cornell wind workshop – 6-13-2009 challenges of large mmw gearboxes in wind turbine applications...
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Cornell Wind Workshop – 6-13-2009
Challenges of Large MMW Challenges of Large MMW Gearboxes in Wind Turbine Gearboxes in Wind Turbine ApplicationsApplications
Michael Sirak, PE, GE Transportation Michael Sirak, PE, GE Transportation Tony Giammarise, GE TransportationTony Giammarise, GE Transportation
Cornell UniversityCornell University 12-13 June 200912-13 June 2009
GE Transportation
Industry Trends
DriveTrain Description
Challenges Moving Forward
Design
Manufacturing
Validation
Cornell Wind Workshop – 6-13-2009
GE … a tradition of innovation
Founded in 1878 as theEdison Electric Co.
130 years of successful operation
320,000 employees worldwide
Strong technology focus … Research centers in Germany, India, China and the U.S.
Cornell Wind Workshop – 6-13-2009
Four segments … aligned for growth
• Aviation• Enterprise Solutions• Healthcare• Transportation
• Aviation Financial Services
• Commercial Finance• Energy Financial
Services• GE Money• Treasury
• Cable• Film• International• Network• Sports & Olympics
• Energy• Oil & Gas• Water
Energy Infrastructure
Technology Infrastructure
NBC UniversalCapital
• Aviation• Enterprise Solutions• Healthcare• Transportation
• Aviation Financial Services
• Commercial Finance• Energy Financial
Services• GE Money• Treasury
• Cable• Film• International• Network• Sports & Olympics
• Energy• Oil & Gas• Water
Energy Infrastructure
Technology Infrastructure
NBC UniversalCapital
Cornell Wind Workshop – 6-13-2009
GE Transportation
•Global Headquarters
•Commercial Operations
•Engineering– Analysis and Diagnostics
Laboratories– Test Development
Laboratories
•Manufacturing– AC Inverters– Heavy & Light
Fabrications– Generators– Traction Motors– Locomotive Assemblies– OHV Wheels– Wind Gearboxes
GE TransportationErie, PA
Founded 19075,500 employees
GE TransportationErie, PA
Founded 19075,500 employees
Gear & Gearbox Manufacturing
Wire & Motor Manufacturing
Fabrication & Machining
Rotating Lab
Cornell Wind Workshop – 6-13-2009
Locomotives
Parts & Service
Propulsion & Specialty Services
Signaling &Comm
FinancialSolutions
Traffic Mgmt
Systems
Transportation2008 Revenue of $5.2 B
Cornell Wind Workshop – 6-13-2009
P&SS … a derivatives business Mining / OHVDrive Systems
for Mining Trucks
Drivetrain Technologies
Wind Turbine Gearboxes
Marine & StationaryEngines for Boats
& Power Generators
TransitPropulsion for Transit Cars
DrillDC/AC Motors for Drill Rigs
15,000 Engines Operational in 20 countries 18000 drives shipped
Land Based Technology Status
Today’s Land Base Utility Class Turbines
• 1.5 – 3.0 MW Upwind Configuration
• 80 – 100 Meter Tower Height
• Conventional 3 stage gearbox
• Distributed component drivetrain
• Full Span Pitch Control
• Tapered Cylinder Steel Towers
• ~65 kWhr/kg tower top mass
• 200 MW + Windfarms
Performance
• 98% Availability
• 40+% Capacity Factor at IEC-II 8.5 m/s
• CF% +10 pts in last 5 yrs
Clipper 2.5-93
Performance• Average 45+% Capacity Factor
• Availability & Cost Not Well Established
• 11 c/kwhr UK Thames Estuary site
Offshore Technology Status Offshore Technology
• Development and demo stage
• 19 Projects, 900 MW Installed, shallow water
• 3 – 4 MW Upwind Configuration
• 80 m towers
• Monopile & gravity foundations < 15m
• Steel Tapered Towers
• Infrastructure not yet available in US
GE 3.6 MW – Arklow Banks
Cornell Wind Workshop – 6-13-2009
US 20% Wind OutlookWind ResourceUS has outstanding wind resource
Broadly distributed thru mid-west & west
Offshore in NE
Technology IssuesNeed for technology improvements to compete with cheap coal
Offshore wind not mature
Turbines 5-10 MW req’d
US Has the Wind Resource
20% Wind Distributes per Demand & Resource
TransmissionCorridors an Essential Part of the Solution
Grid IntegrationIntegration of wind forecasting tools
Consolidation of load balance zones
System Balkanization a barrier
WinDS Analysis to Achieve 20%
Land Technology Improvements
• Turbine size increasing from 1.5 to 5 MW
• 20% Reduction In Capital Cost per kW
• 15% Increase In Capacity Factor
• 30% Reduction in O&M Costs
• GW Scale Windfarms
Offshore Technology Improvements
• Turbine size increasing from 3 to 10 MW
• 20% Reduction In Capital Cost
• 15% Increase in Capacity Factor
• 50% Reduction in O&M Costs
Analysis Summary • Existing Technology Achieves 6-
8% Penetration by 2030
• 20% Requires Technology Improvement
• Improvements In Cost, Capacity Factor, and O&M needed
• One cent reduction in COE - 12 billion dollar economic savings per year
Onshore
Shallow Offshore
Deep Offshore
$1,000
$1,500
$2,000
$2,500
$3,000
$3,500
2000 2005 2010 2015 2020 2025 2030 2035 2040 2045
Cap
ital
Co
st $
/kW
Cornell Wind Workshop – 6-13-2009
7GA87 Gearbox
Cornell Wind Workshop – 6-13-2009
7GA87E – 1.5MW 1:78 ratio Compound Planetary
• 3 stage CP design with helical gearing
• Straddle mounted planet bearings
• Flexible, splined ring gear
• No reversed bending loads on planet teeth
• One high speed stage
• Over 1300 produced
• Oldest fleet at 36 months
Cornell Wind Workshop – 6-13-2009
Current GET Gearboxes Differential Planetary +
Parallel Shaft2.0 – 2.7 MW @ 14.4 – 18 RPM 1400 – 1900 KNm Input Torque60:1 – 97:1 Ratio PossibilitiesApproximate Weight: 39,000 LbsHorizontal and vertical output shaft locations @ 550mm CD2350 / 2150mm Overall Length2 Simple Planetaries + Parallel
Shaft2.3 – 2.9 MW @ 14 – 16 RPM Input Speed1500 – 1920 KNm Input Torque78:1 – 136:1Approximate Weight: 46,500 LbsHorizontal Output Shaft @ 550mm CD2550mm Overall LengthCompound Planetary + Parallel Shaft1.4 – 1.8 MW @ 16 – 20 RPM 700 – 970 KNm Input Torque59:1 – 86:1 Ratio PossibilitiesApprox Weight: 33,000 LbsHorizontal Output Shaft @ 550mm CD.Working on Vertical Output Shaft for 2009.2200mm Overall Length
Cornell Wind Workshop – 6-13-2009
Common Gearbox Components2 Simple Planetary + Parallel Shaft Arrangement
Input Carrier – Connects Gearbox to Blades
Input Carrier Bearings – Supports blade loads
Low Speed Sun Gear – Output of first speed increasing Stage. Inputs power to High Speed Planetary Stage
Low Speed Planet Gears – Typically 3, 4, or 5 gears. Meshes with Annulus and Sun Gear.
Input Housing – Supports gearbox torque and blade loads.
Torque Arms – Transfers torque and wind load to turbine structure
Low Speed Annulus Gear – Non-Rotating, fixed to Input Housing.
High Speed Annulus Gear – Non-Rotating, fixed to Input Housing.
High Speed Sun Gear – Output of second speed increasing Stage. Inputs power to High Speed Parallel Shaft StageHigh Speed Carrier Bearings
– Supports Gear loads
High Speed Gear Bearings – Supports Sun Gear & High Speed Gar loads.
Pitch Tube – Conduit for electric or hydraulic supply to blade control system – rotates at rotor speed.
High Speed Gear – fixed to sun gear, drives high speed pinion.
High Speed Pinion – driven by high speed gear. Drives the generator.
High Speed Pinion Bearings– supports gear and braking loads.
High Speed Planet Gears – Typically 3.
Cornell Wind Workshop – 6-13-2009
Constraints – Design PerspectiveDesign Complexity & challenges
• Dynamic Loads – Extreme coherent gust winds, Turbulent shear winds
• Low “Lamda” – Design challenge to maintain Lamda ratios >1
• High Torque Density
• Loads prediction & understanding
• Torque Arm Design – Currently used for a 1.5-2.0MW turbine Gearbox, but as the MW rating increases, this design becomes complex
• Adequate Cooling & heating – Challenge due to extreme environmental conditions
• Noise control – Huge factor due to noise regulations
• Vibrations
• Seal designs – Current Gearbox industry is challenged is oil leaks either on input side / output side
• Reliability – Design life 20 years
• Weight – Shipping and uptower
Flap Flap deflectiondeflection
Edge Edge deflectiondeflection
Tower Tower loadsloads
Main Shaft Main Shaft MomentMoment
NacelleNacelleYawYaw
Flap Flap deflectiondeflection
Edge Edge deflectiondeflection
Tower Tower loadsloads
Main Shaft Main Shaft MomentMoment
NacelleNacelleYawYaw
Cornell Wind Workshop – 6-13-2009
Growing wind turbine scale necessitates development of new drive train technology
Roller Speed: 92 ft/s
Roller Speed: 65 ft/s
RotationRotation1,500 RPM
3.6 MW HS Pinion Bearing
Rotation1,500 RPM
1.5 MW HS Pinion Bearing
Problem
•Conventional 3-stage gearbox-based drive trains are sub-optimal as wind turbine rated power grows from 1 MW to 5 MW
•Cause is increasing size of problematic HS Pinion Bearings which require decreasing oil viscosities
•Forces a dangerous compromise … select low viscosity oil to support higher speed bearings OR higher viscosity oil to protect the low speed gear stages
Solution
•Develop technology that eliminates the need for the 3rd (high speed) stage of the gearbox
6
8
1 0
1 2
1 4
1 6
1 8
2 0
2 2
2 4
2 6
2 8
0 5 0 0 0 0 0 1 0 0 0 0 0 0 1 5 0 0 0 0 0 2 0 0 0 0 0 0
(µ-in
)
T o r q u e ( lb f - in )
0 . 1 5
0 . 2 0
0 . 2 5
0 . 3 0
0 . 3 6
0 . 4 1
0 . 4 6
0 . 5 1
0 . 5 6
0 . 6 1
0 . 6 6
(µ-m
)
F ilm T h ic k n e s s ( m in )
I S O 3 2 0 - 7 0 C L o w S p e e d S t a g eI S O 4 6 0 - 6 0 C L o w S p e e d S t a g e
+ + + + + + + + +0 . 0 0 5 6 4 9 2 1 1 2 9 8 5 1 6 9 4 7 7 2 2 5 9 7 0
T o r q u e ( N - m )
3 0 0 % T o r q u e
6
8
1 0
1 2
1 4
1 6
1 8
2 0
2 2
2 4
2 6
2 8
0 5 0 0 0 0 0 1 0 0 0 0 0 0 1 5 0 0 0 0 0 2 0 0 0 0 0 0
(µ-in
)
T o r q u e ( lb f - in )
0 . 1 5
0 . 2 0
0 . 2 5
0 . 3 0
0 . 3 6
0 . 4 1
0 . 4 6
0 . 5 1
0 . 5 6
0 . 6 1
0 . 6 6
(µ-m
)
F ilm T h ic k n e s s ( m in )
I S O 3 2 0 - 7 0 C L o w S p e e d S t a g eI S O 4 6 0 - 6 0 C L o w S p e e d S t a g e
+ + + + + + + + +0 . 0 0 5 6 4 9 2 1 1 2 9 8 5 1 6 9 4 7 7 2 2 5 9 7 0
T o r q u e ( N - m )
3 0 0 % T o r q u e
Impact of change from ISO VG 320 to ISO VG 460 oil on Low
Speed Planetary gear film thickness
Film Thickness (mm)
Above Line:Film Thickness > Gear Surface Finish
Cornell Wind Workshop – 6-13-2009
Relative Sizes & Conversion of mils & microns
~ Diameter of human hair, thickness of copy paper~ 0.1mm = 100 microns = .004 inch
1 mil = .001 inch = 25.4 microns
1 micron = 1 m = 1e-6 meters = .001 mm
Film thickness on low speed wind bearings ~ 0.15 microns!
Cornell Wind Workshop – 6-13-2009
Gear Design ProcessIdentify DesignInputs
-Loads-Speed-Size, etc
Preliminary GearSizing
-Ratios-Face width-Diameter, etc
Housing Design-Preliminary sizing-Detailed design
Optimize GearMacro Geometry
-Utilize RMC program-Kissoft program
Bearing Selection-Life-Stiffness-Size-Clearance
Detailed FEA-Housing deflection-Carrier deflection-Shaft deflections-Bearing deflections
3-D Mesh - MicroGeometry
-LVR/LDP-Gear stresses-Load Distribution
AGMA/DINRatings
-Predictor for Gear Life
Validation Testing-Strain gaging-Load Distribution
Profiles-HALT testing
Design Complete
Shaft Design-Diameter-Stiffness
Iteration
Iteration
Cornell Wind Workshop – 6-13-2009
Constraints – Manufacturing Perspective
• Size of Gearing
Size of gears used causes a challenge in manufacturing a quality gear, current industry supported by few suppliers in market
• Heat Treatment Process
Several heat treatment process available but process is generally difficult to monitor and maintain long term process capability
• Steel Quality
• Casting & Machining
• Cleanliness
Plays a major role in the overall reliability of the gear box from performance & life stand point
• Grinding
• Process Quality
Very critical to this business as cost of producing a non-quality part accumulates into a higher maintenance costs
IH process
Gear Mfg defect- not acceptable
Cornell Wind Workshop – 6-13-2009
Paint
Test StandTrim
& Flush A
ssem
bly
2Po
siti
oner
Ass
embl
y 1
Pit
Ship
Sub Assembly
Pump & Cooler
Subs
Prep-to-Ship
1
2
3
4
5
6
7
8
Gearbox production• Process Capability
– Supplier … component characteristic data– Assembly … validated measurement systems– Test … temp, vibration, particulate count, w ear
• Documentation & Systems– M anufacturing instructions– e-Traveler– Quality system audits– Test documentation
• Cleanliness– Pre and post- test gearbox oil flush to ISO 4406– Component cleaning– Lean supermarket
Cornell Wind Workshop – 6-13-2009
Constraints – Validation Perspective• Comprehensive commercial testing
• Component testing
• Sub-system testing
• HALT - Every new production or significant change
• Field testing - ~ typically 6 months field test
• Cost – testing costs are expensive but critical
• Larger gearboxes = larger test stands
Cornell Wind Workshop – 6-13-2009
Reaction at simulated planet pinions
Two synchronous hydraulic jacks used to simulate 1137.6 kNm
Force reacted by ring gear attached to stationary base plate
Component testing … demonstrated 99% reliability at 95% confidence
Input Housing Carrier High Speed Gear Bearing
Cornell Wind Workshop – 6-13-2009
Cold Chamber Lube System Flow Rate
Strain Gauge Testing
Systems level testing
Cornell Wind Workshop – 6-13-2009
Simulates 20 yr life on gearing– Loads increased to decrease total test time– 3x and 2x overloads– Run on dedicated engineering test stand
Monitoring– Bearing and oil temperatures– Oil pressures– Stresses in critical components– Power, torque, and speed– Gear wear patterns– Particle count
Capability– 2.5 MW @ 1440 rpm continuous
HALT “graduation” test
Cornell Wind Workshop – 6-13-2009
Gear Mesh Pattern
- All gear contact patterns were good and passed typical acceptance criteria.
- Gear contact patterns & condition are best indicators of system validation.
- Validates deflection calculations in structures, shafts and bearings
- Validates adequate lube flow
Cornell Wind Workshop – 6-13-2009
Constraints – Maintenance Perspective
• Filtration – Lube oil used needs regular filtration & maintenance
• Contamination of Oil w/metal particles
• Load Management
• Monitor noise
• Periodic oil sampling
• Shipping & Logistics – Weight & shape of the Gearboxes causing a challenge for shipping & logistics
• Condition based monitoring system – Proactively monitors, detects impending drive train issues, enabling increased availability & decreased maintenance costs
• Uptower Inspection Technology – Barkhausen Noise, Eddy Current
• Can only climb two or three towers per day!
Wind farms in Ocean- greater challenge for maintenance
Large Cranes Used for installation, repair & accessibility
Cornell Wind Workshop – 6-13-2009
Barkhausen Noise – Uptower Inspections
.
No other teeth had comparative BH values as the damaged teeth. GB was repaired and placed back in service.
1sttooth
2nd tooth
1sttooth
2ndtooth
Surface defect Caused by grind temper
Leveraging uptower inspection and repair
Cornell Wind Workshop – 6-13-2009
Gear Case Depth Eddy Current Inspection
DescriptionGE-conceived technology that enables non-destructive examination of Gear manufacturing quality
Benefits•Advances state of the art in gear
manufacturing and wind turbine gearbox quality
•Eliminates need for sacrificial parts during gear manufacturing
•Reduces gear inspection process cycle time … manufacturing productivity improvement
•Enables examination of gears after installation in the gearbox
Eddy Current System
Gear Case Depth Profile
0
10
20
30
40
50
60
70
2000 3000 4000 5000 6000 7000 8000 9000 10000
Distance from Edge (µm)
Rc
scan 1
scan 2
scan 3
Gear Case
Case
Cornell Wind Workshop – 6-13-2009
Location of 2 MW generator coupling
3.5 MW IntegraDrive in
the space of a 3-stage 2.3 MW
gearbox
Turbine Efficiency Comparison
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
P/P rated
Effici
ency
IntegraDrive
Standard DFIG
Conventional Gbx &
Generator
IntegraDrive
No. of Bearings 26 11
No. of Gear Meshes 15 6
Efficiency Range 96.5% - 97.0% 99.3%
System Efficiency 90% 93%
Generates 6% higher AEP versus conventional DFIG drive train
Modular flywheel coupling system … common interface for
multiple suppliers
Compound Planetary Gearbox
PM Generator
IntegraDrive geared generator
Cornell Wind Workshop – 6-13-2009
Challenges of Design, Manufacturing Validation of large Gearboxes used in wind Turbine Applications
June 12-13 2009, Cornell University
Mike Sirak
Tony Giammarise
Cornell Wind Workshop – 6-13-2009
X section of a typical 1.5 MW Wind Turbine Gear Drive converts
~ 18 rpm input to 1440 rpm output; hence a speed increasing drive system
GE Energy has the entire system. We at Power Drives are building only the Gear drive portion of the system
This is a talk to show you some of the hardware, and the manufacturing methods/ materials used
Cornell Wind Workshop – 6-13-2009
Stats for a typical 1.5 MW system
Cut in wind speed 3.5m/s
Cut out Wind speed 25m/s
Rotor diameter 77m
Rotor speed 11.0 to 20.4 rpm
Swept Area 4657 m2
Tower height 80 to 100 m
Near Future 2.0 to 2.5 MW near term, land based (already here in Europe)
Stats for a mating gearbox
Input rpm 18
Output rpm 1440
Ratio 85.71
Input power 1660Kw
Input rated Torque 947000 Nm
Cornell Wind Workshop – 6-13-2009
The practical issues with Big wind machines and the scale of things :
• Installation
• logistics and access
• Scale reflected in cost and available suppliers; their capacity and location, logistics
• Unscheduled maintaince
~240 ft, (80 m)
sky hook
Cornell Wind Workshop – 6-13-2009
Gearbox Design is based on a design process where requirements are flowed to Drive Systems from:
•Turbine manufacturers
•public standards
•insuring bodies
•Internally imposed guidelines
Typical Design deliverables include
•Geometrical/Dimensional envelope, details in aux equipment placement
•Power capabilities, input rpm’s output rpm’s
•Weight limit
•Environmental operational conditions
•Temperature extremes
•Wind class
•Emergency stops/overload conditions
•Noise limits
•Reliability guarantees
•Certification from insuring body
Cornell Wind Workshop – 6-13-2009
Gear box materials flow from design requirements, customer requirements and insurance bodies
Structural Components
Moderately large Machined Ductile Iron Castings with
Soundness requirements
Mechanical and Microstructural requirements
Environmental Requirements (Cold weather, -40C)
Gearing
Forged raw materials
Clean Steel Technology required for gear steels
Carburized and hardened
Extensive high tolerance machining AGMA class 12 and higher
Extensive Secondary heat treatments/ finishing operations/ inspections for final acceptance
Cornell Wind Workshop – 6-13-2009
Bearings
Extensive use of rolling element bearings
~ less than 10% mass of a 1.5 MW gear box are the bearings
Commercially produced by the leading global bearing suppliers
Clean steel technology required
Both thru hardened and case carburized utilized
Bearing issues:
design loads and their complete measurement
Global supply issues of capacity timely deliveries
Earlier generation of gear boxes had life limited bearing failures
.
Cornell Wind Workshop – 6-13-2009
20000 lbs of 32000 lbs total of the gearbox mass for a 1.5 MW Box is structural castings. Half of that is in one casting.
Cornell Wind Workshop – 6-13-2009
First stage planetary gears carrier cast ductile iron
Heavy walled Ductile Iron Issues
•Designing for optimized weight to strength ratios
•Soundness of castings and surface quality
•Consistency of Mechanical properties and microstructure throughout
•Cold weather requirement and fracture toughness measurement
•Global supply chains also represent additional manufacturing/ quality risks
Cornell Wind Workshop – 6-13-2009
Ductile (spheroidal) Iron metallurgy
What it it?
Why Ductile?
Standard structural material, Effectively easy to cast, Lower costs as compared to cast steel, better yields and comparable mechanical properties, machines readily, and insuring bodies allow it!
Properties
Common grade used by many Wind turbine producers
100X Microstructure ferritic ductile Iron
Cornell Wind Workshop – 6-13-2009
Other structural Castings found in wind turbine system are similar to those within the gear box.
Hub Casting
Bedplate Casting
Cornell Wind Workshop – 6-13-2009
Bearing locations in a 1.5MW compound planetary gear arrangement
Bearings shown in various colors
Cornell Wind Workshop – 6-13-2009
Examples of Roller bearing types and usage within a 1.5 MW gear box
Cornell Wind Workshop – 6-13-2009
Overview of Wind Gearing
Forged raw materials using
Clean Steel Technology & high Hardenability Steels
Carburized and hardened helical gearing
Extensive high tolerance machining AGMA class 12 and higher for reduction of noise, better load sharing
Extensive heat treatments/ finishing operations/ inspections for final acceptance
Cornell Wind Workshop – 6-13-2009
Clean Steel Technology a Definition
Timken Para-premium
ESR requirement
Steel cleanliness by various melting methods
Air melt requirement
Steel making methods utilized for Clean Steel
•Bottom taping EAF
•Ladle refined
•Deoxidized
•Vacuum degassed
•Bottom poured ingot or con-cast
•Protected from re-oxidation during teeming/casting
•Careful limits on Hydrogen and Oxygen
All of the above need to be done to assure high quality steel
Increasing cost
2x
X
Decreasing steel quality
Double melting
Single melted standard air
Gear & Bearing quality
Cornell Wind Workshop – 6-13-2009
Manufacturing sequence for typical precision Wind gears
Steel making/ ingot production
Grades 18CrNiMo7-6, 43B17, 4820 and similar
Clean steel technology required/ No naughty bits in the steel/ inspect it
Forging operations to rough shape ingot into forged blank
heat it/ beat it / heat treat it and then inspect it
Gear making operations
rough it, hob it ( First outline of the tooth form )
prep it for carburizing
pump carbon into the surface (Extensive diffusion based high temperature controlled cycles changing the near surface to a different alloy!)
quench it to make it hard
temper it to make is a little less hard but improve it’s toughness
grind it to very accurate finish dimensions
inspect it, measure it, making sure it meets print and is free from manufacturing defects
protect it during storage/shipment
Cornell Wind Workshop – 6-13-2009
Micro Hardness of a tooth Chip
30
35
40
45
50
55
60
0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75
distance form ground surface
Ha
rdn
es
s in
HR
C c
on
ve
rte
d f
rom
V
ick
ers HRC;A
HRC;B
HRC;B1
Typical Case Carburized tooth form and the scale of things
Why Case harden gears
•Resist bending Fatigue loads
•Resist Surface contact Fatigue
•Add compressive residual stress to aid in the fatigue loading capabilities
•Core structure remains ductile
•Highest allowable design loads per all international standards
•Large capacity worldwide for this type of hardening process
Case hardening Terms
•Surface Hardness
•Effective Case depth to HRC 50
•Pitch line Case depth
•Root hardness
•Core hardness
A tooth form showing the surface hardening; scale is in mm
Core
region
Distance in mm from ground surface
Effective case depth
Surface Hardness
Cornell Wind Workshop – 6-13-2009
Typical Carburized Gear Process
Steel Run
(Heat)
Ingots
29” square
Billets14.5” round corner
MultsForgingsRough Machining
Heat Treat
Carb/Quench
Hard turn/ Grinding
Assembly into Gearbox
240k lbs 30 ingots/run 1 billet/ingot
6-8 mults/billet1 forging/mult1 gear/forging
2 gears/heat treat 1 gear/grind 1 gear/gearbox
Steel Supplier
Forging Supplier (Q =13)Gear Supplier
GE Transportation
Cornell Wind Workshop – 6-13-2009
916ABP1 HS Gear quality check listProcess Spec Check points Check Frequency
Raw material 9310H grade 2 per C50E76 Must from TIMKENcleanliness per ASTM A534 Every HeatHydrogen content besides chemistry Every Heat
Forging From Canton Drop Forging Reduction ratio
Normalize and temper B50E215 Viual check green painting Every piece
Rough Turning Process sheet Dimension check Every pieceDrilling / tapping Process sheet Dimension check Every piece
Forging soundness AGMA 923 grade 2 UT Every piece
Hobbing Process sheet M.O.P check Every piece
Tooth shapping Process sheet M.O.P check Every piece
Chamfer Process sheet Dimension check Every piece
Carb / Quench Hardness, metallurgical test Every heat lot
Shot peen AMS-S-13165 Coverage/saturation Every piece
Hard turning Process sheet Dimension check Every piece
Enternal tooth grinding Process sheet Gear charts / M.O.P Every piece
Internal spline grinding Process sheet Gear charts / M.O.P Every piece
Dynamic balance Process sheet Every piece
MPI AGMA 923 Every piece
Nital etch AGMA 2007 Every piece
Final inspection blue prints Dimension check, visual check Every piece
Typical Gear Quality Checks
Cornell Wind Workshop – 6-13-2009
Modern Gear Grinders required to meet the tolerance needs for wind gearing. High quality tolerances needed to reduce noise
Cornell Wind Workshop – 6-13-2009
Current grinding technology both measures, distributes stock and self corrects dimensions, before and during grinding
The requirements of Wind Gearing also require large capital investments.
Cornell Wind Workshop – 6-13-2009
Gear Tolerances and the scale of things
Typical AGMA Class 12 gearing found on a 40 inch diameter high speed gear
These magnitudes require temperature controlled grinding processes, temperature controlled measurement processes to produce accurate gears. Accurate tooth form assures uniform loading
Small numbers!
Cornell Wind Workshop – 6-13-2009
Issues in gear manufacture for wind gear systems
•Special problems of large forgings
•Distortion during heat treatment
•Distortion during quenching
•Achieving adequate case and or core properties in large parts
•Damaging hard surfaces during final grind operations
•Capacity worldwide for large high tolerance gear manufacture
Cornell Wind Workshop – 6-13-2009
Design success means:
•Understand the requirements
•Know and measure loads
•Utilize knowledge in Public Standards
•Understand the operating environment
•Detail and define requirements and flow them from System, to sub-System, to each component
•Inspect Components using the right methods and technologies
•Manufacture carefully Utilizing the right advanced and traditional tools
•Test to failure
The outcome is, the ability to achieve the level of reliability desired
Thank you
Cornell Wind Workshop – 6-13-2009
Scale of things: 1.5 MW units
1660 Kw = 2226 HP= 1.6 MW
•GE locomotive=4400 HP,so from a power view, half a locomotive up a pole.
•The entire structure, including the pole is ~ 220 Tons excluding the foundation=weight of locomotive
•The foundation weights ~500 tons
Cornell Wind Workshop – 6-13-2009
Lake Superior Late March w/ machines as cold as the photo looks
Above the Columbia River, mid summer
Operating Environment
-40C to +40 C