new ideas, methods and materials for improving blade repairs
TRANSCRIPT
#WindWebinar
New Ideas, Methods and Materials for Improving
Blade Repairs
#WindWebinar
q This webinar will be available afterwards at www.windpowerengineering.com & email
q Q&A at the end of the presentation q Hashtag for this webinar: #WindWebinar
Before We Start
#WindWebinar
Paul Dvorak Moderator
Windpower Engineering & Development
Tony Gray Key Account Manager
-Wind Energy Sika Corp.
Lou Dorworth Direct Services
Division Manager Abaris Training Resources Inc.
New Ideas, Methods and Materials for Improving Blade Repairs
Meet your presenters…
Introduc)on • Turbine blade damage requires the applica)on of
simple but func)onal repairs given the physical difficulty of the task
• The most common opera)onal damage is from surface impact and rain/dust erosion
• Other damage from bird strike, lightning strike, other
object impact, and/or the propaga)on of manufacturing anomalies
• The repair methods and materials need to be simple but effec)ve in order to maintain the blade’s structural integrity and future opera)onal effec)veness
Types of Damage & Common Repairs
• Erosion damage (without major fiber damage) – Abrade, clean, fill & fair with suitable epoxy or polyurethane filler
• Minor scratches or dings affec)ng surface ply – Abrade, to remove paint around damage down to the laminate surface, fill scratch or ding with filler paste &
apply 1-‐layer of fine glass fabric with epoxy
• Damage into or beyond outer ply of laminate – Remove and replace damaged plies or apply a bonded doubler repair
• Damage into sandwich core structure – Remove & replace damaged core and structural plies in damaged skin or apply doubler repair
• Damage through structure – Remove damage through structure and repair from both sides (if accessible) using repair plies or doublers
• Op)on: Repair from one side using “no backside access” techniques
Note: all repair types are “zone dependent” requiring aerodynamic/aeroelas)c considera)ons
Cri)cal Aerodynamic Areas Aerodynamic Loading of Wind Turbine Blades
Laminar Flow and Boundary Layer
Note the change in laminar flow as angle of aZack (blade pitch) changes in model at right
Blade Repair Zones
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2
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Repairs to turbine blades require considera)on of aerodynamic and aeroelas)c loads on the structure – repair design and approach
may be adjusted to meet zone requirements
Blade Repair Zones Zone 1. For both for aerodynamic and structural purposes; the blade leading must be maintained for the
laminar boundary layer. Zone 1 is from the 20% to 100% span length and to 25%-‐30% of the local chordline. Zone 1 will always require a flush repair.
Zone 2. For aeroelas)c purposes; do not add significant weight to this zone of the blade, so as to maintain
mass balance. Not a major structural region of the blade, however the repair needs to be an aeroelas;c semi-‐structural repair.
Zone 3. Primarily for aeroelas)c purposes; the repair does not necessarily need to be flush for airflow
aerodynamics, but it must not add significant weight behind the shear center. However, trailing edge repairs are typically flush for aeroelas;c requirements.
Zone 4. Not required to be aerodynamically smooth, but may need to be a semi-‐structural or structural
repair based on the severity of the damage and the proximity of the damage to the main load bearing region of Zone 4 (i.e. spar cap). Because of the large enclosed area of the blade in Zone 4 the torsional rigidity is much higher than loca)ons in Zone 3 and aeroelas)c requirements are not necessarily cri)cal. (Note: significant damage to Zone 4 training edge may need a flush semi-‐structural repair.)
Leading Edge Erosion • Most common type of damage
to most cri)cal part of the aerodynamic airfoil – May or may not require structural
ply replacement • Common approach is to repair is
to fill and fair back to smooth aerodynamic surface – Abrasion of damage and
surrounding area prior to fill & fair with epoxy or polyurethane paste
Stepped Removal & Repair • Each damaged layer is removed in
“steps” so as to provide a landing for each replacement layer in the repair.
– Usually bulk mul)-‐axial material; repaired bulk ply for bulk ply.
• Step removal almost always results in damage to underlying structure
• Each bulk repair ply then overlaps the corresponding exposed layer in the structure.
– Faying surfaces do not match axial orienta)on requirements
Typical Stepped Repair Loads are distributed through the repair via
a lap joint into the underlying layers
The resul)ng repair sits above the surface
Copyright © Abaris Training 2015
Filler Ply
Typical Stepped Repair Shear stress distribu)on in a stepped repair
Note peak stress concentra)ons at edges of each step-‐lap within the repair
Copyright © Abaris Training 2015
Filler Ply
Tapered-‐Scarf Repairs • A tapered-‐scarf angle is machined
through the composite structure so as to expose each layer along a gently-‐angled slope.
• Each repair ply then lays over the corresponding exposed layer along the tapered angle. – Recommend mul)ple
unidirec)onal materials for replacement of each mul)-‐axial bulk ply
One Tri-‐axial = Three Unidirec)onal
Typical Tapered-‐Scarf Repair Loads are transferred directly through the edges of each
unidirec)onal element of the mul)-‐axial layer, in plane, on axis, in shear, matching that of the underlying structure
The resul)ng repair is flush with the surface
Typical Tapered-‐Scarf Repair Uniform shear stress distribu)on through a tapered scarf
joint
Trailing Edge Scarf Repair
Damage Damage removal & scarf
Final repair
Vacuum Bagging & Curing the Patch
• Vacuum bag with bleeder & breather layers – Facilitates compac)on of the repair plies
• Heat blanket with thermocouples and process controller – Used to accurately control
cure temperature
Typical Heat Blanket Layup Scheme
Breather/Insula;on
Vacuum Bag
- Apply a minimum of 22 in Hg vacuum and maintain throughout cure cycle
*Heat at 1-5°F/Min
*Cool at <5°F/Min
*Hold at 150°F ± 10°F x 60-70 mins
* Temp based upon lagging thermocouple
Typical Cure Cycle Recipe Based on two-‐part amine cured epoxy resin chemistry
Post-‐Repair Finishing
Gel Coat
Filler Paste
Care is taken to prevent sanding into underlying repair plies
CHOOSING THE RIGHT MATERIALS FOR BLADE REPAIRS TONY GRAY KEY ACCOUNT MANAGER – WIND ENERGY [email protected]
(574) 361-‐8424
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SIKA CORPORATION A LITTLE ABOUT US… § Sika is a world leader in construc)on chemicals
§ Speciality chemical products in automo)ve & industrial markets
8/18/15 | Sika Industry -‐ Inven)ng the Future
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§ Factors in Making a High Quality Repair
§ High Quality Repairs in Less Time
TOPICS
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KEY FACTORS IN MAKING A HIGH QUALITY REPAIR
Mixing and application
Curing and finishing
Suitable product
Environmental conditions!
Substrates & Surface Preparation
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SUITABLE PRODUCT
� Critical damage in main body of blade
� Half way or entirely through 1st ply of fibreglass
Structural Damages Surface Damages � Non-structural damage of surface � Less than half way through 1st ply
of fibreglass
Ø 2C laminating resin + suitable glass fibre fabric
Ø 2C surface filler
Polyester resin & filler – Polyester blades only! Epoxy & Urethane – Good for all blade types
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KEY FACTORS IN MAKING A HIGH QUALITY REPAIR
Suitable product
Environmental conditions!
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ENVIRONMENTAL CONDITIONS
Temperature… Humidity… � High influence on 2C products � Moderate influence on 2C products
High temperatures… à shorten pot life & cure times
(quicker sanding, grinding etc.)
Refer to the Product Data Sheet for Application Temperature & Humidly Range Typical Repair Products:
→ Applica)on temperature: 18C (64F) – 25C (77F) → Max humidity – 70% RH
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KEY FACTORS IN MAKING A HIGH QUALITY REPAIR
Mixing and application
Suitable product
Environmental conditions!
Substrates & Surface Preparation
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MIXING & APPLICATION
Wrong mixing may lead to… � Too Short application time � No or insufficient curing � Too long curing time � Bad end properties (e.g. soft or brittle material)
Correct mixing ensures… � Sufficient application time � Correct curing speed and
homogeneous and full curing � Good end properties after curing & durability
L J
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KEY FACTORS IN MAKING A HIGH QUALITY REPAIR
Mixing and application
Curing and finishing
Suitable product
Environmental conditions!
Substrates & Surface Preparation
August 18, 2015 33
CURING & FINISHING
Curing behavior - Resins � To reach OEM durability a resin repair
must be post cured. � Post curing raises the Tg of the resin.
Takes the resin from a glassy (brittle) state to a flexible (rubbery) state.
� Tg should always be higher than operating temperature of the blade
� Typical OEM spec is 75°C – 80°C (167°F - 176°F)
Curing behavior - Fillers � Some fillers need multiple coats to build
thickness. � Application temperature has a large
affect on the open time & sanding time. � Not all fillers sand the same.
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KEY FACTORS IN MAKING A HIGH QUALITY REPAIR
Mixing and application
Curing and finishing
Suitable product
Environmental conditions!
Substrates & Surface Preparation
August 18, 2015 35
HIGH QUALITY REPAIR IN LESS TIME � Buy your products from a name that you can trust � Chose the wind repair products that:
1. Give the largest temperature & humidity applica;on window
2. Cure fast 3. Are easy to mix
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HIGH QUALITY REPAIR IN LESS TIME TEMP & HUMIDITY APPLICATION WINDOW
Sika Specialty Wind Repair Products
§ Specialized products for up tower blade repair
§ Applica)on temperature 5C (40F) – 35C (95F)
§ Max humidity – 80% RH
Currently available repair season
Extended repair season
Average min & max temp (Northern US)
Commonly Used Wind Repair Products
§ General purpose made for shop environment.
§ Applica)on temperature 18C (64F) – 25C (77F)
§ Max humidity – 70% RH
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HIGH QUALITY REPAIR IN LESS TIME CURING FAST
Commonly Used Wind Repair Products
§ Resin has long post cure )mes depending on resin type used
§ Mul)ple applica)ons of filler must be made to build thickness and fill pin holes
§ Filler sand )mes can be lengthy depending on type used, especially at cold temperatures
Sika Specialty Wind Repair Products
§ Resin has fast post cure )mes. Post cure in as liZle as 30 minutes to reach OEM spec Tg
§ Thixotropic filler materials that builds thick layers with a smooth finish in one applica)on.
§ Filler sand )mes of 35 minutes or less down to 5C (40F)
August 18, 2015 38
HIGH QUALITY REPAIR IN LESS TIME EASY TO MIX
Commonly Used Wind Repair Products
§ Cans of A & B components that must be mixed onsite to reach correct ra)o ()me consuming & error prone)
Sika Specialty Wind Repair Products
§ Ready to go A/B foil packs (Resin)
§ Side by side or coaxial cartridges with sta)c mixer (Fillers)
§ Cartridges save material by only dispensing what is required & can be used on mul)ple repairs
§ Tendency to mix more than is required – causes excess waste
August 18, 2015 39
SIKA SPECIALTY WIND BLADE REPAIR PRODUCTS
Epoxy Repair Resin Polyurethane Fillers
Sikadur® Blade Repair Kits
Sikaforce® 7800 Red & Blue
Hybrid UV Resistant Sealant
#WindWebinar
Paul Dvorak Managing Editor Windpower Engineering & Development [email protected]
New Ideas, Methods and Materials for Improving Blade Repairs
Lou Dorworth Direct Services Division Manager Abaris Training Resources Inc. [email protected]
Questions?
Tony Gray Key Account Manager – Wind Sika Corp. [email protected]
#WindWebinar
Thank You q This webinar will be available at
www.windpowerengineering.com & email
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