The dropping point of a grease is the temperature at which it passed from a semi-solid to a liquid state. ASTM Method D-2265 is the test to determine the cohesiveness of the base oil and thickener of a grease. Dropping point tests are used for quality control such as: to verify that the soap structure has been formed correctly and will withstand high temperatures. The dropping point is not the melting point of lubricating grease, and should not be used to determine the upper operating temperature of a grease.
The ability of a film of lubricant to resist rupture due to load, speed, and temperature.
Emcor is test method to measures the ability of a grease to protect a bearing again corrostion in the presence of water.
The ability of a lubricant to resist chemical decomposition in the presence of water.
Shear stability of Grease
Shear stability, also be called Mechanical Stability, is the ability of a lubricating grease to resist changes in consistency during mechanical working.
Viscosity is a measure of the resistance of a fluid (or gas) to flow under shear stress. It describes the flow resistance or internal friction of moving fluid.
a. Absolute (Dynamic) Viscosity, also called coefficient of absolute viscosity, is a measure of internal resistance. Dynamic (absolute) viscosity is the tangential force per unit area required to move one horizontal plane with respect to an other plane, at an unit velocity, when maintaining an unit distance apart in the fluid.
b. Kinematic viscosity is the resistance of a liquid to flow under gravity. Kinematic viscosity can be measured directly or can be calculated as the ratio of the dynamic viscosity to the its density.
Nowadays, there are a lot of websites have online calculator to help calculate the viscosity at a given temperature, when the viscosity is known at two temperatures.
The Viscosity Index is an arbitrary, measure of a fluids (e.g lubricating oil) change in viscosity relative to temperature change, normally abbreviated to VI.
VI can be calculated based on viscosity @ 40 oC and 100 oC according to ASTM D2227.
Nowadays, there are a lot of websites have online calculator to help calculate the viscosity at 40 oC, 100 oC, or VI when any two values are known (e.g keyword is viscosity index calculator).
Flash point is the lowest temperature at which a liquid in a specified appratus will give off sufficient vapor to ignite momentarily if given an ignition source. There are two basic type of flash point: open cup (test with open cup) and closed cup (test with cup with a lid).
ASTM D92 is test method to determine Cleveland open cup (COC).
Four-ball weld point
In ASTM D2596, four-ball weld point is the applied load at which the lubricant can no longer prevent metal-to-metal contact, measurement unit is kg, used 04 standard steel balls in the test as below
Demulsibility of lubricating oil can be defined as the ability of an oil to release the water. This property is very importanct if the equipment is operating in highly humid or wet environment.
Water is unexpected contamination. Oil is natural hygroscopic, meaning that it absorbs water, so it seems that water is destined to get soaked into the oil in humidity. If an oil has good demulsibility property, when oil is contaminated by water, oil will be separated apart from water. In other words, water will be separated apart from oil and then be drained off. Therefore, oil will be "dry". Conversely, an oil have poor/or no demulsibility, water will contaminates oil and creates emulsion of water-oil. Lubricating components will wear rapidly.
When equipments operates in the absence of water and is climate controlled, then demulsibility may not be importance.
Water washout resistance (of grease)
Water washout resistance is ability of a lubricating grease to resist being removed from a bearing when operated with exposure to water. (Generally measured by ASTM D1264).
Compatibility of synthetic base oils with plastic and Elastomer
Lubricants protect your components from wear and corrosion and should be treated as critical design component. But different lubricant chemistries