Turbine Engine Lubricant and Additive Degradation Mechanisms

Abstract

Modern ester based synthetic lubricants have been used in various formulations with anti-oxidants, phosphorus based anti-wear additives and other additives for many years. The physical and chemical properties of both the basestock and additives are known to change through use. Basestocks are normally thought to degrade through various mechanisms, while additive can either degrade or are used as they react when they complete the function that they are added for. In this chapter, the composition of modern turbine engine lubricants and the mechanisms by which the lubricants degrade over time will be examined. Potential changes in bearing materials being evaluated for future engines and the effects of possible new ionic liquids based additives will be will be discussed as they relate to currently used additives. Also included will be a discussion of effects of degradation on the lubricant properties, how the changes affect turbine engines and how the changes can impact human health. These new materials introduce a number of new possible degradation schemes that must be evaluated before the materials enter widespread use.

Inappropriate Use of Risk Assessment in Addressing Health Hazards Posed by Civil Aircraft Cabin Air

“…The route of entry of the toxicant(s) is critical to the exposure assessment. d) Risk assessment -Finally, the information collected in steps [1][2][3] can be combined into a risk assessment. The validity of this final step is totally reliant on the rigour and completeness of the earlier steps.…”

“…Lubrication oils in gas turbine aero engines require the presence of synthetic lubricants, which include additives, to minimize engine wear at the high temperatures encountered in normal operation [1][2][3]. The majority of the lubricants utilised in turbine engines add cresyl phosphates, generally termed Tricresyl Phosphate (TCP) at approximately 3%.…”

“…These are generally referred to as Triaryl Phosphates (TAP). This then becomes further complicated by the production of pyrolysis breakdown molecules as the oil ages during use [2,4,6,7]. Oil utilised in turbine engines is consumed in normal engine operation and a small proportion of this used oil migrates over oil seals used within the engine [8][9][10].…”

Sources of Onboard Fumes and Smoke Reported by U.S. Airlines

“…The problem with this "bleed air" design is that the oil that lubricates the engine compressors can contaminate the ventilation supply air. This can be caused by an actual mechanical failure or by the effects of engine parts subjected to physical and thermal stress during engine power setting changes, improper oil drainage/reingestion, or overfilling of an oil reservoir during servicing [1][2][3][4]. Additionally, small amounts of oil seep past the engine/APU bearing chamber seals into the compressor air flow, which is considered normal and acceptable if the volume of oil loss over time is within defined limits [1][2][3][4].…”

Inappropriate Use of Risk Assessment in Addressing Health Hazards Posed by Civil Aircraft Cabin Air

“…These are generally referred to as Triaryl Phosphates (TAPs). This then becomes further complicated by the production of pyrolysis breakdown molecules as the oil ages during use [2,4,6,7]. Oil utilised in turbine engines is consumed in normal engine operation and a small proportion of this used oil migrates over oil seals used within the engine [8][9][10].…”