NLGI Lubricating Grease Guide - Chapter 7

NLGI

LUBRICATING

GREASE GUIDE Chapter 7 – Handling and Dispensing Grease Editors Raj Shah William Tuszynski

Lubricating Grease Guide All rights reserved. No part of this publication may be reproduced without written permission from the NLGI.

Seventh Edition, 2022 Published in Liberty, Missouri, U.S.A. Copyright 1984, 1987, 1994, 1996, 2006, 2015, 2022 NLGI Library of Congress Control Number: 2014958517 ISBN: 9798806175220 Imprint: Independently published Copyright: 2022 NLGI Copies available from: NLGI International Headquarters 118 N Conistor Ln, Suite B-281 Liberty, MO 64068 Phone: 816-524-2500 Email: nlgi@nlgi.org Web: www.nlgi.org

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Foreword NLGI was founded with the objective to foster cooperation in the exchange of technical information among its members. NLGI’s mission is to provide resources relevant to the needs of the global grease community. NLGI’s vision is to be recognized as the premier source of support to consumers, researchers, manufacturers, suppliers, marketers and other key stakeholders of the worldwide lubricating grease industry. This guide, along with NLGI’s annual meeting, educational courses, certification marks and other valued offerings, including the NLGI Spokesman, demonstrate the institute’s continued commitment to fulfilling this mission and vision.

Preface The purpose of the NLGI Grease Guide is twofold. It is an introduction to a broad spectrum of subjects related to grease for those new to the field and a reference for industry veterans.

Many in the lubrication industry grasp the principles of fluid lubrication quite easily but find grease application, formulation and manufacture something of a mystery. Because of this confusion, NLGI presents intensive grease education courses to provide a deeper dive into these areas.

This guide is not intended to be a substitute for these courses. Rather, it is an adjunct to the courses. It serves as a reference to users, formulators, manufacturers and marketers of grease during the conduct of their daily business and as an educational source for the less technical student. It is not intended to be an in-depth source for information about lubricating greases but rather to serve as a resource to provide those inside and outside the industry a basic understanding of the key points regarding grease formulation, manufacturing, use troubleshooting and other topics. Readers are encouraged to seek out additional sources as needed. The chapters have been arranged in a sequence that will lead the reader through the subject of grease in a logical manner. However, each chapter stands on its own so that the guide can be used for quick reference. NLGI gratefully acknowledges the experts who have contributed their knowledge, time and energy to each chapter and the companies that supported them.

Acknowledgments Samuel Clemens (Mark Twain) once commented, “Why shouldn’t truth be stranger than fiction?

Fiction, after all, has to make sense.” In the grease world, formulators, manufacturers and users have often found this saying applies to lubricating greases. It is our hope that this edition of the NLGI Grease Guide can make the properties and uses of lubricating greases clearer to both newcomers and veterans in the industry.

This volume is an update to the Sixth Edition, published in 2015, and includes expanded content and new topics relevant to the industry. Each chapter within the Seventh Edition serves as a stand-alone resource. The Seventh Edition includes four new chapters and revisions to existing chapters to reflect the latest developments in grease technology. The chapter order has also changed. While there is logic to the order of chapters, readers are encouraged to follow the chapter order that best suits their needs. The NLGI Grease Guide serves as the textbook to the Basic Grease Course, and it can also be used as a stand-alone reference.

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Each chapter was drafted by one or more lead authors, including: Chapter 1: J. Andrew Waynick, NCH Corporation Chapter 2: Dr. Gareth Fish, CLGS, The Lubrizol Corporation Chapter 3: Dr. Anoop Kumar, CLGS, Chevron Products Company; Dr. Raj Shah, Koehler Instrument Company; Dr. Kuldeep Mistry, The Timken Company; Ajay Kumar Harinarain, Indian Oil Corporation Ltd. Chapter 4: John Sander, CLGS, Lubrication Engineers; Casey Budd, CLGS, Lubrication Engineers Chapter 5: Dr. Patrick Taylor, Klüber Lubrication NA LP; Dirk Ludwig, Klüber Lubrication München SE & Co. KG; Klaus Pommer, Klüber Lubrication München SE & Co. KG Chapter 6: Dr. Jennifer Frias, Nye Lubricants, a member of the FUCHS Group; Jayna DeMedeiros, Nye Lubricants, a member of the FUCHS Group Chapter 7: Roger Miller, M Consulting, LLC Chapter 8: Melissa Quinn, BP U.K.; Phil Booker, BP U.K. Chapter 9: Dr. Carl Kernizan, KV Tech Consulting, LLC Chapter 10: Chuck Coe, CLGS, Grease Technology Solutions Chapter 11: Douglas J. Adams, RSC BioSolutions Chapter 12: Shawne Edwards-Zollar, Afton Chemical Corporation Grease Glossary: Dr. Mary Moon, Presque Isle Innovations LLC; David Turner, CLGS, CITGO Petroleum Corporation Along with the authors, several volunteers dedicated their time to review the chapters. We recognize and appreciate the efforts of this group: Paul Bessette (Triboscience & Engineering), Richard Burkhalter (Covenant Engineering), Nicole D’Ambrosio (Nye Lubricants), Medhi Fathi-Najafi (Nynas), Amanda Harris (King Industries), Dr. Carl Kernizan (KV Tech Consulting), Ajay Kumar Harinarain (Indian Oil Corporation Ltd.), Dr. Anoop Kumar (Chevron Products Company), Dr. Cindy Liu (Klüber Lubrication NA), John Lorimor (Aerospace Lubricants), Teresa Makuvek (FedChem), Dr. N. Pokhrilal (Indian Oil Corporation Ltd.), Melissa Quinn (BP U.K.), John Sander (Lubrication Engineers), Dr. Deepak Saxena (Indian Oil Corporation Ltd.), David Turner (CITGO Petroleum Corporation), Dr. Erik Willett (Functional Products), Dr. Matthias Woydt (Matrilube) and Ray Zhang (Vanderbilt Chemicals).

We acknowledge and are grateful for the time, effort and expertise contributed by the authors and reviewers, and the copyediting services of Gneiss Editing (www.gneissediting.com), to make this volume a success. We also acknowledge the support of NLGI leadership, including the board of directors and Executive Director Crystal O’Halloran, for their support throughout the process.

As in any such endeavor, full credit for the quality of the content belongs to the authors and reviewers while the editors are solely responsible for any errors and omissions.

Editors: Raj Shah, Koehler Instrument Company (ORCID Number 0000-0002-8020-944x) and William Tuszynski, The Unami Group LLC (ORCID Number 0000-0002-0747-04730)

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Table of Contents Foreword Preface Acknowledgments Table of Contents NLGI Information Membership Member Benefits in NLGI Technical Committee and Working Groups Certification Marks Education Certified Lubricating Grease Specialist (CLGS) Chapter 1 – A Historical Overview The Earliest Lubricating Greases Simple Soap-Thickened Greases Complex Soap-Thickened Greases Non-Soap-Thickened Greases Concluding Comments References Chapter 2 – Characteristics of Lubricating Greases Single-Purpose Greases Multipurpose Greases Grease Components References Chapter 3 – Testing of Lubricating Greases Significance of Lubricating Grease Testing Flow & Low-Temperature Properties Heat-Resistance/High-Temperature Capabilities Thermal/Oxidation Stability and Service Life Oil Bleed and Storage Life Water Resistance Properties Corrosion & Rust-Preventive Properties Tribological Properties Friction and Wear Tests Oscillating Motion (Fretting) References

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Chapter 4 – Formulation and Process Development Introduction Conceptualize and Determine Drivers (Ask Questions) Plan (Perform Research & Hypothesize) Chemistry/Engineering (Test) Store/Ship/Sell Example Conclusion References Chapter 5 – Manufacturing Lubricating Greases Introduction Terms Related to Grease Manufacture Processes and Equipment Used Grease Processing Continuous Grease Manufacture Soap-Thickened Greases Complex Soap-Thickened Greases Non-Soap Greases Specialty Thickeners Incorporation of Additives Manufacturing Certifications References Chapter 6 – Food-Machinery Lubricants Purpose Background Food-Machinery Lubricants Current Regulations Manufacturing Food-Machinery Lubricants References Chapter 7 – Handling and Dispensing Grease Grease Packages Grease Package Pumps Intermediate Bulk Containers (IBCs) Bulk Delivery Grease Storage Grease Dispensing, Bulk Storage, Pumping, Flow Control Pumps and Flow Control

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References Chapter 8 – Grease Selection When to Lubricate With Grease Energy-Saving Lubricants Selecting the Right Grease for an Application Automotive Grease Requirements The Hidden Costs of Lubrication Grease Compatibility References Chapter 9 – Troubleshooting Guide Introduction Bearings (Assumes correct bearings in service and installed correctly) Gears Sliding Surfaces Universal Joints Electric Motors Couplings Centralized Lubricators Wet Applications High Temperatures Low Temperatures Heavy Machinery Pins and Bushings Wind Energy Passenger Car Heavy Duty Marine Applications Chapter 10 – NLGI Product Certifications Introduction NLGI GC-LB (ASTM D4950): History and Specifications NLGI HPM and HPM+ Categories: History and Specifications NLGI HPM and HPM+ Comparison to GC-LB NLGI Certification Marks References Chapter 11 – Environmentally Acceptable Lubricants (EALs) Introduction Sustainability Programs and Standards References

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Chapter 12 – Grease Health, Safety & Environment Requirements Introduction Hazard Communication GHS – The Globally Harmonized System and Labeling of Chemicals Labels Safety Data Sheets Chemical Inventory Requirements Transportation of Hazardous Materials Hazard Determination, Handling and Disposal of Used/Waste Greases Requirements of the Community Right-To-Know Act References Grease Glossary Definitions of Terms Relating to the Lubricating Grease Industry NLGI Publications Online Resources Common Industry Abbreviations Index

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NLGI Information NLGI was incorporated in 1933 as the National Association of Lubricating Grease Manufacturers, Inc., for the purpose of writing a code concerning the National Recovery Act. In 1937, the name was changed to the National Lubricating Grease Institute. Its founders were J.R. Battenfeld, Battenfeld Grease & Oil Corporation; Guy Peters, Oil Craft Inc.; and W.H. Sauders, International Lubricant Corp.

Another name change was made to NLGI in 2001.

The institute’s member organizations are in more than 30 different countries worldwide and NLGI’s reach extends to about 50 countries worldwide. This global representation is indicative of the wide interest in lubricating grease. NLGI further promotes the grease industry through its other industry partnerships around the globe.

The NLGI-India Chapter was formed in 1997 with Indian Oil Corporation Ltd, R & D Centre as its headquartered location and Dr. A.K. Bhatnagar, former Director (R & D), Indian Oil Corporation Ltd as founding president.

The objectives of NLGI and NLGI-India Chapter are to disseminate information that can lead to the development of better lubricating greases for the consumer and to provide better grease and lubrication engineering service to the industry.

NLGI promotes these objectives in several ways, including funding lubricating grease research, promoting improved laboratory and field tests and lubricating grease manufacturing improvements.

Technical discussion forums among consumers, producers and educators are provided, and dissemination of technical data relevant to improved manufacturing techniques, new products, new uses and new application and testing methods is fostered.

Today, NLGI continues to promote technical advancement of grease lubrication and contributes materially to greater production, increased machine life and a higher quality of machine performance through better lubrication.

Membership Since 1933, NLGI has provided members with guidelines and resources that have led to better research, products and processes and ensured continued growth in related areas, from marketing and packaging to additives and testing. With more than 200 member companies worldwide, NLGI is the leading organization in the field of lubricating grease. Those who are associated with lubricating grease, whether through products or services, will find that NLGI membership gives them an invaluable edge — the NLGI professional advantage.

NLGI is a not-for-profit trade association primarily composed of companies that manufacture and market all types of lubricating grease. Associated with manufacturers are companies that serve them with equipment, supplies and services. Additionally, some member companies interests are primarily technical.

Another category for membership is “Consumer,” which is for organizations that are users of lubricating grease. NLGI works continuously to strengthen its association by rendering service throughout the entire supply chain.

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Member Benefits in NLGI • • • • • • • • • • • • •

Affordable training, including NLGI’s Basic Lubricating Grease Course and Advanced Lubricating Grease Course.

Complimentary technical information, including NLGI’s annual Grease Production Survey, High-Performance Multiuse Grease (HPM) webinar repository and more.

Complimentary subscription to the NLGI Spokesman publication, including technical articles written by leading industry experts.

Discounted technical articles dating back to 1941.

Complimentary employment listings on NLGI website.

Complimentary membership directory with primary contact details.

Ability to host NLGI’s Hands-On Training Course.

Significant discount on NLGI purchases such as annual meeting registration, reference grease, advertising, sponsorships and more.

Discounted certification marks, including GC-LB, GC, LB and HPM. Ability to increase your network, including immediate access to industry experts.

Recognition for supportive endeavors, including the possibility of being a published author in the NLGI Spokesman or the recipient of one of NLGI’s annual awards.

Ability to contribute through one of NLGI’s committee, task forces or ad hoc groups.

Worldwide support generated by more than 200 member companies that are focused on the issues and problems related to the grease industry.

Technical Committee and Working Groups NLGI’s Technical Committee focuses on keeping NLGI at the forefront of new technology and providing information about lubricating grease operations, manufacturing, research and standards. The Technical Committee incorporates NLGI’s certification marks, working groups, reference grease and annual production survey. The Technical Committee also takes the key role in developing the technical sessions for the annual meeting.

Additionally, NLGI sponsors working groups that focus on a variety of interest topics and serve in conjunction with other technical and industry associations.

Certification Marks In the past, the diversity of specifications for automotive service greases, as established by the original equipment manufacturer (OEM), made it difficult for the marketer of lubricating greases to make available all the many specified products. NLGI, in conjunction with the Society of Automotive Engineers and the American Society for Testing and Materials, developed ASTM D4950 in 1989 as a standard for automotive service greases under the GC-LB certification marks. More recently, NLGI issued an HPM certification, including a core specification and four enhancement performance tags. The GC-LB and HPM certification marks are discussed in more detail in Chapter 10 of this volume.

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Education NLGI offers renowned grease training at the NLGI Annual Meeting as well as other venues.

These courses provide instruction at both the basic and the advanced levels. Course content covers a broad spectrum of subjects and courses are designed to familiarize the student with all aspects of the grease industry including manufacturing, chemistry, application and product characteristics. Course instructors are experienced specialists in their respective topics of discussion. Course participants are supplied with extensive study materials.

Certified Lubricating Grease Specialist (CLGS) In response to an ever-growing need to provide certification for the identification of grease experts, NLGI developed the Certified Lubricating Grease Specialist (CLGS) program. To meet the requirements of this program, the candidate must pass a qualification test covering a broad range of information pertinent to the lubricating grease industry from the chemistry of reactions, manufacturing and additives to field applications. The test is given each year at the NLGI Annual Meeting.

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Chapter 7 – Handling and Dispensing Grease Roger Miller, B.S., M Consulting, LLC, Baton Rouge, La., U.S.

Grease Packages After grease is manufactured, it must be packaged for use. The wide variety of users and applications has given rise to a wide variety of packaging and delivery systems for both small, occasional users of grease to large-volume industrial users.

Cartridges

Although several cartridge sizes appear on the market, the principal size in the United States contains ~14 ounces (~400 grams) of grease. Another common grease cartridge contains 3 ounces (85 grams) of grease. Cartridges are used in portable grease guns, providing ease of use in field applications, e. g., lubricating off-road equipment, farm implements, electric motors.

The tube-shaped bodies of these cartridges generally have been made of fiber with an oil-proof liner. Plastic cartridge bodies are also widely used and function in the same way as the fiber cartridge body (Figure 7.1) One end of the tube is designed with a pull tab, which ends up on the dispensing head of the grease gun, while the other end of the tube is open-ended and covered with a plastic cap, where the plunger is inserted to produce pressure within the grease gun.

Figure 7.1 Plastic cartridge (Photo courtesy of ExxonMobil Corp.)

Other Small Containers

Grease is supplied in smaller containers (cans/tubs) for specific applications where grease is handapplied to a lubricating surface (bearings or bushings). The cans are typically made of tin and come in smaller quantities, varying from 1 to 5 pounds (0.5 to 2.5 kg). Plastic or fiber containers, called tubs, can range from 1 to 7 pounds (500 g to 3 kg), and are typically used in the food industry and other consumer applications. Small, squeezable tubes are also available, ranging from 0.5 to 8 ounces (15 to 225 grams).

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Pails

When grease containers were standardized in the United States, the 35-pound (15.9 kg) pail was chosen. This fill weight is about the same as the quantity of a case of grease cartridges.

The pails may be plastic or metal with press-on or crimped lids, respectively. The sides of plastic pails are tapered to allow nesting and shipment of empty containers, while metal pails are designed with straight sides and cannot be nested.

Figure 7.2 Plastic pail with pressed lid (Photo courtesy of ExxonMobil Corp.)

Container choices are generally driven by many factors, summarized in Table 7.1.

Table 7.1 Container choice factors

Plastic

Metal

Cost

+

-

Weight

+

-

Corrosion Resistance

+

-

Material Strength

-

+

Handling/Dents

+

-

This comparison highlights the recent popularity of plastic containers of all types as producers shift away from metal. Despite the advantages of plastic, grease composition can result in incompatibility with plastic; metal is a good alternative.

Kegs

The keg has been standardized to a 120-pound (55-kg) fill weight. The lid is typically crimped around the perimeter of the top to hold it in place. The keg offers a combination of portability and volume in between a pail and drum.

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Figure 7.3 Keg with crimped lid (Photo courtesy of ExxonMobil Corp.)

Drums

Drums are the most common package style. Although not quite as portable as kegs or pails, they can be moved via forklift and offer a significant storage volume (55 gals/200 l) with typical fill weights of 400 pounds (180 kg). Drum lids are typically held in place with a locking rim and either a hand lever or bolted locking ring.

Figure 7.4 55-gallon drum (Photo courtesy of ExxonMobil Corp.)

Grease drums can be reconditioned for recycled use if polymer-type liners are inserted into the drum before filling. The use of the polymer liner reduces the cleaning required to recycle the drum. Using recycled drums represent a significant cost savings but must be weighed against appearance of the drum if used to package a branded product. The drum liners can eliminate the contamination of the drum with grease and pump off cleanly, with the residual grease clinging to the liner meeting industrial waste standards which can be thrown away with other industrial waste streams. Drum reconditioning cannot remove dents completely, leaving a less-than-new appearance.

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Grease Package Pumps Grease packages (pails, kegs, drums) can be pumped into application with specially designed pumps. Figures 7.5 and 7.6 are examples of the two types of pumps. Figure 7.5 is a vertical piston pump which can be inserted through the package-lid bung hole to the bottom of the container where piston action creates the suction and discharge pressures needed to dispense the product. These are uncommon and not particularly effective in emptying the container, especially when attempting to pump NLGI Grade 1 and 2 products. Due to their high solids content, the greases do not effectively slump to the bottom of the container as the pump slowly discharges and the level drops. The irregular grease surface can starve the pump by introducing air into the suction side of the piston. To improve the performance of these piston pumps, especially when dispensing NLGI Grade 1 and 2 grade products, a follower plate attachment is often used. In general, the plate sits on top of the grease level in the container, sliding down the inside of the container as the level drops while dispensing. There are typically seals designed around the perimeter of the plate which wipe the sides of the container, making them easy to dispose of in a general industrial waste stream, or be sent to be recycled. Another option for follower plate design is shown in Figure 7.6. In this design, the follower plate is attached to the pump, both of which are driven by two pneumatic pistons. As the level in the package drops, the pistons drive the pump-follower plate down, eliminating air entrainment.

Figure 7.5 Drum and keg stub transfer pump (Photos courtesy of Lincoln Industrial Corp)

Figure 7.6 Drum pump with follower plate

Intermediate Bulk Containers (IBCs) When larger quantities of grease are needed, and in multiple locations, Intermediate Bulk Containers (IBCs) become an economically viable option. With capacities which typically range from 2,000–3,000 pounds (907–1,360 kg), they become an attractive alternative to drums if grease consumption requires frequent drum changeout from central systems or factory fill stations. Designed to be portable using a forklift, there are several different designs.

Steel bins, like Figure 7.7, are intended for more fluid NLGI grades, which slump to the bottom where a piston pump can be used to dispense the grease. This particular design does not use a follower plate. Two other examples, shown in Figure 7.8 and 7.9, are cylindrical in design with a follower plate.

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These bins are designed for higher NLGI Grades, 1 or 2, which can be effectively dispensed with the aid of the follower plate. Figure 7.8 uses polyethylene, which brings the benefit of being able to see the grease level in the bin and the capability of taking the bin apart for cleaning and changing service. Figure 7.9 is steel, more durable than the polyethylene bin, but more difficult to clean if a service change is required.

Figure 7.7 Steel IBC Figure 7.8 Polyethylene without a follower plate with a follower plate (All photos courtesy of River City Enterprises)

IBC Figure 7.9 Steel IBC with a follower plate

New on the market is the disposable, polymeric bag-type IBC. As an example, Figure 7.10 shows a disposable IBC from Fluid-Bag. Made from woven polypropylene, the IBC is both durable and flexible.

Once filled, the container is sealed from contamination. Combined with the discharge roller (Figure 7.11), designed to squeeze the bag as it is pumped off, there is very little residual waste. The empty bag can be disposed of in the general industrial waste stream. This also eliminates freight costs for returning rigid totes for refilling. As shown in Figure 7.11, most piston-type pumps previously discussed can be outfitted to dispense from the Fluid-Bag.

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Figure 7.10 Fluid-Bag with stackable frame (Photos courtesy of Fluid-Bag Ltd.)

Figure 7.11 Fluid-Bag setup with semiautomatic dispensing roller

Bulk Delivery For consumers whose grease usage exceeds the economically viable capacity of drums or IBCs, bulk transport and storage are used. Bulk delivery trucks can carry loads up to 40,000 pounds (18,000 kg), making them a viable option for operations with large grease requirements. Examples of large-volume consumers are manufacturing plants with central lubrication systems feeding grease to complex rotating equipment (steel and paper mills) and factory fill manufacturers (bearings, CV joints).

Bulk grease transport tanks are designed using a follower plate with the same benefits as described with IBCs. Most common are horizontal tanks with pneumatically pressured follower plates. Some larger, vertical bins are also used. Some tankers using horizontal tanks utilize a three-tank design, stacked in a triangle to accommodate customers who need multiple products. Examples of are shown in Figures 7.12 and 7.13.

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Figure 7.12 Rear view of bulk grease transporters (Photos courtesy of CITGO Petroleum Corp.)

Figure 7.13 Side view of single cylinder bulk grease transporter

Grease Storage Grease storage should be an important consideration to protect grease lubricating properties. The product may oxidize, bleed, change in appearance or pick up contamination. The degree of change depends on the storage conditions, e.g., length of time in storage, temperature, exposure to the weather elements.

Some greases tend to bleed or release oil in storage. Bleed tends to increase with time and elevated temperature. Oxidation stability of formulated grease is generally very good and does not become a problem unless the storage temperatures are very elevated for long periods of time.

Contaminates can deteriorate grease lubricating properties significantly, one of the worst being water. Unless containers or bulk storage tanks are tightly sealed, water can enter, either through breathing of the container vapor space with temperature changes, or through defects in the physical container.

Some greases, such as sodium soap formulations, tend to soften when contaminated with water. On the other hand, water has been known to cause clay-thickened or calcium complex grease to become firmer.

In either case, a change in penetration can impede the sealing properties of the grease, as well as compromise other grease physical properties.

Appearance changes in storage can also occur. Water can cause dye color changes, i.e., causing red to turn to pink. Aerated grease can degas in storage causing a color change. Severe oxidation can also cause grease appearance to darken.

Grease Dispensing, Bulk Storage, Pumping, Flow Control Grease Dispensing

Grease is applied to lube points at the customer’s site using several types of grease guns, applied by hand, or through complex central injection systems. The choice of method depends on the quantity needed for the lube point, the proximity to a grease source (package container or bulk tank) and the frequency of regreasing needed for the application.

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The following photo depicts a basic lever-type manual grease gun. The cartridge tab, discussed previously, is pulled off of the cartridge tube and placed at the discharge end (head) of the gun, The plastic cap is removed from the other end of the cartridge. The grease gun plunger is inserted through this opening. An internal spring applies constant pressure to aide in dispensing grease. The lever is cocked and compressed until grease begins discharging through the attached hose. The discharge hose can be either flexible or rigid. Typical quantities using this type of gun can range from 1.0–1.5 grams per stroke. Discharge pressures can be significant, in the range of 6,000 psi (41,368 kPa).

Plunger

Discharge Hose Head

Figure 7.14 Lincoln Industrial Model 114 2 (Photo courtesy of SKF – Lincoln Industrial) If the application requirement stipulates frequent relubrication, single-point lubricators are often used. These devices have evolved over time from a simple cup arrangement with a spring-loaded plunger, to gas-driven piston diaphragms, to battery/electric-powered piston pumps to discharge the grease to the lube point. These lubricators come in a variety of volumes, which helps in maintenance and replenishing, or replacing the lubricator chamber. Specifying the model with the desired grease for relubrication along with the frequency and quantity requires consideration with the lubricator supplier. Placement of the device, application temperature and lube point back pressure are just a few of the variables that need to be considered before selecting the correct grease-lubricator combination.

For multipoint lubrication, progressive metering blocks have become common. These are often used in manufacturing plants with rotating equipment that require continuous lubrication. A sequential series of photos are shown here (Figure 7.15) demonstrating the internal flow of these devices:

Figure 7.15 Quiklube progressive metering block (Photo courtesy of SKF- Lincoln Industrial) Generally, grease under pressure (red) flows through the block from top to bottom to fill and pressure piston chambers. As the pressure increases, the pistons sequentially shuttle, moving from the high to low pressure sides and discharging grease (blue) through ports leading to a lubrication point. In

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the example shown above (Figure 7.15), grease flows into the block, slowly increasing the pressure in piston chamber A, while simultaneously filling piston chambers B through D in preparation for discharge later in the cycle. The pressure builds and piston A shuttles, dispensing the chamber through port 2.

While this port is discharging, flow is diverted to start pressuring piston B. When the pressure in piston B is high enough, it dispenses through port 7. The sequence repeats sequentially until it repeats through piston A. The volume dispensed is determined by the piston chamber diameter and length. These blocks can overcome lube-point back pressures up to 1,000 psi (6,985 kPa). When sized correctly, central distribution systems utilizing metering blocks can provide continuous, measured grease for optimum lubrication.

Bulk Storage

Once a batch of grease has been manufactured, tested and released for packaging, dispensing to packaging operations can occur directly from a kettle, an IBC or from a bulk storage tank used to hold multiple batches of grease. In either case, tank design and flow control of grease to the packaging operations need significant considerations.

Newer tank designs utilize features that minimize internal grease clingage and aide in feeding dispensing pumps. Two examples of tank design are shown in Figures 7.16 and 7.17. Figure 7.16 shows a cylindrical tank designed with an internal piston, which acts like a follower plate. This yields all of the benefits for bulk storage that we have previously described. Figure 7.17 shows a cylindrical tank with a cone bottom. The cone bottom encourages grease slumping toward the tank bottom, which also aides in decreasing tank-bottom residual grease. Typically cone angles greater than or equal to 60 degrees from vertical promote slumping. In either case, it is important to design the tank to minimize pump suction line pressure drop. Long suction lines and/or small pipe diameters can cause pump suction starvation through increased pressure drop. This is even more important given the viscosity characteristics of grease — having a solid and liquid phase, which increases viscosity significantly.

Figure 7.16 Bulk grease tank with piston (Photos courtesy of River City Enterprises)

Figure 7.17 Bulk grease tank during transit

Pumps and Flow Control To effectively pump grease at a controllable dispensing rate to a packaging operation, pump selection and flow control systems must be carefully designed. Fundamental to these selections is the

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comprehension of grease viscosity and the effect on the selection of pumps, pipe diameter/length and valves. Greases, being composed of a solid and liquid phase, yield nontypical viscosity characteristics compared to fluids like oil or water. The viscosity behavior is best described in terms of Newtonian physics.

Typically, fluids have a very predictable viscosity. More specifically for these fluids, viscosity does not change as pumping rates change. This behavior is described by the following: µ = Proportionality Constant = .

Shear Stress Shear Rate

=

τ γ

. for Newtonian Fluids ] Linear

τ : Shear Stress γ : Shear Rate μ : Proportionality Constant = Coefficient of Dynamic Viscosity

Shear Stress

Fluids that exhibit a constant viscosity independent of shear rate are classified as Newtonian (assuming constant temperature).

Slope = μ

Shear Rate

Viscosity

For Newtonian fluids, no matter how much the pipe diameter or pumping rate changes, the viscosity remains the same:

Shear Rate

The composition of many Newtonian fluids consists of molecules whose shape or molecular weight easily align with shear planes while under stress in a flow regime. The lack of intermingling across shear planes accounts for the linear relationship between shear stress and rate. For fluids with more complex molecules or multiple phases, intermingling across shear planes becomes significant, affecting the distribution of shear stresses and the viscosity of the fluid. These fluids are termed non-Newtonian.

The following graph depicts their viscosity characteristics with shear rate (Figure 7.18):

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Viscosity (cP)

Thickener

τ CR

Grease

Oil 0

Shear Rate (Sec -1)

Figure 7.18 Non-Newtonian flow characteristics Another way to express shear rate is pump speed. As the speed increases, the stress force applied to the grease becomes greater than the yield point of the solid thickener, after which flow begins. This point is called the critical shear stress (τCR). After the critical point has been reached, the viscosity begins dropping as the shear rate increases, reaching a point where the viscosity closely resembles that of the oil phase. Note the gap between the grease and oil viscosities at higher shear rates. This gap is attributed to the solid thickener contribution to overall viscosity. The graph also demonstrates the characterization of non-Newtonian viscosity as “apparent,” meaning the viscosity is defined by both temperature and shear rate.

Understanding the concept of non-Newtonian characteristics on the apparent viscosity of grease is important in specifying the correct pump for moving grease from the source, either a kettle or bulk tank, to a packaging point. Positive displacement pumps come in a variety of types and viscosity range capacities. NLGI Grade 2 greases can exhibit apparent viscosities up to 30,000 cP (~ 40,000 cSt) at low shear rates in the 38 – 66 °C (100- 150 °F ) range. Comparing this to typical oil viscosity ranges of 100 – 460 cSt at 40 °C (104 °F), the importance of selecting a pump capable of handling these varying viscosities becomes evident.

Flow control of any pumping system is important to match the needed flow rates to the demand.

Poorly instrumented and controlled systems can create over-shearing, leading to grease quality issues, or flow rates too low to meet the demand, i.e., slow packaging rates. The following diagram depicts the elements of a flow control system:

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Supply Valve Tank Or Kettle

SRV

XV

PRV XV

PIC Load Cell

Figure 7.19 Elements of a flow control system Properly designed flow systems have pressure control devices to protect both the pump and piping from over-pressure events. The Pressure Indicated Controller, feeding a response signal to a Pressure Relief Valve (PRV) and the Safety Relief Valve (SRV) are the primary and secondary pressure relief devices. In both cases, the pressure relief path is back to the tank, the SRV being on an independent path unaffected by any event that might block the discharge line from pressure relief. Some designs vent the PRV back to the pump suction. While acceptable from a safety perspective, the preferred relief is back to the tank vapor space, which is not under pressure.

Pump flow control can range from a remote manual on/off control via an operator locally positioned at the fill point, to a feedback control signal from the fill point valve to the source pump. In the latter case, feedback control can be expanded to include a PID (Proportional Integral Derivative) loop developed around pump flow, such as pump discharge pressure modulating pump flow via a variable-frequency AC (alternating current) drive. In either case, the best practice is to not allow the pump to run continuously, either deadheading against a blocked line, or continuously recirculating through the PRV back to the tank. Control schemes like this tend to over-shear the grease, causing loss of penetration and potential off-specification product.

Note that typically the packaging-point control valve is controlled by feedback from the load cell weighing the filled container. The Programmable Logic Controller-governing packaging operation requires a fill-weight set point, from which the packaging-point supply valve will open and close based on the actual versus fill-weight set point (SP).

The most critical component of any grease delivery system is the pump. Errors in matching the correct pump for the delivery application can lead to issues with pump reliability and grease quality. As discussed previously, any pump must be designed to dispense a grease with the inherent apparent viscosity. The piping system (e.g., diameter, length, 90-degree elbows, valves) must be considered along with the viscosity to calculate the overall system hydraulic pressure at the targeted delivery rate. Safety checks to ensure the system pressure does not exceed the Maximum Allowable Working Pressure of the pump are critical. Signs of a system hydraulic pressure that exceeds the pump design are spikes in pump running temperature and frequent shaft seal cartridge/packing leaks and failures. Another consideration of pump selection comes in the type of pump and internal clearances. Gear-type positive displacement

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pumps can, by their nature, impart significant shear while rotating volume through the pump head and dispensing. If the grease being considered for the system is shear sensitive, nonmating gear or other head designs should be considered. A system being designed for a low apparent viscosity grease can experience a phenomenon called internal pump slip. This is caused by a combination of pump discharge pressure and pump head internal clearances. If the discharge pressure becomes too high and the internal clearances are too great, grease will “slip” counterflow by the rotating elements moving volume through the pump head. The slip can become significant if the apparent viscosity decreases and/or the discharge pressure increases. Specification of internal clearances to the pump supplier can minimize the slip occurrence.

References Holland, F.A., Bragg, R.; Edward, A., “Fluid Flow for Chemical Engineers; 2nd Edition,” Edward Arnold, 1995.

Khonsari, M.M. and Booser, E.R., “Bearing Design and Lubrication,” Applied Tribology, Wiley, April 18, 2008, doi: 10.1002/9780470059456.

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Grease Glossary Definitions of Terms Relating to the Lubricating Grease Industry Dr. Mary Moon, Presque Isle Innovations LLC; David Turner, CLGS, CITGO Petroleum Corporation

Additive – Any substance added to a lubricant to modify its properties. Typical examples are antioxidants, corrosion inhibitors, antiwear and extreme pressure (EP) additives.

Adhesion – The force or forces between two materials in contact, such as lubricating grease and a metal substrate, that cause them to stick together.

Age Hardening – Increase in consistency (hardness) of a lubricating grease during storage.

Anhydrous – Without water, for example, a lubricating grease in which no water is detected by ASTM D128. Calcium 12-hydroxystearate grease is called an anhydrous calcium soap grease.

Antioxidant (Oxidation inhibitor) – An additive used to slow the degradation of lubricants by oxidation.

Oxidation is degradation caused by chemical reactions of the lubricant with oxygen. These reactions change the chemical composition, alter the properties and shorten the service life of a lubricant.

Antiwear Additive – An additive used to protect lubricated surfaces from contacting one another under moderate loads. Antiwear additives function by forming a surface layer on metal parts, thus keeping the surfaces separated. For more highly loaded applications, EP additives are required.

Apparent Viscosity – The apparent viscosity of a grease is the ratio of shear stress to shear rate as measured

by ASTM D1092 or other techniques. It is a function of temperature and shear rate. A graph of apparent viscosity versus shear is used to predict the pressure drop in a grease distribution system under steady-state flow conditions at constant temperature.

Appearance – Characteristics of a lubricating grease that are observed by visual inspection: bloom, bulk appearance, color, luster and texture.

ASTM D02.G0 – ASTM International (formerly the American Society for Testing and Materials) is an international standards organization. Committee D02 covers petroleum products, liquid fuels and lubricants. Subcommittee D02.G0 covers lubricating grease.

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API Groups I-V – The lubricating fluid in a grease can be a mineral oil (derived from petroleum), a synthetic fluid or a vegetable-based fluid. Lubricant base fluids are divided into five groups defined by the American Petroleum Institute (API) as follows: Group I – Paraffinic mineral oil, typically produced from petroleum by solvent extraction processes, with a sulfur content of >0.03% and/or saturates <90%. The VI ranges from 80 to 120.

Group II – Paraffinic mineral oil, typically produced from petroleum by a combination of solvent extraction and catalytic processes, with a sulfur content of <0.03% and saturates >90%. The VI is in the range from 80 to 120.

Group III – Paraffinic oil produced from petroleum by severe hydrocracking processes with a sulfur content of <0.03% and saturates >90%. The VI is >120. Group III oils are widely (but not universally) considered to be synthetic. Gas-to-liquid (GTL) base oils are classified as Group III. Group IV – Polyalphaolefin (PAO) fluids are the sole member of Group IV. PAOs are synthetic lubricant base stocks that are synthesized by the polymerization of linear alpha-olefins.

Group V – This Group includes all base stocks not covered elsewhere. It includes all synthetic fluids other than PAOs. Group V includes naphthenic mineral oils, natural esters (vegetable oils), synthetic esters, silicone oils and all other synthetic hydrocarbons (other than PAOs).

In Europe, ATIEL defines similar categories to the API Groups, but in addition has classified poly(internal olefins), i.e., PIOs, as Group VI. Applied Shear Stress – The force applied per unit area of fluid to sustain flow.

Asperity – A microscopic “bump” or ”peak” on a solid surface. Asperities are present on virtually every solid surface due to the machining processes used to make bearings, gears, etc.

ATIEL – The Technical Association of the European Lubricants Industry. ATIEL is a nonprofit association that represents leading European and international engine oil manufacturers and marketers. ATIEL promotes consensus on key technical, product stewardship and sustainability issues. A major focus is the performance of engine oils including wear protection, deposit control, fuel economy and CO2 emissions.

Biodegradable – Biodegradable lubricants rapidly decompose to water, carbon dioxide and minerals due to the action of naturally occurring microorganisms or enzymes present in soil or groundwater.

Readily biodegradable lubricants undergo ≥60% decomposition by mass. Inherently biodegradable lubricants undergo somewhat less decomposition (between 20 and 60%) in OECD 301 testing. They are typically used in environmentally sensitive applications.

Bleeding – The separation of liquid from a lubricating grease, also referred to as “oil separation.”

Blending – The process of mixing components to produce a mixture with desired properties.

Bloom – The surface color (usually blue or green) of a lubricating oil or grease when viewed by daylight reflected at an angle of approximately 45 degrees from the surface. Bloom is associated with the absorption of ultraviolet light in the oil and may not be visible if the sample is viewed using artificial light.

Boundary Lubrication – See Lubrication.

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Bulk Appearance – The visual appearance of grease when the undisturbed surface is viewed in an opaque container. See also Texture. Bulk Appearance is typically described in the following terms: Bleeding - Free oil on the surface or in the cracks of grease.

Cracked - Surface cracks.

Grainy - Small granules or lumps of thickener or additive particles.

Rough - Many small irregularities.

Smooth - Relatively free of irregularities.

Cavitation – The formation of voids due to reduced pressure in lubricating grease or oil. Cavitation of a lubricating grease in a dispensing system can prevent the grease from flowing.

Certification Marks – See NLGI Certification Marks.

Certified Lubricating Grease Specialist (CLGS) – CLGS certification indicates that an individual possesses a level of expertise in the field of lubricating grease as defined by NLGI. Certification is awarded after an individual passes a two-hour exam that consists of 120 questions about lubrication fundamentals and grease types, selection, manufacturing, applications, maintenance, testing, etc.

Channeling – The tendency (usually desirable) of a channel to form when grease is worked in a bearing, leaving shoulders of unworked grease that serve as a seal and a reservoir of oil. Also, the tendency of liquid lubricants and certain lubricating greases to form a plastic structure sufficiently strong to resist flow under gravitational forces at low temperatures. Similar, but not identical to, the pour point of liquid lubricants, channeling is measured with empirical tests such as Method 3456.2 in Federal Test Method Standard No. 791 (D).

Coefficient Of Friction (Static) – The static coefficient of friction (COF) is the ratio of the tangential force that is needed to start relative motion between two contacting surfaces to the perpendicular force (applied load) holding them in contact.

Coefficient Of Friction (Dynamic) – The dynamic COF is the ratio of the tangential force that is needed to maintain relative motion between two contacting surfaces to the perpendicular force (applied load) holding them in contact.

Cohesion – Attractive forces between molecules in a substance. For example, cohesion between molecules in grease contributes to its resistance to flow.

Cold SETT – See SETT. Colloid – A substance that consists of microscopically dispersed insoluble particles that are suspended throughout another substance, typically a fluid. Lubricating grease is a colloidal system of thickener particles or fibers in oil. See Thickener.

Color (of lubricating grease) – The shade and intensity observed when lubricating grease is viewed under conditions that eliminate bloom. For example, lubricating grease in an opaque container such as a metal package can be observed under reflected light from a position approximately perpendicular to the surface. Grease color can also be observed with transmitted light by placing the sample on a transparent plate. It is important to indicate the method used to determine the color of grease. Colors of lubricating greases are best described in terms of the predominant hue such as amber or brown (or perhaps green, red or blue for dyed grease) with a qualifying adjective describing intensity in terms of light, medium or dark.

Color (of lubricating oil) – That shade observed when viewed under transmitted light only. Usually lubricating oil colors are obtained by viewing under specified conditions in test equipment.

Several such methods are available, the most widely used being ASTM D1500, which describes the colors in terms of numbers.

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Complex Soap – A soap thickener wherein the soap crystals or fibers are formed by cocrystallization of two or more compounds, i.e., the primary soap and complexing agents such as metal salts of organic acids or inorganic salts. The complexing agent modifies the grease characteristics and usually increases the dropping point.

Cone Penetrometer – A device described in ASTM D217 and D1403 (ISO 2137) that measures the consistency (hardness) of lubricating grease. The device consists of a freely moving cone and shaft assembly, a pedestal for placing the grease sample below the cone, a locking device to stop the motion of the cone and shaft and a scale for measuring the depth to which the cone penetrates the grease.

Consistency (hardness) – The resistance of a lubricating grease to deformation under the application of force. Consistency characterizes the plasticity of a solid in much the same way that viscosity characterizes a fluid. Grease consistency is measured by cone penetration according to ASTM D217 (ISO 2137).

Corrosion – The gradual destruction and/or pitting of a metal surface due to chemical reactions. The most common form of corrosion is caused by the oxidation of metal, i.e., electrochemical reactions of metal with oxygen and/or aggressive ions. See Fretting.

Corrosion Inhibitor – An additive used in grease to prevent metal corrosion. Test methods for corrosion prevention properties of grease include D1743, D5969 and D6138 for ferrous metals and D4048 for copper. Different chemistries are used to protect different types of metals.

DIN – Deutsches Institut für Normung e. V. (DIN), the German Institute for Standardization, is a nonprofit organization that develops and publishes standards on a wide variety of topics.

Headquartered in Berlin, Germany, DIN is Germany's national standards organization. DIN standards are synchronized with the rest of the world.

Dispensability – The ease with which grease may be transferred from its container to its point of application. Mostly used in discussion of grease dispensing systems, where it includes both the properties of pumpability and feedability.

Dropping Point – Refers to the temperature observed in a laboratory test where a small quantity of lubricating grease is heated until a drop of material separates from the grease. That temperature is adjusted according to ASTM D 2265. The dropping point is not the melting point of lubricating grease. Dropping point is used in many grease specifications. However, this test has very limited relevance to service performance. Dropping point should not be used to determine the upper operating temperature of a grease. To estimate how grease performs at high temperature, certain bearing-life tests may be helpful.

Dry Film Lubricant – Dry or solid lubricants form films that reduce friction without oil. Dry lubricants are often used in locks, certain bearings and applications at high temperatures or oxidizing conditions. Examples include graphite, molybdenum disulfide, boron nitride, PTFE and certain soaps.

Dynamic Friction – Also called kinetic friction, the resistance to motion of contacting bodies as they move relative to one another.

Dynamic Viscosity – The ratio between the applied shear stress and rate of shear of a liquid. The dynamic viscosity can be measured by placing the liquid between two parallel plates and measuring the force required to move one plate while holding the other plate fixed.

Elastohydrodynamic Lubrication – See Lubrication.

Environmentally Acceptable Lubricant or Environmentally Advantaged Lubricant (EAL) – A lubricant meeting application or regulatory requirements on toxicity, bioaccumulation, biodegradability and, in certain circumstances, renewable content.

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Evaporation Loss – That portion of a lubricant that volatilizes in use or in storage. Typical test methods are ASTM D972 and D2595.

Extreme Pressure (EP) Additive – EP additives enhance the load-carrying capacity of a grease under boundary lubrication conditions. EP additives chemically react with the metal surface under conditions of high load and elevated temperature, forming a chemically bonded lubricating film.

Extreme Pressure (EP) Property – The ability of a lubricant to reduce scuffing, scoring and seizure that can occur when highly loaded moving surfaces are in contact. Commonly used laboratory test measurements of the EP level of greases are the Timken OK Load (ASTM D2509, Four-Ball Weld and Load Wear Index (ASTM D2596) and EP by SRV Step Load (ASTM D5706).

False Brinelling – Localized fretting that occurs when the rolling elements of a bearing vibrate or oscillate with a small amplitude while pressed against the bearing race. The mechanism proceeds in stages: 1) asperities weld, separate and form wear particles which may then be oxidized; 2) the wear particles cause abrasive wear. The resulting wear is in the form of depressions that appear similar to Brinell depressions obtained with static overloading. See also Fretting.

Fatigue – Fatigue refers to the initiation and growth of cracks due to cyclic loading.

Feedability – The ability of lubricating grease to flow under suction in a dispensing pump at a rate at least equal to the pump delivery capacity. When the feed of grease is not satisfactory, cavitation can occur at the inlet to the dispensing pump. In such cases, feedability can often be improved by the use of follower plates.

Fiber – Soap thickeners are chemicals that form microscopic fibers during the production of lubricating grease. Some soaps crystallize in the form of threads, which are 20 or more times as long as they are thick. Most soap fibers are microscopic in size, so that the grease appears smooth to the unaided eye. Some greases have a fibrous appearance when fiber bundles are large enough to be seen by the unaided eye. The most common fibrous lubricating greases contain sodium soap thickeners, although not all sodium base greases are fibrous. See Appearance and Texture.

Fibril – An extremely small fiber, barely visible even at the maximum magnification of an electron microscope. Fibrils may collect in bundles to form larger fibers.

Filler – A material added to a grease to increase bulk or density. Examples of fillers are talc, pigments and carbon black.

Film Strength – The ability of a film of lubricant to resist rupture due to load, speed and temperature.

Follower Plate – A plate fitted to the top surface of lubricating grease in a container and designed to assist delivery of grease to the inlet of the dispensing system.

Food Grade – A term used casually to refer to lubricants certified by NSF International for use primarily in food and beverage, personal care product and pharmaceutical processing applications.

Food-Machinery Lubricant – Any lubricant that has received H1 designation from NSF for use “above the line” in manufacturing and packaging food, beverage, personal care and pharmaceutical products.

Four-Ball Weld Point – In ASTM D2596, refers to the applied load at which the lubricant no longer prevents metal-to-metal contact and the standard steel balls used in the test undergo welding.

Fretting Wear – A form of wear caused by vibratory or oscillatory motion of limited amplitude and characterized by the removal of fine particles from the rubbing surfaces. Fretting wear is often followed by localized oxidation, hence the term friction oxidation. See also False Brinelling and Fretting Corrosion.

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Fretting Corrosion – Under conditions of fretting wear, fretting corrosion occurs between a bearing inner ring and shaft or an outer ring and housing. The corrosion occurs at points where the fit is too loose. When the fit is too loose, the metal oxide film can be worn away, allowing oxygen to attack the underlying metal. The buildup of corrosion products can cause severe bearing damage, including cracking of bearing rings.

Friction – The force resisting relative motion between two surfaces that are in contact.

Friction Oxidation – See Fretting Wear.

Gas to Liquids (GTL) – Refers to the conversion of gaseous hydrocarbons, such as natural gas, to liquid synthetic fuels and lubricant base stocks. The GTL lubricant base stocks are classified as API Group III. Gel – An elastic, jelly-like material that resembles a solid but flows like a liquid. Most gels are dispersions of liquids in networks of colloidal particles or polymers.

Grease – See Lubricating Grease.

Grease Worker – A standard laboratory-scale device used to apply shear to a grease. The grease worker consists of a metal cup of standard dimensions, a cover fitted with a handle and a shaft attached to a metal plate drilled with 61 x ¼-inch holes. The cup is filled with grease, the cover is closed and the plate is pushed through the grease sample. The device can be manually or mechanically driven. For ½-scale and ¼-scale penetrations, the equipment is progressively smaller. The equipment details can be found in ASTM D217 (full-scale) and ASTM D1403 (small-scale) and ISO 2137.

Grease Worker Cup – A machined metal cup that holds grease for working. It is also the cup that is used to hold the grease for penetration measurements. A full-scale worker cup holds about 1 pound (~450 grams) of grease. See ASTM D217 for the details of the cup dimensions. Smaller scale (½and ¼-scale) worker cups are described in ASTM D1403.

H1/H2/H3/3H/HX-1 – Designations defined by NSF International for finished lubricants and components used in food-processing applications. H1 lubricants must be colorless, odorless, tasteless, nontoxic and meet other criteria; they are certified for incidental food contact. H2 lubricants may be used in food processing but only in situations where food contact cannot occur. H3 lubricants, also known as soluble or edible oils, are used to clean and prevent rust on hooks, trolleys and similar equipment. 3H lubricants are allowed to be in direct contact with food. HX-1 ingredients must be used to formulate H1 lubricants.

Herschel-Bulkley – A rheological model describing the relationship between applied shear stress and shear rate for a non-Newtonian fluid such as lubricating grease.

Homogenization – The process of very thoroughly mixing the components in a mixture and applying intensive shear to improve their dispersion. Grease is homogenized to disperse the thickener, improve the bulk appearance, improve the yield and reduce the cost of the product.

Hybrid Thickener – A grease thickener where a metallic soap is used with a non-soap thickener. Examples include urea complex thickener where a urea and a calcium complex soap are used together and calcium sulfonate complex where a fatty acid is reacted with residual lime to form a mixed calcium sulfonate soap grease.

Hydrated Soap – A soap that has water associated with its structure. A typical example is a water-stabilized calcium soap grease, which owes its stability to hydrated calcium soap.

Hydrodynamic Lubrication – See Lubrication.

Hydrophilic – Having an affinity for water; capable of uniting with or dissolving in water.

Hydrophobic – Repelling water, incapable of uniting with or dissolving in water.

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Hydrostatic Lubrication – See Lubrication.

Incidental Food Contact – Incidental food contact refers to unintended contact by small amounts of NSF H1 lubricants that may splash, drip, etc. onto products such as food, beverages and personal care products during processing or related operations. The concentration of H1 lubricants in food and beverages is limited to 10 parts per million (ppm).

Incompatibility – Two lubricating greases are incompatible when a mixture of the products has physical or performance properties that are inferior to those of the individual greases. Physical or performance properties inferior to one of the products and superior to the other may be due to simple mixing and would not be considered evidence of incompatibility.

Induction Period (Grease Oxidation) – A period of time during which oxidation occurs at a relatively slow rate. At the end of the induction period, the oxidation rate may become more rapid. Methods of measurement of induction time include ASTM D942 and D5483.

Inorganic Acid – An acid that does not contain a carbon chain. Inorganic acids, such as boric acid, are sometimes used as complexing agents in complex soap greases. Contrast with Organic Acid.

Inorganic Salt – The reaction product of an alkali with an inorganic acid. Inorganic salts, such as lithium borate, are sometimes found in complex soap greases.

Inorganic Thickener – See Non-Soap Thickener.

Insolubles – Components of a lubricating grease that are insoluble in the prescribed solvents in an analytical procedure such as ASTM D128. The analytical procedure should be indicated when specifying insolubles. Additional identifying analytical tests are required to determine the nature and composition of insolubles, which may consist of fillers, additives, certain types of thickeners or impurities.

ISO - The International Organization for Standardization, a nongovernmental, independent organization with a membership of 166 national standards bodies, is based in Geneva, Switzerland. It has developed and published more than 24,000 international standards covering almost all aspects of technology and manufacturing.

Kinematic Viscosity – The resistance of a liquid to flow under gravity. Kinematic viscosity can be measured directly, as in ASTM D445, where it is measured by the time required for a volume of liquid to flow under gravity through a calibrated glass capillary tube referred to as a viscometer. Standard temperatures of 40 °C and 100 °C (104 °F and 212 °F) are typically used. Kinematic viscosity can also be calculated as the ratio of the dynamic viscosity to the density of the liquid.

Load Wear Index (LWI) – An index of the ability of a lubricant to minimize wear at applied loads in the Four-Ball EP Test (ASTM D2596). The applied load is increased stepwise until welding (seizure) occurs. The LWI is calculated based on the wear scars of the 10 highest nonseizure loads.

Lubricant – Any material that is used or applied to surfaces in order to reduce friction and/or wear that can occur when two surfaces are in contact and undergo relative motion. Lubricants are available in various forms: liquids, greases, dry films and coatings.

Lubricating Grease – A lubricant that is a solid- to semifluid dispersion of a thickening agent (thickener) in a liquid. A lubricating grease may be formulated with additives that impart special properties such as resistance to oxidation or wear. An alternative definition (Vold and Vold, 1952) states, “A grease is a lubricant that has been thickened in order that it remain in contact with the moving surfaces and not leak out under gravity or centrifugal action, or be squeezed out under pressure.”

Lubricating Grease Structure – The physical arrangement of thickener particles or fibers in a grease. The nature, form and stability of this structure determine the appearance, texture and physical properties of the grease.

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Lubrication – The use or application of a material (lubricant) to reduce friction and/or wear that can occur when two surfaces undergo relative motion while in contact under an applied load. Friction and lubrication performance depend upon the relative speed of the surfaces, the lubricant viscosity and the applied load.

There are five major lubrication regimes or types of behavior: Boundary Lubrication – The lubricant film is too thin to form a fluid layer that completely separates two surfaces. Asperities on the surfaces collide. Friction and wear depend upon the presence of chemical additives that adsorb and form molecular layers on the surfaces.

Elastohydrodynamic (EHD) Lubrication – EHD lubrication occurs in rolling element bearings and certain gears when very high loads are concentrated on small surface areas. Under these conditions, the surfaces deform elastically or flatten to increase the surface area that bears the load. Lubricant is trapped between the surfaces and its viscosity increases under the pressure. As a result, the lubricant is able to form a hydrodynamic film and separate the surfaces.

Hydrodynamic Lubrication – Under appropriate conditions, the relative motion of two sliding surfaces causes a continuous fluid film to form and completely separate the surfaces. This requires a balance between the sliding speed, the applied load and the lubricant viscosity. Fluid Film Lubrication is another name for this type of lubrication.

Mixed Lubrication – A lubrication regime where the load is supported partially by a fluid film and partially by the surfaces in contact.

Hydrostatic Lubrication – Lubricant is supplied under pressure to a plain bearing. This applied pressure forces the lubricant to form a continuous fluid film that completely separates the surfaces.

Hydrostatic lubrication occurs typically during start-up of plain bearings. Hydrodynamic lubrication becomes effective when plain bearings are in motion.

Luster – The intensity of light reflected by lubricating grease, i.e., its sheen or brilliance. Luster is described as follows: Bright – Reflects light with a relatively strong intensity.

Dull – Reflects light with a relatively weak intensity. Some greases with a high water content may have a dull luster. Certain thickeners and fillers give a grease a characteristic dull luster.

Macroscopic – Visible to the unaided human eye, where the particles are at least 40 μm (0.0015 inch) in size.

Mechanical Stability – See Shear Stability.

Metallic Soaps – Metallic soaps are the most common thickeners used in lubricating greases. Materials such as NaOH (sodium hydroxide), LIOH (lithium hydroxide), Ca(OH)2 (calcium hydroxide) and Al(OH)3 (aluminum hydroxide) contain basic or alkaline hydroxide groups (OH-). These materials are mixed with organic fatty acids in oil and heated to prepare grease. The OH- groups react with acidic H+ ions on fatty acids such as stearic acid. This reaction produces thickener fibers plus water as a byproduct. This reaction is known as saponification.

Microscopic – Not visible to the unaided human eye, smaller than 40 μm (0.0015 inch).

Newtonian Behavior – Simple liquids are said to be Newtonian when the applied shear stress is directly proportional to the shear rate. In other words, the viscosity (applied shear stress/shear rate) of a Newtonian fluid is constant and does not depend on the shear stress or shear rate at constant temperatures.

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NLGI Certification Marks –NLGI licenses certification marks for use on labels of products that satisfy performance criteria and pass laboratory evaluations managed by NLGI. In 1989, GC-LB Certification Marks were designed and standardized by NLGI and ASTM (D4950) to meet requirements for lubrication of automotive wheel bearings and chasses and then written into many OEM specifications. Chassis lubricants are designated L and wheel bearing lubricants are designated G. There are two performance classifications for chassis greases (LA and LB) and three for wheel bearing greases (GA, GB and GC). The automotive industry is in general agreement that the highest performance classifications (LB and GC) are suitable for service relubrication of vehicles. In 2020, NLGI introduced the HPM certification marks. In addition to the general HPM certification mark, there are additional specifications and marks for lubricating greases with enhanced water resistance (WR), corrosion resistance (CR), load-carrying ability (HL) and low-temperature performance (LT).

NLGI Grade – A numerical scale for classifying the consistency of lubricating greases that is based on the ASTM D217 worked penetration test at 25 °C (77 °F). NLGI Grades are also referred to as NLGI Consistency Numbers or NLGI Numbers. In order of increasing consistency (hardness): NLGI Grade

000

Worked Penetration Range, 25 °C (77 °F)

445-475

00 400-430 0 355-385 1 310-340 2 265-295 3 220-250 4 175-205 5 130-160 6 185-115 Some grease suppliers use descriptions such as NLGI Grade 1.5, which indicates that the grease consistency is between that of NLGI Grades 1 and 2.

Non-Newtonian Behavior – Some fluids and many plastic solids, including lubricating greases, exhibit nonNewtonian behavior. In other words, the viscosity (applied shear stress/ shear rate) is not constant; instead, it depends on the shear stress and shear rate at a given temperature. Thus, nonNewtonian fluids are described by their apparent viscosity. Conventional types of viscometers with uncontrolled shear rates are not suitable for measuring the viscosity of non-Newtonian materials.

Non-Soap Thickener – Any of several specially treated naturally occurring or synthetic materials, excepting the metallic soaps, which can be either thermally or mechanically dispersed in liquid lubricants to form lubricating grease. Sometimes called synthetic thickener, inorganic thickener, or organic thickener. Examples include polyurea, calcium sulfonate, bentonite and silica-thickened greases.

OECD – The Organization for Economic Cooperation and Development (OECD) is an intergovernmental organization of 38 developed member countries describing themselves as committed to democracy and a market economy; it seeks to stimulate economic progress and world trade by providing a platform to compare policy experiences, seek answers to common problems, identify good practices and coordinate domestic and international policies of its members.

OECD 301 – Test No. 301: Ready Biodegradability covers six methods that permit the screening of chemicals for ready biodegradability in an aerobic aqueous medium. In general, a solution or suspension of the test substance in a mineral medium is inoculated and incubated, normally for 28 days, under aerobic conditions in the dark or in diffuse light. Degradation is monitored by the

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determination of parameters such as dissolved organic carbon (DOC), CO2 production and oxygen uptake and compared with standard thresholds for biodegradability.

Oiliness Agent – A material that reduces friction by formation of an adsorbed film.

OK Load – The OK load or the Timken OK Load describes the load-carrying capacity of a lubricant. The OK load is measured in a standard test (ASTM D2509). In this test, a bearing ring rotates against a stationary steel block under an applied load. The OK load is the maximum load that can be applied without scuffing or seizure of the steel block. It is used to characterize the EP performance of greases and lubricants. The test is named for the Timken Company, which developed this test machine.

Oleate – An oleate is a salt or ester of oleic acid. Oleic acid is an unsaturated fatty acid with chemical formula C18H34O2 or CH3-[CH2]7-CH=CH-[CH2]7-COOH. Oleate greases are made by reacting oleic acid with an inorganic base to form a salt, i.e., soap thickener.

Operating Temperature – The operating temperature of a grease is the range between the lowest temperature where a lubricated device can be started up in an acceptable manner and the highest temperature where lubrication is adequate. The operating temperature of a grease depends on its formulation (base fluid, thickener, additives). In this context, temperature is measured in the general vicinity of the lubricated contact and not between the loaded surfaces. Low-temperature bearing or flow tests are used often to determine the minimum operating temperature. High-temperature bearing tests are used typically to determine the maximum operating temperature. Dropping point alone is not sufficient to determine the maximum operating temperature of a grease.

Organic Acid – In general, organic acids are organic chemicals with acidic properties. Organic compounds contain primarily carbon (C) and hydrogen (H) and may contain smaller amounts of nitrogen (N), oxygen (O), sulfur (S), etc. Acidic molecules tend to release H+ ions by reacting with basic molecules or dissociating in polar solvents. Most organic acids contain a -COOH or carboxyl group that can release an H+ ion.

Organic Soap – An organic soap is an organic molecule that is formed by the chemical reaction of an acid and a base. Many grease thickeners are organic soaps formed by reactions of organic acids with inorganic bases. For example, grease can be prepared by reacting 12-hydroxystearic acid and lime (calcium hydroxide) in base fluid to form calcium 12-hydroxystearate soap, which thickens the fluid to form grease.

Organic Thickener – See Non-Soap Thickener.

Oxidation Stability – The resistance of lubricants to chemical reactions with oxygen. The absorption of and reaction with oxygen may lead to the degradation of lubricants. Several test methods are in use, including ASTM D942 (IP 142) and D5483. Elevated-temperature bearing test methods such as the Ball Bearing Grease Life Test (ASTM D3336), the Wheel Bearing Grease Life Test (ASTM D3527) and the FE9 (DIN 51281) are also used.

Polyalphaolefins (PAOs) – PAOs are hydrocarbon oils that are synthesized by polymerizing α-olefins. PAOs are API Group IV base oils. They are noted for their chemical purity, consistent molecular weight distribution and high VI and they can be used over a wide range of temperatures.

Poly(internal olefins) (PIO) – PIOs are hydrocarbon oils that are synthesized by dehydrochlorination or chlorination of linear paraffins. They have high viscosity indices and low pour points and are used in engine oils, compressor lubricants and other applications.

Penetration – An arbitrary standard measure of consistency (hardness) based on ASTM D217 (ISO 2137).

The softer the consistency, the higher the penetration number.

The ASTM definitions are:

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Penetration – The depth that a standard cone penetrates a sample of lubricating grease under prescribed conditions of cone weight, time and temperature. Penetration is measured in tenths of a millimeter, sometimes abbreviated as dmm.

Undisturbed Penetration – The penetration of a sample of lubricating grease that has not been stirred or disturbed, measured at 25 °C (77 °F).

Unworked Penetration – The penetration at 25 °C (77 °F) of a sample of lubricating grease that has received only minimum disturbance in transferring to a grease worker cup or dimensionally equivalent container.

Worked Penetration – The penetration at 25 °C (77 °F) of a sample of lubricating grease immediately after it has been subjected to 60 double strokes in a standard grease worker.

Prolonged Worked Penetration – The penetration at 25 °C (77 °F) of a sample of lubricating grease that has been subjected to more than 60 double strokes in a standard grease worker at a temperature of 15–30 °C (59–86 °F). Typical numbers of double strokes used for prolonged working are 10,000 and 100,000. After the prescribed number of double strokes, the sample is brought to 25 °C (77 °F) and worked an additional 60 double strokes; penetration is then measured without delay.

Block Penetration – The penetration at 25 °C (77 °F) of a sample of lubricating grease that is sufficiently hard to hold its shape, determined on the freshly prepared face of a cube cut from a block of grease.

Penetrometer – See Cone Penetrometer.

Plasticity – The property of an apparently solid material that enables it to be permanently deformed, without rupture, under the application of force. Plastic flow differs from fluid flow in that the shearing stress must exceed a yield point before any flow occurs.

Pumpability – The ability of a lubricating grease to flow under pressure through the lines, nozzles and fittings of a grease dispensing system. Pumpability is best indicated by the apparent viscosity at moderate shear rate. See ASTM D1092 and NLGI Steady Flow Charts for Grease.

Reversibility – The ability of a grease to return to its normal consistency after temporary periods at temperatures near or above the dropping point of that grease. Aluminum complex greases are known to have this property.

Rheology – The study of the deformation and flow of matter in terms of stress, strain, temperature and time.

Rheopectic Grease – A lubricating grease that hardens when it is subjected to shear.

Rolling Contact Fatigue (RCF) – The breaking up of a bearing surface due to fatigue process leading to failure. Pitting, spalling and micropitting are all manifestations of rolling contact fatigue.

Roll Stability – The ability of a grease to maintain its consistency when subjected to shear in a rolling steel cylinder containing a cylindrical heavy weight as described in ASTM D1831.

Saponification – The chemical reaction of fatty acids, fats or esters with an alkali metal base to form a metallic salt. This salt is commonly called a soap.

Scoring – A form of abrasive wear that resembles scratches along the direction of motion of sliding surfaces. Causes include contaminated or insufficient lubrication, excessive loads, vibration and lack of antiwear or EP additives in the lubricant.

Scuffing – A form of adhesive wear that produces a dull or matte area on sliding surfaces. Causes include contaminated or insufficient lubrication, excessive loads, vibration and lack of antiwear or EP additives in the lubricant.

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Seizure – A type of damage that occurs when rolling surfaces overheat suddenly or rapidly and metal surfaces, such as bearings and raceways, soften, melt and deform to weld. Causes include inadequate lubrication or contaminated lubricant, excessive speed or load and inadequate clearance.

Set – In the manufacture of a lubricating grease, the change from a fluid to a semifluid or plastic state.

SETT – The word “SETT” is uniquely applied to a particular type of product, i.e., Cold Sett greases, which change from a fluid to a semifluid or plastic state after component combination and often after packaging.

Shearing – Slipping or sliding of one part of a substance relative to an adjacent part. In a solid, such action involves cutting or breaking of the crystal structure, but in a fluid or plastic material, shearing does not necessarily destroy the continuous nature of the substance.

Shear Rate – The rate of a slip within a substance engaging in flow. The average or mean shear rate in a pipe or tube is proportional to the average velocity divided by the radius of the tube. Therefore, shear has the dimensions of the reciprocal of the time and is usually expressed in the unit of reciprocal seconds (sec-1). The mean shear rate is reported in the determination of apparent viscosity in ASTM D1092.

Shear Stability – The ability of a lubricating grease to resist changes in consistency during mechanical working. Working may be in any of several types of laboratory machines or may be in actual service. This may also be called Mechanical Stability.

Shear Stress – The force per unit area causing shearing in a substance. In fluids, the ratio of the shear stress to the shear rate is the viscosity of the substance.

Simple Soap – Simple soaps are grease thickeners that are prepared by reacting a single organic acid with one or more inorganic bases. Complex soaps are prepared from two or more organic acids.

Slumpability – See Feedability.

Soap – See Soap Thickener; Complex Soap; Saponification.

Soap Crystal – See Soap Thickener Soap Thickener – Many greases are prepared by reacting organic acid(s) and inorganic base(s) in base fluid to form salt crystals. These crystals are partially soluble in base fluid and form colloidal particles or fibers dispersed in the fluid. These particles or fibers are responsible for the semisolid consistency of grease and are referred to as soap thickeners.

Sol – A suspension of particles of colloidal dimensions in a liquid. These systems possess the gross properties of a liquid.

Squeeze Film Lubrication – A lubrication state in which surfaces that are thickly coated or flooded with lubricant move toward each other at sufficient speed to develop fluid pressure to briefly support a load. Because of its viscosity (or apparent viscosity), the lubricant cannot immediately flow away from the area of contact. Squeeze film lubrication occurs, for example, between gear teeth and between wrist pins and their bushings.

SRV – Schwingung (Oscillating) Reibung (Friction) Verschleiz (Wear). An SRV® machine is used to evaluate the friction and wear properties of liquid lubricants and lubricating greases in a variety of contacts. SRV tests measure interactions between a lubricant and two specimens in a loaded contact undergoing rotational or sliding oscillatory motion. Two of a number of standard tests that use an SRV machine are ASTM D5707 (friction and wear) and ASTM D5706 (stepwise EP).

Static Friction – Resistance to motion as contacting bodies begin to move from rest.

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Steady-State Flow – A fluid is described as undergoing steady-state flow when its properties at any given condition are unchanging, as is the case during laminar flow.

Stearate – A stearate is a salt or ester of stearic acid. Stearic acid is a fatty acid with chemical formula C18H36O2 or CH3-[CH2]16-COOH. Stearate greases are made by reacting stearic acid with an inorganic base to form a salt, i.e., a soap thickener.

Stringiness – A term that is used casually to refer to a qualitative visual assessment of the ability of a grease to form threadlike “strings.” See Tackiness.

Syneresis – Loss of liquid lubricant from a lubricating grease due to shrinkage or rearrangement of the structure. The shrinkage may be due to either physical or chemical changes in the thickener.

Syneresis is a form of oil separation.

Synthetic Grease – A grease composition in which the liquid lubricant is something other than a mineral or vegetable oil.

Tackiness – The adhesive-cohesive property of a grease, i.e., how well a grease adheres to the surface that it lubricates. In the adhesive industry, tackiness is defined as the force applied to separate two solid surfaces joined by an adhesive layer in its liquid state. In the grease industry, tackiness is qualitatively considered as the ability of a grease to form threads as it is being pulled apart, e.g., when a small amount of grease is held between the thumb and forefinger of an operator and the operator increases the gap between their thumb and forefinger. Research is underway to develop a formal definition and quantitative test method to measure tackiness and adhesion of grease.

Texture – Properties of lubricating greases that are observed visually when handling grease. Texture is described in the following terms: Brittle – Has a tendency to rupture or crumble when compressed.

Buttery – Separates in short peaks with no visible fibers.

Long Fibers – Shows tendency to stretch or form a string consisting of a single bundle of fibers.

Resilient – Capable of withstanding moderate compression without permanent deformation or rupture.

Short Fibers – Shows short break-off with evidence of fibers.

Stringy – Stretching into long, fine threads with no visible evidence of fiber structure.

Tacky – Having adhesiveness, especially to metal surfaces. Greases with polymers tend to be tacky.

Other terms, such as Smooth, Rough, Grainy, etc., are defined under Bulk Appearance.

Thickener – The solid particles that are relatively uniformly dispersed in a liquid lubricant to form the structure of lubricating grease. The solid particles may be fibers, platelets, amorphous particles or polymers.

Thixotropy – Decrease in grease consistency (softening) as a result of shearing, followed by an increase in consistency (hardening) after shearing is stopped. Thixotropic age hardening is a relatively prolonged process proportional to aging time and is seldom, if ever, complete. In contrast, the apparent viscosity increase in non-Newtonian systems with decreasing shear rate is instantaneous and fully reversible. Lubricating grease is both thixotropic and non-Newtonian.

Timken OK Load – See OK Load.

Translatory – A synonym for translation or linear motion in DIN and other European specifications and standards.

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Viscosity – The absolute or dynamic viscosity (η) in centipoise (cP) is a measure of the internal resistance of a fluid to flow. Absolute viscosity is typically measured with a rotational viscometer.

Lubricants and base oils are usually described in terms of their kinematic viscosity (ν) in centistokes (cSt), which is defined as the ratio of the dynamic viscosity to the density of a fluid.

Kinematic viscosity is typically measured with a flow-type viscometer; an operator measures the length of time that it takes for a fluid to flow through a capillary tube. Thus, kinematic viscosity corresponds to the speed at which a fluid flows under the application of a certain force, typically gravity. The terms “heavier” and “lighter” are used casually to refer to oils and lubricants that have higher and lower viscosities, respectively.

Viscosity Index (VI) – The VI of a base oil or lubricant describes its change in viscosity with temperature.

The VI value is usually obtained according to ASTM D2270 from a calculation based on data for the kinematic viscosity at 40 °C and 100 °C (104 °F and 212 °F).

Water Resistance – The ability of lubricating grease to withstand the addition of water to the lubricant system without adverse effects. Water resistance is considered to be made up of four components: Water Washout Resistance – The ability of a lubricating grease to resist being removed from a bearing when operated with exposure to water. Generally measured by ASTM D1264 or ISO 11009.

Water Absorption – The characteristics of a lubricating grease when water is added: Water Soluble – The lubricating grease absorbs the water and then becomes semifluid.

Water Absorbent – The lubricating grease absorbs relatively large quantities of water with little or no change in consistency and without a separate phase of free water.

Water Resistant – The lubricating grease does not absorb more than small amounts of water, does not change appreciably in consistency and most of the added water is a separate second phase.

Water Corrosion Resistance – The ability of a lubricating grease to prevent corrosion of metal surfaces in the presence of water. May be measured either statically by standard tests or dynamically by operation of bearings with water added to the lubricant reservoir, as in ASTM D1743, D5969, D6138 and ISO 11007.

Water Spray Resistance – The ability of a grease to resist displacement from a surface by the impact of a water spray. The test method used is ASTM D4049.

Lubricating greases for various types of service may not need any of the water resistance properties described above. They are not measures of quality except for specific situations where water resistance is required.

Wear – Damage that involves the cumulative and gradual removal of material from surfaces. Several types of wear are described below: Abrasive Wear – Damage that occurs when surfaces are in contact and undergo relative motion and cutting or abrasion by hard particles removes material from the surfaces.

Adhesive Wear – Damage that occurs when two surfaces are in contact and undergo relative motion and high loads and/or temperatures cause asperities to weld and then immediately separate, removing material from one or both surfaces. Adhesive wear can be mild (frosting), moderate (scuffing) or severe (galling, scoring, seizing).

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Corrosive Wear – Damage that occurs when chemical or electrochemical reactions at a surface result in the removal of material. Corrosion can be localized (e.g., pitting) or general.

Electrical Discharge Wear – Removal of material from solid surfaces due to sparks or highamperage electrical discharge.

Erosive Wear – Progressive loss of material from the surface or edge of a solid component when a liquid or a large number of solid particles impinge upon it.

Fatigue Wear – Wear of a solid surface that is caused by fatigue, i.e., repeated heavy loading, that causes dents, cracks, fracture and removal of fragments from a metal surface.

Fretting Wear – Wear that occurs as a result of fretting, i.e., small amplitude oscillations or vibrations between two solid surfaces that are in contact.

Polishing Wear – Wear that occurs when very fine, hard particles in a lubricant remove material from a solid surface, producing a brightly polished surface.

White Etch Cracking – Bearing failure characterized by the appearance of white cracks on the surface of the bearing. White etch cracks are typically found in high-stress applications such as wind turbine gearbox bearings. In situ hydrogen generation by corrosion or other causes and stray electrical currents have been implicated as factors leading to white etch cracking.

Working – The subjection of lubricating grease to any form of agitation or shearing action beyond simple transfer to any test apparatus, package or application.

Yield – The amount of grease of a given consistency that may be made with a specific amount of thickening agent. As the yield increases, percent thickener by weight decreases.

Yield Stress – (also yield value or yield point) – The minimum shear stress required to produce flow of a plastic material. It can be estimated by the intercept on the shear stress axis of a shear stressshear rate curve by extrapolation of the straight portion of the curve. See Apparent Viscosity.

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NLGI Publications NLGI Spokesman Index

An invaluable index to all articles published in the Spokesman from 1941 to the present is available from the NLGI International office. A searchable database of all NLGI Spokesman technical articles is available at www.nlgi.org/nlgi_article.

Other NLGI Publications

Recommended Practices Line Strainers for Centralized Dispensing Systems Standard Unit of Measurement for Centralized Systems Viscosity of the Base Fluid in Lubricating Grease Storage of Lubricating Grease

Other NLGI Literature

Chassis and Wheel Bearing Service Classification System Classification of Lubricating Grease Steady Flow Charts for Grease Glossary of Terms Grease Production Survey Reports NLGI Information Brochure

Online Resources Professional/Industry Associations

NLGI – www.nlgi.org NLGI-India Chapter – www.nlgi-india.org European Lubricating Grease Institute (ELGI) – www.elgi.org Independent Lubricant Manufacturers Associations (ILMA) – www.ilma.org Society of Tribologists and Lubricating Engineers (STLE) – www.stle.org ASTM International – www.astm.org ASM International – www.asminternational.org American Society of Mechanical Engineers (ASME) – www.asme.org American National Standards Institute (ANSI) – www.ansi.org Society of Automotive Engineers International (SAE) – www.sae.org American Chemical Society (ACS) – www.acs.org American Institute of Chemical Engineers (AIChE) – www.aiche.org

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Government Agencies

United States EPA – www.epa.gov U.S. Code of Federal Regulations – http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&tpl=%2Findex.tpl U.S. Patent & Trademark Office – www.uspto.gov Canada DSL - http://www.ec.gc.ca/substances/ese/eng/dsl/dslprog.cfm European Chemical Agency (ECHA)/REACH - http://echa.europa.eu/home_en.asp European Chemical Substances Information System (ECIS) – http://ecb.jrc.ec.europa.eu/esis/index.php?PGM=ein

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Common Industry Abbreviations AAM AAMA AAR ABIL ACC ACEA ACS AGMA AIAM AIChE ALI ANSI AOCS APE API APRAC AQL ASME ASTM ATA ATC ATIEL

Alliance of Automobile Manufacturers American Automobile Manufacturers Association American Association of Railroads Agriculture-based Industrial Lubricants American Chemical Council Association des Constructeurs Europeen d’Automobiles American Chemical Society American Gear Manufacturer’s Association Association of International Automobile Manufacturers American Institute of Chemical Engineers Auto Research Laboratories Incorporated American National Standards Institute American Oil Chemists Society Association of Petroleum Engineers American Petroleum Institute Air Pollution Research Advisory Committee Acceptable Quality Levels American Society of Mechanical Engineers ASTM International American Trucking Association Technical Committee of Petroleum Additive Manufacturers in Europe Association Technique de I’Industrie Européenne des Lubrificants (European Oil Marketers Association) BIA Boating Industry Association (now NMMA) BLF British Lubricants Federation (see UKLA) BNP Bureau de Normalisation des Petroles (France) BSI British Standards Institution CCPA Canadian Chemical Producers Association CEC California Energy Commission CEC Coordinating European Council (European Chemical Industry Council) CEN Conseil Europeen de Normalisation CEPA Canadian Environmental Protection Act CFR Code of Federal Regulations (U.S.) CGSB Canadian General Standards Board CMA Chemical Manufacturers Association CNPC China National Petroleum Corporation CONCAWE Conservation of Clean Air and Water Europe COP Code of Practice

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CPC CPPI CRC CVMA DCC DBL DIN DKA DOD DOE DOT EC EC EC ECE ECHA EEC EI EIA ELGI EPA ETS EU EUROPIA FERC FTC FTP GAO GFC GM GSA HAPEM HEI IChemE IEA IFP ILMA IP ISO JAMA JARI JASO

Chinese Petroleum Corporation Canadian Petroleum Products Institute Coordinating Research Council, Inc Canadian Vehicle Manufacturers Association Daimler Chrysler Corporation Daimler Benz Liefervorschrift Deutsches Institut für Normund Deutscher Koordinieungsausschuss Department of Defense Department of Energy Department of Transportation Environment Canada European Community Japan’s Environmental Council European Environmental bureau European Chemical Agency European Economic Community Energy Institute (formerly the Institute of Petroleum) Energy Information Administration (DOE) European Lubricating Grease Institute Environmental Protection Agency (U.S.) Engineering Test Services European Union European Petroleum Industry Association Federal Energy Regulatory Commission Federal Trade Commission Federal Test Procedure (EPA) General Accounting Office (U.S.) Groupement Francais de Coordination General Motors General Services Administration (U.S.) Hazardous Air Pollution Exposure Model Health Effects Institute Institute of Chemical Engineers (U.K.) International Energy Agency Institut Francais du Petrole Independent lubricant manufacturers Association Institute of Petroleum (U.K.) – See EI (Energy Institute) International Organization for Standardization Japanese Automobile Manufacturers Association Japanese Automotive Research Institute Japanese Automotive Standards Organization

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JAST JIS JPI JSAE LMOA LRI LSC MIL MITI MOD MOE MOL SDS MTAC MVMA NAAQS NACE NAFTA NATC NCRP NCWM NEB NEDO NHTSA NIST NLGI NMMA NPRA NRC NRCC NUTEK OECA OMB OMS OPEC ORD OSHA OTA PADD PAJ PAPTG PMAA

Japanese Society of Tribologists Japanese Industrial Standards Japanese Petroleum Institute Japanese Society of Automotive Engineers Locomotive Maintenance Officers Association Lubricant Review Institute Lubricant Standards Committee Military Specification Ministry of International Trade and Industry (Japan) Ministry of Defense (U.K.) Ministry of Energy (U.K.) Ministry of Labor (Japan) Material Safety Data Sheet Multiple Test Acceptance Criteria Motor Vehicle Manufacturers Association National Ambient Air Quality Standard (U.S.) National Association of Corrosion Engineers North American Free Trade Agreement Net Additive Treat Cost National Cooperative Research Program National Conference on Weights and Measures National Environmental Board (Thailand) New Energy and Technology Development Organization (Japan) National Highway Traffic Safety Administration National Institute of Standards and Technology (U.S.) National Lubricating Grease Institute (U.S.) National Marine Manufacturers Association (U.S.) National Petrochemical & Refiners Association (U.S.) Natural Resources Canada National Research Council of Canada Swedish National Board for Industrial & Technical Development Office of Enforcement and Compliance Assurance Office of Management and Budget (U.S.) Office of Mobile Sources (EPA) Organization of Petroleum Exporting Countries Office of Research and Development (EPA) Occupational Safety and Health Administration Office of Technology Assessment (DOE) Petroleum Administration for Defense District Petroleum Association of Japan Product Approval Protocol Task Group (CMA) Petroleum marketers Association of America

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PTIT PTT QPL SAE SCAQM SIP(s) SWRI TAG TISI TMA TMC TMC TRC UEIL UKLA UKOIA UKPIA UNEP U.S.S.

Petroleum Technical Institute of Thailand Petroleum Authority of Thailand Qualified Products List (U.S. Military) Society of Automotive Engineers South Coast Air Quality Management (California) State Implementation Plan(s) Southwest Research Institute Technical Advisory Group (CMA) Thailand Industrial Standards Institute Truck Manufacturers Association The Maintenance Council Test Monitoring Center (ASTM) Transportation Research Center Union Européenne de l’Industrie des Lubrifiants United Kingdom Lubricants Association U.K. Oil Independents Association U.K. Petroleum Industry Association United Nations Environment Programme U.S. Steel

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NLGI

LUBRICATING

GREASE GUIDE The NLGI Lubricating Grease Guide is an introduction to a broad spectrum of topics related to the grease industry, geared towards both those new to the industry and to industry veterans. The chapters have been arranged in a sequence that will lead readers through the subject matter in a logical order. Additionally, each chapter is self-standing so that the NLGI Lubricating Grease Guide can be used for quick reference. With the addition of four new chapters including Formulation, Food Machinery Lubricants, NLGI Certifications, and Environmentally Acceptable Greases, the seventh edition is a must have for anyone dealing with lubricating greases.