Industrial machinery often operates in a climate controlled environment, thus there is no reason to use multi-grade oils (in fact, it may be harmful). The differences in viscosity of an SAE 20 and SAE 5 oil relative to being poured on the same angled surface.Ĭonversely, the aforementioned AW-68 hydraulic oil has an ISO VG rating of 68 this, in turn, allows it to be classified as a single-grade lubricant, or straight-grade oil. In short, for engine lubricants, the lower the "W" rating, the lower the pour-point will be. Instead of it taking 15 minutes to warm up your engine oil, potentially damaging your engine, these additives allow for quicker lubrication of all engine components, eventually evening out at operating temperature. To be clear, 5w-20 motor oil is an example of a Multi-viscosity oil - these oils contain a VI improver to compensate for the range of temperatures an automotive engine may be exposed to: these additives allow for cold startups without sacrificing lubrication efficiency. Shop Industrial, Manufacturing, Automotive Lubricants: Petroleum Service CompanyĪside from the industrial applications which specifically require a High Viscosity Index (HVI) oil (when machinery is exposed to a wide range of temperatures), many industrial lubricants lack VI improvers because the machinery in which they operate are not subject to changes in temperature. Static over a wider range of temperatures this occurs via unique additives referred to as "Viscosity Index Improvers" (VI improvers). When it comes to automotive engine lubrication, we often prefer oils with a low viscosity spectrum, but a "High Viscosity Index"- in short, this means that the viscosity stays Liquid water has an extremely narrow viscosity spectrum (in the range of 33 F to 211 F) when compared with honey: meaning that the viscosity of water goes relatively unchanged over that temperature range alternatively, honey would pour much slower at 33 F compared to 211 F, which means that its viscosity spectrum is much wider (in said temperature range). ![]() But what about water? Whether near freezing or just about to boil, water pours relatively the same. Honey when you heat it up: it immediately becomes easier to pour once it reaches a certain temperature also, when cooled, the consistency of honey thickens. Lubricants resembling this liquid are higher viscosity oils. This is because honey is more viscous than water and has a much higher viscosity.Īlternatively, this fluid is a great deal thicker - somewhat like honey. Immediately - but a glass of honey would slowly spill over, giving you a second to react. If you were to knock over a glass of water, the liquid would spill out Take, for example, this comparison of two common substances with different viscosities: water and honey. In a nutshell, the thicker the fluid is, the more resistance to flow it will demonstrate. Viscosity is the measure of a fluid's resistance to flow (under certain conditions). This liquid's water-like state is reminiscent of a lower-viscosity lubricant. Viscosity and though the word may sound a bit dense, it's actually pretty simple: it is a number value for the relative thickness (or weight) of your oil or lubricant. These numbers are representative of a lubricant's Numbers in 5w-20 might signify? Or - should you work with machinery that requires an industrial lubricant - the AW-68 on your pail of hydraulic oil? All rights reserved.If you've changed your own oil before, then chances are you know what the "w" in 5w-20 means (HINT: it stands for winter grade, or rating). Copyright © 2023, Columbia University Press. The Columbia Electronic Encyclopedia, 6th ed. To keep one layer of fluid moving at a greater velocity than the adjacent layer, a force F is necessary, resulting in a shearing stress F/A, where A is the area of the surface in contact with the layer being moved. ![]() The difference in velocity between adjacent layers of the fluid is known as a velocity gradient and is given by v/x, where v is the velocity difference and x is the distance between the layers. If the difference in velocity between the fluid at the sides of the pipe and that at the center, or between the moving object and the fluid through which it is moving, is not too great, then the fluid flows in continuous, smooth layers that is, the flow is laminar. When a fluid is moving through a pipe or a solid object is moving through a fluid, the layer of fluid in contact with the sides of the pipe or the surface of the object tends to be in the same state of motion as the object with which it is in contact that is, the layer of fluid along the side of the pipe is at rest, while that in contact with the moving object is carried along at the same velocity as the object.
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