![]() It is important to note that this method assumes the viscosity temperature relationship of the lubricant (viscosity index = 90). To use this method, the type of gear set, gear geometry, operating temperature and the speed of the slow speed gear must be determined.Īfter calculating the pitch-line velocity of the slowest gear in the unit, the required viscosity grade can be read from the chart using the highest likely operating temperature of the unit. Other charts exist for worm gears and open gearing. ![]() The chart in Figure 1 is applicable to spur, helical and beveled enclosed gear sets. In this method, assumptions are made concerning the load, viscosity index and the pressure-viscosity coefficient of the lubricant. One of the most common methods for determining viscosity is the ANSI (American National Standards Institute) and AGMA (American Gear Manufacturers Association) standard ANSI/AGMA 9005-E02. Because it is difficult to determine the load for most viscosity selection methods, the load is assumed and the determining factor becomes speed. The viscosity for a gear lubricant is primarily chosen to provide a desired film thickness between interacting surfaces at a given speed and load. Therefore, it is important to understand the methods for viscosity selection and the factors that affect the requirement. Unfortunately, the manual does not always exist or the machine operates outside the conditions for which the OEM’s recommendations were made. Viscosity – Often referred to as the most important property of a lubricating oil.Īdditives – The additive package used in the lubricant will determine the lubricant’s general category and affects various key performance properties under operating conditions.īase Oil Type – The type of base oil used should be determined by the operating conditions, gear type and other factors.Ĭhoosing an appropriate viscosity grade is usually as simple as finding the recommendation in a component’s maintenance manual. In order to choose the best lubricant for a gear set, the following criteria must be addressed: Proper lubricant selection is a cornerstone of any excellent lubrication program.Ī good understanding of this allows the lubrication engineer to maximize machinery reliability under normal conditions, as well as use lubricant specification as a problem solver in abnormal conditions. When selecting lubricants for industrial gearing, numerous factors must be considered beyond simply selecting a product from the maintenance manual’s QPL, including product availability, operating conditions, the preferred lubricant brand and product consolidation efforts. In addition to understanding and being able to interpret the specifications given by equipment manufacturers, it is important to understand why, and be able to make changes when necessary. It is therefore important for the individuals responsible for selecting lubricants to posses a fundamental understanding of how to specify lubricants for gearing. ![]() While some original equipment manufacturers (OEMs) provide generic specifications that consider pertinent parameters, others give only a general specification that may not even consider operating temperatures. Unfortunately, this solution may not always provide optimum lubrication for a given gear set, or maximum efficiency in managing lubricant inventory. How do you know which lubricant is the best fit for a given application? Typically, it is as simple as searching through a maintenance manual and selecting a product from the QPL (qualified product list).
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