On a Roll: Raising standards for collecting bearing data

Writer: Eric Bearing Limited

SKF is developing a fully commercial version of its Sensor Roller – which will gather detailed information from large bearings such as those used in wind turbines.Information is everything in modern engineering. The ability to collect and analyse ‘big data’ is practised across the sector, from factory floor production to operating remote windfarms.

This is increasingly done by smart components that gather, analyse and transmit process data. For bearings, critical details such as load, rotation speed and temperature can be used to calculate bearing life. This, in turn, helps to improve the performance – and lengthen the life – of key assets.

One system that can perform this is SKF’s Sensor Roller system. It uses rollers embedded with sensors to gather several types of data. This data can be transmitted wirelessly to maintenance staff, allowing them to gain an instant picture on the state of a piece of machinery. It is typically used in large bearings, as the roller must be of a minimum size (in order to accommodate the electronic components).

Magic performance

The Sensor Roller system grew out of the older Magic Roller system, which was developed more than 30 years ago. The Magic Roller was relatively crude by modern standards: for example, it used a large external coil to power the roller electronics. Incorporating the coil, which was relatively expensive, also required equipment to be modified.Also, it was only capable of measuring loads and could not gather other data such as temperature and rotation speed directly. Overall, the system was relatively limited in its use, and was generally aimed at troubleshooting.

The modern Sensor Roller system is far more sophisticated and is becoming more so as product development continues. To date, SKF has spent around three years improving and modifying the product into an advanced prototype. Different versions and sizes continue to undergo rigorous testing. Now, it is installed in a large wind turbine bearing for a one-year field trial. The aim is to make Sensor Roller a fully commercial product – that can last as long as the bearing itself – within two years. Such a system will enable continuous process control, with the opportunity for SKF to offer long-term Rotating Equipment Performance (REP) contracts.

Sensorised roller

Sensor Roller consists of a hollow roller containing various measurement sensors, associated electronics and a battery. The sensors measure three types of data: load, temperature and rotation speed. All three are critical in determining bearing life, which has a direct effect on asset life. While temperature and rotational speed both influence bearing life, the effect of load is far more significant.

The roller has three accelerometers that measure acceleration in three directions plus a tri-channel gyroscope that measures rotational speed in three axes. Together, this shows the complete motion of the roller. Accurate measurement of rotational speed can reveal if the roller is moving or sliding – rather than truly rolling – which can cause overheating and subsequent deterioration.Measuring temperature is relatively simple but is critical in one particular area: lubrication. If bearings run too hot, lubricant thins out; this reduces levels of protection, potentially causing metal-metal contact between raceways and rollers.

The roller itself is long enough to accommodate three separate load measurement points. This allows it to detect a variety of different effects. For instance, a mismatch between loads along the roller can highlight misalignment of the raceway. This can result in serious problems if not corrected. A polar plot of the load can show whether the bearing is loaded correctly and can even pinpoint imperfections in the design of the bearing and/or the surrounding structure.  ERIC BEARING LIMITED are professional SKF bearing distrbutor , there are rich stock for SKF bearings , if you need , pls do free to contact me . 

The way that load is transferred in these types of large bearings depends heavily on the system into which they are installed. For instance, large SKF bearings for wind turbine main shafts are 4m in diameter.Compared with a typical small bearing, the rings for these large bearings are relatively thin. This means that ring stiffness is much lower, so that the structure has a huge influence on bearing performance. Measuring all relevant parameters therefore helps both SKF and each customer to understand the application in greater detail, by demonstrating exactly how a bearing is performing in each application and under varying operating conditions. This knowledge can then be used to improve reliability and efficiency, while reducing whole-life cost.