Combining sensor inputs measuring different parameters provides versatile monitoring option for reduced operating costs of wind turbines.

Sensor Arrays Keep The Energy Flowing

monitoring to improve uptime and reduce total costs of operation. By carefully studying the


variables that need to be measured, bearing specialist Schaeffler came up with a combination of sensors that are capable of monitoring the critical influencing variables for damage prevention.

REAL TIME OPERATING DATA By evaluating and interpreting real time operating data across a number of variables, safety factors can be more accurately defined but to have full visibility of this data, new sensor concepts were required for recording variables that have not been monitored before. To achieve this, Schaeffler used established temperature and

vibration sensors together with the company’s GreaseCheck grease sensor, a new LoadSense Pin and a roller set sliding distance sensor.

GREASE SENSOR The “GreaseCheck” is an optical system that allows changes in the condition of the grease to be detected early. The 5mm wide sensor head records turbidity, water content and grease temperature. Users can classify the condition of the grease during operation as ‘good’ or ‘bad’ by setting individual threshold values for turbidity and water content. Wind farm operators can use GreaseCheck to determine re-lubrication intervals for new turbines without having to go through the costly process of taking and analysing grease samples. Because the condition of the grease is continuously monitored, operators can respond by initiating maintenance measures when changes are detected.

LOADSENSE PIN In the case of pre-assembled rotor bearing systems that are flange-mounted to the adjacent construction, the preload of

❱ ❱ A novel approach of combined sensor data analytics is being used to monitor large wind turbine bearings

lthough applicable to any heavy duty rotating machinery monitoring application, the latest sensor fusion technology is finding particular use in wind turbine

❱ ❱ The LoadSense Pin sensor using a similar measuring approach to conventional strain gauges

the screw connections that are used partially determines the bearing’s load distribution and so has a direct effect on its performance capability and operating life. “LoadSense Pin” monitors this

screw preload using a new sensor based on the company’s Sensotect thin-layer sensor technology and uses strain-gauge based measurement methods. The LoadSense Pin’s sensor coating is applied directly to the end face and (for temperature compensation) the outside surface of a small steel cylinder. The sensor is pressed into a bore on the component where measurements are to be made, and thus experiences the same expansion as the material that surrounds it. This means that, unlike conventional adhesive strain gauges,

the LoadSense Pin is integrated directly into the bearing ring. Schaeffler’s LoadSense Pin allows the preload of the flanged

bearing’s screw connections to be monitored during operation, which means that the screws can be tightened as required, eliminating the need for preload inspection at fixed intervals. This increases the reliability of the bearing system and reduces the maintenance costs at the same time.

ROLLER SET SLIDING DISTANCE SENSOR This inductive sensor records the number of times that a rolling element passes the sensor head during a fixed number of rotor shaft rotations. The rolling motion of the contact partners in the bearing always means sliding movements – which are small when the design is correct. This micro- slippage between the driven bearing ring and the rolling element set changes the circumferential speed of the rolling element set and therefore the frequency with which the rolling elements pass the sensor head. When the inner geometry of the rolling bearing is known, the mean sliding distance and micro-slippage can be very accurately calculated as an average over time from the number of rolling element passes which allows various load, friction and lubrication conditions to be deduced. This measurement is simple, extremely reliable and allows conclusions to be made about operating conditions (including kinematics) in the rolling bearing.

DAQ, Sensors & Instrumentation Vol 2 No. 1 /// 9

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