The right turbine oil provides reliability for power plant
Written by John Sander
Turbine Problems
The highest profile turbine oil-related problem experienced at power plants has been the formation of sludge and varnish, but various other problems also have been reported. These problems include:
• Lubricant consumption
• The formation of a gel-like material on the turbine chiller bundles
• Electrostatic spark discharge in the turbine filtration systems
• Corrosive wear on the turbine thrust plate bearings
• Reduced life from the turbine oil

For obvious reasons, turbine owners and manufacturers have become frustrated with the performance of many turbine lubricants. General Electric, one of the major turbine manufacturers, issued a service bulletin regarding varnishing. These types of problems did not occur in the past, which leads to the question: why are they occurring now?

At the 2007 Lubrication Excellence Conference in Louisville, Ky., one of the presentations was based on a paper by William Moehle and his associates titled "Practical Approaches to Controlling Sludge and Varnish in Turbine Oils". Moehle's paper provides an accurate, concise description of the mechanism for the varnish and sludge formation in turbines. Figure 2 in his paper is a flowchart that illustrates the complex mechanism that results in the formation of turbine sludge and varnish. Moehle pointed out that turbine oils were not the sole cause of the problems. He summarized this by using an illustration of a chain, shown in Figure 3 in his paper.

The problems identified by Moehle and his associates were the result of a chain reaction from various combinations of inferior lubricant formulation, thermal degradation, additive depletion and poor fluid maintenance.

With its properly formulated lubricants and its reliability partner products and services, such as filtration systems, sight glasses, oil analysis and training, Lubrication Engineers, Inc. can provide a comprehensive solution for all of these problems. This paper, however, will focus primarily on the lubricant formulation link of the chain.