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GlossaryA B C D E F G H I J K L M N O P Q R S T U V W X Y ZAAcid NumberASTM D974: A measure of the acidic constituents present within the lubricant. Most rust inhibitors used in turbine oils are acidic and contribute to the acid number of the new. Increases from the new oil level are monitored, and for the most part, increases reflect the presence of acidic oxidation products. Though less likely, increases in acide number could be attributed to contaminants, mixtures of products, and/or chemical transformations. Appearance Visual assessment for sample clarity, cloudiness, separations, visible debris or free water, etc. CCleanliness CodeISO: 4406:99: Turbine journal bearing clearances (10 to 20 microns) and hydraulic servovalve clearances (2 to 5 microns) dictate the need for clean oil. Excessive bearing wear and servovalve sticking can result if tight cleanliness standards are not maintained. Color ASTM D2500: New turbine oils are typically light in color. Darkening will occur with age and service. Periodic comparisons of the sample color are useful in spotting significant and/or rapid changes due to contamination or fluid degradation. Copper Corrosion ASTM D130: The copper strip test measures the potential corrosive nature of a lubricant and the possible difficulties with yellow metals, such copper and brass or bronze components, within a system. Back to Top DDemulsibility/Water SeparabilityASTM D1401: This test measures the ability of a lubricant to separate from water. New turbine oils are designed to have good water separability characteristics. Polar contaminants influence turbine oil’s ability to separate from water. This is particularly crucial to steam turbine applications where water contamination is most prevalent and separation in the reservoir is essential. Contamination control technologies such as oil/water coalescers also depend on turbine oil’s water separability characteristics to function properly. FFoaming CharacteristicsASTM D892: Measurement of the oil’s tendency to foam and the stability of the foam after it is generated. Some foaming is a typical occurrence and antifoaming agents are blended into the oil to assist with the rapid release of entrained air bubbles. These additives will deplete with time and must be monitored. Excessive foaming is indicative of mechanical or lubricant problems requiring investigation and correction. Fourier Transform Infrared (FTIR) Fourier Transform Infrared: Infrared Spectroscopy is applied to measure organic molecular components. FTIR can be applied to monitor for additive depletions (antioxidants), organic degradation products (oxidation), and the presence of various contaminants. Back to Top PParticle CountISO 11171: A count of the number of particles present greater than given micron sizes per unit volume of fluid. The results reflect the solid contaminants present and are applied to assess fluid cleanliness and filtration efficiency. Cleanliness levels are also represented by the ISO 4406 classification system to classify the particles larger than 4-μm, 6-μm, and 14-μm per milliliter of fluid (for example: 18/16/14). QQuantitative Spectrophotometric Analysis (QSA)An analysis technique for purposely isolating and measuring the specific lubrication degradation by-products responsible for varnish formations. This is not a measure of varnish already formed; it is a determination of the lubricants propensity to form varnish and can be applied to preventing varnish formations and build-up within the system. Results are represented as the Varnish Potential Rating (VPR) with a scale of 1 to 100 severity rating. Back to Top RRemaining Useful Life Evaluation Routine (RULER)Technology to determine antioxidant levels. The antioxidants are measured by electrically charing a prepared sample and measuring chemical changes within it. The technique uses a solvent to chemically activate the oxidation inhibitor additives in the sample. Rotating Pressure Vessel Oxidation Test (RPVOT) (Previously RBOT). One of the most important properties of turbine oil is its oxidation stability or resistance. RPVOT test is a controlled, accelerated oxidation of a lubricant to determine the level of remaining antioxidant additives. Results are evaluated and compared to new oil levels. Rust ASTM D665 A: Rust particles act as oxidation catalysts and can cause abrasive wear in journal bearings. Rust Test ASTM D665: Antirust protection provided by the lubricant is of significant importance for turbine systems. Antirust inhibitors will deplete during lubricant service and can also be affected by water contamination, adsorption onto wear and debris particles, and/or chemical reactions with contaminants. Back to Top SSpectrochemical AnalysisASTM D6595: Specific trace metals are measured and monitored for wear and corrosion levels, airborne or internally generated contaminants, oil additives, and water treatment additives. Particles detected are typically 8-μm and less and results are reported in parts per million (ppm) by weight. TTurbine Oil Monitoring (TOM)ASTM D4378: to maintain effective lubrication of all parts of the turbine and guard against the onset of problems associated with oil degradation and contamination. Turbine Oil Quality (TOQ) Test includes spectrochemical and physical properties analyses, total acid number (TAN), appearance, water content, color, rust resistance capability, particle count analysis, copper corrosion, water separability, and foaming tests. Turbine Lubricant Assessment (TLA) The most comprehensive test package available for turbine oils. It covers the majority of the testing outlined in the TOQ, in addition to determining the varnish potential, additive levecls and degradation mechanisms. Each report includes customized, detailed interpretations and recommended actions. Turbine Oil Stability Test (TOST) ASTM D943: This test attempts to determine the expected turbine oil life by subjecting the test oil to oxidative stress using oxygen, high temperatures, water and metals catalysts, all of which increase sludge and acid foratmion. This test is impractical as an in-service oil test and is rarely performed because it can take up to one year to complete. Back to Top VVarnishASTMD.02C.01: A thin, hard, lustrous, oil-insoluble deposit, composed primarily of organic residue, & most readily definable by color intensity. It is not easily removed by wiping with a clean, dry, soft, lint-free wiping material and is resistant to saturated [light hydrocarbon] solvents. Its color may vary, but it usually appears in gray, brown or amber hues. Viscosity ASTM D445: Viscosity is the most important characteristic of turbine oil and can be readily affected by more types of influences than any other property. Maintaining the proper viscosity is crucial to retaining oil film thickness under hydrodynamic lubrication conditions. WWater by Karl Fischer
ASTM D6304: Testing for water, particularly in steam turbines, is important because water is a precursor to oil exidation and rust formation. It can be more accurate than simple weight loss because in the weight loss method volatiles other than water can be lost which is translated into an artificially high water content. Knowledge of the moisture content can be important since some polymers degrade when molded wet resulting in reduced properties.
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