Standard Guide for Instrument and Precision Bearing Lubricants—Part 2 Greases

Importancia y uso:

4.1 The purpose of this guide is to report on the testing of, to discuss and compare the properties of, and to provide guidelines for the choice of lubricating greases for precision rolling element bearings (PREB). The PREB are, for the purposes of this guide, meant to include bearings of Annular Bearing Engineer's Committee (ABEC) 5 quality and above. This guide limits its scope to lubricating greases used in PREB.

4.2 The number of lubricating greases used in PREB increased dramatically from the early 1940s to the mid 1990s. In the beginning of this period, petroleum products were the only widely available base stocks. Later, synthetic base oils became available. They included synthetic hydrocarbons, esters, silicones, multiply alkylated cyclopentanes (MAC) and fluorinated materials, including perfluorinated ethers and the fluorosilicones. This broad spectrum of lubricant choices has led to the use of a large number of different lubricants in PREB applications. The U.S. Department of Defense, as a user of many PREB, has seen a significant increase in the logistics effort required to support the procurement and distribution of these items. In addition, as time has passed, some of the greases used in certain PREB are no longer available or require improved performances due to advanced bearing technology/requirements. This implies that replacement lubricating greases must be found, especially in this era of extending the lifetime of DoD assets, with the consequent and unprojected demand for sources of replacement parts.

4.3 One of the primary goals of this study was to take a broad spectrum of the lubricating greases used in PREB and do a comprehensive series of tests on them in order that their properties could be compared and, if necessary, potential replacement greases be identified. This study is also meant to be a design guide for choosing lubricating greases for future PREB applications. This guide represents a collective effort of many members of this community who span the spectrum from bearing manufacturers, original equipment manufactures (OEMs), grease manufacturers and suppliers, procurement specialists, and quality assurance representatives (QARs) from DoD and end users both inside and outside DoD.

4.4 It is strongly recommend that, prior to replacing a grease in a PREB, all of the existing grease should be removed from the bearing. Reactions may occur between incompatible greases resulting in severely degraded performance. When users have more than one type of grease in service, maintenance practices must be in place to avoid accidental mixing of greases. In addition, all fluids used specifically to prolong storage life of PREBs (preservatives) should be removed prior to lubricating the bearings. Reactions may occur which would degrade the grease.

4.5 The base oils, thickeners, and additives dictates grease performances. The properties of many base oils can be found in the previous study (Guide F2161). This study included a discussion of elastohydrodynamic lubrication theory.

Subcomité:

F34.02

Volúmen:

01.09

Número ICS:

75.100 (Lubricants, industrial oils and related products)

Palabras clave:

ball bearings; ester oil; instrument and precision bearing lubricants; mineral oil; perfluoropolyether oil; polyalphaolefins; silicon oil; pennzane; thickener; lubricating grease;