rotor shaft bearing

Turbines use a wide variety of bearings. Large ones include huge 2-m diameter main-shaft bearings with two opposing rows of cylindrical rollers to handle enormous thrust and radial loads. These support the shaft that holds the hub and rotor. Slew bearings mount between nacelles and towers to let nacelles rotate as needed. These can have 3 to 6-m diameters with gear teeth machined into outer ring surfaces.
Another bearing, a hybrid design, aimed at wind-turbine generators provides insulation against electric currents. Their use can minimize the risk of premature bearing failures due to erosion from electric currents. The manufacturer says the units can maximize lubricant effectiveness for long-term performance, even under poor lubrication conditions.

These ball bearings are said to benefit from a deep groove that combines steel rings and bearing-grade silicon nitride (ceramic) rolling elements. The balls are lighter, harder, less dense, and more durable than all-steel bearing counterparts, and they conform to standard bearing dimensions.

Benefits to its use are said to include higher reliability than conventional bearings along with reductions in life-cycle costs, total operating costs, and maintenance requirements. The bearings can supposedly upgrade existing wind-turbine generators without redesigning them.

Custom bearing may be a solution where conventional designs have come up short. Products of several bearing manufacturers support pitch, yaw, and gearbox applications in systems from 200 kW to 5.0 MW. The firms can design bearings to meet performance and life requirements with the most economical bearing design. Experience with offshore applications help specify appropriate corrosion resistant coatings such as zinc, paint, or other surface treatments. Material requirements can be met for operating temperatures down to –40C and below.

Other bearings appear conventional but have been modified. For example, in an electric environment, electrolytic corrosion from stray currents threatens bearing performance. One design uses coated angular-contact ball and cylindrical rollers to insulate the bearings from electric current. A ceramic coating applied to the outer surface and side faces of the outer ring prevents current from passing though the bearing. The design provides an insulation resistance of at least 2,000 MΩ. Under normal operating temperatures, this alleviates electrical arcing and early failure. The bearings come with or without seals or shields, and are interchangeable with standard, non-insulated bearings. The units are usually available with bores of 50 to 160-mm dia.

Another way to handle stray currents provides a discharge path to ground. One solution would provide a low resistance path from shaft to frame. A device called a bearing-protection ring meets the criteria. It uses principles of ionization to boost its electron-transfer rate and promote the efficient discharge of the high-frequency-shaft currents induced by many wind turbine generators. It channels harmful currents away from the bearings to ground.

The ring surrounds the generator shaft with many of conductive microfibers. The stiff yet flexible fibers provide high-density contact points — parallel paths of least resistance from the motor shaft to ground. The fibers reduce voltage buildup on the generator shaft by conducting instantaneous currents of many tens of amperes and discharging from tens to thousands of volts with MHz frequencies. The ring is especially suitable for use at high frequencies because its fibers tend to compensate for variations in roughness of the shaft surface, or microscopic misalignment of the ring and shaft, or both. When a microfiber looses mechanical contact with the rotating shaft, electric contact is quickly re-established somewhere else along the ring, due to local field emissions.

Windpower Engineering & Development

One application for disc springs is to preload bearings.

Disc Springs look like conically-shaped washers, a shape that lets them take an axial load. They can be used individually or assembled into stacks for a required deflection. Spirol Disc Springs’ performance characteristics are predictable, letting designers calculate a minimum life cycle. They also provide high levels of load/force in a small space, unlike other springs which require a significantly larger footprint to carry the same load. Their predictability, high reliability, and unparalleled fatigue life make the disc springs preferred over other types of springs in critical applications such as safety valves, clutch and brake mechanisms for elevators and heavy equipment, and supports for industrial pipe systems.

The two major updates to the newly expanded product line are larger sizes per DIN 2093 Group 2 (now available up to 250-mm dia.), as well as a full range of stainless steel Discs. Details are provided in the updated Disc Spring design guide.

The company’s Application Engineering team can assist with a best method of stacking the discs for the required force-deflection characteristic when multiple Disc Springs are required.

Spirol International Corp.
www.spirol.com

Windpower Engineering & Development

Massive, precision-engineered bearings and seals like those made by The Timken Company are central to wind power production. The largest of these rolling element bearings weighs more than five tons, with an ID of nearly 2 m.

Such large bearings require sophisticated measuring and testing capabilities that replicate dynamic wind forces. For that purpose, Timken will establish the USA’s only wind-energy research center focused on advanced development of wind-turbine bearings.

Timken will build the $11.8 million Wind Energy Research and Development Center in collab-oration with Stark State College, the Stark County Port Authority, and Stark Development Board. The 18,000 ft2 center will anchor the new Stark State Emerging Technologies Airport Campus on 15 acres of property adjacent the Akron-Canton Airport in Ohio, on the borders of the City of Green in Summit County and Jackson Township in Stark County. The center will secure 65 jobs directly, while creating a research practicum and technical certifi-cation program for Stark State College students to acquire critical experience conducting research, development, and testing of large wind-turbine bearings.

From left-to-right at the ground breaking ceremony for Wind Energy R&D Center stands Tom Chiappini-COO & Treasurer, Stark State College; Ward J. Timken, Jr.; Doug Smith, Timken- Senior Vice President, Technology & Quality; and Steve Paquette, President-Stark Development Board

Funding for the project combines more than $6 million invested by Timken, $2.1 million from Ohio’s Third Frontier Commission, and a $1.5 million loan from the Ohio Air Quality Development Authority’s Advanced Energy Jobs Stimulus Program. “This partnership will support the development of clean energy academic programs and internships for students,” says President of Stark State College John O’Donnell.

“We’ll have the resources to validate material and design properties while gleaning invaluable performance data on the mission-critical components working inside large turbines in dynamic conditions,” said Timken Senior VP of Technology Douglas Smith.

WPE

Windpower Engineering & Development

HS Series bearings provide four-point contact in deep groove gothic arch raceways.

The HS Series slewing ring bearings offer high load and thrust capacity for their size and are featured in a new data sheet from Kaydon Bearings Division. Outside diameters range from 20 to 47 in. (500 to 1,200 mm). Most HS sizes are available from stock and forgings are stocked for the rest.

HS Series bearings provide four-point contact in deep groove gothic arch raceways. With about twice the load capacity of Kaydon RK Series bearings (up to 139,900 ft-lbs.) in the same envelope, they are ideal for medium-duty to heavy-duty applications such as cranes, aerial lifts, digger derricks, chute swivels, lift truck rotators, and industrial turntables. A rectangular cross-section gives the HS Series even greater stiffness than the lighter RK Series, which reduces distortion and allows lower internal diametral clearance. Kaydon HS bearings are available with internal gearing, external gearing or no gearing. Standard features include two fittings for lubrication and integral seals to protect against contamination. The new HS Series data sheet is available for download at http://www.kaydonbearings.com/downloads.htm#other.

Kaydon Corporation Bearings Division
http://www.kaydonbearings.com/

Windpower Engineering & Development

These are just a few of the Thomson bearings available.

A recent Mechanical Motion Solutions brochure provides an overview of key product features and specs for the Thomson family of mechanical and electromechanical motion equipment. The brochure is available in English, French, German, Italian, Korean, Portuguese, Spanish, Swedish and Turkish.

Featured technologies include Linear Ball Bushing bearings and 60 Case LinearRace shafting, profile rail linear guides, ball and lead screws, specialty ball screws and components, True Planetary gearheads, linear motion systems, positioning slides, precision linear actuators, linear actuators, worm gear screw jacks, clutches and brakes, and precision balls.

Updates include information on the company’s new 400 Series Profile Rail Linear Guides and Micron AquaTRUE Planetary Gearheads. 400 Series Profile Rail Linear Guides are a cost-effective devices engineered to deliver accurate, reliable, and compliant linear motion in straightforward automation applications. Micron AquaTRUE Planetary Gearheads are the industry’s only 100% stainless steel gearheads intended to satisfy the demanding performance requirements of food, beverage, and pharmaceutical handling, packaging and dispensing applications.

A recent Mechanical Motion Solutions brochure provides an overview of key product features and specs for the Thomson family of mechanical and electromechanical motion equipment. The brochure is available in English, French, German, Italian, Korean, Portuguese, Spanish, Swedish and Turkish.

Featured technologies include Linear Ball Bushing bearings and 60 Case LinearRace shafting, profile rail linear guides, ball and lead screws, specialty ball screws and components, True Planetary gearheads, linear motion systems, positioning slides, precision linear actuators, linear actuators, worm gear screw jacks, clutches and brakes, and precision balls.

Updates include information on the company’s new 400 Series Profile Rail Linear Guides and Micron AquaTRUE Planetary Gearheads. 400 Series Profile Rail Linear Guides are a cost-effective devices engineered to deliver accurate, reliable, and compliant linear motion in straightforward automation applications. Micron AquaTRUE Planetary Gearheads are the industry’s only 100% stainless steel gearheads intended to satisfy the demanding performance requirements of food, beverage, and pharmaceutical handling, packaging and dispensing applications.

Thomson
www.thomsonlinear.com.

Windpower Engineering & Development

SKF DryLube Bearings come in four main variants to satisfy a range of applications. Tags: SKF, drylube bearings, maintenance free

SKF DryLube Bearings eliminates need for grease relubrication while performing reliably and almost maintenance-free over a wide temperature range. These next-generation high-temperature bearings especially suit hostile and extreme-temperature applications.

SKF DryLube Bearings are filled with a dry lubricant based on graphite or molybdenum disulfide with a resin binder. The dry lubricant is injected into the free space of the bearing, bonded to the cage, and cured until it solidifies. During bearing operation, the dry lubricant maintains a thin film on the bearing’s raceways and rolling elements to protect against metal-to-metal contact and potential damage caused by solid contaminants.

The bearings can lubricate applications up to 350ºC (660ºF), achieve higher speed capabilities than standard graphite-cage counterparts, and exhibit minimal lubricant loss over time. They also improve worker safety by reducing fire risks, eliminating slippery surfaces, and contributing to “green” operating objectives when compared with many oils and greases.

SKF Inc.

www.skfusa.com

Windpower Engineering & Development

SKF High-Capacity Roller Bearings include a lightweight brass cage to promote lower inertia to reduce the risk of roller smearing, cage guidance on the inner ring (shoulder) contributes to reduced roller slip, and more.

Separable High-Capacity Cylindrical Roller Bearings support high-speed shafts and high-speed intermediate shafts in wind turbine gearboxes. These reliable bearings have a higher load-carrying capacity and eliminate risks of roller-to-roller smearing and adhesive wear in service. Exchangeability with standard counterparts allows fitting them to existing design envelopes whether in initial designs or replacement upgrades.

The compact bearing combines and builds on the advantages of conventional and SKF High-Capacity Roller Bearings. Key features and benefits include a lightweight brass cage to promote lower inertia to reduce the risk of roller smearing, cage guidance on the inner ring (shoulder) contributes to reduced roller slip, reduced risk of smearing, and higher reliability. In addition, the right amount of play between rollers and cage bars provide greater safety and reliability, and black-oxidized rollers improve running behavior and oil-film buildup for more stable running conditions.

During maintenance, especially up tower, the separable design promotes quick and easy dismounting and mounting to help reduce operating, maintenance, and lifetime costs/kWh.

SKF USA Inc
www.skfusa.com

Windpower Engineering & Development

Some Goldwind turbines will ride on Timken bearings. This direct drive unit is in Minnesota.

The Timken Company and Xinjiang Goldwind Science & Technology Co., Ltd. have signed a memorandum of long-term strategic collaboration in the United States to cooperate on a range of technical services, products, and aftermarket support for the development, supply and maintenance of advanced wind-turbine components.

The memorandum’s three-year term extends and broadens an existing relationship between the two companies, with opportunity to multiply significantly their current collaboration. To support these efforts, Timken will develop additional capacity in China and at its other facilities focused on wind energy technology to support Goldwind’s expansion globally.

The memorandum reflects the highest level of collaboration between the companies, including the following Timken capabilities:

• Original-equipment design and engineering services;
• Testing at Timken’s new Wind Energy Research and Development Center scheduled to open in 2012
• Supply of bearings and adjacent power-transmission components
• Optimization of wind-turbine installations
• Field services and aftermarket lifecycle support for Goldwind’s growing installed base, including on-line intelligence monitoring systems, and
• Integrated supply-chain management and wind-farm sustainability services.

Goldwind and Timken executives said the memorandum reinforces their commitment to develop sustainable wind energy projects to strengthen the global balance of green power generation. The companies began collaboration on 1.5 MW wind turbines. In 2010, they signed an agreement valued at $26 million supporting development of additional, multi-megawatt projects.

Goldwind
www.Goldwindamerica.com

Timken Co.
http://www.timken.com/

Windpower Engineering & Development

A cross-sectional size of 25 mm x 32 mm so the UltraWind P1 Seal is intended to easily retrofit standard elastomer seals.

The Timken UltraWind P1 Seal is a significant wind-turbine bearing seal with a polyurethane design that provides increased resistance to abrasion for longer wind-turbine service life and more reliable performance than most other commonly used sealing materials. “Seals have an integral role in maximizing wind-turbine uptime and productivity because they prevent lubrication leakage and bearing contamination,” said Hans Landin, director of Process Industries original equipment and wind energy at Timken. “However, over time the cumulative impact of abrasive forces caused by varying loads and speeds, as well as extreme temperature fluctuations, rain, snow, debris, and lubrication challenges, can significantly reduce seal performance in wind-turbines. The new UltraWind P1 Seal addresses the problem with the latest polyurethane technology.”

In addition to its durable polyurethane base, the Timken UltraWind P1 Seal contains a variety of other features, including:

• A flexible sealing lip that handles misalignment or run-out in the application of the bearing. The lip’s special profile also helps minimize heat generation and cone wear while helping to accommodate bearing deflections.
• A corrosion-resistant, stainless steel garter spring that helps prevent rust.
• A machined design for a broader, more diverse range of applications, plus ease of installation via stress minimization. This design also allows for multiple positions at the cone lip OD contact; and

The Timken Company
www.timken.com

Windpower Engineering & Development

Learn how to properly maintain your wind turbine bearings

Replacing failed bearings in wind-power equipment is no easy task. But after 20 years of concentrated effort, bearing manufacturers have devised designs that carry loads that fluctuate with wind gusts and work well in electric fields around generators. Viewers of this Webcast will hear presenters discuss the problems with bearing that shorten their life and more importantly, how their recent designs improve wind-turbine reliability.

Windpower Engineering & Development