Turbine Oil Analysis

What is Turbine Oil?

Turbine oil is usually mineral-based, special oils with high oxidation resistance, enriched with rust and corrosion inhibitors. It is used for bearing lubrication, heat transfer and system cleaning in systems such as gas turbines, steam turbines, hydraulic turbines and generators.

Turbine oil testing laboratories routinely monitor customer samples to detect deterioration of the physical and chemical properties of turbine oil, contamination, particles, metals and water. Lubricant monitoring tests provide useful tactical data to help predict and avoid unwanted turbine oil lubrication failures. Timely replacement of aging turbine oils and related turbine maintenance are effective tools that customers should use to protect their investment in expensive turbomachinery.

The main recommended tests are detailed below:

• Kinematic Viscosity: Kinematic viscosity describes the resistance of an oil to flow under the influence of gravity. This parameter is the most fundamental physical property of a lubricant. Turbine oil must be fluid enough to meet the requirements of the system even at different temperatures. An increase in viscosity over time may indicate oxidation or contamination. A sudden drop in viscosity usually indicates incorrect oil addition or external contamination. New generation instruments enable fast and accurate measurements in the field.
• Total Acid Number (TAN): Total Acid Number measures the amount of acidic compounds in the oil. Over time, the acidity of the oil increases due to oxidation, which can lead to corrosion of metal surfaces. TAN analysis is used to understand how chemically degraded the oil is. When the limits specified in OEM (Original Equipment Manufacturer) manuals are exceeded, it is recommended to change the oil. A sudden increase in TAN may indicate abnormal conditions in the system.
• Water Contamination: Water is one of the most common contaminants in turbine oil systems. Water ingress into the oil system reduces the function of the lubricant and increases friction between metal surfaces, leading to wear. In turbine systems, it is generally recommended to keep the water content below 100 ppm. Thanks to modern analysis technologies, water content measurements taken in the field are highly consistent with laboratory results.
• Antioxidant Additive Status: Turbine oils are formulated with special antioxidant additives to provide resistance to oxidation at high temperatures. These additives are consumed over time and the oxidation resistance of the oil decreases. A drop in antioxidant levels indicates that the oil can no longer fulfill its full function. These additives need to be monitored regularly, especially to avoid problems such as varnish and sludge formation. Some spectrophotometric instruments used in the field offer a simple way to check additive levels.
• Particle Count: The amount of particles in the oil indicates how clean the oil is and is a critical parameter, especially in hydraulic systems and turbine lubrication circuits. This test, performed in accordance with international standards such as ISO 4406 or SAE AS 4059, provides information not only on the level of cleanliness, but also on the possible sources of the particles. Advanced analyzers display the type of particles and the character of wear, contributing to the identification of the source of failures.
• Elemental Analysis (ICP): Measures the level of metals (wear metals, additives and contaminants) present in the oil. Analyzed using Inductively Coupled Plasma (ICP) technology, metal elements in the oil are detected at ppm level. In particular, monitoring elements such as iron, lead, copper and aluminum gives important clues about possible wear points in the system. It should be interpreted by considering the limit values recommended by OEM companies.
• Wear Residue Analysis (Ferrography / WDA): Ferrography magnetically separates ferrous particles in turbine oil, allowing microscopic examination. This test allows the type of wear to be determined, e.g. sliding, notch or fatigue type wear to be clearly distinguished. This analysis, performed by trained experts, helps to establish preventive maintenance plans, especially for critical turbine systems.

In our laboratories serving in many parts of Turkey, Turbine Oil Analysis is carried out in accordance with the relevant legal regulations and standards.