Balancing sustainability with reliability for hydraulic oils in wind turbines

On average, hydraulic oils have a lifetime of 4-6 years when used in the pitch control of wind turbines. It is essential that these critical pieces of equipment have minimal downtime. However, for offshore applications especially, these oil change out procedures are time consuming and costly for oil volumes of 200-600 liters. It has been found that when these oils meet the time-based values for change out, the hydraulic oils still meet the OEM oil condition requirements.

Typically, oxidation occurs within 4-5 years for most mineral hydraulic oils whether they are zinc based or ashless. During oxidation, the antioxidants and some antiwear additives are depleted such that they no longer protect the oil. Therefore, many perform their oil change out during this time. However, if the oil could be rejuvenated to a healthy state, then there would be no need to perform these changes. This would increase the reliability and overall sustainability of these wind turbines. 

This paper presents the findings from pilot projects in Europe and Asia focusing on wind turbines both on and offshore utilizing hydraulic oil lifetime extension strategies. These strategies include the use of a patented solvency enhanced formulation specifically addressing antiwear and antioxidant additives for hydraulic oil. These are aimed at enhancing life expectancy by multiples of 3 or 4. The data presented supports a high chance of feasibility alongside excellent operating conditions, giving rise to a more sustainable approach to hydraulic oils in wind turbines