A mechanism of thermo‐oxidative degradation of polyol ester lubricants

Bakunin, V. N.; Parenago, O. P.

doi:10.1002/jsl.3000090204

Cited by 35 publications

(40 citation statements)

References 10 publications

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“…This has led to their wide spread use in automotive and turbine applications (Bakunin and Parenago 1992). However the newer lubricants suffer one major disadvantage compared to mineral hydrocarbons, namely their affinity for water.…”

Section: Lubricantsmentioning

confidence: 99%

“…The outcome is a self-supporting, progressive oxidation (autooxidation) of the lubricating oil. It is assumed that this mechanism of auto-oxidation also applies to the oxidative degradation of POE-based lubricating oils, at least during the initial phase of oxidation (Duncan et al 2002, Bakunin and Parenago 1992, Jensen et al 1984. Many aspects of POE oxidation remain unclear and it appears that two approaches to the oxidation mechanism of POE lubricants exist; one mechanism emphasizes the import of alcoholic fragments, while the other approach provides experimental evidence for the import of acyl fragments.…”

Section: Initiation Chain Propagation Chain Branching Chain Terminationmentioning

confidence: 99%

“…Many aspects of POE oxidation remain unclear and it appears that two approaches to the oxidation mechanism of POE lubricants exist; one mechanism emphasizes the import of alcoholic fragments, while the other approach provides experimental evidence for the import of acyl fragments. Bakunin and Parenago (1992) suggest that the actual process includes both mechanisms and all polyol fragments participate in the oxidative degradation, the details of which are dictated by chemical structure and environmental conditions.…”

Section: Initiation Chain Propagation Chain Branching Chain Terminationmentioning

confidence: 99%

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Using Acid Number as a Leading Indicator of Refrigeration and Air Conditioning System Performance

Cartlidge¹,

Schellhase²

2003

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EXECUTIVE SUMMARYAir conditioning and refrigeration equipment needs to provide long-term reliable use. However, over long periods of time, stress induced deterioration of the refrigerant and/or lubricant will occur which can cause changes in the system chemistry resulting in decreased operating efficiency and potentially can lead to a failure of the system. A number of degradation processes contribute to the deterioration and are reflected by changes in parameters such as acidity, moisture content, viscosity, dissolved metal content, etc., which are all related to the formation of increasing amounts of acids over time. Total acid number (TAN), which includes both mineral acids and organic acids, is therefore a useful indicator which can be used to monitor the condition of the system in order to perform remedial maintenance, when required, to prevent system failure. A literature review was performed to assess the acidity characteristics of the older mineral oil and newer polyolester (POE) refrigeration systems as well as to evaluate acid measuring techniques used in other non-aqueous systems which may be applicable for refrigeration systems.Failure in the older chlorofluorocarbon/hydrochlorofluorocarbon (CFC/HCFC) / mineral oil systems was primarily due to thermal degradation of the refrigerant which resulted in the formation of hydrochloric and hydrofluoric acids. These are strong mineral acids, which can, over time, severely corrode the system metals and lead to the formation of copper plating on iron surfaces. The oil lubricants used in the older systems were relatively stable and were not prone to hydrolytic degradation due to the low solubility of water in oil.The refrigerants in the newer hydrofluorocarbon (HFC)/POE systems are much more thermally stable than the older CFC/HCFC refrigerants and mineral acid formation is negligible. However, acidity is produced in the new systems by hydrolytic decomposition of the POE lubricants with water to produce the parent organic acids and alcohols used to prepare the POE. The individual acids can therefore vary but they are generally C 5 to C 9 carboxylic acids. Organic acids are much weaker and far less corrosive to metals than the mineral acids from the older systems but they can, over long time periods, react with metals to form carboxylic metal salts. The salts tend to accumulate in narrow areas such as capillary tubes, particularly if residual hydrocarbon processing chemicals are present in the system, which can lead to plugging.The rate of acid production from POEs varies on a number of factors including chemical structure, moisture levels, temperature, acid concentration and metals. The hydrolysis rate of reaction can be reduced by using driers to reduce the free water concentration and by using scavenging chemicals which react with the system acids.The critical TAN value is the acid level at which remedial action should be taken to prevent the onset of rapid acid formation which can result in system failure. The level of 0.05 mg KOH/g of oil was established fo...

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Section: Lubricantsmentioning

confidence: 99%

Section: Initiation Chain Propagation Chain Branching Chain Terminationmentioning

confidence: 99%

Section: Initiation Chain Propagation Chain Branching Chain Terminationmentioning

confidence: 99%

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Using Acid Number as a Leading Indicator of Refrigeration and Air Conditioning System Performance

Cartlidge¹,

Schellhase²

2003

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“…The production of acids first increases the hydrogen ion concentration of oil, which leads to corrosion. The subsequent formation of insoluble resins increases the viscosity and inhibits lubrication (Bakunin and Parenago 1992). Hence, the improvement of the stability of lubricating oils to suppress their breakdown is usually performed by additives.…”

Section: Introductionmentioning

confidence: 99%

Voltammetric Determination of Dinonyl Diphenylamine and Butylated Hydroxytoluene in Mineral and Synthetic Oil

et al. 2016

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A method is reported for the determination of diphenylamine and butylated hydroxytoluene in mineral and synthetic oil. The procedure used differential pulse voltammetry with a glassy carbon electrode. This method was then used for determining these antioxidants in supporting electrolyte consisting of dilute sulfuric acid and sodium dodecyl sulfonate in ethanol. Anodic peaks were obtained for both analytes. Oxidation peaks at 250 mV were observed from a mixture of butylated hydroxytoluene and dinonyl diphenylamine, allowing their simultaneous determination. This approach was successfully used for the determination of dinonyl diphenylamine and butylated hydroxytoluene in fortified mineral and synthetic oils with good accuracy and precision.

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“…At the initial step, α-acylhydroperoxide is formed in a way similar to the oxidation of hydrocarbon [90]. This intermediate by-product then decomposes via two routes, one the usual degradation into free radicals via O-O bond splitting and the other route involving hydroperoxide decomposition into both peroxy acids (together with an aldehyde) and so-called peroxy ester [90]. The liquid phase oxidation of these peroxy esters yields low molecular carboxyl acid (acetic), methyl alcohol and methyl acetate.…”

Section: Ageing Of Synthetic Ester Insulating Oilsmentioning

confidence: 99%

Condition monitoring of biodegradable oil filled transformer

Mudiyanselage¹,

Bandara²

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Natural and synthetic ester insulating oils have higher fire points and excellent biodegradable characteristics. Therefore, in order to reduce the adverse environmental impact and to improve the fire safety of transformers, there is an increasing demand for natural and synthetic ester insulating liquids as a transformer insulating oil. However, present understanding on ageing behaviour of ester oil-paper composite insulation system and knowledge on application of existing condition monitoring tools for ester based insulation systems are inadequate. This impedes the cost effective and reliable field applications of ester insulating oils, particularly application of natural esters. To reduce this knowledge gap, series of controlled ageing experiments are performed in this research project to provide a better and comprehensive understanding on ageing behaviour of ester oil-paper insulation systems. Furthermore, applicability of existing chemical and electrical based condition monitoring techniques for ester oil-paper insulation systems is systematically investigated in this research project.In this thesis, ageing behaviour of dry pressboard insulation in mineral and three different ester insulating oils under simulated transformer operating environment is investigated. Moreover, the ageing behaviour of natural ester-pressboard composite insulation in moisture rich environment is also compared with that of mineral oil-pressboard system. Degree of polymerisation of pressboard samples measured at different ageing interval is used in this research to determine the ageing condition of pressboard. Moreover, applicability of oil related diagnostic parameters such as concentration of dissolved furanic compounds, acidity value, Dielectric Dissipation Factor (DDF), viscosity and colour to assess the degree of degradation of both ester and mineral insulating oils is thoroughly investigated in this research project. The potential of FTIR (Fourier Transform Infrared spectroscopy) techniques for characterising the degree of degradation of paper insulation is also discussed in this thesis. In addition, this thesis concentrates on characterisation of the charge dynamic in insulating oil through modelling of their dielectric responses.The comparison of gassing behaviour of ester and mineral insulating oils under two different low temperature faults and low energy electric discharge condition is also presented in this thesis.Dissolved Gas Analysis (DGA) results presented in this thesis depicts that faults gases detected in ester and mineral oil samples subjected to a similar fault are akin in type but quantitatively different. The quantity of fault gases produced in two different natural ester oils is also dissimilar.For example, soy-based natural ester produces a large quantity of ethane (C2H6) under low temperature overheating condition than sunflower oil based natural ester. Therefore, this research project investigates the applicability of well-established DGA interpretation schemes namely Duval II | P a g e triangle, IE...

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A mechanism of thermo‐oxidative degradation of polyol ester lubricants

Cited by 35 publications

References 10 publications

Using Acid Number as a Leading Indicator of Refrigeration and Air Conditioning System Performance

Using Acid Number as a Leading Indicator of Refrigeration and Air Conditioning System Performance

Voltammetric Determination of Dinonyl Diphenylamine and Butylated Hydroxytoluene in Mineral and Synthetic Oil

Condition monitoring of biodegradable oil filled transformer

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