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Characterization of the Ageing Process in Aviation Lubricant Oils through an Experimental Simulation of the Bleed Air System Conditions
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Resumo(s)
In addition to the well-known concern about flight security, concerns regarding air supply quality and the effects of exposure to the synthetic lubricants oils (SLOs) among cabin air environment, became a matter of study over the last decades. Oils are prone to thermal and oxidative degradation during service in engine compressors as they are exposed to extremely high temperatures and pressures, as well as by contaminants sources among the bleed air system.
A qualitative Risk assessment towards bleed air contamination identified a total of 50 risks, in which only 2 risks related to the contamination of both engine and auxiliary power unit air supplies, were classified as moderate (orange scale). From a general perspective, the set of analysed risks, even the most critical ones, are strictly controlled and mitigated by routine procedures of engine maintenance and inspection.
The following study approaches a comprehensive investigation and characterization of SLOs and its toxic effects among cabin air. Laboratory accelerated degradation tests were performed at two most common oil brands, by the means of a designed vacuum distillation test methodology. The variations in composition during the lifetime of oil as well as its properties were measured within a hypothetical flight scenario.
Experimental results proved significant changes between the patterns of fresh and aged SLOs. Oil vapours analysis through GC-MS, detected a total of 404 compounds, among which 112 were detected in both oil brands. The increased presence of several oil breakdown products, like aromatic hydrocarbons, carboxylic acids, and ketones was also evident. A Hazard Assessment was applied to validate the safety and health profile of each chemical, relying upon the Classification and Labelling database of the European Chemical Agency. Compounds of particular interest among literature review were found as well, such as N-Phenyl-1-naphthylamine, and Naphthalene.
Despite the overall findings of potential risks of exposure to certain chemicals within oil breakdown products towards both oils, no recorded of severe or adverse health effects can be directly assigned to cabin air contamination. It is important to recognize that these types of events are difficult to determine due to its infrequency and unpredictability. Also, no single detected contamination ever reaches critical or unusual concentrations among cabin air environment, and several studies regarding cabin air already proved to be less polluted compared to typical indoor environments – offices, schools, dwellings.
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Palavras-chave
cabin air environment synthetic oil lubricants degradation bleed air system Risk