Lubricants for Steam and Gas Turbines

The two types of stationary turbines used for power generation are steam turbines and gas turbines. A turbine oil is designed to provide effective lubrication to all parts of a stationary turbine.

A typical turbine oil consists of a highly refined paraffinic mineral oil which has been formulated with one or more of the following additive packages:

• Oxidation inhibitors
• Rust inhibitors
• Metal deactivators
• Pour point depressants
• Extreme pressure additives
• Foam suppressants

The use of a high quality oil is the best assurance for long service life and the recommendations of the turbine manufacturer should be followed. The oil should be selected based on data from the oil supplier. However, it is very important to take an oil sample from the first fill to develop data that can serve as a baseline for future comparisons. A one gallon retain sample is recommended.

The in-service monitoring of a turbine oil ensures long, trouble-free operation of a power plant and it is the responsibility of the power plant operator to have a program of sampling and testing that will guard against the onset of problems associated with oil degradation and contamination.

Many of the monitoring tests for steam turbines are also applicable to gas turbines. The operational factors for a given turbine determine the severity level to which the turbine oil is exposed. Steam turbines operate at lower levels of severity and longer service life can be expected. Gas turbines operate at higher severity levels and turbine oils require more frequent monitoring and testing. The more severe a turbine system, the shorter the service life for a given oil.

ASTM D 4378 is the standard practice for in-service monitoring of turbine oils. It should be consulted for background information on how turbine oils perform and how they degrade in service. Our recommended test package is based on ASTM D 4378.