While formation of deposits in machinery used under high temperature conditions is inevitable, it needs to be minimized as much as possible. Desorption of deposits, though rarely reported, also needs to be addressed, as it could cause secondary damage. There have been a number of reports on the formation of high-temperature deposits and the effects of additives, none of which, however, addresses the desorption phenomenon as part of the deposit formation mechanism. Paying attention to the polar properties of lubricating oils and evaluating the formation, dissolution, and desorption of deposits by lubricating oils, the formation mechanism of high-temperature deposits was considered. Taking notice also of the changes in polar characteristics of oils with the progress of oxidative degradation of oil, we examined the influence of oxidative degradation of oils on the tendency to form high-temperature deposits. Furthermore, the countermeasure to prevent from deposit formation is also considered.
Under severe bearing conditions, deposits form on the loaded part of bearing pads and if this happens excessively, it could lead to unacceptable rises in temperature and vibration. Deposits are mainly organic compounds, formed as oxidation by-products, which are insoluble in lubricating oil and can be the precursor to deposits. In this study, the deposit precursor in lubricating oil was investigated in detail and the deposit production mechanism was demonstrated. Furthermore, the difference of oil type effects and the dependence of conditions on deposit formation are also considered.
In the compressor housing of a turbocharger with oil mist atmosphere, soft semi-solid deposit could be observed even at the lower temperatures below 200°C. Sticky or hard deposit at higher temperatures above 300°C is well-known, which can be demonstrated by standard test such as the Panel Coker Test. However, the semi-solid deposit formation has not been reported and understood. In this research, the deposit in the compressor housing was analyzed and the formation mechanism was presumed basing on the composition of the deposit. To validate the presumption, the deposit formation was demonstrated using newly designed test method. Furthermore, the dependence of conditions on the formation and the countermeasure to prevent from deposit formation are also considered.
Hard solid deposit formation has been inevitable problem in marine use turbocharger, and many engineers have struggled with it for years. It is due to low quality fuel, and the deposit results in the deterioration of the performance. In addition, the deposit is hard so that it is difficult to be removed at periodical maintenance. However, hard solid deposit formation has not been reported and understood. In this study, the deposit in actual service turbocharger was analyzed, and the dependency of operation condition on the deposit formation was investigated. And the deposit formation was demonstrated using newly designed test method, vapor phase coking deposit evaluation test. Furthermore, the countermeasure to prevent from deposit formation is considered, and it was found the deposit formation is largely influenced by ingredient of metal.
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