Tag: grease

Understanding Multipurpose Greases

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Since the invention of the wheel, operators have used grease to help run their bearings. Grease technology remained similar until the industrial revolution, where heavy machinery and advancing technology required lubricating grease to keep up. In the last few decades, grease technology has advanced so much that there is probably a grease tailor-made for any application. However, this has resulted in the loss of an “All-Purpose Grease.”

Multipurpose is not All-Purpose

Many applications are similar in regards to operating temperature, loads, speed, etc. and could be lubricated with the same grease. This creates an illusion that one grease can lubricate all of your machinery. It is tempting to do so because of the benefits of lubricant consolidation, increased purchasing power, and simplified lubricant storage. Greases are uniquely formulated to operate at certain loads, speeds, temperatures, etc. This means that a grease will work optimally for one application, but subpar for another.

In the transport industry, there used to be separate greases for chassis and wheel bearings. This changed when lithium greases emerged and proved to be suitable for both chassis and wheel bearings. These multipurpose greases became popular, but there were certifications needed in order to be truly “multi-purpose.” The National Lubricating Grease Institute (NLGI) has “L” certifications for chassis greases and “G” for wheel bearings. They were paired with an “A”, “B”, or “C” to denote the severity of operations; “A” being the lightest and “B”/”C” being the most severe duty. Most multipurpose greases carry the NLGI GC-LB certification. These are the gold-standard greases for heavy-duty transport operations.

The “Multipurpose” nomenclature is a great marketing tool, but can mislead people into thinking a grease has more “purposes” than it actually does. There is a place for multipurpose greases, but engineers have to evaluate the operation and the grease’s characteristics before selecting the appropriate greases and plans for consolidation.

Selecting the Proper Greases

Some OEM recommendations are simple like, “Use a lithium #2 grease.” Whereas others are complex and list different specifications that ensure optimal performance. Some specifications to consider include:

  • NLGI Grade/Thickness
  • Thickener Type
  • Base Oil Type and Viscosity
  • Dropping Point
  • Oxidation Stability
  • Pumpability
  • Water resistance characteristics
  • EP characteristics

These specifications will help guide you in selecting the appropriate grease. By evaluating these characteristics, you are less likely to over-consolidate your greases and achieve optimal performance. More greases mean a greater probability of cross-contamination, this can be mitigated with proper storage and labeling.

Twin Specialties offers a Full Line of Greases

When selecting the proper grease, talking to manufacturers and informed distributors helps greatly. Twin Specialties has a full line of greases from manufacturers like Shell and Castrol. We work with manufacturers to help find the right product that meets any OEM specification. Contact us if you are looking for the correct grease or just more information.

How to Select the Right Grease

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Selecting a grease or lubricant is one of the most crucial decisions you make in regards to any machine. Your selection might make the difference between cost savings, reduced downtime, or significant unexpected costs and failures. For oil lubricants, many OEMs specify what product or what type of product is recommended for each component of their equipment. This simplifies the selection process. However, OEM grease specifications are much broader. Most of the time OEMs simply recommend the National Lubrication Grease Institute (NLGI) specification.

This presents both flexibility and options, but also introduces more room erroneous decision-making and poor lubrication. Simply using the NLGI grade is not enough. You have to look at other factors to ensure you grease and machine work properly and does not fail. We will look at some key factors that every operator needs to consider.

Base Oil Viscosity

A grease is composed of 3 ingredients: thickener, oil, and additives. The NLGI number indicates the thickness of the thickener, but does not specify the viscosity of the thickened base oil. The underlying base oil has its own viscosity just like any lubrication oil. If a piece of a equipment calls for a certain lubricating oil with a specific viscosity, it is easy to find a grease that has the same base oil viscosity and similar additive package.

If viscosity requirements are not specified, you can use the chart below (courtesy of ExxonMobil and Noria).

The two factors required are operating temperature and DN or NDm, which are the bearing speed factors. To calculate those speed factors, simply use the following formula:

  • DN = (rpm)*(bearing bore) and
  • NDm = (rpm)*((bearing bore + outside diameter) / 2)

The intersection of DN and Temperature will point you towards the required ISO viscosity. This chart assumes viscosity index.

Base Oil Type and Additives

Once a viscosity is identified, you need to figure out what additives and base oil you need. Similar to oil lubricants you must assess your operations and figure what additives are necessary or unnecessary. For example, light loads and high-speed applications do not require a grease with extreme pressure (EP) additives, but a heavily loaded application will need those EP additives. The chart below breaks down the needed additives for various bearings.

Courtesy of Noria

Most greases use mineral oil and only require mineral oil. However, synthetic base oils are recommended for certain extreme temperature applications. Applications with low or high operating temperatures or a wide range of temperatures, a synthetic base oil is recommended. Synthetic base oil greases are also recommended for users who want to longer regreasing intervals.

Grease Thickener

Unlike lubricating oils, greases include thickeners. The two factors that distinguish grease are type and consistency. As mentioned earlier, consistency is based on the NLGI scale. The scale ranges from 000 (most fluid) to 6 (least fluid). The most common and most recommended NLGI grade is #2. Most OEMs specify the NLGI grade and matching that number is a simple process (especially if you require a NLGI 2 grease).

The other factor for thickeners is the type of thickener. The differences between each type of thickener are present pros and cons for each application. The most common types are lithium soap, lithium complex, and polyurea. Lithium soap greases are low-cost general-purpose grease and perform well in general applications. Lithium complex is similar to lithium soap, but is preferred for applications with higher operating temperatures. Polyurea greases have good high-temperature properties and have high oxidation stability and bleed resistance. When switching greases, it is important to understand thickener compatibility to make sure the new grease does not fail.

Cost and Other Considerations

When purchasing a grease, a basic lithium grease will be cheaper than a sophisticated polyurea grease. It is up to you to determine the tradeoffs between grease costs and performance gains/losses. Purchasing a higher quality grease may lead to longer regreasing intervals and less machine failure.

To save costs, consolidating greases may be wise, but be wary of over-consolidation. This may result in some machines not using an appropriate grease.

Other attributes should be considered depending on the application. Some grease exclusive attributes include:

  • Drop Point
  • Mechanical Stability
  • Water Washout
  • Bleed Characteristics
  • Pumpability

Certain attributes are focused specifically on heavy loads and should be considered for heavy load-low speed applications. These include:

  • Four-Ball Tests
  • Timken OK Load

Additionally, industry specific requirements will also dictate grease selection. These industries have strict requirements and require greases to be certified by certain 3rd-party regulators:

Conclusion

Unlike oils, greases have many more factors for product selection. These factors should be considered for each application as each grease is designed and manufacturer specifically for each application and have a delicate balance of thickener, oil, and additives.

Twin Specialties carries a wide variety of greases to meet you application needs. We work directly with you to make sure we provide the right product that delivers performance while being mindful of the total cost of grease and maintenance. Contact Twin Specialties to learn more about our grease product lines.

What are Aerospace Lubricants?

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On May 30, 2020, NASA and SpaceX partnered to send American astronauts from US soil to the International Space Station for the first time since 2011. As a new era spaceflight begins, government entities like NASA and private enterprises like SpaceX will work to innovate their rockets and push boundaries for human space flight. Lubricant manufacturers are tasked with the same challenges to create lubricants that will aid in the journey to reach our ambitious goals.

What are Aerospace Lubricants?

Lubricants in used in aerospace applications such as, space travel, commercial airlines, and defense, are like other lubricants, but face more stringent performance demands. In order to be classified as an aerospace lubricant, products must pass tests that are created by the Department of Defense (DoD) known as “MILSPECS.” To ensure safety and performance for aerospace applications, the MILSPECS create standardization to meet DoD objectives. These MILSPECS test different performance factors such as: corrosion protection, shear stability, compatibility, and water sensitivity.

What Differentiates Aerospace Lubricants?

In addition to meeting various MILSPECS, aerospace lubricants are engineered specifically for aircraft engines and fuel systems. The key difference between aerospace lubricants and non-aerospace lubricants is weight. In space operations, weight is crucial because more fuel is needed, which can become costly. It could also put a strain on how many other supplies could be included in the launch. As the safety of astronauts and functionality of equipment is vital, these lubricants cannot fail.

In space applications, lubricants face the most demanding tests. With temperatures in space at near Absolute-Zero and reentry temperatures reaching 5000 F, lubricants must perform in a wider-range of temperatures than their Earth-bound equivalents. Additionally, lubricants must be able to operate in a vacuum environment. This is on top of all of the crucial navigational and life-supporting machines that make space travel possibly. These machines cannot suffer any breakdowns or down time as they support life and other functions both in space and on Earth. Aerospace lubricants must have a long life to maintain these critical operations.

In defense operations, completing the objective is key and your lubricant must perform to ensure the objective is met. These lubricants have to: withstand extreme-temperature jet engines, cargo aircraft landing gears, precise navigational tools, and other wide-temperature components. By selecting lubricants that meet the right MILSPECS you can ensure proper performance and success in your aerospace operations.

Aerospace Lubricant Manufacturing

Aerospace lubricants in today’s markets can be in the form of liquids or greases. Most use synthetic base oils to achieve desired results and improve efficiency. Most of these lubricants are made of perfluoropolyether (PFPEs) or Multiply Alkylated Cyclopentane (MACs). Several large manufacturers produce these products that meet various MILSPECS. Twin Specialties has access to a wide variety aerospace and MILSPEC lubricants from Shell and Castrol. Contact us to learn more about our catalog.