General Alarm Limits for Turbine and Circulating Oil

Turbine systems are full-flow lubrication, requiring a large quantity of oil. The oils specified are usually mineral based; coming from highly refined base stocks. The components have little tolerance for contamination or oxidation; these systems require frequent sampling. Manufacturers have provided excellent guidelines on how the oil must be maintained for trouble-free operation. Water contamination is particularly undesirable, as it tends to form an emulsion with the oil, which in turn reduces the lubricity and induces corrosion. Heat transfer characteristics are also reduced which leads to elevated bearing temperatures. Water contamination control is usually very tight and many filter systems contain coalescing filters. Particle contamination can clog lubrication ports, in-line filters and control systems. Turbine systems are required to maintain a low level of particle contamination. Viscosity of the oil tends to remain stable over many years, mainly because of the lubrication function. Oxidation is a concern and total acid number condemnation limits are low compared to other types of equipment.

The following table defines specific alarm limits for turbine and circulating oils and will serve as a useful guide for monitoring turbine oil condition:

Oil Analysis Sampling Frequencies for Power Generation

Turbine and circulating oil analysis sampling is generally performed in conjunction with other activities or reliability inspections, such as vibration data collection. Consider several factors when determining frequency:

• Safety Risk (i.e., loss of life or limb if catastrophic failure occurs).
• Criticality of Equipment (or lack of redundancy).
• Environment (wet, dry etc).
• Operating Conditions (load, speed).

Further guidance may be sought by consulting with the laboratory, the equipment manufacturer and oil supplier. The following is designed as a guide to establish a proper interval.