Wind turbine blade bearing friction

Wind turbine blade bearing enables pitching of blades for power control and rotor braking and is a critical component. High blade bearing friction is undesirable, as it may be associated with excessive heating of the surfaces, damage and inefficient operation. Thus, continuous observation of bearing friction level is crucial for blade bearing health monitoring systems. A novel algorithm for online monitoring of bearing friction level is developed combining physical knowledge about pitch system dynamics with state estimator, i.e. observer theory and signal processing assuming realistic sensor availability. Results show estimation of bearing friction torque required for condition monitoring, and a corresponding indicator signal which represents estimation of a relative friction coefficient.

Blade bearing for wind turbine

Wind turbines must be aligned optimally to the wind in order to prevent extreme loads and to provide the highest possible energy output.
The blade angle is always optimally adjusted to the wind speed via the balde bearing in order to control the performance of the wind turbine.The high loads from the dynamic stresses on the rotor blades must be safely dissipated into the rotor hub via the raceways and the screw connections.Very high loads occur in some instances from the dynamic load of the rotor blades. These loads must be transferred securely via the raceways and the screw connections of the blade bearings into the rotor hub. Single or double row four point contact ball bearings with a cage are used here, with internal or external gearing or without gearing, depending on the drive design.
As an essential component of the turbine safety design, blade bearings must ensure that the blades can be reliably and consistently adjusted under all operating conditions. A long operating life and high reliability are achieved thanks to the optimized dimensioning of the bearings and a maintenance concept tailored to the turbine and the operating conditions.The bearing can be produced with internal or external gear teeth or without gear teeth depending on the blade adjustment concept of the turbine.
In addition, the blade angle can be adjusted using electric or hydraulic systems. These use sealed plain bearings with the maintenance-free fabric, protected against corrosion by means of the corrotect plating.

Wire Race Ball Bearings

UWE wire race ball bearings comprise four race rings, balls,ball cage.The four race rings fit their raceway thanks to a specially developed grinding procedure-exactly adjusted to the ball diameter. Therefore, the rolling process does not occur directly between the rolling elements and enclosed construction, but rather smoothly on the four open race rings.
This special construction principle produces an extremely compact bearing, which also suits very small spaces. Another plus: the low friction and high load capacity of UWE wire race bearings reduce energy consumption.

UWE keeps designing and developing

UWE is experts in special bearings and satisfy unusual wishes. When antifriction is needed,we offer a broad range of options for this purpose. Parameters such as load rating, stiffness, preload and adjustment are just as variable as height, width and bore shape or the different materials.
The choice of design and materialfor the surrounding component is flexible. Steel, aluminium, non-corrosive, plastic or brass -our customers have free choice.This applies equally to the rolling elements, cages and race rings. There are different materials available for these too. The adjustability of the bearings does not stop there: we have different gears, seals, diameters, ball profiles etc. for our customers. It is not just the selection range that is unique, but also the way the bearings are made: in contrast to conventional bearings,the rolling process does not occur directly between the rolling elements and enclosed design, but rather smoothly on four open race rings. The raceways are matched to the ball diameter using a special grinding process. This special design principle produces an extremely compact bearing, which also suits very small spaces. Another plus: the low friction and high load capacity of our Antifriction Bearings reduce energy consumption.

UWE slewing ring installation munual

1.Slewing Ring Identification
If UWE finished bearings, all of these are accompanied by UWE signage. The signage is located near the soft belt (ball holes)of bearing raceway or according to user’s requirements . Signage on the identification code (Product Code) is the only available queries.
2.Important marker
(1)There is a raceway hardening soft belt mark on the outer ring and inner ring in the finished bearing.Soft position is on ball filling hole without marking if bearing has ball hole ring; marking "small hole" or compliance with "S" corresponding to hardened soft belt if there is no ball hole ring. Soft belt and marker can be determined according to user requirements.
(2)For toothed products, there are three biggest teeth relative to the raceway beating, located smallest (the tooth), maximum (external gear) diameters on the beating circle, and has a circular hole marker on the  tooth tip surface. Painting with red or green on the top of tooth.
3.Check before assembly
(1)Carefully open the package, not to damage the bearing surfaces and seals, especially bearing end faces, otherwise it will affect the quality of the bearing assembly. If you find the hole plugs shedding, will require detailed examination, cleaning, must ensure no foreign object into the lubrication raceway.
(2)Check and make sure that the installing bearing is matching your host.
(3)Confirm that the installing bearing has no shock and damage during transport.
(4)Check the seal is not broken.
(5)Check the hole location and ensure that no foreign object into the lubrication raceway.
(6)Check the beating tooth maximum point whether clear.
(7)Check whether the location marker on the soft belt clear.
(8)Check the anticorrosive coating surface is not damaged.

slewing ring introduction

Slewing bearing is a kind of special structure of rolling bearing,mainly including four-point contact ball slewing bearingcross roller slewing bearingthree row roller slewing bearing which are applied to wind power pitch/ yaw system, crane, ladle rotary table, etc. It keeps rolling bearings, machinery installation and gear transmission organic unifies in together, carrying axial load, radial load and tilting moment of joint action. It has compact structure, large carrying capacity, flexible operation, convenient maintenance and long service life, playing the role of supporting, rotating and driving. The instruction manual is for wind turbine bearing and other oversize slewing bearing.

slewing ring transportation and storage

During the transportation and the storage of UWE slewing rings, horizontal position is recommended; pay great attention to avoid any stroke, particularly in the radial direction.The slewing bearings must not be exposed to the elements,and must be used in short.It's recommended storage in shelter out of all weathers.If the expected storage time is superior to twelve months, it is advisable to ask for the treatment of those surfaces that normally don't receive it.On request, it is possible to have the surfaces treated with protective oil, washable with naphtha or grease removers.The slewing bearings are usually packed on a pallet of the same size, and wrapped with PE material; on request, It is also possible to supply a special packaging (according to the specific needs), using supports and materials fit to guarantee the best static and dynamic conditions for the transport and the storage of our bearings.

Special design, heavy-duty performance of wire race bearing

When weight savings and corrosion resistance needed, UWE wire race bearings are designed sucessfully. Wire race bearings are in a variety of military and commercial applications, especially wire race roller bearing.They give the load capacity of steel bearings with 60% less weight. UWE wire race bearings have stainless steel wire raceways in aluminum (or steel) support rings. In addition to saving weight, this design is more tolerant of non-rigid or out-of-flat mounting structures since it minimizes increases in rotational torque. With stainless steel wire and rolling elements and anodized aluminum support rings, UWE wire race bearings are very corrosion-resistant. They also offer thermal compatibility for support rings and mounting structures (i.e., aluminum with aluminum, or steel with steel).Bolt holes are provided for mounting.Various configurations are available,usually custom-designed to support a specified combination of thrust, radial and moment loads. When weight savings and corrosion resistance needed, UWE wire race bearings are designed sucessfully. Wire race bearings are in a variety of military and commercial applications, especially wire race roller bearing.They give the load capacity of steel bearings with 60% less weight. UWE wire race bearings have stainless steel wire raceways in aluminum (or steel) support rings. In addition to saving weight, this design is more tolerant of non-rigid or out-of-flat mounting structures since it minimizes increases in rotational torque. With stainless steel wire and rolling elements and anodized aluminum support rings, UWE wire race bearings are very corrosion-resistant. They also offer thermal compatibility for support rings and mounting structures (i.e., aluminum with aluminum, or steel with steel).Bolt holes are provided for mounting.Various configurations are available,usually custom-designed to support a specified combination of thrust, radial and moment loads. 


UWE large-diameter bearings are in the majority of cases supplied with spur gears. A gear cut into one of the bearing rings offers the advantage that an additional driving gear wheel is not required, which helps to reduce design work and costs.In the case of highly stressed gears, a tip radius should be provided on the pinion, and in the case of tip relief, an additional radius at the tip edge will be necessary.Mainly provided are bearings with corrected gearing, addendum modification coefficient x = 0.5 see DIN 3994, 3995.For gears subjected to high tooth flank stress,hardened gears have proven very satisfactory. Depending on module and ring diameter, the gear rings are subjected to spin hardening or individual tooth induction-hardening, the latter predominantly in the form of tooth contour hardening.Both methods provide improved flank load carrying capacity as well as higher tooth root strength. Flank hardening with hardness phase-out in the region of the root radii leaving the root radius unhardened will reduce the load capacity at the root. Hardened gears will require an individual calculation.We need to know the pinion data in order to be able to check the meshing geometry. During the installation of the large-diameter bearing and the drive pinion, adequate backlash must be assured.The backlash is adjusted at 3 teeth marked in green and is to be at least 0.03 x module.After final assembly of the equipment and after tightening all of the fastening bolts, the backlash must be checked using a feeler gauge or a lead wire.

Fastening bolts

The critical load curves shown in the static diagrams relate to strength class 10.9 bolts with a clamping length of 5·d and prestressed to 70 % of the yield point. For bearings without indicated bolt curves, the entire load capacity range below the critical load curves is covered by strength class 10.9 bolts.Analysis of the bolt curves must be based on the maximum load without factors.UWE technical quotation will show the number of bolts,strength class and required prestress for the bearing concerned and the loads indicated.Unless mentioned otherwise, the following shall be assumed:
a) The axial load Fa is supported, i.e. the axial operating force FA from the axial load does not exert any tensile stress on the bolts.
b) The bolts are equal spaced around the hole circles.
c) The mating structures are meeting our technical requirements.
d) Bearing and mating structures consists of steel.
e) No resin grouting provided.
f) The clamping length Ik is at least 5·d for bearings with a fully annular cross section and at least 3·d for profiled bearings, e.g. KD 210 type series.
g) There are at least six free threads available in the loaded bolt section.Where deviations in these conditions occur,prior consultation with us will be required.In order to avoid prestress losses due to creeping, the surface pressures in the contact areas between bolt head and nut/material of the clamped parts should not be exceeded. The selected product and strength classes of bolts and nuts must be guaranteed by the manufacturer to DIN/ISO standards.


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