Oil in water vs water in oil emulsion8/17/2023 The first is from colloidal condensation due to a supersaturated state of water in oil. There are two common ways emulsified water can form in oil. The first sample is dry oil while the middle sample and the right sample have increasing amounts of emulsified water, hence the cloudy, turbid appearance. Figure 1 shows three samples of hydraulic fluid. This noteworthy parameter is referred to as turbidity, which actually increases the oil’s viscosity. They are what cause the oil to become hazy or cloudy depending on oil concentration. These micro-globules are basically locked in the body of the oil and as such become a homogeneous part of the oil, physically and chemically. Stoke's Law plays a role too (Google it). The smaller the water globule, the greater the relative interfacial area of water contacting the oil, which holds the water tighter and longer in the body of the oil. Also influencing this is the high oil-water interfacial area which relates to the contact area between the water and the oil. This is due to polarity, relating to cohesive forces between the water and the oil, especially its additives. Emulsified water does not separate quickly, or at all in many cases. Instead it has been more accurately referred to as emulsified water or a microemulsion. Water that is held tightly in micro-globules in the oil is no longer referred to as free water. This means it will separate below (most common) or above the oil phase depending on oil density. Free water has been redefined as being water that, by force of gravity, will phase out of the oil. In the last 30 years or so most of the literature, including Noria’s publications, refer to water as having three states. Historically, water contaminated oil has been said to exist in two states, the first dissolved water (bound molecularly in the matrix of the oil) and the second free water (not molecularly bound). If you want world-class lubrication, you must have world-class inspection. If you want world-class reliability, you must have world-class lubrication. It is imperative that we train our eyes and be keen inspectors which is integral to Inspection 2.0. By far, the most important, effective and practical condition monitoring sensor is the eyeometer (I love that word!). Three of these states are clearly visible and not only tell us about the presence of water, but also about the condition of the oil. The understanding of its coexistence has evolved over the years from the initial perception of two states, then three and now four. ![]() It’s important to know how it behaves and coexists when it invades our oil, machine or system. ![]() Why is this important? Water is a highly destructive contaminant.
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