The Effects of Thickeners on the Low Temperature Properties of Open Gear Greases Raymond Drost, Donald Howard, Huafeng (Bill) Shen, PhD Bel-Ray Company, LLC Abstract
Open gears operate under severe conditions, often at their design limits. Severe conditions include extreme pressures, varying speed and contamination. Possibly the most important aspect of open gear lubricant selection is low temperature pumpability and the ability of the lubricant to be applied through a centralized lubrication system at the lowest anticipated ambient temperature. Considering the cost of downtime of an electric rope shovel or walking dragline in a mining operation, choosing the correct open gear lubricant for the application is critical. When it comes to selection, open gear greases using various thickeners are available and their low temperature performance needs to be examined. While keeping the additive system constant, lab samples of an open gear grease were blended with four thickener types; Aluminum Complex, Lithium Complex, Calcium Sulfonate Complex and Organo-clay. The open gear lubricants’ low temperature properties were evaluated using standard tests to determine the effects of the thickener type on their low temperature properties.
Keywords
Open gear lubricant; Thickener; Ventmeter; Grease Low Temperature Properties.
Introduction
The earliest open gears have been used since the beginning of rotational machinery and were made using wood with cylindrical pegs and lubricated with animal fat. Engineers developed metal gears during the British industrial revolution in the mid-18th century. It was not until a century later that open gears and the way they were lubricated were modernized. Large heavy-duty
open gears are a very common method of transmitting power. In addition, they are the most economical type of gear drive where high load-carrying capacity is required under severe shock load conditions for extended periods of time. Typically, there are two varieties of gear systems; Type 1 and Type 2. For the extent of this paper, only Type 1 gear systems will be discussed. Type 1 open gear systems consist of a motor, typically an actuator and a rack system on machinery such as the hoist and drag drives of mining shovels and draglines. The main difference between Type 1 and Type 2 gear systems is the operation. During operation, Type 1 systems change speeds and are bi-directional, whereas Type 2 systems operate at constant speeds and in the same direction. Due to the nature of Type 1 systems, different physical and performance properties need to be examined in order to properly lubricate these systems with maximum efficiency for reduced cost of operation and down time of the equipment. Variable speed and directional changes under heavy loads could pose the toughest conditions the lubricant can handle. For this reason, EP properties to protect against friction and wear, tackiness for adhesion to the gears, corrosion resistance and the ease of pumpability are all important factors in choosing the correct open gear lubricant for the application. Several industry standards have been established for performance properties as well as another important factor; base-fluid viscosity. As aforementioned, open gear lubricants encounter some of the harshest conditions a lubricant can face. Therefore, a proper film thickness of the lubricant is critical in ensuring optimal performance
- 12 VOLUME 80, NUMBER 5
