Today’s turbine gearboxes are having to support increasingly heavy loads and require proper lubrication to operate at peak performance while minimising wear and providing extended drain intervals. Rob Pears, ExxonMobil Fuels and Lubricants’ business development manager, UK and Ireland, briefs World Wind Technology on maintaining optimum wind turbine productivity in particularly harsh offshore environments.

What considerations go into lubricating a wind turbine gearbox?
Rob Pears: Wind turbine gearboxes have unique lubrication needs compared with other industrial sectors. Standing hundreds of feet high offshore, and often situated in remote locations, turbines operate in wide temperature ranges, and are vulnerable to wear, water contamination, rust and corrosion. Furthermore, their isolated locations can make routine maintenance visits very costly. Therefore, any in-service lubricants must last as long as possible and offer sufficient equipment protection to avoid unscheduled downtime.

How has wind turbine lubrication changed over time?
In the past, gearbox lubricant changes were typically carried out every 18 months for mineral gear oils and every three years for synthetic alternatives. As gearbox technology has vastly improved, operators are demanding enhanced performance from their lubricants. Extended drain intervals are of particular concern, as the cost of just the lubricant for a complete ‘drain-flush-fill’ for a mid-sized turbine can exceed $5,000.

The total expense is compounded by other overheads from production downtime to the prohibitively high cost of vessel hire for offshore installations.Not only must wind turbine gearbox lubricants provide protection from the elements, they must also do so for extended periods to keep costs down. Regular use of a used- oil analysis monitoring system, such as ExxonMobil’s Signum, enables maintenance professionals to track the condition of the equipment and the lubricant to increase oil drain intervals.

Is it a challenge to meet these elevated performance standards?
ExxonMobil is well-equipped to handle this challenge through its technology leadership and application expertise in the wind sector. The company’s scientifically engineered approach to product development, excellent industry insight and technical know-how enables it to deliver high-performance lubricants that are optimised for individual applications. This is ExxonMobil’s ‘Balanced Formulation Approach’.
This process enables it to develop lubricants that deliver exceptional performance for all sectors and performance characteristic requirements, and across all critical areas, from corrosion control to withstanding extreme temperatures.

Balanced formulation takes a two-fold approach. First, a team of scientists evaluates the lubricant design in a series of stringent laboratory tests to determine its performance capabilities. Then, the lubricant candidate is taken out into the field where full-scale, dynamic testing is conducted on actual industrial equipment. A product must excel in both tests before it receives the ExxonMobil seal of approval. For wind turbine gearboxes, ExxonMobil recommends Mobil SHC Gear 320 WT.

What about Mobil SHC Gear 320 WT makes it such an excellent product for wind turbine gearboxes?
It is backed by a seven-year, limited warranty (additional terms and conditions apply), and is formulated to help deliver outstanding protection for critical turbine components over long oil-drain intervals – a major consideration for wind farms. In extensive bench and rig testing, the lubricant has demonstrated its ability to deliver the specific performance benefits required to support turbines operating in a wide range of onshore and offshore conditions, including:

  • outstanding protection against micropitting and wear
  • reliable foam-control performance
  • exceptional water tolerance
  • superb oxidative stability and excellent viscometrics, even at temperatures as low as -45°C.