The National Lubricating Grease Institute (NLGI) and the European Lubricating Grease Institute (ELGI) have long partnered in several joint working groups for advancement in areas such as: grease cleanliness, food-grade greases and grease shelf life. This article provides an update on these particular groups from the individual chairs, Joe Kaperick and Anuj Mistry.

Grease Cleanliness Working Group Update
The Grease Cleanliness Working Group continues to make good progress in defining a system for categorizing the cleanliness of grease as well as beginning work on developing robust methodologies for measuring this property. This group has held discussions at both the NLGI and ELGI annual meetings and, more recently, by teleconference to address these areas.

Background: The working group has agreed to the following draft definition of grease cleanliness: "A measure of the suitability of a grease to be used in such applications in which contamination by particulate matter would cause damage to the pieces in contact with the lubricant. The extent of contamination can be measured by examination of the size, number and/or hardness of the particulate matter."

This group is assessing the feasibility of combining the results from two test methods as a measure of grease cleanliness.

  • "Standard Test Method for Estimation of Deleterious Particles in Lubricating Grease" (ASTM D1404) is being evaluated as a potential indicator of abrasiveness or hardness of particulate matter. This method uses acrylic plates to quantify the number of particles that will cause scratching and, therefore, provide an indication of the potential for these particles to cause damage.

  • The Hegman Gauge is being evaluated as a potential indicator of the number and size of the particles. "Standard Test Method for Fineness of Dispersion of Pigment-Vehicle Systems by Hegman-Type Gauge" (ASTM D1210) is a current method used to measure pigments in coatings. The NLGI-ELGI working group hopes to adapt this standard for use with greases.

A rating system is being considered that combines the ratings from both ASTM D1404 (abrasiveness) and the Hegman Gauge (number and size). An example of such a grid is shown in the diagram at right.

Ratings could be determined as follows:

ASTM 1404

Count arc-shaped scratches that appear on highly polished acrylic plates when grease is forced between two such plates and rotated.

Rating:

1 = less than 10 scratches

2 = 10 to 40 scratches

3 = more than 40 scratches

Hegman Gauge - count and size

Rating:

A = Clean (0 particles greater than 100 microns)

B = Moderate dirt (1-5 particles greater than 100 microns)

C = Dirty (more than 5 particles greater than 100 microns)

Greases would have a "Cleanliness Rating" of between 1A (very few particles, small, not very hard/damaging) and 3C (many particles, larger, hard with potential for damage).

Note: The numerical ranges are merely for demonstrative purposes. Actual ranges will need to be determined after considerably more work and discussion by the group and should then reflect a range reflective of the likely amount of contamination found in commercial greases.

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Recent work: A "mini-round robin" was completed last year to look at feasibility and robustness of the proposed methods. Results show a rough correlation between ratings of "clean" and spiked samples but also illustrate potential issues of repeatability and reproducibility that will need to be addressed before this methodology can be accepted for widespread use. Discussion of these issues has focused on the variations in equipment and method, as well as difficulties in determining repeatable results.

As of late, work has been to develop a series of standards spiked with incremental amounts of SAE A-4 coarse dust to be used in a more extensive round robin. At least nine companies will be involved, with the goal being to refine the methods through discussion of observations made by the individual laboratories during data generation. It is hoped that the samples will be distributed by September (this article was produced in mid-August) with a goal to complete the testing by the end of the year.

To obtain further information or participate in this working group, contact chairperson Joe Kaperick at 804-788-6393 or joe.kaperick@aftonchemical.com.

Food-Grade Lubes and Grease Shelf Life Working Groups
The Food-Grade Lubricants and Grease Shelf Life working groups meet twice a year at the ELGI and NLGI annual meetings in Europe and the United States.

The Food-Grade Lubricants Working Group aims to discuss and communicate effectively on topical issues that affect the use of food-grade lubricants (H1). It works collectively as suppliers and end-users for potentially effective solutions.

Major lubricant and additive suppliers as well as end-users participate at these meetings with a goal to keep up with developments within the NSF and InS Services and other developments with respect to the registration and use of food-grade lubricants as well as potential implementation and implications of ISO 21469. The overall aim of the working group is to provide a forum for collection and dissemination of suitable information for the requirements of the global grease community. The group's current focus is the ISO 21469 standard, with a view to getting a better understanding of the standard itself, the certification process and its potential implications related to its implementation within industry.

Grease shelf life is part and parcel of lubricating greases as far as suppliers and end-users are concerned and is vital within the grease industry. The aim of the Grease Shelf Life Working Group is to establish valid, recognized procedures and test methods to predict shelf life of bulk greases. Major lubricant and additive suppliers as well as end-users participate at these meetings. The group seeks to conduct a series of round robin exercises using standard NLGI reference greases as well as long-term retained grease samples to evaluate typical lubricating grease properties. The current focus is to finalize the round robin test protocol.

To obtain further information or participate in these working groups, contact chairperson Anuj Mistry via e-mail at amistry@belray.com.

About NLGI

NLGI is an international technical trade association that serves the lubricating grease and gear lubricant industry. Its objectives include promoting research and testing for the development of improved lubricating greases and exploring means for better lubrication engineering and methodology. For more information, visit www.nlgi.org.

This grid combines the ratings from both ASTM D1404 (abrasiveness) and the Hegman Gauge (number and size).