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Premature bearing failures in wind gearboxes and white etching cracks (WEC)

Kenred Stadler, SKF programme manager renewable energy application development centre, Schweinfurt, Germany (corresponding author)
Arno Stubenrauch, SKF manager development cluster roller and plain bearings, Schweinfurt, Germany.

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Wind turbine gearboxes are subjected to a wide variety of operating conditions, some of which may push the bearings beyond their limits. Damage may be done to the bearings, resulting in a specific premature failure mode known as white etching cracks (WEC), sometimes called brittle, short-life, early, abnormal or white structured flaking (WSF). Measures to make the bearings more robust in these operating conditions are discussed in this article.

Ambitious worldwide renewable energy targets are pushing wind energy to become a mainstream power source. For example, the Global Wind Energy Council, GWEC1, expects that the currently installed wind energy capacity of 200 GW will double within three to four years, keeping open the aspir­ational goal of 1,000 GW of installed capacity by 2020.

Despite high wind turbine availability (> 96 %, depending on turbine), and a relatively low failure rate of mechanical components compared with electrical components, failures on mechanical drive trains still create high repair costs and revenue loss due to long downtimes2.

In most wind turbine concepts, a gearbox is commonly used to step up the rotor speed to the generator speed. Today, the actual service life of wind turbine gearboxes is often less than the designed 20 years. Failures can be found at several bearing locations, namely the planet bearings, intermediate shaft and high-speed shaft bearings (fig. 1).

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Much premature wind gearbox bearing damage results in a failure mode that is not caused by the classic rolling contact fatigue (RCF) mechanisms (fig. 2). While these classic mechanisms are sub-surface initiated fatigue as well as surface initiated fatigue and can be predicted by standard bearing-life calculation methods (refer to ISO 281 and ISO/TR 1281-2), premature crack failures are not covered by these methods. However, attempts to calculate bearing life have been made when detailed information of the case is available (e.g., local effect of hoop stresses)37.

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ISO 15243 describes the visual appearance of the classic rolling contact fatigue mechanisms.

White etching refers to the appearance of the altered steel microstructure when polishing and etching a microsection. The affected areas, consisting of ultra fine nano-recrystallized carbide-free ferrite, appear white in a light optical micrograph due to the low etching response of the material.

Known to occur only occasionally in some industrial applications such as paper mills, continuous variable drives, marine propulsion systems, crusher mill gearboxes or lifting gear drives, in wind applications the frequency of premature failures seems to be higher (but might be also related to a larger population of installed machines). Commonly, early cracks have occurred within the first one to three years of oper­ational time or at 5 to 10 % of the calculated rating life (fig. 3).

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Mostly occurring on the inner ring, as shown in fig. 4, the visual appearance of early cracks varies from straight cracks (“axial cracks”) to cracks in combination with small spalls and large/heavy spalling. Based on SKF’s knowledge from increased field experience, it is concluded that early failures by cracks are neither linked to a particular type of bearing (fig. 5) nor to a particular standard heat treatment (fig. 6) 6, 7, 8, 9, 10.

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The failure appearance, however, is associated with the heat treatment (e.g., residual stress field), the stage of failure progress and very likely also to the operating conditions or bearing position (e.g., stress field from loading). As can be seen in fig. 6, for early cracking in this specific application, cracks in martensite rings tend to grow straight into the material (suggesting the straight “axial” crack appearance, e.g., fig. 6a), whereas in bainitic (fig. 6b) as well as in carburized case hardened rings, the cracks tend to grow circumferentially below the raceway (explaining the spalling/flaking type of appearance, e.g., fig. 6c). Nevertheless, in a very advanced failure stage, the inner ring raceways are often heavily spalled, independent of the heat treatment.

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Challenges due to operating conditions in wind turbine gearboxes
Wind turbine gearboxes are subjected to a wide variety of operating conditions that may push the bearings beyond their limits (e.g., with respect to load, speed, lubrication and combinations of  these). The wind energy segment faces some of the toughest challenges for extending bearing life and reducing the occurrence of premature failures while at the same time reducing the overall cost of energy.

There are many opinions in the public domain summarizing common indications of severe operating conditions in conjunction with premature failures in wind turbine applications. These include:

  • periods of heavy and dynamic loads/torques – leading to vibrations and rapid load changes (e.g., transient raceway stress exceeding 3.1 GPa, heavy loads of 15,000 per year, impact loads)6, 7, 11, 12, 13, 14, 15, 17, 18
  •   depending on turbine type, additional radial and axial forces by the rotor, axial motion of the main shaft – leading to dynamical loading, higher stresses of gearbox components especially at the first stage19, 20
  • occasional connecting and disconnecting of the generator from the power grid – leading to torque reversals and bouncing effects (e.g., can lead up to 2.5 – 4 times higher nominal torque, impact loads)12, 15, 21
  • rapid accelerations/decelerations and motions of the gearbox shafts13, 15
  • misalignment, structural deformations (nacelle hub, housings)11
  • lubricant compromise between needs of gears and bearings as well as between low-  and high-speed stages, insufficient oil drains and refill intervals22
  • harsh environmental conditions – eventual large temperature changes and consequently larger temperature differences between the bearing inner ring and housing than expected when starting up, dust, cold climate, offshore, moisture23
  • idling conditions – leading to low load conditions and risk of skidding damage (adhesive wear)23
  • some design requirements can be conflicting, e.g., increasing rolling element size will increase the load carrying capacity but simultaneously increase the risk of cage and roller slip and sliding damage6, 7, 17, 23.

As stated, bearings may fail for other reasons not attributed to falling below best practice standards24, 25 and from other industrial experiences. Statistical evaluations of a limited number of offshore wind turbines2 indicate clearly a correlation between failure rate, wind speed and heavy and fluctuating loads. The trend towards larger turbine sizes with higher power-to-weight ratios will invariably lead to more flexible supporting structures11 that, in turn, will influence the load sharing and load distribution within the rolling bearings as well as on other drive components. According to reference 26, in “young”, heavily loaded applications having a highly innovative product design life cycle, sufficient experiences are often lacking with respect to the machine’s endurance. Independent of wind turbine and gearbox manufacturers, the presence of cracks on bearings is sometimes interpreted as indicative of uncontrolled kinematic behaviour19, 27.

Possible “rolling surface crack” drivers and review of hypotheses
The occurrence of premature failures is heavily discussed within the wind industry and independently investigated by wind turbine manufacturers, gearbox manufacturers and bearing suppliers as well as universities and independent institutions. Unfortunately, a consistent theory does not exist today. To list and explain all WEC failure root cause hypotheses would go beyond the scope of this paper.

Nevertheless, many of the existing theories from literature can be briefly summarized as shown in fig. 7. Many papers (for example, reference 10) discuss a local change in the bearing material microstructure into WEC by certain influen­cing factors.

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As influence factors, the following drivers are often mentioned:

  • material
    microstructure, heat treatment, natural hydrogen content, cleanliness (different type of inclusions), residual stresses, etc.
  • loading
    overloads, peak loads, impact loads, torque reversals, vibration, slip, structural stresses, electric currents, etc.
  • environment
    lubricant, additives, corrosion, tribochemical effects, hydrogen generation, temperature gradients, contamination (e.g., water), etc.
  • others
    mounting (e.g., scratches), transport, quality aspects, etc.

To increase the complexity, most influencing factors are also correlated.

Thus, driven by a single factor or by a combination of several factors, WEAs develop locally in the bearing steel matrix. The WEAs will then be the nucleation sites of cracks that finally propagate to the bearing raceway. As a consequence, the bearing will fail by spalling or so-called WSF.

Most common hypotheses can be further divided into hydrogen enhanced WEC developments28, 29, 30, purely load/stress related WEC developments preferable at inclusions31, 32 or some combination of reasons33.

Some of the above damage mechanisms seem to influence, for example, applications such as

  • paper mills (e.g., water in oil – corrective action based on condition of lubrication)34
  • marine propulsion systems (e.g., exceeding stresses – corrective action based on special through-hardened clean steel and stress reduction)32, 34
  • alternator and generator bearings (e.g., damaging current – corrective action by use of special greases and/or hybrid bearings, special steels)6, 35, 36.

Nevertheless, in general, the relevance of the common WEC hypotheses to premature wind gearbox failures is not sufficiently clear yet.

Potential root cause of WEC in wind gearboxes according to SKF experience
According to SKF experience, most early bearing failures are related to lubrication or other surface-related issues and can partly be estimated by the SKF advanced bearing-life model. SKF internal investigations have revealed that many cracking failure modes in wind gearbox bearing positions most likely have their origin at or near the surface (0–150 µm) and propagate into the material under the influence of a corrosion fatigue process6, 7, 16.

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There are several indicators that can support this hypothesis:
Wind gearbox bearings are relatively large, and for larger bearings the crack initiation and propagation mechanism can differ compared to small bearings6, 16. For instance, a deeper radial cracking is reported in larger bearings at moderate loads due to the residual stresses and higher hoop stress37.

In case of premature wind gearbox bearing failures, the failure occurrence suggests fast crack propagation. The fast branching and spreading crack propagation can be explained by the presence of chemical influencing factors such as oxygen and ageing products of the lubricant at the crack faces/tips6, 16, 38. In a completely sub-surface crack system, we have vacuum conditions and consequently significantly slower crack growth from pure mechanical fatigue38. In other words, already at an early stage, the cracks or crack systems must be connected to the surface to allow the entrance of oxygen and lubricant.

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Hydrogen-assisted fatigue can lead to similar effects28, 33, or to accelerated classic rolling contact fatigue6, 35, 36; however, this would require, for example, aggressive corrosive environment or continuous high-frequency electric current passage. The presence of free water leads, likewise, to a highly corrosive environment34, but elevated water contents in the lubricants are claimed to be under control by the turbine manufac­turers. Moisture corrosion in wind gearboxes is usually not seen during SKF investigations. If that can be excluded, then regenerative passivating tribolayers usually provide a barrier to corrosion and hydrogen absorption into the steel, if continuous and intact. All told, if hydrogen absorption occurs in the steel, it is detrimental; however, the available evidence of this failure mechanism in wind gearboxes is relatively weak.

Nevertheless, SKF tribochemistry studies confirm the local generation of hydrogen in severe mixed friction contacts. To continuously generate hydrogen, fresh, interacting metallic surfaces are needed. This could lead to a local weakening effect on the surface, facilitating a surface crack generation. However, in wind gearboxes, severe wear is hardly seen on the failed bearing raceways, which would allow hydrogen permeation. Thus, hydrogen permeation through the bearing raceway (without any additional factor) seems not to be likely. A potential additional factor could be the relative aggressive wind oils, eventually in combin­ation with contaminants39, 40, 41. In SKF’s experience, the performance of wind gearbox oils can be distinguished from surface initiated failure mechanisms39 (e.g., surface distress). To quantify the relevance, further investigations are needed. At the moment, the role of hydrogen generation is seen as a local effect generated in the crack systems due to lubricant entry leading to the mecanism of corrosion fatigue cracking (CFC)6, 16.

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The normally moderate bearing load conditions in wind gearboxes, the absence of compressive residual stress build-ups (in the area of the maximum von Mises equivalent stress) as well as the decrease in the X-ray diffraction line broadening close to the raceways in failed bearings (e.g., due to mixed friction – shear stresses and vibrations) shown by ma­terial response analyses further support a surface or near-surface failure initiation6, 7, 16. Lately, it is known that not only inadequate lubrication conditions, but also certain vibration effects at higher frequencies, are able to reduce the film thickness and consequently increase the risk for conditions of local mixed friction42, 43.

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According to reference 44, the generation of WEC networks is less influenced by Hertzian pressures, and most influencing factors are surface based. The often-disputed role of butterfly crack generation at inclusions, which show a similar altered microstructure as seen in WEC, is considered as part of the classic fatigue mechanism that is well covered in the bearing-life model7, 44, 45. Little experimental evidence is reported that supports butterfly cracks propagating into WEC networks10.

A high butterfly density is a sign of overstress or very heavy loading (> 3 GPa), but excessive loads are claimed not to exist by the turbine manufacturers. This seems to be supported by standard gearbox HALT tests. A highly accelerated life test (HALT) is a stress testing methodology for accelerating product reliability during the engineering development process. There, the metallurgical investigations often show an elevated number of butterfly formations in the bearings due to heavy-load test conditions, but failed bearings from the field often do not show a significant increase in butterfly formations6, 7. Especially at the high-speed stages, the loads are usually moderate, but bearings can still fail by cracks / WEC without showing a significant population or even individual exemplars of butterflies6, 7. It seems that standard gearbox HALT tests do need further adaptations to reflect the early failure mechanisms as seen in the field.

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Nevertheless, the occurrence of unexpected high sub-surface stress-induced bearing damage32 also by inclusions cannot be fully excluded as long as the exact contribution of transient running conditions is not fully understood. The exact loading of wind gearbox bearings in the field is very much based on wind field simulations, later on further reduced to quasi-static load assumptions; and moderate bearing loads are assumed at nominal conditions. Non-steady-state conditions should be kept in mind and are increasingly taken into account by the wind industry.

Potential mechanism for damage propagation:
There is a general agreement that it is not nominal wind gearbox operating conditions but rather transient, partly unknown, conditions that lead occasionally to disturbed bearing kinematics, loading and lubrication. Basically, it is assumed that high surface stress concentrations can be reached, e.g., by vibration-induced local mixed friction6, 16, 47, misalignment or other events as already mentioned.  At boundary lubricated patches at asperity level, the stress concentration of the tensile stresses can increase and open a crack under repeated cycles (areas of high stresses just below the roughness)48, 49.

As schematically shown in fig. 8, transient conditions can trigger surface cracks, possibly accelerated by tribochemical effects6, 16, 39, 40, 41, or sub-surface cracks that reach the raceway when starting at weak points such as inclusions close to the surface (< 150 µm)6.

The inclusions can be soft MnS or hard oxides that naturally exist in any bearing steel. In addition, small MnS lines at the raceway can sometimes be dissolved by the lubricant and act also as potential surface cracks6, 16 and/or environmental corrosive cracks. Examples of a shallow surface crack are shown in figs. 9 and 10, and often it requires significant effort and experience to find them at an early stage6, 7, 16.

The cracks shown in figs. 10 and 11 are generated in an automotive rolling-sliding contact at high traction and contact pressures, similar to potential wind load situations of around 3 GPa18.

Once the bearing raceway is locally damaged, the highly EP doped lubricant will penetrate into the crack. Depending on the crack orientation, hydraulic effects will additionally push the crack propagation46. As indicated in fig. 12, the lubricant (often aged and/or contaminated with water) will react inside the material at the fresh metallic crack flanks. In other words, a corrosion fatigue crack propagation process, CFC, is triggered.

This leads to a hydrogen induced microstructure transformation by means of hydrogen release from decomposition products of the penetrating oil (additives, contamin­ants) on the rubbing blank metal crack faces that in turn further accelerate the crack propagation6, 7, 16. This conclusion is also supported by spatially resolved determin­ations of the hydrogen content in damaged bearing rings, which confirm that hydrogen absorption occurs late in the damage process7, 16. As shown in fig. 13, a fractographic investigation in the preparative opened forced fracture face close to the inner ring crack reveals an intercrystalline microstructure that indicates mater­ial embrittlement by hydrogen, released from the ageing lubricant products6, 7, 16, 41, whereas distant from the CFC crack, a normal largely transcrystalline fracture face is seen. Further indication of such a CFC mechanism is found by EDX analysis of lubricant and additive residuals within the opened crack system6, 7, 16.

Inside the crack system, the mechanism of CFC will then transform the microstructure locally into white etching areas and lead to the typical appearance of an irregular WEC network (e.g., figs. 2, 6, 14). Thus, WEC are considered as secondary; a by-product of the CFC mechanism, as the hydrogen released and energy dissipated at the crack flanks result in a local change of the microstructure then appearing as a white etching crack decoration.

The distribution and intensity of the WEC decoration effect is relatively complex. It depends very much on the distribution of lubricant residuals inside the crack network, the local rubbing effect in the crack faces and the local equivalent stress fields.

Finally, fast three-dimensional crack propagation/branching in combination with crack returns will lead to a fast failure of the concerned rolling bearing surfaces.

Conclusion and SKF prevention strategy
The fast growth of the wind industry as well as the trend to increasing turbine sizes erected at locations with turbulent wind conditions puts significant challenges on the rolling bearings in the drive train. One consequence of this evolution of a relatively young industry has been premature gearbox bearing failures. Over the years, the discussion in the industry was mainly focused on the influence of bearing material and heat treatments. Recently, there is a general agreement that specific wind conditions can lead to disturbed bearing kinematics, loading and lubrication. In other words, the root cause failure will not be found inside the bearing only. The complete application interfaces between the bearing and the gearbox / turbine need to be considered.

The phenomenon of wind gearbox bearing failures by cracks / WEC has been described. A failure hypothesis has been introduced. SKF investigations reveal that cracking failure modes in critical wind gearbox bearing positions most likely have their origin at the surface or near surface and propagate further into the material under the influence of a corrosion fatigue process.

Due to the high complexity of a wind turbine as well as the very different bearing locations that can be affected, it is very unlikely that there is only one application condition root cause. However, it can be stated that any condition that leads to disturbed bearing kinematics, such as high vibration levels and high sliding friction, should be avoided in order to reduce micro-wear and high tensile stresses.

To effectively support the wind industry, SKF as a bearing manufacturer is focusing on bearing modifications that aim to reduce the risk of premature bearing failures and increase bearing robustness under the specific conditions of wind gearbox applications. The solution strategy takes into account mainly the hypothesis introduced, but also addresses the common theories on WEC.

Most failure prevention strat­egies have been positively confirmed by internal investigations and SKF field experience. Today’s state-of-the-art failure prevention measures are:

  • SKF special passivation
  • to stabilize the near surface microstructure
  • to make the bearing more resistant to chemical attack and hydrogen
  • to reduce micro friction under peak loading
  • to improve running-in
  • SKF special clean steel for the most stressed component
  • to reduce further the amount of inclusions that can act as stress raisers in the material or on the surface
  • SKF deep surface strengthening process on the most stressed component (prototypes)
  • to allow a conditioning of the component (shake down – the nominal loading in wind is relatively moderate)
  • to increase the resistance against surface crack initiation and sub-surface crack propagation.

In summary, a bearing modified as described above can reduce premature failures but needs to be combined with further improvements of the total design in light of the actual application conditions. Therefore, collaboration between all partners in the design process is needed and advanced calculation tools should be used to analyze the operating conditions to identify critical operating conditions and to eliminate the potential damaging ones. A stronger focus on component testing combined with real-size dynamic tests (e.g., in research institutes such as NREL, NAREC, Fraunhofer, etc.) should enable reproduction of damaging operating conditions and the testing of potential solutions.

References (pdf)

 

Kenred Stadler, SKF programme manager renewable energy application development centre, Schweinfurt, Germany (corresponding author)
Arno Stubenrauch, SKF manager development cluster roller and plain bearings, Schweinfurt, Germany.

source: Evolution – the business and technology magazine from SKF

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哥德堡,2013年4月7日——在2013年汉诺威工业博览会上,斯凯孚以“展现斯凯孚知识工程的力量”为主题,推出了一系列产品和解决方案.     近年来,我们将知识集中运用于开发解决方案和不断创新中,以帮助客户在今天、明天乃至未来立于不败之地。我们正在关注完全经过实践验证的解决方案 —— 这些方案在盈利能力和可持续性上具有可以量化的效益. 现在,与斯凯孚合作所带来的优势比以往更多。我们贴近行业客户,并且找到了巧妙的方法利用所获得的知识创造有形价值。今天,我们致力于在资产生命周期从设计至维护的各个阶段中,对机械资产进行追踪,帮助客户改善流程,从而产生更好的结果。 自1907年起,斯凯孚就已成为全球技术供应商中的领导者。斯凯孚的根本优势在于其能够不断开发新的技术,然后运用这些技术创造具有竞争优势的产品。这主要得益于我们将来自斯凯孚技术平台(轴承和轴承单元、密封件、机电一体化、服务和润滑系统)的专业知识与从40多个行业总结得来的实践经验相结合。我们把这称为斯凯孚知识工程。 斯凯孚知识工程是三大业务维度的结合: 1. 文化/地理维度:理解我们生活和工作所处的地区和文化 斯凯孚是一家全球化公司,在世界各地设立分支机构。不论身处何地,我们能够完全理解斯凯孚客户,甚至他们客户的需求。我们的驻地专家在全球各行业专家的支持下,深度分析客户需求,并从全球案例中找到相似情况下的成功案例。 所有这些解决方案的成功实现都依托于一个全球范围的生产系统和细致入微的服务支持网络。 2. 客户维度:工业和行业 斯凯孚为超过2,000,000家客户提供服务。斯凯孚在应用领域中十分活跃,迄今为止,重点关注于约40个行业。涉猎如此之多的领域使斯凯孚积累了足够的经验,能够根据行业特定需求开发产品和服务,并且熟知来自一个行业的知识何时能够被成功应用于另一个行业。这意味着我们已充分了解应用需求和工况,开发出相匹配的解决方案,并且根据行业技术和工程发展不断改善各种解决方案。 3. 竞争力维度:我们的五大技术平台 SKF专家团队在多个领域具备竞争力,如:轴承及轴承单元、密封件、机电一体化、服务和润滑系统,各个团队紧密合作,提供先进的综合解决方案。 通过斯凯孚解决方案工厂网络,中小型原设备制造商客户和终端用户获得了个性化的支持,解决了所面对的特殊挑战。在此,他们能够运用斯凯孚集团五大平台的广泛经验,并且能与本地的斯凯孚工程师进行讨论。斯凯孚通过这一方式为客户提供或开发定制解决方案。 斯凯孚解决方案工厂所提供的各种支持包括:应用工程、轴承和润滑分析、远程状态监测分析、工程咨询、直线运动系统、动力传动产品、密封解决方案、能源和可持续发展管理、资产管理系统和专业技术、主轴翻新、轴承再制造以及各种培训计划。 每一家斯凯孚解决方案工厂都是该网络的一部分,可将全球任一地点获得的知识快速传递并应用至另一个地方。这加速了解决方案的开发,并且促进了知识库的不断扩大。 斯凯孚核心竞争力为知识工程提供支持 自1907年斯凯孚创立以来,SKF集结整个集团的力量,专注于研发领域,获得了无数创新成果,且建立了全新的轴承业标准,开发出全新产品和解决方案。2012年,公司共完成663项发明,初始登记在案的专利申请数量为421件。基于这些专业知识的积累,斯凯孚能够帮助客户提高生产效率,取得更大的成就,创造更多利润。 斯凯孚能够持续开发增强客户竞争优势的产品和服务,这一能力来自两个途径:投资于核心技术领域和专业人士并整合由此获得的知识来满足特定要求。 生命周期管理: 在斯凯孚研究项目中,主要致力于改善客户应用生命周期中的环保性能的项目比重不断增加。这意味着无论在产品生命周期的哪个阶段,我们都会考虑产品或制造流程的环保效益。 为了支持这一积极的发展并促进更具环保性能的技术的使用,斯凯孚近期致力于生命周期管理方案,旨在不断提高斯凯孚产品和制造流程的环保性,同时通过调整日常业务方法和工具将这些知识应用于实践。 可持续发展/环境: 一百多年来,斯凯孚始终关注可持续发展。自从我们于1907年开发出全球第一款自调心球轴承起,斯凯孚就已认识到通过减少摩擦,使运转更加顺畅的重要性。当摩擦减少时,所需的能量也会相应减少。今天,大家都深知使用化石燃料发电对环境所产生的影响。在斯凯孚,我们坚信保护自然环境实际上也是造福于我们的业务,并且是我们所应该做的。现在,我们迈入第2个百年,看到了更大的机遇,同时也承担着更大的责任:我们要在解决全球环境可持续发展这一难题上扮演重要的角色。2005年,我们提出了斯凯孚超越零(SKF BeyondZero*)概念,旨在实现以下两个目标: 减少斯凯孚运营对环境的负面影响,以及 通过创新和提供更具环保性的新技术、产品和服务,增加斯凯孚解决方案对环境的正面影响。 斯凯孚超越零结合了这两大目标,是斯凯孚针对地球所面临的环境问题,作出全方位积极贡献的一次尝试。 全新的斯凯孚超越零组合以及斯凯孚新气候战略和参加世界自然基金会气候拯救者项目的相关目标同样证明了斯凯孚对可持续性和环境的承诺。至今,斯凯孚是唯一一家被纳入气候拯救者项目的工业工程公司。该项目旨在以一种符合实际、可以衡量并且能够被外部专家验证的方式减少二氧化碳等温室气体的排放。斯凯孚专注于汽车和众多客户行业,始终致力于开发能够在设备和机械生命周期各阶段实现这些目标的产品和解决方案。 在汉诺威工业博览会上,斯凯孚展台展出了众多斯凯孚超越零组合产品和解决方案。其中一款引人注目的新产品便是专为污水处理设施通气鼓风机系统开发的驱动解决方案。该产品配备高能效高转速永磁电机、有源磁性轴承 (AMB) 和集成AMB控制系统,能够减少高达40%的能耗。当用于350千瓦鼓风机中时,每年可节能500,000千瓦时,相等于减少了375吨二氧化碳排放。 传感化/状态监测: 为了满足客户对于降低安装成本、缩短安装时间以及增加部件寿命的需求,斯凯孚开发出能够高效利用无线技术的产品。 越靠近接触区进行运行状态监测,系统性能研究就越精确。除了温度之外,速度、旋转方向和振动之外,安装在轴承或轴承座外侧的传感器还能监测载荷,斯凯孚继续致力于这一领域的开发,取得了轴承状态监测领域的突破性创新 —— 基于无线技术的斯凯孚洞悉(SKF Insight™)。现在,借助在各种技术上的突破性进展,轴承无需外部电源、传感器、电缆或电子数据采集装置就能持续传送运行状态 ,因为一切都集成在轴承内部。 斯凯孚洞悉(SKF Insight™)解决方案包括: 测量转速、温度、速度、加速度、声发射和载荷等重要参数的微型传感技术组件。 自供电 —— 智能轴承可利用应用环境自行产生运行所需的电能。 无需安装传感器或电缆的简洁设计 —— 智能无线通讯技术集成于轴承内部,使其能够在传统WiFi无法运行的环境中进行通讯。 智能轴承网络

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