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Lubricating Grease
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
Greases are characterized by their chemistry and physical properties. For example, a grease formulated from lithium 12-hydroxystearate and a polyalphaolefin would be referred to as a lithium-thickened synthetic hydrocarbon. Moreover, a grease formulated with amorphous silica and a dimethylpolysiloxane would be called an inorganically thickened silicone. Grease is most often designated by the nature of the thickener and the base fluid. Greases are more complicated physically than oils since they are composed of both solids and fluids. However, numerous tests are available to characterize the physical attributes of various greases. Table 38.8 is a partial listing of available grease tests. The color and appearance of a grease do not necessarily relate to quality, since trace level of color bodies or chromophores present in antioxidants can alter the color of a grease with time. However, color and appearance should be mentioned in technical literature since these attributes may vary with lot and line personnel are sensitive to such changes. Dyes are frequently used to provide a distinctive color to a specific grease. The consistency of grease is measured in accordance with ASTM D217 and similar standards issued by other countries. P0 refers to the unworked penetration of a grease while P60 is the worked sixty-stroke penetration. It is the P0 consistency that is experienced by dispensing equipment while the P60 is used to designate the NLGI grade of the grease.
Lubricating Bearings and Other Machine Elements
Published in Heinz P. Bloch, Kenneth E. Bannister, Practical Lubrication for Industrial Facilities, 2020
Heinz P. Bloch, Kenneth E. Bannister
They are valid for commonly available greases having a mineral oil base and with no EP additives. Of the grease types listed, lithium and more particularly lithium 12-hydroxystearate base greases are those most often used for bearing lubrication.
Microstructure Characterization of Degraded Grease in Axle Roller Bearings
Published in Tribology Transactions, 2019
The grease lubricant investigated in this study was a NLGI Grade 3 grease, mineral oil based with lithium 12-hydroxystearate soap thickener and less than 5 wt% of additives (23). The properties and corresponding tests of fresh and unused grease are listed in Table 1. Aged grease samples were obtained from 20 used field axle SRBs, which were removed from urban commuter trains as part of the maintenance programme. The outer diameter of each SRB is 220 mm. Three types of aged grease were categorized and are listed in Table 2. The age of grease samples was categorized according to the total distance traveled by the train’s axle SRBs. The average operating conditions of the field bearings are summarized in Table 2. Aged grease sampling was done in the regions between rollers and the inner surface of the outer race, as indicated in Fig. 1b. For each bearing, grease sampled from different locations was placed into the same container. A fresh and unused grease sample (Fig. 1a) was also prepared and examined as a materials baseline, to characterize the degradation of grease microstructure.
Effect of Micro Nano-Structured Copper Additives with Different Morphology on Tribological Properties and Conductivity of Lithium Grease
Published in Tribology Transactions, 2022
Mengyuan Zhu, Ningning Song, Shengmao Zhang, Yujuan Zhang, Laigui Yu, Guangbin Yang, Pingyu Zhang
The as-prepared Cu NSs, Cu MWs, and Cu Ps were separately mixed with lithium base grease (made from a base oil blend of two mineral oils thickened with lithium 12-hydroxystearate) at mass fractions of 1wt%, 5wt%, 10wt%, 15wt%, and 20wt%. The resultant mixtures were premixed with a glass rod in beakers and then fully mixed with a three-roller machine to obtain the lithium conductive greases containing micro nano-structured Cu fillers with different morphologies.
A Model for Shear Degradation of Lithium Soap Grease at Ambient Temperature
Published in Tribology Transactions, 2018
Yuxin Zhou, Rob Bosman, Piet M. Lugt
Generally, the degradation of grease is classified as chemical or mechanical aging. This article focuses on the mechanical aging of lithium 12-hydroxystearate–thickened grease. This type of grease takes the major share of the worldwide industrial grease market and is widely applied in rolling bearings due to its wide temperature applicability, relatively good mechanical stability, water-resistant properties, and low cost (Lugt (1)).