Translating the viscosity is a good first step and can be sufficient for most general-purpose applications. This is a good approximation for most oils, but will lead to a small error when converting between ISO/AGMA and SAE for high Viscosity Index oils. The chart assumes the oil has a Viscosity Index of 95. Oil gets thinner according to its Viscosity Index, and the chart is calculated with a specific Viscosity Index (VI 95 default) ISO VG measures oil at 40✬ and a given range to +/-10% of their stated value, so ISO VG 100 oil will have a viscosity between 90 and 100 cSt at 40✬.ĪGMA has redefined its grades to align with ISO standards, so they line up exactly. Oils grades that are on the same horizontal line (with the correct Viscosity Index) on the chart are equivalent. This article was originally posted at pioneer-engineering.Several organizations (ISO, SAE, AGMA) have created competing standards to define oil viscosity ranges, but most of them mean the same thing. But if this sounds like a foreign language that you do not understand, it's okay, as long as you now realize that your equipment may be in jeopardy of shorter life cycles and there is potential for cost saving improvements that will greatly enhance your equipment's reliability.Īll of this and a lot more is covered in our public or private training class, "Intro to Machinery Lubrication & Oil Analysis." I encourage you to check it out.even if we're speaking the same language! You are likely on top of your game and know exactly which oils and viscosities belongs in each application throughout your facility. If all of this is making sense, I commend you. 0W, 5W, 10W, etc., and straight weights 30, 40, and 50 are designations for crankcase oils, while 70W to 85W and 80 to 250 are designations for automotive gear oils. Society of Automotive Engineers (SAE) Crankcase and SAE Gear classifications are different yet. This stands for Saybolt Universal Seconds - or - Saybolt Seconds Universal, you'll see it stated either way. SUS - or - SSU is not in use much anymore, but you may still find it referenced on an older gearbox nameplate or an OEM (original equipment manufacturer) manual. The AGMA uses a #1 through #8A designation. ISO VG is stated at 40☌.ĪGMA specify grades an oil's viscosity for industrial gear applications, also at 40✬. This ranges from an ISO VG 2 to an ISO VG 3200. The International Standards Organization (ISO) is the universally accepted method for stating oil viscosity (ISO VG) through-out industry (ISO 3448). Stating an oil's viscosity is found in many different formats depending on the application. Normally viscosity is inversely proportional to temperature, meaning as the temperature of an oil increases, its viscosity generally will decrease. ![]() Viscosity should always be measured at a given temperature. Viscosity is what carries the load, separating surfaces in relative motion from touching, thus reducing friction and wear, extending equipment life. While this is the most common understanding of viscosity, a more technical definition of viscosity is a measurement of the oil's internal resistance or its resistance to flow by gravity. Along with this, viscosity is the easiest thing to mess up!Ī simple definition of viscosity is the thickness of an oil. ![]() Viscosity is the most important physical property of a lubricant, and viscosity is the most important specification for a lubricant. The importance of proper oil viscosity in your large array of equipment and the varying lubrication regimes they present is one of the most important maintenance practices one can focus on in their facilities. If you have a gearbox with a manufacturer's nameplate instructing you to use the American Gear Manufacturer's Association (AGMA) #4 viscosity oil at a given operating temperature, or if it specified a 750 SSU viscosity oil, would you know exactly what viscosity oil you need? If your grease application specified a base oil viscosity of 220 cSt for a given operating temperature would you know which of your greases might fit that specification, if any?ĭoes it really matter? Oil is oil, grease is grease, and more is better, right?
0 Comments
Leave a Reply. |