How Does Extreme Pressure Grease Work?

The American Society for Testing and Materials (ASTM) defines lubricating grease as: "A solid to semifluid product of dispersion of a thickening agent in liquid lubricant. Other ingredients imparting special properties may be included" (ASTM D 288, Standard Definitions of Terms Relating to Petroleum).

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Grease Anatomy

As this definition indicates, there are three components that form a lubricating grease. These components are oil, thickener and additives. The base oil and additive package are the major components in grease formulations, and as such, exert considerable influence on the behavior of the grease. The thickener is often referred to as a sponge that holds the lubricant (base oil plus additives). By adding the proper grease to your maintenance routine, you guarantee your facility is operating at peak performance. 

Figure 1. Grease Anatomy

Base Oil

Most greases produced today use mineral oil as their fluid components. These mineral oil-based greases typically provide satisfactory performance in most industrial applications. In temperature extremes (low or high), a grease that utilizes a synthetic base oil will provide better stability.

Thickener

The thickener is a material that, in combination with the selected lubricant, will produce the solid to semifluid structure. The primary type of thickener used in current grease is metallic soap. These soaps include lithium, aluminum, clay, polyurea, sodium and calcium. Lately, complex thickener-type greases are gaining popularity. They are being selected because of their high dropping points and excellent load-carrying abilities.

Complex greases are made by combining the conventional metallic soap with a complexing agent. The most widely used complex grease is lithium based. These are made with a combination of conventional lithium soap and a low- molecular-weight organic acid as the complexing agent.

Nonsoap thickeners are also gaining popularity in special applications such as high-temperature environments. Bentonite and silica aerogel are two examples of thickeners that do not melt at high temperatures. There is a misconception, however, that even though the thickener may be able to withstand the high temperatures, the base oil will oxidize quickly at elevated temperatures, thus requiring a frequent relube interval.

Additives

Additives can play several roles in a lubricating grease. These primarily include enhancing the existing desirable properties, suppressing the existing undesirable properties, and imparting new properties. The most common additives are oxidation and rust inhibitors, extreme pressure, antiwear, and friction-reducing agents.

In addition to these additives, boundary lubricants such as molybdenum disulfide (moly) or graphite may be suspended in the grease to reduce friction and wear without adverse chemical reactions to the metal surfaces during heavy loading and slow speeds.

Table 1. NLGI Consistency

Function

The function of grease is 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. Its major practical requirement is that it retains its properties under shear forces at all temperatures it experiences during use. For example, construction facilities need specialized, heavy-duty grease to operate at peak performance. 

Applications Suitable for Grease

Grease and oil are not interchangeable. Grease is used when it is not practical or convenient to use oil. The lubricant choice for a specific application is determined by matching the machinery design and operating conditions with desired lubricant characteristics. Grease is generally used for:

1. Machinery that runs intermittently or is in storage for an extended period of time. Because grease remains in place, a lubricating film can instantly form.

2. Machinery that is not easily accessible for frequent lubrication. High-quality greases can lubricate isolated or relatively inaccessible components for extended periods of time without frequent replenishing. These greases are also used in sealed-for-life applications such as some electrical motors and gearboxes.

3. Machinery operating under extreme conditions such as high temperatures and pressures, shock loads or slow speed under heavy load.

4. Worn components. Grease maintains thicker films in clearances enlarged by wear and can extend the life of worn parts that were previously lubricated by oil.

Functional Properties of Grease

1. Grease functions as a sealant to minimize leakage and to keep out contaminants. Because of its consistency, grease acts as a sealant to prevent lubricant leakage and also to prevent entrance of corrosive contaminants and foreign materials. It also acts to keep deteriorated seals effective.

2. Grease is easier to contain than oil. Oil lubrication can require an expensive system of circulating equipment and complex retention devices. In comparison, grease, by virtue of its rigidity, is easily confined with simplified, less costly retention devices.

3. Grease holds solid lubricants in suspension. Finely ground solid lubricants, such as molybdenum disulfide (moly) and graphite, are mixed with grease in high-temperature service or in extreme high-pressure applications. Grease holds solids in suspension while solids will settle out of oils.

4. Fluid level does not have to be controlled and monitored.

Characteristics

As with oil, grease displays its own set of characteristics that must be considered when being chosen for an application. For example, if you work in a high-pressure environment, more of your lubrication needs would be met with a heavy-duty grease. The characteristics commonly found on product data sheets include the following:

Pumpability

Pumpability is the ability of a grease to be pumped or pushed through a system. More practically, pumpability is the ease with which a pressurized grease can flow through lines, nozzles and fittings of grease-dispensing systems.

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Water resistance

This is the ability of a grease to withstand the effects of water with no change in its ability to lubricate. A soap/water lather may suspend the oil in the grease, forming an emulsion that can wash away or, to a lesser extent, reduce lubricity by diluting and changing grease consistency and texture.

Consistency

Grease consistency depends on the type and amount of thickener used and the viscosity of its base oil. A grease's consistency is its resistance to deformation by an applied force. The measure of consistency is called penetration. Penetration depends on whether the consistency has been altered by handling or working. ASTM D 217 and D methods measure penetration of unworked and worked greases. To measure penetration, a cone of given weight is allowed to sink into a grease for five seconds at a standard temperature of 25°C (77°F).

The depth, in tenths of a millimeter, to which the cone sinks into the grease is the penetration. A penetration of 100 would represent a solid grease while a penetration of 450 would be semifluid. The NLGI has established consistency numbers or grade numbers, ranging from 000 to 6, corresponding to specified ranges of penetration numbers. Table 1 lists the NLGI grease classifications along with a description of the consistency of how it relates to common semifluids.

Dropping point

Dropping point is an indicator of the heat resistance of grease. As grease temperature increases, penetration increases until the grease liquefies and the desired consistency is lost. The dropping point is the temperature at which a grease becomes fluid enough to drip. The dropping point indicates the upper temperature limit at which a grease retains its structure, not the maximum temperature at which a grease may be used.

Oxidation stability

This is the ability of a grease to resist a chemical union with oxygen. The reaction of grease with oxygen produces insoluble gum, sludges and lacquer-like deposits that cause sluggish operation, increased wear and reduction of clearances. Prolonged exposure to high temperatures accelerates oxidation in greases.

High-temperature effects

High temperatures harm greases more than they harm oils. Grease, by its nature, cannot dissipate heat by convection like a circulating oil. Consequently, without the ability to transfer away heat, excessive temperatures result in accelerated oxidation or even carbonization where grease hardens or forms a crust.

Effective grease lubrication depends on the grease's consistency. High temperatures induce softening and bleeding, causing grease to flow away from needed areas. The mineral oil in grease can flash, burn or evaporate at temperatures greater than 177°C (350°F). This is why it is imperative to have a quality high-temperature grease for this type of environment. 

Low-temperature effects

If the temperature of a grease is lowered enough, it will become so viscous that it can be classified as a hard grease. Pumpability suffers and machinery operation may become impossible due to torque limitations and power requirements. As a guideline, the base oil's pour point is considered the low-temperature limit of a grease.

References

1. Pirro, Wessol. Lubrication Fundamentals. New York: Marcel Dekker, .

2. U.S. Army Corps of Engineers. Engineering and Design - Lubricants and Hydraulic Fluids. EM -2- CECW-ET, .

At Lubchem, we are committed to ensuring that your heavy machinery operates at its best. We understand that the performance and longevity of your equipment depend on proper lubrication. However, there are some common misconceptions about extreme pressure grease that we’d like to address. Let’s dive into these misunderstandings and set the record straight.

What Is Extreme Pressure Grease?

Before we tackle these misconceptions, let’s clarify what extreme pressure grease is. Extreme pressure grease is a specialized lubricant designed for heavy machinery. This grease is subjected to high-pressure and high-load conditions. These kinds of greases provide exceptional protection against wear and friction. 

Misconception 1: “All Greases Are the Same.”

This is a common misconception, but it couldn’t be further from the truth. Grease isn’t a one-size-fits-all solution. Different machines and applications require specific types of grease. Using the wrong grease can lead to poor performance and costly breakdowns. We make our high-pressure greases to withstand extreme conditions. You should only be using this grease for demanding applications, such as heavy machinery. 

Our products are engineered to provide superior protection and performance. We know our products are up to address the unique needs of your heavy machinery.

Misconception 2: “More Grease Is Always Better.”

Using excessive grease is a misconception that can lead to problems. Over-greasing can cause overheating, waste resources, and, paradoxically, increase friction and wear. Following the manufacturer’s recommended lubrication schedule is crucial. 

Misconception 3: “One Size Fits All.”

Another misconception is that one type of grease can work for all applications. In reality, different machines, industries, and operating conditions need specialized lubricants. Extreme-pressure grease is designed to withstand heavy loads, high temperatures, and severe working conditions. At Lubchem, we understand that the one-size-fits-all approach doesn’t cut it when it comes to lubrication. We’re dedicated to providing tailored solutions.  Part of that goal is helping you select the right extreme-pressure grease for your specific machinery and needs.

The Benefits of Proper Lubrication

Proper lubrication is critical for the performance and longevity of heavy machinery. By using the right extreme-environment grease, you can extend the lifespan of your equipment, reduce maintenance costs, and enjoy improved overall performance. Don’t let these misconceptions prevent you from experiencing the benefits of quality lubrication.

Lubchem’s Commitment to Quality

We are committed to exceeding industry standards and regulations for extreme-pressure lubricants. Our products undergo rigorous testing to ensure they meet the demands of heavy machinery in extreme conditions. When you choose Lubchem, you’re choosing a partner dedicated to delivering top-notch lubrication solutions.

Trust Lubchem

In conclusion, extreme pressure grease is a critical component of heavy machinery maintenance, and it’s essential to debunk these common misconceptions. Remember that not all greases are the same, more isn’t always better, and one size doesn’t fit all. Lubchem is here to provide the right extreme-pressure grease for your machinery, ensuring optimal performance and longevity. Contact us today for expert guidance and reliable lubrication solutions to keep your heavy machinery running smoothly.

If you have questions or need guidance on extreme pressure grease for your heavy machinery, don’t hesitate to reach out to Lubchem. We’re here to help you make the right choice for your equipment’s needs.