当你旋转机械的总体管理alth, the condition of your rolling element bearings plays a critical role. A single bearing failure alone can cause machine shutdown, resulting in costly downtime and production loss.
At Bently Nevada we offer a wide range of bearingcondition monitoringtools, software, and equipment for early bearing fault detection and diagnosis. From vibration sensors to data acquisition tools and diagnostic software, we have the solutions you need to keep your plant running efficiently and effectively. Properly designed and carefully lubricated bearings can have virtually infinite life. However, given enough time all REBs will eventually fail through a fatigue mechanism that can be greatly accelerated by poor installation, overloading, improper lubrication, or contamination.
Explore Bently Nevada's full range of asset performance management and monitoring solutions for protecting your plant-wide machinery and preventing unplanned downtime.
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滚动元件轴承取决于极其薄的润滑剂层，以使滚动元素/竞赛接触降至最低。滚动元件实际上是一定程度的，并且润滑剂形成了一种弹性水力动力楔，可使元素分开。元素的分离是典型表面粗糙度的几倍，小于微米（或几英寸）。润滑流体还实现了消除通过在元素和种族之间非常小的缝隙中剪切产生的热量的目的。如果润滑供应不足，则会发生金属对金属接触，从而产生磨损并可能涂抹种族。润滑剂必须干净并且适合负载和工作温度的合适类型。滚动元件轴承可以长时间生存，而相对较少的润滑剂可以很好地生存。过度润滑可能会导致润滑剂剪切应力高温，并实际上导致轴承衰竭。
轴承润滑问题的一些迹象包括：
- 变色
- 得分和剥离
- Roller end/Bearing metal temperature
- 轴承锁定
润滑剂的清洁度对于悠久的寿命至关重要。如果污垢颗粒直接或通过石油系统进入轴承，则颗粒可能会被困在滚动元件和种族之间。如果粒子具有足够的硬度，则在粒子接触处产生的极端应力将导致种族和/或元素材料的局部塑性变形。这将产生一个永久性凹坑，将充当潜在的裂纹成核位点。即使是被困在滚动元件和种族之间的微米大小的碎片也可能导致局部塑料屈服，并在两种表面或两个表面形成一个小坑。坑边界的相对较小的半径充当应力浓度因子，并大大增加了疲劳裂纹的可能性。大粒子也可以以减少元素滚动动作和增加滑动运动的方式堵塞。在滑动运动过程中，污垢颗粒可以像犁一样起作用，在竞赛表面形成永久性凹槽。
轴承油污染问题的一些迹象包括：
- Bearing wear
- Bearing pitting
- Bruising
Many bearings have been doomed during installation. Bearings must be handled carefully and installed in accordance with manufacturer’s specifications. If interference fits are used on the bearing rings, care must be taken to avoid deformation or cocking of the rings during installation. Cocked or misaligned bearing rings will produce abnormal loads in the bearing. Incorrect fits can also subject the bearing to abnormal loads. And although this may seem obvious, bearings should never be pressed on in such a way that the press load is delivered across the rolling elements. The high press loads can cause the balls to permanently dimple (brinell) the races.
Bearing misalignment often results from improper fit of housings and shafts. Common issues include:
- Bent shafts
- Out-of-square shaft shoulders
- 隔离垫片
- 固定的夹紧螺母
- 安装不当和宽松
If the designer fails to consider all the possible loads that can occur in service, the bearing selected for the application could be incorrect. If the service loads exceed the design intention, then the bearing will fail prematurely. It is important for the designer to be aware of the static and dynamic loading that may be present in service. On the other end of the load spectrum is the situation where the bearing is very lightly loaded. In this condition the roller skids rather than rolls, which is also not desired. It is also possible that during assembly or repair a wrong bearing was installed.
Bearing life is very sensitive to loading. Bearing loads can be classified into static loads, which have constant magnitude and direction, and dynamic loads, which can vary in both magnitude and direction. To properly size a bearing at the design stage, a machine designer must consider both types of loading and their influence on the predicted life of the bearing. If during service the loads in a machine deviate significantly from design values, bearing life will be affected. Misalignment is an important source of excessive static load. Properly designed and sized couplings will accommodate misalignment to some degree, but if misalignment exceeds the capability of the coupling, then excessive loads may appear at the bearing. Another important source of static load is a belt drive. Dynamic loads are introduced by many rotor malfunctions, but may also result from the work the machine is doing. Unbalance, rub, or aerodynamic or fluid-induced instability can produce dynamic loads that exceed design limits and reduce bearing life. Also, coupling malfunctions may introduce excessive static and dynamic loads.
Brinelling is a form of non-rotating load damage. When a rotor is stopped, the rolling elements in bearings remain in one position. If the machine is subjected to a shock load, the elements (especially balls) can plastically deform the races, creating a permanent set of pits. This has happened to new machines being shipped by rail or truck. The machines arrive at the plant only to find that the bearings are ruined. To prevent this kind of damage, vulnerable machinery is usually rotated on turning gear during shipment. It is normal that a spare (stand-by) machine is exposed to some level of vibration while not operating. Its static load will press lubrication away from the bearing load zone, allowing metal to metal contact between elements and races. If the vibration is high enough, when the primary machine fails after a long period of service the spare machine’s bearings may fail due to brinelling damage shortly after it is put on-line and before the primary machine is repaired. A preventative measure is to run the backup machine periodically.
Improper electrical grounding can cause a current to flow through rolling element bearings. If arcing occurs, small quantities of bearing material are vaporized in the small, high temperature electric arc. This vaporization effectively removes material from the rolling element or bearing race or both. The resulting pit acts as a stress concentrator that is capable of nucleating a fatigue crack, leading to eventual failure. The damage caused by the electrical arc is similar to electrical discharge machining (EDM), and takes place on motors with a variable frequency drive. On rare cases this can also be due to buildup of static charge from the process fluids and materials.
Assuming that a bearing is properly loaded, clean, and supplied with a correct amount of clean lubricant of the proper type; failure of a typical rolling element bearing is still inevitable because of fatigue. Rolling element-bearing loading differs substantially from the type of loading that is found in other engineering structures where an endurance limit can be used to guarantee freedom from fatigue failure. Unfortunately, no such endurance limit exists for rolling element bearings, and fatigue failure of these bearings will eventually occur. As the bearing evolves toward fatigue failure, spalling occurs on the outer race, inner race, or elements. As rolling elements encounter spall pits (or as damaged elements rotate), the impact/response vibration tends to repeat at characteristic frequencies, called bearing defect frequencies, often referred as fault frequencies. Each bearing has a set of defect frequencies associated with inner race, outer race, element, and cage defects that are determined by its particular geometry and operating speeds.
The an ideal scenario, machines with Rolling Element Bearings would be monitored in the same way as critical journal bearing machines (vibration transducers at each bearing, bearing temperature, Keyphasor† sensor, online monitor). However, it can be economically difficult to justify that level of monitoring. The best method for monitoring bearing temperature, wear and overall condition is throughonline monitoring- using either a permanently installed, continuous or scanning systems. With an online system, a propertransducer suiteis needed to detect when a machine is having a problem.
在没有在线监控系统的情况下portable data collector(PDC)是下一个最好的方法。的一个重要组成部分tablishing a PDC route is defining how often the data is taken. The more often the data is collected, the more likely an early bearing failure detection will be made. But as a consequence, the cost of the condition monitoring will be higher due to more frequent data collection and analysis. The route creation and timing depend on the machine operating hours, running speed, load, process and environmental conditions, and so on.
有关滚动元件轴承监控的更多信息，请联系内华达州的宽松应用程序和解决方案架构师或机械诊断服务工程师，以帮助您提出建议。
Case Studies
Orbit 60 Series内华达州的下一代机械保护和状况监测是旨在在广泛的工业应用中，旨在成为所有关键机械资产以及跨植物资产的最先进的系统。Orbit 60 Seriesis built on a fully distributable architecture that allows you to monitor all your assets regardless of complexity or location and is intrinsically cyber secure.
OurSystem 1†Condition Monitoring softwarehas been designed as an all-in-one answer to even your most difficult machine asset management and health monitoring challenges. Building on the strategic pillars ofConnectivity，，，，Analytics，，，，and可视化System 1平台提供了整个植物的关键资产监控数据和分析解决方案，您需要保持植物平稳运行并避免不需要的停机时间。
System 1’s connected platform gathers and stores important machine health data across your entire enterprise in one central location, for real-time analysis, diagnosis and preventative condition-based maintenance planning. Make data-informed decisions and achieve true operational intelligence withSystem 1。
当您需要实时振动和温度监测以及在无线网络中快速，简单部署多个传感器，加密数据传输，较长的电池寿命以及在危险环境中工作的能力时，Ranger Pro就是您的答案。