VGB oil laboratory tests oil blends to avoid cost-intensive oil change in a hydropower plant
The energy transition and the associated priority feed-in of renewable energy require a high degree of flexibility from conventional, plannable generation plants, which is often associated with serious problems due to the design of conventional thermal power plants (frequent load changes, start-up and shut-down, etc.). In contrast to volatile renewables (wind and solar), hydropower is a renewable source of energy that is reliably supplying power due to its base load capability and plannability, i.e., some of the most important requirements – namely security of supply and system stability – are met by hydropower.
Similar to any conventional power plant, hydropower plants and their components such as turbines and hydraulic systems as well as drives for gates, slides and flaps, require large quantities of lubricating oils. Often, several thousand litres of lubricating oil are used in the entire plant. Due to the low thermal load in hydropower, these oils can usually be operated for very long lifetime of several decades (20 to 40 years on average). Regular inspections and thus the early detection of system malfunctions and impending damage ensure the safe and smooth operation of power plants and prevent unscheduled unavailabilities and repairs.
Particularly oil losses as a result of small leakages, require regular refilling of oil in order to maintain the oil level needed. However, operators and maintenance engineers are often faced with major challenges in this regard: The original oils used according to design are often no longer available on the market. The procurement of replacement oils is difficult, and often there are also no longer any data sheets available that can provide information on the composition of the original oil, in order to be able to use equivalent oils according to the properties of the original materials. Oils cannot necessarily be blended with each other. Different oil qualities can cause incompatibilities, which in turn pose considerable risks, e.g. loss of oil properties or tearing of the oil film. This can lead to damage ranging from bearing damage to machine damage up to total turbine failure. In order to avoid a complete oil change, the VGB Oil Laboratory supports VGB members and customers in identifying oils that can be blended with the oils still in use and guarantee safe and reliable further plant operation.
In the current case, the VGB Oil Laboratory carried out tests which proved that blends of suitable oil types allow the continued operation of the plant without cost-intensive complete oil changes. In these oil blending tests, a temperature profile is used to simulate several years of operation and oil ageing. Different blend ratios also show how these oils could possibly affect operation. A wide variety of blends can be set, leading to the identification of the optimum oil combinations for a particular system.
Only a few national and international laboratories have the know-how to carry out such tests. One of the experts in this field is the VGB Oil Laboratory, which, as an independent, supplier-neutral service provider, offers tailor-made support to VGB members and customers. Thanks to the expertise and experience of the laboratory team, the operator of the particular hydropower plant was able to save about 50 T€. In addition, costs were saved that would otherwise have been incurred for a complete oil change.