The criteria for testing lubricants and petroleum products toe the line
According to Oklahoma-based Ranken Energy Corporation, more than 6,000 products, such as lubricants, are made from petroleum. To keep all of these products as safe as possible and composed as intended, they must meet many test standards for lubricants and petroleum products. Many of these standards get very specific in what they measure and how.
BYK-Gardner’s website helps scientists and engineers keep track of the many standards related to lubricants and petroleum products. The site can be searched for ASTM or ISO standards applicable to their instruments.
From ASTM International (West Conshohocken, PA), online resources also exist. For example, its petroleum standards page states: “ASTM’s petroleum standards are instrumental in the evaluation and assessment of the physical, mechanical, rheological, thermal, and chemical properties of crude oils, lubricating grease, automobile and aviation gasoline, hydrocarbons, and other naturally occurring energy resources used for various industrial applications.” The description adds that these materials are tested for many features, including “their composition, purity, density, miscibility and compatibility with other fluids and materials, toxicity, and thermal stability among others.”
Beyond understanding the physiochemical characteristics of these materials, test standards provide even more valuable information. As the ASTM site points out: “These petroleum standards allow petroleum refineries, automotive and aviation companies, and other geological and chemical processing plants to appropriately examine and process these fuel oils [and] ensure their quality towards safe and efficient use.”
Keeping such standards in place and optimized, however, turns out to be a very big task.
It takes a team
ASTM’s Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants oversees all of the organization’s standards related to lubricants and petroleum products. Established in 1904, D02’s roughly 2,500 members meet twice a year to manage more than 800 standards. According to ASTM, D02 overviews the “promotion of knowledge and the promulgation of standard specifications, classifications, test methods, practices, guides, and terminology” for many technical fields, including lubricants “derived in whole or in part from petroleum and nonpetroleum sources, including synthetics (such as ester lubricating oils), biological, or naturally occurring (mined) materials.”
These standards can be found in a collection of ASTM books, including the Guide to ASTM Test Methods for the Analysis of Petroleum Products and Lubricants, which was sponsored by D02. One test described in this guide is acid number by potentiometric titration, or D664, which is equivalent to other standards, such as ISO 6619. According to this guide, “New and used petroleum products may contain acidic constituents that are present as additives or as degradation products formed during service, such as oxidation products.” Titration with bases can be used to measure these acids, and the acid number is the results. “The acid number is used as a guide in the quality control of lubricating oil formulations,” the text notes. “It is also sometimes used as a measure of lubricant degradation in service.”
This guide includes many other tests, including D2510, which measures the adhesion of solid-film lubricants. As the text states: “Effective solid-film lubricant coatings must adhere to surfaces to provide adequate lubrication in applications with restricted access where fluid lubricants cannot easily be replenished.” Otherwise, metal can rub on metal and reduce the life of surfaces that contact each other. For a solid-film lubricant to work effectively, it needs enough adhesion to stay in place. D2510, as the guide describes it, “measures the adhesion of solid-film lubricant coatings when submitted to contact with water and other fluids.” The guide describes the basics of the test, and points out that it’s “a qualitative pass-fail test and no estimates of precision or bias can be made.”
Standards on the move
The work of ASTM’s D02 is never done. In 2018, for example, this committee approved D8181, which is a new standard for bio-based fuels that can be used as an alternative to conventional diesel fuel. According to the description of D8181: “This specification describes an alcohol-carboxylic acid blendstock which is to be blended with fuel oils to produce a microemulsion of inverse micelles that is to be used as a test fuel oil.” The microemulsion blendstock is combined with a fuel oil for a test. ASTM notes that the microemulsion test fuel oil “is intended for testing and demonstration purposes in specialty applications such as compression-ignition engine and burner fuel applications.”
Also in 2018, D02 developed D8211, which tests for gases that ignite when touching hot surfaces. Some gases are less likely to ignite than others. This test can be used to distinguish such gases, which can be relevant in automotive, heating, and other industries.
In some cases, new standards might not apply to the most expected technology. In May 2018, for example, ASTM released information about D8164, which D02 approved for selecting digital-contact thermometers (DCTs). As ASTM explained: “The guide will help manufacturers, standards developers, and users of DCTs in the petroleum industry. The criteria are based on the design and characteristics of liquid-in-glass (LiG) thermometers that have also successfully been used in the committee’s test methods.” So, the standards don’t just discuss what to test and how, but also the instruments to use.
For example, some standards involve how to collect samples. In November 2017, ASTM’s D02 developed its D8112 standard, which “is applicable for collecting representative fluid samples for the effective condition monitoring of steam and gas turbine lubrication and generator cooling gas sealing systems in the power generation industry.” It continues, “In addition, this guide is also applicable for collecting representative samples from power generation auxiliary equipment including hydraulic systems.” ASTM points out that such a standard ensures the collection of representative and repeatable standards.
The field of test standards for petroleum products and lubricants, like most other areas, continues to evolve. Old standards get updated, and new ones emerge. The criteria for performing a test can change, and so can the method of sample collection and the instruments used in testing. Keeping up with the changes takes considerable effort, and that makes online tools particularly useful for staying current in test standards.
Mike May is a freelance writer and editor living in Texas. He can be reached at [email protected]