Wind turbine operators must monitor their equipment to ensure optimal performance. This is usually done with permanent condition monitoring installations, but sometimes these are not adequate. In these cases, a mobile system can sometimes get the job done at a lower cost and with less effort.
A permanent condition monitoring system (CMS) for wind turbines uses vibration measurements to assess the mechanical condition of the turbine's powertrain. Best practices and standards have been developed over the last 15 years and the results are generally reliable for wind farm operators.
But what if a wind farm's turbines are not equipped with a permanent CMS? A retrofit installation is possible, but the operator may not be able to justify the necessary capital investment because the business is too old or the site is too fragile. In this case, a mobile CMS concept from SKF could be the right solution.
This means that an online CMS device customized for temporary use will be installed for a limited period of time – from an hour to a few days, following an appropriate process – ensuring results with a reasonable level of quality in terms of problem detection and identification.
Reduce the risk of unplanned downtime
The mobile CMS collects data such as vibrations using a speedometer. Data is optimized via a mobile data connection to the SKF remote diagnostics center. Contextual information about the selected parameters is compiled and analyzed from the data. Based on these results, event reports and proactive maintenance recommendations are provided to the wind farm operator. This reduces the risk of unplanned downtime and loss of operating revenue.
The mobile CMS device is the same as those installed in permanent systems, but comes in a rugged industrial case with splash-proof connectors, an integrated SIM card and an antenna slot for mobile signals.
Some operators have tried using a standard portable device, such as a vibration data logger, to monitor equipment, but this approach has some disadvantages. The operator is generally not permitted to remain at the turbine while it is being started, and the standard device can produce poor results due to wind variation as the tool is moved through the machinery. Although both options allow measurements in a short space of time, the SKF mobile CMS concept has many advantages.
Ensure correct assessment
There are some fundamental aspects to ensure a correct assessment of a turbine's mobile CMS. Typical cases that the mobile CMS concept can address include performing an end-of-warranty assessment of a turbine, checking the integrity of a new wind farm, tracking a specific mechanical issue, optimizing an inspection video with a borescope, refining an analysis or planning shutdown activity for lubricant maintenance.
Of course, you cannot expect the same performance from a few hours of registration with a mobile CMS and long-term 24/7 monitoring from a permanent CMS. Permanent monitoring can ensure that all small deviations are detected, allowing accurate monitoring and any mechanical degradation can be detected and sent to relevant personnel via an automatic alarm function.
As with ongoing monitoring, a mobile CMS must collect a minimum amount of information to limit analysis uncertainty. This information should include kinematic data such as asset models, gearbox speed ratios, bearing reference, and turbine power curve. Ideally, it should also include technical records such as asset age, component reviews and lubricant analysis, as well as selected key parameters such as temperature and debris monitoring.
The placement of the sensors is ideally adapted to the load zones depending on the design of the turbine drive. Therefore, a minimum amount of wind load on mechanical components is required to be able to detect and evaluate possible problems and determine their severity. SKF offers an inductive probe with magnetic holder connected to the mobile CMS system.
Need for a wider speed range
A permanent CMS allows the operator to be selective in terms of data acquisition regarding sample collection speed and active power under similar load conditions, resulting in a consistent trend. With the mobile CMS it is a little more challenging. In view of the limited measurement window, a wider speed range is required. Classification of records of similar load conditions will be done later with the CMS software. However, you still need to use the maximum allowable delta speed parameter, which protects against CMS data degradation that can occur when the wind fluctuates.
By following the mobile CMS process, it is also possible to compare the CMS values of specific machines, providing an overview of the condition of each component.
Furthermore, the mobile CMS provides accurate kinematic and qualitative measurements, thereby strengthening diagnostic accuracy and operational and maintenance decisions.
Conclusion
A mobile CMS can be a great benefit-risk operation, keeping in mind the use cases it is suited for, and can be a valuable addition to your existing O&M protocol.
It should also be noted that installation and measurement tasks can be performed without the need for specific skills. However, database creation, data analysis and data reporting are then handled by the specialist partner. Conclusions can be provided during the measurement campaign as data is sent directly to the remote diagnostics cloud.
