According to the ASTM (American Society for Testing and Materials), lubricating grease is a solid to semifluid product formed from the dispersion of thickening agents in a liquid lubricant. As per the aforementioned definition, there are three components that form a lubricating grease, those of which include an oil, thickener, and additives. The base oil and additives serve as the major constituents in grease formulations and influence the behavior of the grease. Meanwhile, the thickener is often referred to as a sponge that holds the lubricant. By incorporating the correct grease in your maintenance operations, you can ensure your facility is operating at peak performance.
Anatomy of Industrial Grease
While most greases produced today take advantage of mineral oils for their fluid components, these variations only provide satisfactory performance in most industrial applications. In applications with varying temperature extremes, greases with synthetic-based oils provide better stability.
Thickeners, on the other hand, are materials that, when mixed with a selected lubricant, produce a solid to semi-fluid structure. Current grease formulations utilize metallic soap as their thickener of choice. These soaps include lithium, aluminum, clay, polyurea, sodium, and calcium. Recently, complex thickener-type greases are garnering popularity due to their high dropping points and excellent load-carrying capabilities.
Generally, complex greases are made by combining conventional metallic soaps with a complexing agent, with the most widely used being a lithium based complex grease. They are made by combining conventional lithium soap and a low-molecular-weight organic acid as the complexing agent. By contrast, nonsoap thickeners are also popular options, especially in high-temperature environments. For instance, bentonite and silica aerogel are two thickeners that do not melt at high temperatures.
However, there is a major misconception that even though a thickener may withstand high temperatures, the base oil will still oxidize quickly at increased temperatures; thus, it will require a regular relube schedule. Additives play several roles in a lubricating grease. This includes enhancing the existing desirable properties, suppressing existing undesirable properties, and introducing new properties. Common additives are oxidation and rust inhibitors, alongside extreme pressure, antiwear, and friction-reducing agents. In addition to these additives, boundary lubricants like molybdenum disulfide or graphite are often suspended in the grease to reduce friction and wear without producing adverse chemical reactions.
Function and Applications of Grease
Grease is intended to remain in contact with and lubricate moving surfaces without leaking out under the force of gravity, centrifugal action, or being squeezed out under pressure. One of its major benefits is that grease retains its properties under shear forces at all temperatures during use. For example, construction facilities necessitate heavy-duty grease to operate optimally.
It is important to note that grease and oil are not interchangeable as lubricants. Grease is utilized when oil is not a suitable option. Typically, lubricant selection is determined by matching the machinery design and operating conditions with desired lubricant characteristics. Because grease remains in place for long periods of time, a beneficial lubricating film forms, protecting machinery that runs intermittently or is in storage.
Moreover, high-quality greases can easily get into hard-to-reach areas and inaccessible components, remaining intact for long periods of time without needing relubrication. They also find use in sealed-for-life applications like within some electrical motors and gearboxes. In worn components, grease can provide protection in clearances that have been enlarged by wear and extend the life of damaged parts.
Similar to oil, grease has its own set of characteristics that have to be taken into consideration when selecting grease for an application. In a high-pressure environment, heavy-duty grease is a good option. Some of these characteristics include pumpability, water resistance, consistency, dropping point, and oxidation stability, among others.
Industrial Part Sphere is a leading distributor of industrial greases, lubricants, and sealants, all of which have been sourced from top global manufacturers that we trust. Kickoff the procurement process with a competitive quote on any desired item in our catalogs and see how we can fulfill your operational requirements. For additional inquiries, call or email us at any time; we are available 24/7x365!
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