists of the yaw drives the braking system and the yaw bearing located between tower and nacelle It adjusts the wind energy converter accor ding to the current wind direction Usually the rotor is turned into the wind with high wind speeds above the upper wind speed limit the reverse process will be carried out to reduce the stress that effects on the wind energy converter Yaw bearing Yaw bearings are slowly turning fourpoint large roller bearings with their toothings loca ted at the inside or
81. ly or its position has to be adjusted Thread cones and other auxiliary devices for positioning the nacelle on the tower head flange can be assembled after lifting the nacelle further While lifted by the crane the nacelle is guided by members of the ground team with the help of ropes All bolts should be screwed into the bearing ring when the nacelle is still hanging some millimetres above the tower flange The nacelle should be set down only after All bol tings have to be tightened Assembly work at the rotor Assembling the entire rotor as whole Position the two cranes and the nacelle in its transport devices in a way that all three bla des of the rotor laying on the ground can be easily reached by the cranes from all sides The pitching devices of the blades inside the hub have to be in a position that allows an assembly with the rear blade edges showing sidewards or to the front The blade is hooked to the main crane via the loops hinged around the blade root and hooked to the auxiliary crane at the relevant spot of the blade end edge protection Af ter that it can be lifted After disassembling the transport devices it is moved in horizontal position towards the hub which is attached to the transport device and threaded into the boreholes of the blade bearing Tighten the nuts temporarily with a torque below the final value to be taken from the as sembly or maintenance manual of the WEC After propping the blade tips wi
82. mplete when buying a wind energy converter Type tests The type test expires with the disassembly of the wind energy converter Because of this the extent and type of the new type test has to be agreed with the responsible approving authority at the location prior to every re installation In certain circumstances a simpli fied permission procedure can be used where only the fail safety of the wind energy con verter has to be proven Technical drawings In general no technical drawings of the components are delivered with the wind energy converter But overview drawings of the WEC with a determination of every component should be available in any case DISASSEMBLY AND TRANSPORT OF USED WIND ENERGY CONVERTERS Disassembly and transport of used wind energy converters The influence of the differing designs and versions on transport and as sembly The different design characteristics of the different WEC designs require partly very indi vidual solutions for transport and assembly For many versions corresponding special devices have been developed Transport devices for blades hub nacelle and tower segments Fixing devices for the main frame Crane crossbeams to hinge the fixing devices of the nacelle Fixing devices for every tower segment Devices for an assembly of the tower cables Some wind energy converters need devices for craning the hub or the completely assem bled rotor The assembly of a lattice tower
83. n ones those that were installed most often into account Aiming to help investors and project managers of potential second hand wind farms or turbine sites to plan and to carry out the project the study on hand can be a compendium but cannot claim to be exhaustive as this is nearly impossible Though the longtime branch experience of the authors mentioned before ensures that it is a valuable guide that hopefully will be able to accompany many new used turbine projects on their way to a successful commissioning and operation Rostock August 2005 Dr Kristina Koebe Project manager CONTENT Content FORE WON naira A ee A 4 Abt this Study eink aetna 5 What this Study 5 For whom is the study designed What is xpertiSe csscssssscssssssssssssssscsssssssssssssssessssssessssssoesessessessssessessssessesessssossessessessssesesesssesenes 7 What is eXpert ccccssssscsssssesesssssescsssssesessssesessessesessossesessessesessossesessessesestossesessosaeerssosaescsteseesestoraees 7 Damage evaluations 8 Different occasions different kinds of expertises AN
84. nd energy converter is already dismantled statements on the condition of the tur bine are even more difficult to make than for a defective idling turbine On the other hand components like for instance the blades the tower and the nacelle casing are easy accessible and can be well inspected Even here it is crucial that the switchboards are sto red in a dry location the best would be to heat them via an external power source The drive engine and the bearings of the blades and the nacelle adjustment must be set in mo tion from time to time However this is practically impossible Expert support of a re installation project To give optimal support for the purchase of a used wind energy converter a so called se cond hand WEC the following tasks should be fulfilled Expertise of the installed turbine on the original site basis for the purchase decision Surveillance of the dismantling recording disassembly damages Expertise of dismantled components inspection of spots which are usually not acces sible Surveillance of the installation recording assembly damages Surveillance of the commissioning check of the system settings Status oriented inspection of the re assembled turbine contract basis for insurers The actual extent of the support depends mainly on the experience and competence of the project leader However an expertise before purchasing a turbine can not be replaced by any other in spection After re commi
85. nity for second hand purchasers who can buy the plants to a reasonable price and thanks to the low invest ment costs are able to ensure a profitable further operation on new sites Actually this trend can only be welcomed as it goes along with a certain democratisa tion of the wind market Now even potential WEC operators with less investment capital will be able to realise wind farm projects an opportunity for individual operators and al so for countries where the establishment of wind energy is only slowly developing due to a lack of capital base These facts give reason to expect that the coming years will face a further upward trend on the second hand market for wind energy converters For the project planning of a wind farm or an individual WEC with used wind energy converters it is vital to know the performance and first of all the technical condition of a plant because finally the technical condition is the criterion for the financial success of the project A plant that is permanently generating costs can be hardly profitable There fore it is recommended to verify the technical condition already before the purchase pre ferably before the dismantling on the original site has started All aspects to be taken into consideration are summarized in the chapter Expertises What can this study achieve The present study is designed to serve as guideline for individuals and institutions with the intention to
86. nnections Stall turbines are provided with a direct connection between rotor blades and hub Pitch and ActiveStall turbines are provided with a blade bearing between blade and hub Detailed information can be found in the homonymous chapter In general rotor hubs are made of EN GJS 400 18U LT GGG40 3 cast material This material provides a sufficient strength and disposes of an appropriate tensibility and notch bar impact value Rotor hubs are subject to normal material fatigue although external wear is not recognizable However maintenance work and renewed disassembly and assembly of wind energy con verters can lead to coating damages corrosion protection Such damages can be easily eliminated by renewing the coating In this respect special attention must always be paid to the paint specification of the manufacturer where available Stall turbines Long holes for the pitch control are located in the hub flanges of the stall turbines Its length effects the possible control range Therefore during assembly special care must be taken on the correct position of the blades towards the hub If the position is not confor ming the optimal pitch can not be controlled That may lead to a permanent low output or a frequent shut off of the turbine due to overload at high wind speeds THE INDIVIDUAL COMPONENTS OF THE WEC ActiveStall and pitch turbines The setting range of the pitch for turbines with pitch control amounts to 90 in most ca
87. nto horizontal position directly above the ground The devices at the bottom of the component have to be disassembled while the tower seg ment is still hanging at the main crane When the segment is hanging above the foundation flange either the stay bolts of the foundation have to be threaded into the holes or if a single component moulded into the foundation is used the bolts are plugged from the top through the two flanges The latter should be done preferably at a tower segment hanging directly above the connection The manufacturing tolerances amount to about one millimetre Thus even a slight displace ment of the fully rested segment might cause that a number of bolts cannot be plugged in to the congruently positioned holes After the bolts are tightened temporarily with a power wrench the upper fixation tools can be unscrewed and lowered to the ground with the crane This procedure is repeated with the other tower segments Take care that the ends of the ladder are meeting each other appropriately Assembly of the nacelle The nacelle with the fixing devices is hooked to the crane A long rope is attached to the rear end of the main frame It allows to control rotations of the freely hanging nacelle from the ground The bolts towards the transport device have to be loosened The crane operator pulls the crane hook until the nacelle hangs several millimetres above the ground It has to be checked whether the nacelle hangs horizontal
88. nverter have to be activated by the power authorities Disassembly of wind energy converters Required information for the disassembly Surroundings Before cranes can be transported and installed it has to be ensured that such vehicles can operate on the territory and where the heavy load bearing areas for the cranes are located The gravelled areas were dismantled in some WEC sites and have to be constructed new ly Is the access road for cranes accompanying and transport vehicles that was used during the installation of the wind turbine still accessible New routings new buildings water courses electrical transmission lines and other things might have occurred that might re strict the access The dimensions weights and balance of all items that have to be carried by the crane and a low loading truck are relevant for many aspects of the disassembly Selection of the roads and bridges that have to be cruised Load bearing capacity and arrangement of the cranes Selection of the fixing devices Load bearing capacity of the transport vehicles Organisation of the loading with the interim storage etc Rotor Is the rotor disassembled as a star i e all three blades still connected to the hub or is each blade disassembled separately at hub height In general the disassembly of the rotor should be agreed with the manufacturer of the wind turbine or the rotor blades under any circumstances this will ensure that no
89. o called slowly turning large roller bearings are designed as blade bearings For electric pitch drives the pinion of the drive bites into the inner toothing of the bearing ring The outer bearing ring is connected with the hub via a screw joint The same applies to the connection of inner bearing ring and blade During assembly special attention must be taken to the correct tightening torque and tigh tening methods to be applied For this purpose each individual case must be referenced in the assembly and maintenance manuals The blade bearings are sealed with grease to reduce the friction and provide a sealing and prevent corrosion The grease coating must be replaced regularly Make sure that during re lubricating a so called grease collar of new grease establishes alongside the entire bearing gap and or alongside of all seal rings The lubrication intervals can be referenced in the maintenance manuals of the wind energy converter Rotor bearing For rotor bearings different concepts exist 1 the 3 point bearing 2 the rotor bearing on two main bearings 3 the integration of the bearing into the gear The 3 point bearing In the so called 3 point bearing the rotor shaft rests on a rotor bearing and the torque re action bar of the gear In this case the rotor bearing is a so called self aligning roller bea ring which is located relatively close to the shaft flange The rotor bearing is placed in a casing that is supported on
90. ommissioned Evaluation of assembled non operative WECs The previous specifications of the individual characteristics of an expert have shown that many evaluations can only be made while the wind energy converter is in operation If the WEC is non operative the most important information of all will be to find out the reason for the standstill Is the information about the standstill plausible What are the explana tions and proof given for the condition In case of doubt a competent person should make a survey report at that point Further crucial items How long did the turbine stand still Why was the damage not eliminated by the seller himself Can the rotor move freely or is it locked The locking of the rotor over a longer peri od can quickly lead to bearing damages as the rolling bodies constantly remain in the same position displace the lubricating film and thus causing corrosion at the run way The same applies to blade bearings and the azimuth bearing that need to be set in motion from time to time Many turbines must only be locked up to specified wind speeds higher wind speeds may cause damages to this component Is the turbine still connected to the grid If confirmed error and temperature indexes of the control may be inspected If not confirmed switchboards can become damp or even start to molder in adverse weather conditions Switchboards must be always kept dry Evaluation of dismantled WECs If the wi
91. oper operation of the safety devices for personal safety has to be ensured at any ti me during the installation of the tower General course of the assembly Preparation of the wind turbine The following preparatory work have to be carried out prior to the assembly Place the stay bolts with a template if this type of connection to the foundation is in tended Provide and assemble the required fixing devices of the nacelle the tower segments and the blades Place the bolts where they will be needed later The tower bolts for example could be packed into bags and fixed on stable spots with tightening straps and thus be availa ble on every single platform This will save several crane procedures later Protect the control cabinet on board crane loose items tightening straps etc Prepare the temporary power supply for the control and the drive engines of the wind energy converter Installation of the foundation The foundation has to be installed at an early stage Concrete needs time to mature until its final stability A period of several weeks has to be planned for this which depends on the temperatures during the maturing period and partly on the additions to the concrete If stay bolts shall be moulded into the foundation for the connection between the founda tion and the first tower segment an extra day should be planned to level the thread bars exceeding form the foundation using templates and to clean the flange The
92. or re installation Boltings Inform yourself in advance about the pick ups of all relevant boltings to ensure that the appropriate tools are available when loosening the boltings DISASSEMBLY AND TRANSPORT OF USED WIND ENERGY CONVERTERS Corrosion Rotten boltings are one major problem during the assembly of older plants If for exam ple the hub and the centering ring of the shaft flange are connected with each other by corrosion it can be a very time consuming procedure and cause high crane and personal costs to pull the hub away from the spigot It may take hours or even days to get additio nal tools or to develop alternative solutions The assembly team the transport vehicles and the cranes remain available but have to wait inactively until the work can be conti nued Required auxiliaries for the disassembly The following auxiliary devices are particularly required for the disassembly of the WEC Tools especially electrical or hydraulic power wrenches and hammers to loosening the boltings Current supply via the grid or an emergency power supply Walkietalkies with spare accumulators for construction site manager the crane opera tor the working teams 3 ground teams and one team at the hub to release the rotor maximum Long ropes that can be grasped very well to move the crane cargo Main crane and auxiliary crane Lorries Transport devices for tower segments nacelle hub and blades Covers for tower segments nacelle
93. ors can be easily connected to the grid Compared to simple asynchronous generators they are quite ex pensive and have a low coefficient of efficiency Main frame The main frame is the basic frame of the wind energy converter All other components are installed on it or attached to it All forces and torques created at the rotor are transmitted via the rotor bearing gearbox bearing and generator bearing over the main frame into the tower As the main component of the nacelle the main frame is of essential importance If it fails at a critical spot this can cause the destruction of the entire wind energy converter during further operation In general two materials are used for main frame manufacturing 1 a properly weldable structural steel for instance 5235 2 the cast material EN GJS 400 18U LT as it is also used for rotor hubs Both materials can be processed fairly good Main frame made of cast material The advantage of the cast material is that it can be transformed into various forms This allows softer connections between different thickness and an adaption of the main frame to any stress level In addition the material has good damping characteristics It is one disadvantage that holders steps and other mounting facilities have to be screwed in But as this was already done during the first assembly of the plant it should be not re levant here Main frame made of structural steel Main frames made of steel are weldin
94. ostly connected with filling up the empty pit dismantling the construc tion road and the crane site both able to carry heavy loads as well as re naturing the con struction site Foundations of wind energy converters of the power class around 500 kW have got an ed ge length of more than 10 metres thicknesses around 2 metres and a weight of more than 500 tons this mass has to be crushed and transported away for the required removal Recovery of earth cables Depending on the contract situation the earth cables up to the next junction have to be re covered out of the ground as well Recycling of components that are not used for the re installation disposal Some projects are not suitable for a recycling of all transportable components Therefore it should be considered for instance whether a new construction of the tower is even cheaper In case the used wind energy converter shall be installed some thousand kilome tres away it can indeed make sense to bring only the technologically high grades compo nents there The non used residuals of a wind energy converter that has been disassembled for recon struction have to be disposed of and incur costs Alternatively they can be sold as used components to a dealer or to another operator or sold as scrap to a scrap dealer For wind turbines that experienced an average before it is possible that a repair of the components is not worth it here items have to be disposed of as well The remov
95. own the blade by means of a basket hanging from a crane rope the so called basket is relatively inexpensive for smaller turbines However the disadvantage is the wind vulnerability of the basket and the permanent risk of colliding with the blade Contact with the crane operator is kept via walkie talkie Working platforms Self climbing working platforms are fastened with steel ropes upward in the nacelle and are often supporting at the tower Assemble and disassemble of the equipment requires slightly more time than other methods The operating panel is situated directly at the wor king platform Use of lift platforms The best way to carry out on site inspections are lift platforms The operating panel is also part of the working platform which can be independently moved to all interesting spots The hourly rates are slightly higher than for other methods Further expert work an overview Work with crane and lift platform All activities performed with a crane or lift platform require sufficiently solid ground around the wind energy converter Measurement of grounding resistance and coating thickness The grounding resistance and the coating thickness of the coatings are measured with special equipment Vibration measurements of the drive train Measurements for a vibration diagnosis of the drive train are carried out with acoustic sensors which are connected to a data logger The applied sensors are fastened by means
96. ratures the oil becomes cool and thickens Such an oil cannot reach the most important lubrication spots of the bearings which might cause bearing damages For these conditions the gearbox oil of such cold climate versions is preheated In this re spect it is important to ensure a good circulation at the heating as otherwise parts of the oil might be heated too much and burn The inspection of the gearbox of used plants An inspection of the gearbox should be carried out prior to the disassembly or during a maintenance if possible Special attendance should be given to a detailed documentation here as this is helpful for further maintenances and possible later repairs For a gearbox inspection oil samples will be taken and analysed If the toothings are accessible via the housing cover its status should be inspected and do cumented with photographs Possible damages are Tooth fracture as a results of bending strain at the tooth bottom Tooth flank fatigue pitting as a result of material fatigue Seizure due to combined occurrence of compression and sliding speed Tooth fracture Tooth fracture require that the gearbox be disassembled and repaired Such a problem is caused by exceeding the highest tolerable strain the tooth breaks at the bottom The appe arance of this tooth breaking provides information about possible reasons of the damage violence or fatigue fracture Tooth flank fatigue Material fatigue o
97. rce transmitting boltings are Blade hub connections the connections blade pitch bearing and pitch bearing hub included Hub shaft connection Shrinkable disc connection shaft gearbox Boltings of the gearbox with the main frame Both boltings of the yaw bearing The flange bolting inside the tower Boltings of the brake calliper Bolting of the generator coupling All surfaces of the connected components have to be metallically bare clean and free of grease before the assembly can be started to enable the required coefficient of friction The corrosion protection put on for transport and storage has to be removed before con necting them In some cases a zinc silicate layer can be put on the surfaces that serves an increase of the friction coefficient This layer must not be removed as otherwise relati ve motions of the connected components might occur Bolts have to be protected against corrosion too Because of this HV bolts are zinc gal vanized or hot dip galvanized Hot dip galvanization provides better corrosion protection than galvanizing with zinc but can be used up to a certain strength of material M30 and certain strength class 10 9 only With larger diameters and strength classes the pheno menon of so called hydrogen embrittlement occurs a certain period of time after tigh tening the bolts the bolt heads are torn down This might happen very suddenly and even endanger persons as the bolt head is shot
98. requires totally different assembly procedures and periods than the installation of a conical steel tower Possible tower versions are Anchored steel mast Anchored lattice mast Lattice tower Conical steel tower Concrete tower consisting of segments Concrete tower cast at the construction site site concrete Mixing variants of concrete and steel tube Conical steel towers on three legs There are among others the following options for a rotor assembly Assembly as star all three blades are assembled to the hub already on the ground The rotor as a whole unit is lifted by the crane and assembled to the already set nacelle the easiest option for two blade rotors Single blade assembly at hub height all three blades are lifted separately by the crane and assembled to the already assembled hub Two blades are pre assembled on the ground in V position the third blade is lifted with the crane separately afterwards and assembled to the already assembled hub The following chapters describe some typical variants and conditions of the disassembly transport and assembly of wind energy converters with three blade rotors Availability of information and devices Not only many different special devices but also special knowledge about the course of work will be needed for the disassembly transport and assembly of a wind energy con verter If you do not plan to assign the manufacturer to carry out this pro
99. rotection regulations the WEC is equipped with fire di stinguishers In most cases in the tower foundation as well as inside and below the nacel le The escape routes inside the WEC must not be obstructed Please find out where the fire distinguishers are located and how to handle them before you climb the WEC Please note The protection of persons is the highest priority If there may be the danger that the fire cannot be extinguished with the existing equipment fire distinguisher the following ru les of conduct will apply Leave the turbine as soon as possible Call the fire department Help injured or needy persons Do not stay under the WEC Leave opposite to the wind direction In case of burning cables Do not inhale the smoke contains hydroclorid acid Weather conditions Climbing the WEC should only be considered at good weather conditions Never climb a turbine if a thunderstorm is approaching Always leave the turbine immediately if a thunderstorm is approaching there is particular danger to life when you stay in the nacel le The same applies to storm high wind speeds and other adverse weather conditions Un der all these conditions do not climb the WEC or leave the turbine without delay Do not stay under the WEC at high wind speeds Before climbing the WEC always find out the position and handling of emergency swit ches and fire distinguishers Only climb the WEC at good weather conditions
100. s are familiar with all current general conditions and regulations and thus should be integrated into the scheduling in an early stage Component transport All larger components of the wind energy converter are stored on special devices connec ted to the loading space of the lorry with straps or boltings during the transport Blades The blades of smaller wind energy converters with a blade root diameter less than about one metre can be stored in a threesome on one lorry in most cases With larger rotorblades it has to be estimated whether the dimensions in loaded condition allow a storage of two blades on the same loading space or a separate transport vehicle is needed for every single blade due to a necessary tilting of the blade If the blades are protected with cargo straps attached to the loading area the loaded rear edges have essentially to be equipped with edge protection against breaking With wind turbines that have blade tip brakes the periscope segments have to be transported separa tely or have to be protected against unintended moves The openings at the blade root should be protected with tarpaulins against water or dirt Nacelle The nacelle is fixed to a supporting frame with some bolts The total height of the trans port should not exceed the normal headroom For some plant types the height can be re duced by removing the nacelle cover In this case admittedly the cover needs to be trans ported separately Protect
101. s if the angle of incidence of the airflow at the rotorblade becomes too large The airflow does not run along the blade profile but parts from it Thus air vortexes occur and the uplift disappears Elastic limit The elastic limit of a material is the stress force per area a material can bear without any plastic lasting irreversible distortion If the stress remains below the elastic limit only elastic reversible distortions occur The material returns to its original form after the stress has been released If the elastic limit is exceeded plastic distortion occurs that re main there even after the stress release GLOSSARY Vortex Generator Vortex generators are small panes often only about 0 01 m that are attached to the blade surface These panes are alternating inclined towards left and right and create a small tur bulent airflow on the blade surface The distances between the panes have to be kept very carefully to ensure that the turbulent layer suspends precisely at the rear blade edge It is peculiar that these tiny turbulences prevent a blade stall at lower speeds The rotorblades of wind energy converters tend to a blade stall near the blade root at lo wer wind speeds where the profiles are very thick Because of this some newer rotorbla des have a stripe about 1 metre long and with vortex generators on it at the blade inlet 51 de near the blade root Hydrogen embrittlement Hydrogen embrittlement is caused by the
102. sensor After the ma ximum cable twist has been reached the WEC control system triggers a de twisting pro cess Because of the very high reduction ratio this process will take some time The conical steel tower can be entered via a lockable door Lattice tower Unlike conical steel towers the lattice tower does not provide any protection against en vironmental influences The same applies to tower ascents and descents towards and from THE INDIVIDUAL COMPONENTS OF THE WEC the nacelle of the wind energy converter Due to this open construction all components inside the tower have to be protected against environmental influences separately The single tower segments are connected with bolts which means that the assembly eff ort is very high The boltings have to be checked at regular intervals for details about that please consult the maintenance manual of the WEC At first only a certain amount of bolts will be checked If this check shows that the tightening torque is too low at a cer tain percentage of bolts all boltings of this segment connection have to be checked An adaptor is located between tower and nacelle yaw bearing that connects the steel profiles of the lattice tower with the yaw system It provides an access to the nacelle of the wind energy converter A ladder for the nacelle access is attached to the lattice elements of the tower as well as the cables that lead from the control cabinet into the nacelle T
103. ses and is limited by end points Therefore these turbines require also reasonable care for the correct positioning of the blade during blade assembly The inner hub The internal part of the hub can be reached via a hatch This hatch is usually located op posite to the shaft fastening Some WEC types are provided with a covered hatch The inner hub of wind energy converters without pitch control contain only the hydraulic distribution system for the hydraulic cylinders of the inner blade root The hub of turbines with electric pitch control contains the actuators the switch cabinets with the support and frame system and the standby battery power supply UPS Wind energy converters with hydraulic pitch are provided with a hydraulic cylinder in the hub the associated hydraulic accumulator the mechanical actuator system and the control switchboards The hydrau lics is supplied via a distribution system from the nacelle The checking of used wind energy converters should also include inspection of internal structures for corrosion leakages and functioning Pay special attention to possible con tact corrosion at the electrical connections All screw joints should be checked and re tightened where applicable Details can be referenced in the maintenance and service ma nual of the WEC All rubber bearings should be replaced by new ones if possible Pitch and ActiveStall systems Pitch and ActiveStall systems have generally the same design
104. similar to the lamella coupling Maintenance and inspection of the generator coupling The flexible components of the generator coupling are exposed to a maximum of stress Because of this they should get special attendance during the maintenance Torn down coupling items might cause a remarkable damage of other components due to their high rotational speed up to 1500 min and the high kinetic energy resulting from this The imbalance from a torn down coupling item must not be underestimated Under certain conditions the GFP cover of the wind energy converter might be punctured by frag ments Rubber items and items made of plastic should be inspected for possible cracks or materi al brittleness Rubber items go beyond the normal wearout processes inspect them for material fatigue Possibly damaged components have to be exchanged Consider that the costs that occur with an exchange of this item are much lower than those occurring with consequential damages and repairs Occasionally a safety clutch can be located at the generator side familiarize yourself with its functioning In addition the height of the release torque has to be checked or in case of a new assembly re adjusted Apart from this the safety clutch is operated wear less Generator The generator is the last link of the WEC s drive train It transfers mechanical energy into electric energy Synchronous as well as asynchronous generators are used here In most cases th
105. splays to the parties involved the possible scope of issues and gives assistance to ask the right questions in the planning phase However the statements in the study make no pre tence to completeness An exhaustive guidebook can not be provided facing the variety of plants being on the market and various obstacles in the implementation of projects The requirements of insurers or certification institutes technical prerequisites etc must be generally re inquired at the companies EXPERTISES Expertises What is an expertise An expertise is designed to survey and examine the entire wind energy converter by an independent expert Depending on the kind of expertise the extent of investigations may widely differ For instance after commissioning it is sufficient to inspect the converter a status oriented inspection may require oil samples comprehensive measurements at the drive train endoscopying or ultra sonic expertises at the blades The inspection results are summarized in a document This document should meet a number of minimum require ments partly specifications may exist that must be complied with in the implementation and text edition What is an expert The terms expert and surveyor are not protected basically everybody can characteri ze himself as competent However there exists a number of criteria from which you should specify a competent expert The three most significant criteria are shortly listed belo
106. ssioning a status oriented inspection is compulsory because otherwise no insurance agency will be ready to conclude a contract On what you should pay attention initial selection cri teria for a used WEC Select an insurance company before launching the project and clarify which requirements must be complied with In case of doubt cooperate with a competent independent consultant Inquire also smallest details and matter of courses Request an insight into the documentation and check it for completeness Check whether individual components had to be frequently replaced Request the documentation regarding the yield of the turbine EXPERTISES If the turbine is part of a wind farm also request the documentation of the yields of the other wind energy converters Pay attention that promised features and possible damages were named accurately and form part of the concluded contract Contact other operators of the same turbine type and ask for their experience Make sure that the documentation associated to the wind energy converter is complete Check all available documents for their completeness by way of the following list Type testing or individual testing Certificate of conformity Building permission Maintenance requirements specification Maintenance contract Installation and assembly record Commissioning record Soil expertise Grounding record Logbook of the turbine usually a blotter with handwritten entries
107. sual inspection of components Surfaces covered with grease or areas filled with leak oil can not generally be cleaned on mere suspicion Information received by the WEC control like for instance error indexes maximum tem peratures performance curves and pitch angle tables must be regarded with special care The majority of lists filed in the controls can be manually modified if the password is known Therefore even a dressing up of values can not be excluded What else can be measured There are some measurements that are not required by an expertise However they give additional significant conclusions about the condition of the WEC Temperature of individual components Maximum temperatures exist for the majority of components like gear generators drive engines engine breaks switchboards accumulator sets hydraulic systems and in parti cular for all bearings These temperatures must not be exceeded If they are exceeded EXPERTISES this may be an indication for erroneous components acting as a heat source or compo nents which fail at too high temperatures like shaft seals which may cause gear dama ges due to occurring leakages By most of the system controls the maximum values are measured and filed in indexes For older wind energy converters some series of measurement may be quite useful Insulation of generator windings If the insulation value of the generator windings 15 too low over many years ther
108. t expertise after commissioning However it should be extended by the following items Inspection of all documentations of maintenance and service work Inspection of the rotorblades see chapter of the same title Temperatures listed in the control system if possible Visual inspection of the gearbox toothing Analysis of the gearbox oil Investigation of damages Survey report An investigation of damages is limited exclusively to the occurred damage and its direct environment No statements are made for the remaining wind energy converter An investigation of damages can not replace the other expertises described in the study Recurring inspection The type testing or building permission can contain requirements for periodically recur ring inspections Normally the time intervals are 2 years a corresponding maintenance contract can include 4 year intervals during the first 14 years of operation If the specified deadlines are not observed the building permission can be cancelled and the type certificate for the wind energy converter will no longer be valid This results also to a loss of the insurance coverage for the turbine and provides a risk to all other contracts based on the building permission The objective of the Recurring Inspection is the check of safety installations and the structural integrity of the construction The tasks comply with the expertise prior to the expiry of the guarantee period however must be
109. th pallets or something similar at the well know spots the straps are removed from the crane hook and assembled to the next blade If not special devices are available two loops are put around the blade roots of two blades and hooked to the crane after the pre assembly of the rotor Long guide ropes have to be attached to all three blade ends In addition a crane loop has to be assembled to the blade showing downwards This crane loop has to be hooked to the auxiliary crane The sensitive rear edges of the blades have to be protected with special edge protection as usual With the help of the two cranes the rotor is lifted for several metres Afterwards only the main crane lifts the rotor further The auxiliary crane keeps the height of the blade tip and readjusts the position until the rotor is hanging in horizontal position Three ground teams guide the rotor with ropes over the entire craning process On top of the shaft flange the crane has to push the hub over the shaft level until the bolts can be plugged in The hub must not bend out of line and the centering must not be dama ged Long thread rods or thread cones can be used as aid THE RE INSTALLATION OF THE WIND ENERGY CONVERTER After tightening the boltings between hub and shaft flange temporarily the loops can be removed Now the electric and hydraulic connections of the hub can be connected The final torque can be applied to the boltings The boltings of the blade pins
110. the engine carrier Self aligning roller bearings are designed for very high axial and radial loads They con sist of 2 rows of symmetric barrel rollers and a hollow spherical runway of the outer ring This allows turning around their radial axes and prevents power transmission from ben ding or torsion The rotor thrust is completely absorbed by the main bearing The bearing of the planet carrier is located inside the torque reaction bar of the gear Through the elastic bearing of the torque reaction bar the rotor shaft is resting in a way that torsions up to a certain level can be ensured This mobility reduces the forces applied on the torque reaction bar and thus the impact on the components However the disadvantage of this kind of bearing is that bending moments must be pro vided at the entrance area of the gear The rotor bearing on 2 main bearings The version is designed in a way that the rotor shaft rests on two main bearing to that the bending moments from the rotor can be absorbed by the two main bearings Only the dri ve torque is transmitted to the gear a significant advantage of this type Similar to the 3 point bearing the bearings are designed as self aligning roller bearings The rotor thrust can be either absorbed by the fore or aft bearing The rotor bearings can be either indivi dually or together mounted in the bearing casing The integration of the bearing into the gear The 3rd version is the integration of th
111. tion BWE Damage evaluations Modern wind energy converters are complex technical constructions which consist of many mechanical and electric components The production of these components includes some manufacturing tolerances and under certain circumstances even hidden manufac turing deficiencies The installation of a turbine or improper storage may also cause da mages There are no one hundred percent damage free wind energy converters The competence of a specialist is required to evaluate the damage potential i e the possi ble consequential damages which may arise from a deficiency Naturally the corrosion damage at a sensor fitting remains without any consequences whereas a rusting welding seam at the main frame or tower may lead to the destruction of the complete installation The turbines are designed to meet the technical requirements for 20 years This is a task to be fulfilled In this respect it is vital to realize the consequences of a damage on time and where required introduce measures to ensure that the planned life expectancy will be achieved EXPERTISES Different occasions different kinds of expertises An overview Expertise after commissioning At the time of the WEC commissioning the operator arranges for an expertise which is designed to analyse the condition of the newly installed WEC in total At the same time possible rework and residual work are specified release for payment is issued etc Exper
112. tions see glossary Loose lightning protection must be re affixed to the rotorblade in order to ensure the required lightning protection Functional testing of the tip brake for stall blades Pay special attention to the smooth running of the entire tip mechanism in order to ensure the faultless brake operation of the wind energy converter In worst case scenarios a non conforming tip mechanism may cause a brake operation failure The consequences would be WEC operation with overspeed which may then lead to the destruction of the wind energy converter The serviceability of the tip brake be checked by lowering the hydraulic pressure insi de the hydraulic cylinders of the rotorblade below the triggering value while the wind energy converter is standing still In doing so the tip brakes of the blades should be ex tended and activated When checking the braking function of the WEC the tip brakes should be activated too as the hydraulic pressure will be reduced at first Checking the screw connections between rotorblade and hub The rotorblades are connected with the hub by clamping bolts The winding of the bolts should be running smoothly and be free of corrosion Further information on the screw connections can be referenced in the homonymous chapter Checking the anchorage of the blade s tension rod The blade should be free of cracks and do not rove Rotor hub The rotor blades are connected with the rotor hub by flange co
113. tiously brought into upright transport position and moved on the lorry by crane The disassembly of the nacelle There are different devices and procedures available for the fixation of the nacelle at the crane hook Take always care that the nacelle with its mostly very high centre of gravity can never slip within the fixing devices A nacelle that hangs leaning on the crane can hardly be put on the transport devices without larger damages A rope minimum length double hub height is fixed to the rear end of the main frame It allows controlling the turning of the freely hanging nacelle from the ground Turn the hub side of the nacelle into the wind Afterwards the energy supply of control system and drives can be removed The crane devices are hooked at the crane hook or crossbeam of the main crane The crane operator loads the crane hook with a load as high as the dead weight of the na celle Now the service team members should loosen the boltings of the tower head and the na celle until the nacelle can be lifted for about one centimetre Thus the crane operator is able to grope towards the real load on the crane To screw out the entire bolt the nacelle will be put tightly on the tower head once again DISASSEMBLY AND TRANSPORT OF USED WIND ENERGY CONVERTERS While it is lowered to the ground by the crane the nacelle is directed by the members of the ground team with the help of the ropes To bring the screw holes of the bo
114. tise prior to expiry of guarantee period Prior to the expiry of the guarantee period of a WEC many operators arrange for a pro found inspection of the overall condition The purpose is to specify which work has to be completed by the manufacturer before he can be released from his liability for the turbine Investigation of damages Survey report Any damages of a wind energy converter require that an expert is called in to investigate the extent of the damage and its repairability Recurring investigation The periodically recurring investigations are required by the certification body and the competent building department in Germany every 2 to 4 years These investigations are designed to verify the safety installations and the structural integrity Status oriented investigation These periodically recurring investigation every 1 2 or 4 years are required by the in surer of the wind energy converter It is designed to identify so called initial damages and avoid consequential damages What kind of documentation is required for a WEC ex pertise The evaluation of a WEC also includes the review of the available documentation which is designed to give a complete overview of the structure the operation and history of the turbine As a minimum the following documents must be available Building permission Operating instructions Circuit diagrams and hydraulic diagrams Commissioning record Results of former oil analyses
115. ttom flange of the nacelle into the right position to wards the transport device threading cones or other long and bending strong rods can be screwed into some of the screw holes The disassembly of the tower Concrete tower Depending on the construction type single component groups attached to the concrete to wer can be disassembled prior to the demolition As the height of the building makes it difficult to crushing with special devices difficult the same applies for cast concrete to wers as for those consisting of cemented segments They have to be blasted The residuals that lay on the ground have to be crushed and removed from the site The ground next to this tower ruins has to have enough bearing capacity that excavators and fully loaded lorries may drive on it Lattice tower As a principle lattice towers can be disassembled beam by beam starting at the top of the tower In practical work this is not too easy for safety and working technology reasons With smaller lattice towers it is sufficient to loosen the foundation boltings and to put down the entire tower to the ground with the help of the two cranes To take it into pieces a smaller crane can be used only which is much cheaper Larger lattice towers have to be brought to the ground segment by segment To define the separation spots a detailed knowledge about the former installation process would be very helpful Conical tower The disassembly of all tower segments is
116. uld be made Naturally even with due care and profes sional handling the life expectancy of all components 15 limited That applies also to the large power transmitting components i e rotor hub bearing casing rotor shaft gear main frame and tower It is generally recognized that the life expectancy of a wind energy converter amounts to twenty years A possible further operation after this period depends also on the more or less optimal external conditions for instance the turbine site just to name one In either case the further operation of the wind energy converter after expira tion of the regular life expectancy should be duly considered for every individual case and coordinated with the permission body In order to ensure an adequate operation of the wind energy converter the individual components must be maintained at regular intervals This includes for instance that the EXPERTISES pre load of the screw joints is regularly checked The length of the intervals depends on the component and the age of the WEC further details can be referenced in the mainte nance and service manual of the WEC With the assembly and re installation of a WEC all power transmitting screw joints must be newly pre loaded afterwards checked and possibly pre loaded at regular maintenance intervals Lubricants and supplies All lubricants and supplies must be substituted before the WEC is re commissioned Lubricants Grease in the bl
117. w A preferably comprehensive professional experience the ideal case long occupation in the wind energy branch Membership in a corresponding association for instance in the advisory board of the Bundesverband Windenergie Deutschland German Windenergy Association The certification Officially appointed and sworn in expert these persons passed an examination to furnish proof of their expertise and professional competence at the Chamber of Commerce Only this official appointment gives authorisation to bear the certification An expert must be independent in his work An employee of the manufacturer can not furnish an impartial expertise for the customer That also applies vice versa All parties involved in the project to be surveyed must be in the position to accept the observations and conclusions of the expert from which his totally neutral position is automatically ari sing Any connections to one of the partners must be notified beforehand In doing so the other parties have the opportunity to make a decision whether the connection can be ac cepted Under certain conditions depending on the requirements of certification bodies building authorities or building departments experts must be either accredited or approved by the se bodies Most countries provide a list where all accredited experts and surveyors are li sted In Germany for instance such a list can be obtained from the German Windenergy Associa
118. was carried out last Assembly instruction Some manufacturers differentiate between instructions for the hall assembly of the sin gle components and the installation of the wind energy converter on the future site The installation manual is the most important document for the re installation of a used wind energy converter nevertheless both documents should be handed over to you There will usually be a checklist record or something similar to document the installation process too it has to be filled in signed and filed in the plant file by the executing mechanic Commissioning instruction and commissioning record Here all working steps that belong to the proper commissioning of the wind energy con verter are described Therefore this document is very important for the commissioning of a used wind energy converter as well It serves as a clear base for possible later discussion in case problems or faults occur as all working steps of the re commissioning are recor ded during the execution in the commissioning record This record has to be signed by all participants and filed in the WEC file Circuit diagram For every wind energy converter there are electrical and if there are hydraulic compo nents also hydraulic circuit diagrams They display the structure and operation of the electrical and hydraulic system which is needed for maintenance and possibly occurring repair work Because of this pay attention that they are co
119. will be higher or lower than predicted However these measurements are only useful if the loads calculated for the components of the wind energy converter are available for the purpose of comparisons As a result of such investigations estimations can be made regarding the residual life expectancy of the turbine or load reducing corrections of the aerodynamics of the rotor In addition problems be identified by this method which be elimina ted or reduced by a modified operation mode That applies for instance to drive engine vibrations that affect the WEC loads Alignment of generator and gear At most turbine types the gear and generator carrier are fastened with rubber vibration dampers on the main frame That allows both components to move independently from each other so that the distance between both components 15 varying That permanent varying of the distance called relative motion may exceed 10 mm in so me cases a condition which must be compensated during the transmission of the torque from the gear to the generator shaft The compensating is performed by cardan shafts of various types However even their mobility is limited if the operating range is exceeded damages may occur To prevent da mages the horizontal and vertical misalignment and the angularity of gear shaft and ge nerator shaft must be specified This can be determined by dial gauges or laser measuring systems The expertise of used wind
120. with the blade bearings can only be brought to the final tor que when the rotor of the wind energy converter can be operated via the control system Assembly work at the rotor the assembly of single blades The two cranes have to be positioned in a way that both the main crane and the auxiliary crane can reach the blade root and the blade tip and can lift the blade until hub height in horizontal position If necessary it is required to assemble an auxiliary drive to the drive train The hub has to be brought into a position where the blade can be assembled horizontally still hanging on the cranes and locked there Tightening crane loops are hinged around the blade root and the blade tip of the assem bled blade Both loops are attached to long ropes for saving them from the ground The loop of the blade root is hooked to the main crane the loop at the blade tip to the au xiliary crane For an assembly to wind energy converters without pitching devices the blade has to be positioned in the loop according to the its later position during plant ope ration A later correction of incorrectly assembled blades cannot be done without cranes Now the cranes lift the blade until hub height while keeping it permanently in horizontal position to avoid that it slips out of the loops Both cranes have to be coordinated so that the crane ropes are hanging perpendicularly all the time Two ground teams have to pro tect the entire craning procedure w
121. y converters with 1500 kW and more annual The extent of inspections complies with the expertise prior to the expiry of the guarantee period however contains a number of additional items Vibration diagnosis of the drive train Endoscopying of all equal gearings Temperature check in the cooling system Check of the maintenance contract Check of the Annual Report related to the technical operation of the turbine Vibration diagnosis of the drive train Some wind energy converters are already equipped with stationary measuring systems for the vibration analysis of the drive train the results of which can be used for evaluation If such a measuring system is missing the vibrations must be measured at the casings of the drive train components i e main bearing gear and generator in the course of the experti se For gearless turbines the measuring tasks are limited to the recording of vibrations at the rotor bearings Background for the measurements and the analysis based on them is that the rolling mo tion of the rolling body in the bearings and the relative movements of the theeth in the ge ar generate vibrations which can be measured with acceleration sensors as structure born noise at the casings If all diameters the number of teeth of a gearwheel and the number of rolling bodies in the respective bearings are known the measured vibrations can be allocated to the indivi dual bearings and equal gearings If the regu

The expertise of used wind energy converters

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