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    Category: Degradation Mechanisms

    Where can Ion Resin Exchange Filters be Used?

    Rafe sits down with Peter Dufresne – Executive Vice President at EPT Clean Oil to discuss all things regarding varnish and varnish remediation. Where can…

    Rafe Britton 17 December 2021
    0 Comments

    How do you Choose an Ion Exchange Resin Filter?

    Rafe sits down with Peter Dufresne – Executive Vice President at EPT Clean Oil to discuss all things regarding varnish and varnish remediation. How …
    Rafe Britton 17 December 2021

    How do Ion Exchange Resin Filters Target Unwanted Molecules?

    Rafe sits down with Peter Dufresne – Executive Vice President at EPT Clean Oil to discuss all things regarding varnish and varnish remediation. How do…

    Rafe Britton 17 December 2021
    0 Comments
    Industrial water filtration unit

    How do Ion Exchange Resin Filters for Oil Differ from Those for Water?

    Rafe sits down with Peter Dufresne – Executive Vice President at EPT Clean Oil to discuss all things regarding varnish and varnish remediation. How do…

    Rafe Britton 17 December 2021
    0 Comments
    IIoT Chip

    How do we Use Online Oil Sensor Data in a Condition Monitoring Program?

    Rafe sits down with Dr Guillermo Miro – Application Engineer at Atten2 to discuss all things regarding online/inline oil sampling and analysis. He explains that…

    Rafe Britton 12 December 2021
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    Oil samples lined up in order of colour, plus an Atten2 oil sensor

    What Are the Different Kinds of Online Oil Sensors?

    Rafe sits down with Dr Guillermo Miro – Application Engineer at Atten2 to discuss all things regarding online/inline oil sampling and analysis. He explains that…

    Rafe Britton 10 December 2021
    0 Comments

    How Does Lubricant Oxidize? A Beginner’s Guide

    Oil oxidation is an undesirable series of chemical reactions involving oxygen that degrades the quality of an oil; it is the primary degradation mecha…
    Rafe Britton 5 December 2021

    What is Nitration of Lubricating Oil?

    Nitration refers to an unfavourable condition in which the oil in gas engines is saturated with insoluble or soluble nitrogen oxide compounds. The combustion chamber…

    Rafe Britton 2 December 2021
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    What is Micro Dieseling of Lubricating Oils?

    Microdieseling is pressure-induced thermal degradation of oil. An air bubble moves from a low or negative pressure zone to an area of high pressure. The air undergoes…

    Rafe Britton 30 November 2021
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    What is Micro Dieseling of Lubricating Oils?

    Forum Description

    Microdieseling is pressure-induced thermal degradation of oil. An air bubble moves from a low or negative pressure zone to an area of high pressure. The air undergoes adiabatic compression and heats up to 1000 degrees Celsius. These extreme temperatures can carbonize oil at the bubble interface resulting in sludge, soot, tar & varnish and increased oil oxidation. https://youtu.be/V9I6eV3Rs9g For micro-dieseling to occur we require two key ingredients: entrained air and a rapid increase in pressure. Let's look at how each manifests in a hydraulic system.

    Air

    These are the four types of air-in oil contamination
    • Dissolved Air - invisible air, just like the carbon dioxide trapped in a bottle of coke before opening
    • Entrained air - unstable microscopic air bubbles
    • Trapped pockets or air free from dead zones, high areas
    • Foam - akin to the head on a beer or foam in a glass of coke
    For micro-dieseling to occur, we need air bubbles to enter to pump. Entrained air will do this naturally, but hydraulic systems are designed to operate with a regular amount of entrained air. Issues tend to arise when an abnormally high amount of entrained air enters the system by:
    • Pump operation is almost dry due to insufficient fluid volume
    • Insufficient residence time
    Alternatively we may convert dissolved air into entrained air by reducing the suction side pressure. This reduces gas solubility of the oil.
    • An orifice can experience pressure drop
    • Pressure drops through pipes and via hoses
    • Turbulence caused by valve opening and closing
    • Shock waves caused by sudden valve closings and cessation pump operation
    • Pressure drop caused by sudden valve opening
    • Piston rods are subject to external force
    • Suction resistance

    Rapid pressure increase

    Rapid increases in pressure are generally brought about by the activity of pumps. In hydraulic systems this means that the location for micro dieseling is similar to cavitation.  What follows is a compression of the air bubble, which contains hydrocarbons at the oil interface. You will already be familiar with how a diesel engine works. During compression, the mixture of the sprayed gasoline and the rising temperature of the compressed air results in ignition. Your oil will turn black because the burnt fuel is not fully converted to water or carbon dioxide, forming soot and tars. This is normal for diesel engines. Engine oils contain detergents and dispersants to handle high levels of soot without needing to be changed. When the same phenomenon occurs in hydraulic oils, it leads to:
    • Oil darkening (soot loading)
    • Wear (soot is abrasive)
    • Valve sticking (due to build-up of tars and varnish)
    • Increased bulk oil temperature (high temperature air bubbles equalise with oil system)
    • Accelerated oxidation
    • Decreased oil life
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