Three Reasons Why Turbine Oil Degrades

Today’s turbines are designed to deliver higher output and efficiency to cope with the increasing demand for power. But today’s operating conditions and equipment design place increased stress on turbine oils. 

For turbine operators, this creates heightened pressure to ensure effective performance of turbine oils in these harsh conditions, to help avoid unplanned equipment downtime.

Understanding the reasons why turbine oils degrade in service is the first step in monitoring your oil’s condition, to ensure trouble-free operations.

It is important that you consistently monitor all these factors throughout the life of your turbine oil.

1.     THERMAL AND OXIDATIVE DEGRADATION

Turbine oils operate in high-temperature environments and are exposed to air and catalytic metals during operation.

Fast flow rates and short reservoir residence times mean more opportunities for air and oil to interact and react. This creates oxidation by-products that can lead to the formation of sludge and varnish.

Higher operating temperatures raise the rate of oxidation and thermal degradation of the turbine oil, which means that sludge and varnish formation occurs more rapidly at higher temperatures. This sludge and varnish can lead to increased bearing temperatures, stuck valves and blocked filters, which can cause unplanned downtime and lower productivity.

2.     CONTAMINATION

Turbine oils are subject to a variety of contaminants, including:

• water, especially in steam turbines
• dust and other ingress materials, including incorrect oil
• internally derived contamination, such as wear metals like copper, iron and lead.

These contaminants often contribute to oil degradation issues. Wear metals may speed up the oxidation of the oil. Water hampers the ability of the turbine oil to dissipate foam and to provide rust and corrosion protection, and may promote other degradation processes such as hydrolysis.

3. ADDITIVE DEPLETION

Although some additive depletion is normal, excessive or accelerated additive depletion can significantly reduce an oil’s life and performance.

For example, the demulsifiers that help the oil to shed water and antifoam additives can be removed by ultra-fine filters, or may agglomerate if the oil is not circulated for a while. This can decrease the oils’ foaming performance or its ability to separate water.

Taking Action

An oil monitoring programme such as Shell LubeAnalyst provides detailed oil and equipment analysis and advice specifically tailored for your machinery. This can help extend the life of critical turbine components and help to extend the life of your turbine oil, ultimately resulting in lower costs, less unplanned downtime and improved operational efficiency.