旧油分析.pptVIP

* The rust protection properties of a lubricant are difficult to evaluate since the rusting of ferrous specimens begins immediately when exposed to air and water. The Rust Test is conducted by immersing a standard steel specimen in a mixture of distilled or synthetic seawater and the oil under test. The oil and water mixture is stirred continuously during the 24 hour test. The specimen is then examined and rated on a scale as to amount of rusting that has occurred. The Rust test is a four hour test. * Corrosion by organic acids can occur on the bearing inserts used in automobile engines or the non-ferrous (bright) metals used in hydraulic pumps. Corrosion inhibitors form a protective film on the bearing surfaces that prevents the corrosive materials from attacking the metal. The film may either be absorbed on the metal or chemically bonded to it. The Copper Strip Corrosion Test is a common test to evaluate the corrosiveness of an oil. Polished copper strips are immersed in heated oil for a specified period of time. The copper strip will react to the corrosive elements in the oil. The amount of corrosion will be compared to reference strips that are numbered. The number of the closest comparison is reported. * Oxidation is a condition that generally occurs when the oil is in service. The higher the operating temperature, the higher the level of oil agitation, the greater the exposure to active metals will increase the oxidation rate of the oil. For example, there is a “General Rule of Thumb” that oil oxidation rates double for every 10 C (18 F) rise in temperature. Depending on the oil oxidation begins to occur at 45 C (110 F) to 50% C (120 F). Tests to measure oxidation take time and to speed them up, temperatures are increased and the amount of oxygen and catalytic materials are increased. Unfortunately the correlation with real service becomes less reliable. * * Thermal Stability is the measure of oil degradation at high temperatures with minimal expos