Published: Jan 1989
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Several years ago a study group was set up at ASTM (American Society for Testing and Materials) under Subcommittee C (Turbine Oils) of Committee D-2 on Petroleum Products and Lubricants to develop a standard for in-service monitoring of steam and gas turbine oils. The study group included well qualified and experienced representatives from turbine equipment builders, oil producers, the power generation industry, and consultants among its members. The objective was achieved and an ASTM standard D 4378, entitled “Practice for In-Service Monitoring of Mineral Turbine Oils for Steam and Gas Turbines” was issued as a single standard in 1984 and is now included in the Annual Book of ASTM Standards. In developing the standard, it was recognized that turbine oils are unique lubricants requiring the highest degree of oxidation stability and resistance to sludge formation and are expected to give years of service. Also, the high cost of oil changes and unplanned shutdowns had to be balanced against the cost of laboratory manpower and equipment for analytical testing.
This paper covers the results of an initial study of monitoring practices within the power generation industry and discusses in some detail why some methods in use for many years are of doubtful significance and should be eliminated. It also describes the development of sampling and testing schedules. To follow the oxidative degeneration of the oil, the well-established TAN (Total Acid Number) test is retained and used in conjunction with the Rotary Bomb Oxidation Test, (RBOT) (D 2272) to provide a much more reliable indication of remaining service life. Other properties of the oil which must be retained in service are discussed, and major significance has also been given to the interpretation of test data and appropriate action steps.
The technical merit of D 4378 and its acceptance by the international community is confirmed by the fact that it has been used by a joint working group of ISO (International Standards Organization) and IEC (International Electrotechnical Commission) as a basis for an international maintenance and use guide.
oxidation, antioxidant, turbine severity, oxidation stability reserve, degradation, oil service life, contamination, oil make up rate, warning limit
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