HAMBURG/HERZOGENAURACH/SCHWEINFURT, May 13, 2004. The development of new wind turbines leads to new challenges for this industry: Rolling bearings must withstand highly dynamic loads and operating conditions, not all of which have been fully researched. INA and FAG engineers are performing basic work here and develop new solutions with their customers.

Rotor bearing supports

In many cases, the rotor is supported by two bearings: in the form of a classic locating/non-locating bearing support, as a bearing support requiring adjustment or as a "non-locating bearing" with a bearing in the three-point support aided by the gearbox. The input shaft bearing of the gearbox is often used as a non-locating bearing for the rotor. INA's and FAG's range of catalog products is so extensive that it covers the majority of all applications. Suitable bearings are designed and manufactured in close cooperation with the customer, for instance in cases where the rotor bearing supports are completely connected to the gearbox. Multi-MW equipment for offshore applications use rotor bearing units from two large rows of bearings with relatively little distance between them. In a 3-MW plant, the outside diameter of such bearings can be more than two meters. However, integrating rotor and gearbox bearings allows short section heights.

The housing for the bearing supports was also designed by FAG. FEA calculations ensure that forces and moments are supported in an optimum way and using as little material as possible. Lubricants, seals and other accessories are also supplied from a single source. In this way, all components are integrated in the complete bearing supports system without any problems. Our goal is to follow a product development process with our customers that considers all important aspects of an application in order to increase equipment availability.

Gearbox bearing supports

Rolling bearings in the gearbox, usually cylindrical roller bearings, connect shafts, gears and housings. Any failure in the interaction of these components results in rolling bearing damage. Even minor changes can be recorded and diagnosed by the monitoring services supplied by F'IS (FAG Industrial Services) - long before the actual damage occurs. This makes it possible to plan for maintenance work ahead of time.

Condition monitoring meets the special requirements of the wind power industry. Operating conditions for rolling bearings in wind turbine gearboxes are not comparable to those in stationary gearboxes. In wind turbines, highly dynamic effects can occur that include extreme peak loads, heavy load changes, weak loads with long time periods and extreme temperature fluctuations. Rolling bearings are exposed to wind load dynamics from the rotor and to the dynamics of the electrical network.

The deformation of the gearbox housing places an additional load on the bearings. Peak loads are also a result of fast braking operations using high speed brakes. Recently developed simulation calculations for the cynamic behavior of the driveline will lead to complete load factors and complement previous factors from analogies and measurements.

Condition monitoring for bearings

Monitoring vibrations in wind turbine bearings allows operators to prevent unplanned downtimes, detect damage at an early stage and watch damage progress. Emergency shutdowns are initiated for predefined conditions, thus preventing subsequent damage. Service and maintenance can be planned. Remote monitoring and online data transmission are state of the art at F'IS and are especially attractive for offshore facilities that are not accessible for months at a time. Costs for hardware and monitoring by FIS specialists are only a fraction of the costs of a damaged gearbox - not to mention unplanned machine downtime. The Wind Turbine Protection System - or WiPro for short - is one of just a few condition monitoring systems that meet the requirements listed by Allianz Zentrum für Technik.

Lubrication

The lubricaton system used plays an important part in the reliability of the bearings. Oil performance, effectiveness of additives and cleanliness with regard to contamination all determine the quality of a system. Some of the problems that
were found could clearly be attributed to inadequate lubrication. This experience was the basis for requirements for powerful filtration systems and condition monitoring for important lubricant parameters such as operating temperature, contamination, water content and viscosity.

Service

INA and FAG place a great deal of emphasis on providing customers with expert advice regarding the selection of economical bearing supports. Experienced external sales engineers at more than 100 locations in all of the important world markets guarantee that customers benefit from this unique expertise.This service includes the use of Bearinx® to calculate bearings as well as advice on design, mounting and lubriation. Program packages offering linked calculations and the possibility to print out results, including graphics, are indispensable for design and documentation.

In addition, a detailed analysis of operating and condition characteristics provides important information for making improvements in the future. The Schaeffler Group's Industrial Division and F'IS offer their customers visual monitoring by experts as well as thorough investigations using a scanning electron microscope, X-ray structural analyses and lubricant tests.

As wind turbine performance increases, so do rolling bearing dimensions. This is why bearings must be mounted very carefully, a task requiring experience. F'IS offers worldwide mounting services carried out by experienced setup experts and certified service partners when it comes to the acceptance of adjacent components, installation and dismantling, inspection and maintenance. In short - by working with INA, FAG and F'IS, customers obtain increased operational safety.

The Schaeffler Group, which includes the INA Group, FAG and LuK, is one of the leading rolling bearing manufacturers and automotive suppliers worldwide. A total of 54,000 employees achieved sales of approximately 7 billion euros last year.


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