are poor lubrication practices threatening this promising source of clean energy

8/8/2019 Are Poor Lubrication Practices Threatening This Promising Source of Clean Energy

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Are poor lubrication practices threatening this promising source of clean energy?

The skyrocketing costs of crude oil and natural gas have had many effects on lubricant

requirements. One of these is the growing demand for wind turbines as generators of electr

from renewable resources.

During the last 20 years, manufacturers of gearboxes and gear oils used in wind turbines have expended great deal of effort to design and develop the best products. Unfortunately, all of their excellent work appto be in jeopardy as a result of poor monitoring and maintenance by wind turbine owners.

Banning, Calif.-based Frontier Pro Services conducted an informal survey of approximately 75 wind farmoperators in the United States. The survey revealed potentially serious threats to wind farms due mainly industrywide shortage of qualified turbine technicians.

Many wind farm operations and maintenance teams are so resource constrained that they are barely able keep up with unscheduled maintenance repairs. Even regularly scheduled preventative maintenance suchgearbox lubrication and oil changes are falling behind. It has also been reported that some wind farmoperators do not want third-party companies to do the work for them as they want to keep control of the

maintenance.Gearbox failures account for the largest amount of downtime, maintenance and loss of power productionwind farm operators. Failures can total between 15%-20% of the price of the turbine itself. According toFrontier Pro Services, most gearboxes Fail as a direct result of improper lubrication and lack of routinemaintenance. Most gearbox failures are preventable, which should make wind turbine gearbox maintenanhigh priority.

In any gearbox, if the gear oil is not properly monitored and replaced as needed, bearing and gear wear wlead to more serious and costly damage to the drivetrain. For example, when a $1,500 wind turbine gearbbearing fails unnoticed, it can lead to an electricity production loss and the unscheduled replacement of a$500,000 gearbox and a crane cost of up to $70,000 to access the failed components.

Routine and simple fluid analysis can save the typical wind farm operator thousands of dollars in repair

work, provided, of course, they have the technicians available to perform the work.

Costa Mesa, Calif.-based Varelube Systems, Inc., supplies lubrication and hydraulic systems and otherequipment to wind farm operators in the U.S. They also represent two companies that manufacturediagnostics equipment for monitoring oil in wind turbines. However, the wind farm market has beenunreceptive to this concept, citing the cost per unit to add monitoring technology

. It is difficult to understand why a wind farm operator would buy a $2 million wind turbine and not beinterested in understanding the condition of the oil in the most expensive item in the machine-the gearboApparently they are willing to pay $500,000 to replace the gearbox and put in a crane but have no interes

oil monitoring technology.According to Varelube, some wind farm operators are afraid to admit they have experienced anyequipmefailures or what they were. Gearbox and wind turbine manufacturers are reluctant to reveal how manygearboxes have failed or how much money they have allocated for warranty claims.

Frontier Pro Services believes that with so many wind turbines behind on inspections and regular servicethere is real cause for concern. Clearly, a shortage of trained technicians, a lack of routine gearbox and goil monitoring and a reluctance to install automated monitoring equipment could be storing up significanproblems for the future.
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If the service life of a wind turbine is intended to be 30 years, gearbox failures every 10 years or so couldseriously impact the economics of generating electricity using wind power.

Percentage of Materials Used in Current Wind Turbine Component

Large Turbines and (Small Turbines1)

Component/Material

(% by weight)

Permanent

Magnetic

Materials

Pre stressed

Concrete

Steel Aluminum Copper Glass

Reinforced

Plastic

Wood

Epoxy

Carbon Filam

Reinforced

Plastic

Rotor

Hub 95-100 5

Blade 5 95 95 95

Nacelle 17 65-80 3-4 14 1-2

Gear Box 98-100 0-2


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and load carrying capacity."

One objective is to make components lighter, and new materials being developed will help achieve that gDevelopments with surface finish such as REM technology and electro polishing, some of which are beinused in the racing industry, are having some real significant impact in gear life.

Chinnusamy says there are many challenges in machining gears for wind turbines. Gears for wind turbinapplications are typically large in diameter and have wide face widths, requiring very exacting materialcomposition and heat-treatment processing. The gear design must be optimized to insure low rollingresistance and long life, to minimize costs of maintenance, down time, and repair of the gear box assembonce they have been commissioned in the field. Every step in the manufacturing phase of these gears mucarefully processed, documented and controlled to achieve the high quality, consistency, accuracy andreliability that is demanded for operation in these environments.

The use of carburized steel for these gears is common and the associated heat treatments and stress-reliefoperations have to be exacting to minimize part distortion and growth, as well as to achieve the propermetallurgical properties required. Often, a preheat treatment of the forging or bar stock is necessary on la

gears to minimize part distortion.

Chinnusamy says heat treatment can cause cracks, so careful processing with predetermination of stockallowance for grinding and final case depth must be considered. Inspection for cracks with magnetic partinspection and for grinding burns utilizing nital etching is an important inspection tool. Plus, off centercrown grinding of the tooth geometry may be needed to properly distribute the load on the gear teeth.

To efficiently make gears for this application, Chinnusamy says there are often modifications needed in ttooling. Rigid, heavy-duty hobbing machines are needed for the coarse pitch gears, using roughing hobs gear milling (gashing) cutters. Likewise, coarse pitch diamond dressing rolls and special grinding wheelabrasives are required for the large, high-accuracy gear grinders to produce efficient, accurate results andprevent grinding burns and cracks.

Cutting fluids used must have the proper viscosity, the right amount of extreme pressure additives, and mbe directed to the exact location of the work piece and cutting tool interface to maximize results. These fhave to be routinely sampled and adjusted for optimum results.

In building the gearbox, it's also important to establish the correct bearing clearances/preloads and propegearbox operating temperature that is critical to long life. Sophisticated measuring techniques with bearininspection gages can only insure these results. The type and method of lubrication and proper sealing weiheavily on the performance of a gearbox. The verification of gearbox performance through computerizedanalysis and testing is a crucial step to insuring long life.

"The critical factor here, as with all similarpower transmission applications, is that the gears are properlydesigned and manufactured," says Chinnusamy. "The other mechanical components that make up theassembly, along with the gearing, must be applied and designed so the overall system performance does have any shortcomings that could affect the performance and life of the unit."

Wind Turbine
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Wind energy is a converted form of solar energy. A wind energy

system transforms the kinetic energy of the wind into mechanical or

electrical energy that can be harnessed for practical use. Mechanical

energy is most commonly used for pumping water in rural or remote

locations. Wind electric turbines are used to generate electricity.

Turbine systems include a rotor, or blades which convert the wind's

energy into rotational shaft energy; a tower to support the rotor and

drive train; a nacelle including a gearbox and a generator; and

electronic equipments such as controls, electrical cables, ground support equipments, and

interconnection equipments.

When the rotor rotates, the load on the main shaft is very heavy. It runs with approximate

revolutions per minute but generator has to go a lot faster. It cannot use the turning force

increase the number of revolutions and that is why wind turbine uses gear to increase the

speed.

Types of Gears used in Wind Turbines

Wind turbines vary in sizes and according to their size and function they use a variety of

different type of gears for easy and comfortable working.

Helical gears - Are used to minimize noise and power losses.

Worm gears - Are used to drive the toothed wheel rim on the yaw bearing of the turbine.

Bevel gears - Used to redirect the shaft from the horizontal gas turbine engine to the vertrotor.

Pinion gears - Are used for accuracy evaluation and for grind temper testing.

It is important to monitor the different components of the offshore wind turbines to limit an

avoid damage and downtime. Gearbox should be closely monitored by measuring the noise

level, visually monitoring, by measuring its vibration and by analysing the oil serving as

lubrication during service checks

Helical Gears

Helical gears connect parallel shifts but the involute teeth are cut at

an angle to the axis of rotation. Two mating helical gears must have

equal helix angle but opposite hand. They run smoother and more
http://www.gears-manufacturers.com/helical-gears.htmlhttp://www.gears-manufacturers.com/worm-gears.htmlhttp://www.gears-manufacturers.com/bevel-gears.htmlhttp://www.gears-manufacturers.com/pinion-gears.htmlhttp://www.gears-manufacturers.com/helical-gears.htmlhttp://www.gears-manufacturers.com/worm-gears.htmlhttp://www.gears-manufacturers.com/bevel-gears.htmlhttp://www.gears-manufacturers.com/pinion-gears.html


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gear has concave faces to fit the curvature of the worm in order to provide line of contact instead of poincontact. They are cut helically for better mating. Worm gears can provide a high angular velocity betweenon-intersecting shafts at right angles. They are capable of transmitting high tooth loads, the onlydisadvantage is the high sliding velocities across the teeth. They provide ultimate power ratio.

Advantages of Worm GearsThe efficiency of worm gear depends on the lead angle, sliding speed, and lubricant, surface quality andinstallation conditions. They offer smoothest, quietest form of gearing. They provide high-ratio speedreduction in minimal spaces. Worm gears are used when large gear reductions are required. Worm gear hunique property of easily turning the gear. The gear cannot turn the worm because the angle on the wormshallow and when the gear tries to spin the worm, the friction between the two holds the worm in place.

Worm gears work under difficult conditions, presenting unique lubrication demands. The types of oils mcommonly used to lubricate worm gears are compounded mineral oils, EP mineral gear oils and syntheti

Worm Gear MechanismWorm gear is always used as the input gear. For the operation of worm gear, torque is applied to the inpu

end of the worm shaft by a driven sprocket or electric motor. The worm and the worm shaft are supporteanti-friction roller bearings. Because of high friction worm gears are very inefficient. There is lot of frictbetween a worm gear and the gear being driven by the worm gear. When used in high torque applicationthe friction causes the wear on the gear teeth and erosion of restraining surface.

Types of Worm GearsThere are three types of worm gears:

Non throated- a helical gear with a straight worm. Tooth contact is a single moving point on theworm drive.

Single throated- has concave helical teeth wrap around the worm. This leads to line contact.

Double throated- called a cone or hourglass. It has concave teeth both on the worm and helical g

ApplicationsWorm gears are widely used in packaging machinery, material handling, machine tools, indexing and foprocessing. They are used widely in conveyor systems. They are also used in torsen differential, used onsome high-performance cars and trucks. They serve as speed reducers in many different industries.

Bevel Gears

Bevel gears connect intersecting axes and come in several types.

The pitch surface of bevel gears is a cone. They are useful when the

direction of a shaft's rotation needs to be changed. Using gears of

differing numbers of teeth can change the speed of rotation. They

are usually mounted on shafts that are 90 degrees apart, but can be

designed to work at other angles as well.


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Bevel gears permit minor adjustment during assembly and allow for some displacement du

deflection under operating loads without concentrating the load on the end of the tooth. Fo

reliable performance, they must be pinned to shaft with a dowel or taper pin. Bevel gear se

consist of two gears of different pitch diameter that yield ratios greater than 1:1.

Types of bevel gears

The bevel gears can be of varied types and the types are known by the teeth of the gears.

Different varieties are:

Straight Bevel Gears:In straight bevel gears teeth have no helix angles. They either have equal size gearswith 90 degrees shaft angle or a shaft angle other than 90 degrees. Straight bevel acan also be with one gear flat with a pitch angle of 90 degrees. In straight when eactooth engages it impacts the corresponding tooth and simply curving the gear teethsolve the problem.

Spiral Bevel Gears:Spiral bevel gears have spiral angles, which gives performance improvements. Thecontact between the teeth starts at one end of the gear and then spreads across thewhole tooth. In both the bevel types of gears the shaft must be perpendicular to eacother and must be in the same plane.

Hypoid Bevel Gears:The Hypoid bevel gears can engage with the axes in different planes. This is used inmany car differentials. The ring gear of the differential and the input pinion gear areboth hypoid. This allows input pinion to be mounted lower than the axis of the ring gHypoid gears are stronger, operate more quietly and can be used for higher reductioratios. They also have sliding action along the teeth, potentially reducing efficiency.

Angular Bevel Gears:These are bevel gears whose shafts are set at an angle other than 90 degrees. Theyuseful when the direction of a shaft's rotation needs to be changed. These gears perminor adjustment of gears during assembly and allow for some displacement due todeflection under operating loads without concentrating the load on the end of the to

Applications

A good example of bevel gears is seen as the main mechanism for a hand drill. As the hand

of the drill is turned in a vertical direction, the bevel gears change the rotation of the chuck

a horizontal rotation. The bevel gears in a hand drill have the added advantage of increasin

the speed of rotation of the chuck and this makes it possible to drill a range of materials. T

are important components on all current rotorcraft drive system.

The bevel gears find its application in

Locomotives

Marine applications

Automobiles
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Printing presses

Cooling towers

Power plants

Steel plants

Defence and Railway track inspection machine

Pinion Gears

Pininon gear is a small cogwheel. The teeth fit into a larger gear wheel.Rotational motion is converted into linear motion when the pinion turns andmoves the rack. Pinion gears are engineered to be the best gears and hence verypopular in various industrial applications.

How does a Pinion Gear Operates?Pinion gear system involves the use of a small round gear called pinion and alarge flat gear called rack, more the number of teeth in the pinion gear, more isthe speed of rotation. Pinion with smaller number of teeth produces moretorque. Pinion is attached to the motor shaft with glue. Rotation of pinion isdone by rotation of pinion about a fixed center that helps the rack to move in the straight line. If the rackmoved and the pinion rotates then the center of the pinion moves taking along the pinion with it.

Materials of ConstructionThe gears are constructed from materials like

Cast iron

Steel

Aluminum

Bronze

Carbon steel

Hardened steel

Working Principle

Law of gearingA primary requirement of gears is the constancy of angular velocities orproportionality of position transmission. High-speed gear trains alsorequire transmission at constant angular velocities. Constant velocity isthe 'conjugate action' of the gear tooth profile. A common normal to thetooth profiles at their point of contact must pass through a fixed point onthe line of centers called the pitch point. Any two profiles engaging eachother and satisfying the law of gearing are conjugate curves.


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Gear GeometryThe essential features of a gear mesh are:Center distance: The distance between the centers of two pitch circles.

Pitch diameters: The tangent to two basic circles is the line of contact in gear vernacular. Whereline crosses the line of center establishes the pitch. The ratio of pitch diameters gives the velocityratio.Pitch: It is a measure of tooth spacing along the pitch circle. There are two basic forms. Circularpitch is the direct measurement of distance of one tooth center to the adjacent tooth center. It is eqto the pitch circle circumference divided by the teeth. Diameter pitch is the measure of the numbeteeth per inch of the pitch diameter. Both the pitches are inversely related to each other and perman easy transformation from one to the other.Number of teethPressure angle of the contacting involutes: The angel between the line of force between meshingteeth and the tangent to the pitch circle at the point of mesh. Gears must have the same pitch and

pressure angel to mesh.Module: It is the ratio of pitch diameter to the number of teeth. It is mainly used for metal gears. higher module indicates coarser tooth spacing.Gear train: When two or more gears are meshing, it is called a gear train.Gear box: It is an automotive assembly of gears and associated parts by which power is transmitfrom the engine to the driving axle.Shafts: Cylindrical rods made of metal used for power transmission, linear motion and various opurposes in industries.Sprockets: Teeth like projection arranged on a wheel rim to engage the links of a chain.Pinions: Small tapered gear that meshes with a larger gear or rack.

KineticsWhen two gears are connected they rotate in opposite directions. The gear that does the driving isknown as the driver and the other is known as the driven gear. If two gears have the same numbeteeth then one turn of driver gear causes the driven gear to turn once. When connected to a powersource it applies torque to the input shaft driving it at a considerable speed. For a single pair of gethe output shaft rotates at a different speed as that of the input shaft. The torque applied on the oushaft drives the load. One essential for the proper meshing of the gears is that the size of the teeththe pinion should be the same as the size of the teeth on the wheel. The module must be commonboth the gears. Pitch circles contact one another at the pitch point and the pinion's pitch line velocmust be identical to the wheels pitch line velocity. At the pitch point develops a tangential compoof action-reaction due to contact between the gears. When the driver gear is smaller than the drivgear then speed is reduced and it amplifies torque in proportion to their teeth numbers. The only w

that the input and output shafts of a gear pair can be made to rotate in the same sense is byinterposition of an odd number of intermediate gears. These do not affect the speed ratio betweeninput and output shafts. Such a gear train is called a simple train. If there is no power flow througthe shaft of an intermediate gear then it is an idler gear.

Introduction


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Gear is a toothed machine part, such as a wheel or cylinder that mesheswith another toothed part to transmit motion or to change speed ordirection. Gears are a means of changing the rate of rotation of a

machinery shaft.

Mechanical engineers sometimes don't use gears and rely on the adventof electronic control and the availability of toothed belts because gearsfor high power machinery are difficult to design. Even though for highpower machinery like automotive transmission, gears are the optimalmedium for high accuracy and low energy loss.

Gears are of several categories and can be combined in a multitude of ways, some of which aremeshing circular spur gears, rack and pinion spur gears, and worm gears. Helical and herringbonegears utilize curved teeth for efficient, high-capacity power transmission. Worm gears, driven byworms transmit motion between non-intersecting right-angle axes. Gears mate or mesh via teeth wa very specific geometry.

ApplicationGears being an important part of a machine have immense usage within various industries. Theseindustries include automotive industries, coal plants industry, steel plants industry, paper industrymining and many more. In these industries they behold a wide area of application. They are used conveyors, elevators, kilns, separators, cranes and lubrication systems.

Gears are used for two basic purposes; increase or decrease of rotation speed and increase or decrof power or torque. Torque is a measure of a force to produce torsion and rotation about an axis.

increase speed and reduce torque a large drive gear is coupled to a smaller driven gear. To reducespeed and increase torque a small Lego gear turning a larger gear is used. They are also used forenhancement for positioning systems.

Gear geometryThe essential features of a gear mesh are:Center distance: The distance between the centers of two pitch circles.Pitch diameters: The tangent to two basic circles is the line of contact in gear vernacular. Whereline crosses the line of center establishes the pitch. The ratio of pitch diameters gives the velocityratio.Pitch: It is a measure of tooth spacing along the pitch circle.Number of teethPressure angle of the contacting involutes: The angel between the line of force between meshingteeth and the tangent to the pitch circle at the point of mesh.

GearboxesThe global supply capacity of gearboxes is presently enough to cover the demand from the wind industry.Nevertheless, supply information from wind turbine manufacturers indicates that constraints still exist in thgearbox supply chain for various reasons. According to the published development plans of the leadingsuppliers, there will be no constraints in the gearbox supply chain up to 2012. This assumption is based,


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however, on the premise that the supply of large gearbox bearings will catch up with demand from themarket. Unfortunately, there is no sign that the shortage situation for large bearings can be fully resolved ithe next two years. It is therefore inevitable that gearbox supply constraint will continue to be a problem.

Wind Turbine Supply Chain Strategies:2009-2020

The global wind turbine supply chain faces the challenging task of bridging the gap between the high levgrowth and the bottlenecks of 2008, and the resumption of high growth expected in 2010. Although somcapacity investments have been frozen and new market entries postponed, 2009 has offered the industry abreather to retool its strategy for longer-term, sustained growth as demand becomes more consolidatedglobally. The global wind turbine component supply market will be shaped by the following key trends inear term as the industry looks forward to the next economic cycle, including:

Global wind turbine demand will likely rebound by the end of 2010 to levels equal to or above th

seen in 2008. Global cumulative installed wind power capacity is expected to jump from 122 GWover 227 GW between 2008 and 2011.

Outsourcing opportunities are increasing as OEMs seek expansion. While specific components suas control systems and blades are often manufactured in-house, OEMs are honing their supply chto optimize product quality by relying on outsourcing.

Product size is becoming a key strategic differentiator for component suppliers. As turbines scaleMW and larger, logistical issues require component suppliers to adapt to OEM needs with newproduct dimensions -- and not all existing players are prepared to make those investments.

Investment levels will reach new heights, with the blade, tower, generator, gearbox, and bearingmarkets combined totaling nearly US$30 billion per annum by 2020, led by towers and blades.

Global Demand Forecasts, 2009-2020: Rebounding Toward Steady GrowthThe global wind industry saw expansive growth in 2008, topping 120 GW installed worldwide with anannual increase of 23 percent. In the long term, Emerging Energy Research anticipates this figure will rissteadily to over 600 GW installed by 2020. However, the industry finds itself in the midst of a globalrecession in which project postponements, order cancellations, and company downsizings have becomecommonplace. Framed within the long-term context of cumulative megawatts installed through 2020, EEanticipates a compound annual growth rate of 18 percent between 2009 and 2020. Key assumptions behithese forecasts include:

Long-term policy is favorable.

Wind's position improving in the generation mix.

Utility participation is increasing. Grid issues persist, but are gradually addressed.

Offshore evolves as a key contributor.

Table 1: Global Wind Power Cumulative MW Installed by Region: 2000-2020


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Competitive Trends in Component Supply

The onset of the 2006-2008 turbine shortage, followed by the current recession, has begun to reshape thecompetitive structure of wind turbine component segments. The number of new entrants has proliferatedacross the supply chain: more in towers, while less new entrants in gearboxes, bearings, and generators inmost markets. At the same time, blade suppliers continue to compete with internal production. Key trend

observed in these segments include:

Blade suppliers weighing investments, positioning versus in-house supply. In 2009, wind turbblade suppliers face increasing competition at a time when demand has faced a short-term dip. Fowith choosing between waiting out the market to invest, or plowing ahead with heavy CAPEXcommitments, players have had to define themselves as global or local players able to act as proddevelopment partners and relevant options for localized cost reduction. While OEM in-house supcontinues to play a key part in the market, at an estimated 40 percent of total supply, independentblade suppliers have opportunities to position themselves based on targeted sales for turbine modin specific markets.

Gearbox suppliers steadily diversifying as market expands globally. Trends in gearbox supplindicate a steady shift in terms of the globalization and scale of the segment. Segmentation of thecompetitive landscape by product portfolio and delivery volume presents a market dominated bythree key players; however, scaling regional players in China and Europe promise more intensecompetition in the next three to five years.

Full portfolio, integrated bearings suppliers lead; pitch and yaw providers entering. The globearings supply industry can be split between players with global reach and a full suite of productfor wind turbines, and smaller niche players serving specific markets with one or two bearings tyRecent explosive growth of the wind industry has welcomed many new firms, often from largecompanies supplying several sectors, to diversify their sales into wind energy.


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Local tower supply booming, bursting with market slowdown. The global tower supply markremains a collection of local and regional markets driven by competition among nearby suppliersa share of OEM demand. This dynamic is reflected in the competitive structure of the market, inwhich most players remain contained to their region serving a select group of OEMs. This trendcontinued in 2008 and 2009 as tower suppliers seek to entrench themselves, leveraging localpresence, and, in some cases, expanding service offerings, though the current market slowdown hcomplicated capacity increases.

Generator supply increasingly competitive as turbine size scales, markets become more divThe competitive structure of the generator market remains relatively uneven, with a split betweenleading global suppliers such as ABB and Converteam, followed by mid-sized regional manufactand smaller start-up operations spread between Asia, Europe, and North America. Generally mid-sized players can be seen gaining new clients as expanding OEMs diversify, while smaller OEMstart-ups have formed partnerships with single suppliers in efforts to launch their products.

Table 2: Competitive Market Structure Overview, Wind Turbine Component Segments

Note: Bubble size indicates relative market valueSource: Emerging Energy Research

This article is an excerpt from EER's market study, Wind Turbine Supply Chain Strategies 2009-2020,released in July 2009. The full study is available for purchase at emerging-energy.com.


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http://www.energypulse.net/centers/article/article_displaym?a_id=2160

TimkenSUPPLYING CHINESE

WIND GEARBOX MANUFACTURERThe Timken Company signed a long-term, multi-year agreement with Nanjing High Speed GearManufacturing Co.,Ltd. with wind turbine gearbox bearings. NGC manufactures gear transmission equipment for windpower, marine,construction and industrial equipment in China. The agreement determines that Timken will supplytapered and cylindrical roller bearings for use in NGCs wind power gearboxes. Initial revenue isestimated at $30 million for

Timken. This is another great success for Timken in the China wind energy market sector. NGC is aglobally recognized brand and a leader in the industry, says Mike Connors, president of processindustries at Timken. Our strategy is to work with leading companies in the industry, companies thcompete on product performance, durability and reliability and that demand the highest level ofexpertise in friction management and power transmission from their suppliers.
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are poor lubrication practices threatening this promising source of clean energy

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