We’ve talked before about lubrication, specifically ball bearings. Too much, or not enough, simply won’t work. Writing a guest post at LUDECA, Dave Tiffany, Reliability Specialist for Pioneer Engineering, asks …..
Does it really matter? Oil is oil, grease is grease, and more is better, right?
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. Viscosity is the most important physical property of a lubricant, and viscosity is the most important specification for a lubricant. Along with this, viscosity is the easiest thing to mess up!
Tiffany offers a simple definition of viscosity: it’s the thickness of an oil. Taking that definition further, he writes that “…viscosity is a measurement of the oil’s internal resistance or its resistance to flow by gravity.” Viscosity reduces friction and wear by separating surfaces in relative motion so they won’t touch.
To measure it, he writes, you need to measure viscosity at a given temperature. Viscosity will generally decrease as the temperature of the oil increases.
Stating an oil’s viscosity is found in many different formats depending on the application. The International Standards Organization (ISO) is the universally accepted method for stating oil viscosity (ISO VG) through-out industry (ISO 3448). This ranges from an ISO VG 2 to an ISO VG 3200. ISO VG is stated at 40°C.
AGMA specify grades an oil’s viscosity for industrial gear applications, also at 40°C. The AGMA uses a #1 through #8A designation.
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. This stands for Saybolt Universal Seconds – or – Saybolt Seconds Universal, you’ll see it stated either way.
Tiffany writes that oil has even more classifications from the Society of Automotive Engineers (SAE) and that the classifications for Crankcase and SAE Gear are different yet.
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.
Even if you aren’t sure what viscosity is related to a specific piece of equipment, knowing there is a difference is a positive step. Taking extra steps to familiarize yourself with your equipment’s specific lubrication requirements greatly improves its reliability and life cycle.