Krzysztof Płonka
diagnostician and practitioner, working at the Ecol Oil Analysis Laboratory, responsible for the interpretation of test results and customer support in the area of lubricant analysis.



The series of publications focusing on the lubricants analysis for wind energy sector is my proposal for consideration, enhancing the knowledge and discussion.

We will consider: What can we learn from regular oil analysis? Are the tests results, without any additional comment, sufficient to draw useful conclusions for proper maintaining and operation of the transmission? We will also try to answer the question of what the wind farm operators follow when making decisions while operating.

Feel free to discuss and follow further publications.


Predictive maintenance based on actual technical state of the machine park is nowadays one of the most popular strategies. Rigid time periods between maintenance operations become more and more often replaced by specialized diagnostic programs. Having a precise data which concerns technical condition of the machines, simplifies making optimal decisions and allows maximizing the potential of owned devices.


In the case of oil diagnostics in wind turbine gearboxes, the results provide not only direct information about condition of the lubricant, but also indirectly show the technical state of the gearbox. Usually, oil is sampled during periodic inspections of wind turbines and recommended, safe period between analysis is 6 months. Lab report should contains at least information about viscosity, amount and type of the contaminants, wear metals content and lubricant degradation symptoms.


Results obtained in a laboratory allow the operators to make decisions about further required maintenance activities, such as additional bypass filtration need, oil exchanging etc. in case of crossing the alarm limits of particular parameters or on the other hand –  lack of such necessity and possibility for further trouble-free work of the gearbox (in case when lubricant parameters meet safety limits).

Fig. 1. Interior of wind turbine gearbox


The question arises: how to determine the optimal limit values of the analyzed parameters, which would be useful for the operator?

Generally, in the technical documentation of the gearbox, we can only find information about specific products approved by the manufacturer or the required lubricant cleanliness class, however it is in vain to look for information about the recommended boundary values for wear metals or the oil degradation symptoms.

Luckily we are not helpless in this matter – one of tools useful in setting limit values is statistical analysis, which will be discussed wider in the next paper.

Meanwhile, as part of the conclusion of this publication, I would like to present you a chart which shows set of iron content results as a normal distribution from a population of approx. 1000 oil samples taken from the wind turbine gearboxes located in Poland over a period of 5 years.



Fig. 2. Standard distribution of the iron content in given sample population.


At the end I would like to ask:

Is it possible to draw useful conclusions on proper gearbox operation without any additional remarks?


See also:
Lubricating oil analysis in wind turbine gearboxes – part 2

Lubricating oil analysis in wind turbine gearboxes – part 3


Visit also: