Lubricant leaders like Shell and Fuchs make high-quality turbine oils that keep the latest turbine technology operating effectively and well-protected.
However, how frequently these lubricants need replacing is not always clear. Changing turbine oil based on condition instead of than interval-based changes is an accepted best practice for many turbine engineers. However, understanding the conditions that determine whether a fluid is no longer fit for purpose is critical to avoiding exposing equipment to harm by using turbine oil for too long, or replacing oil when it can still be of service.
Experts agree turbine oil needs changing when its performance deteriorates to a point where it no longer properly lubricates and protects the turbine’s components. The change is typically dictated by professional monitoring of the oil in use an examination of its physical appearance and chemical properties – particularly its antioxidant levels.
Here, we explore when to change turbine oils including useful indicators, recommended change intervals and some of the factors that impact oil lifespan.
Signs your turbine oil needs changing
Like any other lubricant, turbine oil degrades in time and starts to lose its effectiveness. Turbine operators understand that there are several indicators that suggest turbine oil needs changing.
A visual inspection of the oil offers important information. Fresh and functional turbine oil is usually amber in colour and transparent. However, as it ages, it takes on contaminants. This manifests in a darkness and cloudiness, indicating it’s time for a change.
The presence of particles suspended in the oil or droplets of water are also clear signs of contamination that can reduce the effectiveness of the oil.
Turbine oil is designed to be thermally stable and keep equipment at the correct operating temperature. As turbine oil deteriorates, its viscosity can change, causing overheating. As a result, an increase in operating temperature is another tell-tale sign.
Unusual noise or vibration from the turbine engine is also a giveaway. When functional, turbine oil lubricates, reducing friction in between moving parts. The sound of knocking, grinding or ticking indicates worn components caused by oil degrading and being unable to perform its essential job.
Other obvious indicators include warning and oil change lights illuminated on control panels, and other equipment user interfaces and excessive blue or grey smoke emitting turbine exhausts.
Finally, degraded system performance should never be overlooked. A decrease in engine power, greater fuel consumption or sluggish mechanical operations are all signs that the turbine oil has deteriorated.
Recommended oil change intervals
The industry standard for working out the end of turbine oil’s active service life is typically when its antioxidant levels have dropped to 25 per cent of its original concentration. However, many original equipment manufacturers (OEMs) cite changing turbine oil every 8,000 to 16,000 hours, while others strongly advise making changes informed by condition monitoring.
The RULER Test can detect the volume of antioxidants present in the turbine oil. It supplies a graph that shows peaks for antioxidants detected, enabling a comparison with new oil to work out depletion. It can effectively assess the useful life left of the turbine oil by monitoring the antioxidant depletion rate.
Factors that influence oil life
The active service life of turbine oil is impacted by a wide range of different factors. While turbine oil is designed with properties that make it thermally stable, extreme operating temperatures can cause the oil’s useful characteristics to degrade quicker, shortening its life span. Similarly, heavier load and duty cycles also put pressure on the oil, breaking down its additives that help it perform at optimum.
The presence of contaminants such as water, dirt or metals can also reduce the useful service life of an oil. Excessive moisture can result in oils becoming watery, reducing their lubricity and protective properties, while sludge from a build up of debris like dirt and metals can make them overly thick and slower to pump.
Oil formulation also plays a part, as not all turbine oils are designed equally. The latest full-synthetic solutions are more expensive to order but are specially formulated to provide maximum performance and efficiency in the most intensive operating environments and applications. They often include wider operating temperature ranges and additives that give them extreme pressure, antioxidant and anti-corrosive characteristics that extend their lifespan.
