Using Schffler Solutions to Reduce System Costs

2014-03-10 | 000-004-880 DE-EN

SCHAEFFLER AG, BARCELONA/SCHWEINFURT

Schaeffler at the EWEA 2014 in Hall 6, Booth 6C50

Using Schaeffler Solutions to Reduce System Costs

Schaeffler offers reliable components that can withstand very high loads and, due to their individual design, contribute towards reduced system costs for wind turbines. The system cost valuation, in other words, the analysis of the overall system and the interaction of the subassemblies fitted in this system, plays an important role in price and cost optimization.

The design and bearing geometry selected for the bearing support, the materials used, and the application-specific bearing design, through to validation of the application are also important contributing factors that Schaeffler takes into consideration in order to increase reliability and efficiency whilst reducing system costs.

INA slewing rings with optimized internal geometry

Wind turbines must be adjusted according to the wind conditions. The tower and the rotor blades are adjusted so that they make optimal use of the wind conditions and are not subject to excessive loads that could cause damage. The high loads that occur from the dynamic load of the rotor blades must be transferred safely via the raceways and the screw connections into the rotor hub.

Schaeffler currently develops and manufactures slewing rings with an outside diameter of up to 4,100 millimeters that are used as pitch bearings for wind tracking applications. Due to their design, they can transmit radial and axial loads as well as tilting moments. They are designed as single row or double row four-point contact bearings without gear teeth or with internal and/or external gear teeth. Their reliable operation is an essential prerequisite for the cost-effective operation of wind turbines.

As a significant component of the safety concept of a turbine, slewing rings must ensure that the rotor blades can be reliably and evenly adjusted under all operating conditions. A long operating life and a high level of reliability are achieved by optimally dimensioning the bearings and by a maintenance concept specially designed to suit the turbine and the operating conditions.

Shaeffler has developed a special method for making steel running surfaces to ensure low frictional torque and a highly effective sealing action to protect the bearing. Thanks to their optimized internal geometry, INA slewing rings are characterized by having a lower frictional torque than conventional pitch bearings. This allows the use of more compact gearboxes, low-torque motors, and less powerful convertors, which, in turn, leads to reduced system costs.

In collaboration with the steel industry, Schaeffler has developed a quenched and tempered steel, which is specially designed for slewing rings subject to extreme loads during tower and blade adjustment. This newly developed steel also enables complete quenching and tempering of large ring cross-sections, which, in turn, provides maximum strength. Furthermore, zinc flame-sprayed surfaces, multi-layers of painting, and finished seal running surfaces ensure the highest level of reliability, operating life, and protection against premature damage such as fatigue in the raceway and surface corrosion. The bearings are suitable for temperatures of up to minus 40 degrees Celsius due to the material and the applied surface protection.

High-Capacity bearings in gearboxes: Increased load rating with reduced friction

The bearing technology in wind turbine gearboxes is faced with the challenges posed by highly-dynamic forces with extreme peak and minimum loads, sudden alternating loads, and also varying operating temperatures. Planetary gear bearing supports are extremely challenging bearing positions because of the high radial loads that occur. Only a limited amount of space is available for this bearing support, and the planetary gears, which have comparably thin walls, tend to distort leading to rotation of the bearing outer ring in the planetary gear. The FAG high-capacity cylindrical roller bearing combines the advantages of full complement bearings and cage-type bearings due to the particularly streamlined design of the cage. This allows space for at least one additional rolling element in the bearing and increases the load rating. Due to the bearing cage, the high-capacity bearing has a significantly lower friction than full complement variants which simplifies bearing mounting: The cage design is self-retaining so that the rolling elements are retained in the cage when the ring is removed.

In addition, all cylindrical roller bearings are offered with black oxide coated rolling elements. Schaeffler has developed the coating system Durotect B, which minimizes the risk of damage caused by slippage, improves the running-in behavior, and last but not least, provides protection against corrosion.

Modern simulation and calculation programs

Schaeffler uses state-of-the-art calculation and simulation programs to ensure optimal designs for bearings for wind power gearboxes are produced. This applies for the entire system starting from a single rolling bearing and its components, the adjacent construction, through to the entire power transmission system.

The software Bearinx can be used to model and calculate all bearing types, complex shafts, shaft systems and even complete gearboxes. The internal load distribution in the bearing is calculated precisely - including contact pressure taking account of the rolling element profile. Based on the individual rolling contact loads, Bearinx determines the calculated bearing life more precisely than ever before. The dynamic behavior of the entire wind turbine is mapped with hybrid, multi-body simulation (MKS). Individual components of the power transmission system and the entire turbine design can be improved in the development phas

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