May / June 2020 NLGI Spokesman

Modern Technology Improves the Grease Making Process Arnold Josefson Emerson Automation Solutions Measurement Solutions - Systems Houston, TX ABSTRACT This paper gives a concise review of the history and implementation of programmable logic controls, digital control systems, and digital instruments to replace analog instruments in batch and continuous grease manufacturing systems. These technologies improve grease-making operations and the repeatability of grease formulations in production..

INTRODUCTION Reproducibility of grease production has been an issue that has plagued the industry nearly as long as grease has been produced. This challenge became more apparent when higher performance products became the standard due to increasingly tight specifications dictated by original equipment manufacturers (OEMs).

Wikipedia defines a true grease as having the following properties: “A true grease consists of an oil and/or other fluid lubricant that is mixed with a thickener, typically a soap, to form a solid or semisolid. Greases are a type of shear-thinning or pseudo-plastic fluid, which means that the viscosity of the fluid is reduced under shear. After sufficient force to shear the grease has been applied, the viscosity drops and approaches that of the base lubricant, such as the mineral oil. This sudden drop in shear force means that grease is considered a plastic fluid, and the reduction of shear force with time makes it thixotropic” So, grease is really thickened oil. The thickener is used to provide the shear-sensitive performance.

The thickener could be an organic soap, an inorganic powder like fumed silica, a calcite matrix, polymer matrices, or even tar. For this discussion we will concentrate on organic soaps; they are used in the most common and commercially important types of grease.

What is so hard about that?

THE PROBLEM STATEMENT It is not unusual for grease makers to comment that they can use the same formula and the same raw materials, but obtain different results for batches of grease. Quality control of grease is based on physical measurements of the final product through tests, including ASTM standards, IP standards from the Energy Institute, and British Defence Standards (Def Stan) issued by the Ministry of Defence of the United Kingdom (MODUK): Grease laboratory tests: • Dropping Point, ASTM D566, IP 396 • Cone Penetration, ASTM D217, IP 50 • Oxidation Stability, ASTM D952, IP 142 • Copper Corrosion, ASTM D130, IP 112 • Corrosion Preventative Properties, ASTM D1743, IP 220 - 36 NLGI Spokesman | VOLUME 84, NUMBER 2 | May/June 2020