Wind turbine blades need regular inspections and maintenance just like the rest of the turbine. While drones with high-res cameras may speed inspections, repairs will still be done with wind technicians on platforms and ropes. In this webinar Lou Dorworth of Abaris Training explores methods for repairing several types of common repairs, and Tony Gray will discuss the materials that best complete the work and more.

1. #WindWebinar
New Ideas, Methods and
Materials for Improving
Blade Repairs

2. #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

3. #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…

4. 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

5. 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

6. Cri)cal
Aerodynamic
Areas
Aerodynamic
Loading
of
Wind
Turbine
Blades

7. Laminar
Flow
and
Boundary
Layer
Note
the
change
in
laminar
flow
as
angle
of
aZack
(blade
pitch)
changes
in
model
at
right

8. Blade
Repair
Zones
1
2
34
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

9. 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.)

10. 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

11. 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

12. 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

13. 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

14. 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

15. One
Tri-­‐axial
=
Three
Unidirec)onal

16. 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

17. Typical
Tapered-­‐Scarf
Repair
Uniform
shear
stress
distribu)on
through
a
tapered
scarf
joint

18. Trailing
Edge
Scarf
Repair
Damage
Damage
removal
&
scarf
Final
repair

19. 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

20. Typical
Heat
Blanket
Layup
Scheme
Breather/Insula;on
Vacuum
Bag

21. - 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

22. Post-­‐Repair
Finishing
Gel
Coat
Filler
Paste
Care
is
taken
to
prevent
sanding
into
underlying
repair
plies

23. CHOOSING
THE
RIGHT
MATERIALS
FOR
BLADE
REPAIRS
TONY
GRAY
KEY
ACCOUNT
MANAGER
–
WIND
ENERGY
GRAY.TONY@US.SIKA.COM
(574)
361-­‐8424

24. 24
|
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

25. 25
§ Factors
in
Making
a
High
Quality
Repair
§ High
Quality
Repairs
in
Less
Time
TOPICS
25

26. 26
KEY
FACTORS
IN
MAKING
A
HIGH
QUALITY
REPAIR
Mixing and
application
Curing and
finishing
Suitable product
Environmental
conditions!
Substrates &
Surface Preparation

27. 27
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

28. 28
KEY
FACTORS
IN
MAKING
A
HIGH
QUALITY
REPAIR
Suitable product
Environmental
conditions!

29. 29
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

30. 30
KEY
FACTORS
IN
MAKING
A
HIGH
QUALITY
REPAIR
Mixing and
application
Suitable product
Environmental
conditions!
Substrates &
Surface Preparation

31. 31
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

32. 32
KEY
FACTORS
IN
MAKING
A
HIGH
QUALITY
REPAIR
Mixing and
application
Curing and
finishing
Suitable product
Environmental
conditions!
Substrates &
Surface Preparation

33. August
18,
2015
33
CURING
&
FINISHING
Curing behavior - Resins
ž To reach OEM durability a resin repair
must be post cured.
ž Post curing raises the Tg of the resin.
Takes the resin from a glassy (brittle)
state to a flexible (rubbery) state.
ž Tg should always be higher than
operating temperature of the blade
ž Typical OEM spec is 75°C – 80°C
(167°F - 176°F)
Curing behavior - Fillers
ž Some fillers need multiple coats to build
thickness.
ž Application temperature has a large
affect on the open time & sanding time.
ž Not all fillers sand the same.

34. 34
KEY
FACTORS
IN
MAKING
A
HIGH
QUALITY
REPAIR
Mixing and
application
Curing and
finishing
Suitable product
Environmental
conditions!
Substrates &
Surface Preparation

35. August
18,
2015
35
HIGH
QUALITY
REPAIR
IN
LESS
TIME
ž
Buy
your
products
from
a
name
that
you
can
trust
ž
Chose
the
wind
repair
products
that:
1. Give
the
largest
temperature
&
humidity
applica;on
window
2. Cure
fast
3. Are
easy
to
mix

36. 36
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

37. 37
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)

38. 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

39. 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

40. #WindWebinar
Paul Dvorak
Managing Editor
Windpower Engineering
& Development
pdvorak@wtwhmedia.com
New Ideas, Methods and Materials for Improving Blade Repairs
Lou Dorworth
Direct Services Division Manager
Abaris Training Resources Inc.
lou@abaris.com
Questions?
Tony Gray
Key Account Manager – Wind
Sika Corp.
gray.tony@us.sika.com

41. #WindWebinar
Thank You
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