Thirty-three years ago, when the author’s company began testing used lubricants as a predictive maintenance tool, the battle-cry against innovation and progress was that used lubricants, especially engine oils, are too heterogeneous; one can never be assured of a truly representative sample. With the testing equipment available at that time, it is not surprising that only limited in-service lubricant analysis persisted.
When it became evident that the effect of the programs was not the extension of oil drain intervals but rather the increased availability of revenue-generating equipment for production, industry instead dubbed these innovators profiteers. At one time, no equipment owner or operator would consider establishing an in-service lubricating oil testing program. Today, used oil analysis and equipment condition-monitoring programs are acknowledged as a major contributing factor to the increased efficiency and operating availability of machinery in modern industry.
The necessity of a classification system by which materials are identified against which qualities of the materials are measured, was acknowledged as far back as 1898 with the formation of the American Society for Testing and Materials (ASTM). In the United States, the American National Standards Institute (ANSI) is another governing body, while the Standards Council of Canada serves Canadian markets; the author is aware of 36 national standards organizations worldwide.
Equality Among Voices
The interests of the consumer, manufacturer and government are represented in standards councils. The standards themselves result from a consensus of all interested parties; no one group dominates the process. As an example, the Light-Duty Engine Lubricant Group Subcommittee B cooperates closely with the American Petroleum Institute (API), the Society of Automotive Engineers (SAE) and with similar organizations throughout the world. This brings together experts in current and future engine design, lubricant and additive manufacturing and development, and other specializations. Together they develop the product, the performance tests and specifications. Similar activities occur in the other subcommittees.
D.02 Division Lines
ASTM D.02 is the committee for petroleum products and lubricants and was founded in 1904. It is subdivided into multiple subcommittees of which there are three general classes: lettered subcommittees (products), numbered subcommittees (properties) and CS subcommittees (services).
Each of the 11 lettered subcommittees is organized around a specific class of products. Subcommittee B, for example, is responsible for automotive lubricants and is further divided into: Passenger Car Engine Oils, Heavy-Duty Engine Oils, Automotive Gear Lubricants and Fluids, Automotive Greases and Two-Stroke Gasoline Engine Lubricants. The organization is designed to address new topics, or further clarify existing ones in the event of an industry demand, within the subcommittee itself or any of its subdivisions.
The mission of these lettered subcommittees, quoting from ASTM in reference to Subcommittee B, is “The promotion of knowledge, specifications and methods of test and nomenclature for automotive lubricating oils. This will include those lubricants used in the power train and chassis components of self-propelled wheeled vehicles including passenger cars, trucks, buses, industrial power plants, high-speed diesels and tractors.” The scopes for the other lettered subcommittees such as Gasoline and Oxygenated Fuels, Turbine Fuels, Diesel and Hydraulics are similarly worded and equivalently comprehensive.
Although most of the product subcommittees utilize unique test methods such as bench engine tests for heavy-duty engine oil, many tests are common to several classes of products. Such tests come under the jurisdiction of Properties Subcommittees, often referred to as the numbered subcommittees. The Properties Subcommittees are comprised of testing-equipment design experts. It is a forum for testing-equipment manufacturers to present new equipment or propose new test methods for potential establishment as an ASTM standard. Additionally, when users identify problems, complaints or limitations of a particular test method they are reviewed at the semiannual meeting. The Properties Subcommittees also evaluate data obtained from ASTM’s International Laboratory Cross-Check Program.
Global Cross-Check Programs
The ASTM D.02 Interlaboratory Cross-Check Programs started in 1993. The first products included were: Motor gasoline, aviation turbine fuel, No. 2 diesel fuel and new engine lubricants. Today there are more than 1,500 laboratories participating worldwide.
Although D.02 standard test methods are the priority of the program, there is usually enough sample provided that if some laboratory has its own method for defining a property or a variation of a D.02 method, it can perform the variation as well as the D.02 method. Statistical comparison can then be made to determine the effect of those modifications.
The ASTM Interlaboratory Cross-Check Program for In-Service Oil Monitoring started in May 2001. At the present time, three samples of used diesel engine oil are sent out annually. The system is designed for flexibility by means of a consensus; should there be a demand for a test not currently in the program, it can be inserted upon sufficient agreement among the participants. Subcommittees also propose additions to the program. This may be important to equipment manufacturers, especially heavy-duty engine manufacturers, as they become more heavily regulated on environmental issues.
The current program is limited to in-service diesel engine lubricants, but there are plans to expand it to other types of used oils contingent upon adequate industry demand. For diesel engine oils, the usual tests such as viscosity, base number, acid number, flash point, elemental analysis, etc., as defined by the current D.02 test methods are called for, plus two additional tests which are not D.02 standards: particle counting and Fourier transform infrared spectroscopy (FTIR).
OEMs, lubricant manufacturers and industrial end-users who out-source laboratory work would be well-advised to demand that their laboratories participate in the ASTM Cross-Check Program because it will offer insight on how well equipped they are to perform the tasks, helping to guarantee quality work and accurate results. Many of the tests performed on used lubricants are similar to, if not the same as those performed on the unused lubricant when a statement of quality and properties is required. However, although the process of developing a test method may have application to a used lubricant, the greater focus was on new products. For this reason, there is ample opportunity to refine a given method for the analysis of used lubricants.
Quoting ASTM, “[The] Interlaboratory Cross-Check Programs provide participating laboratories with a statistical quality assurance tool, enabling them to compensate their performance in the use of ASTM methods against other laboratories worldwide.” In addition to providing feedback to labs, the program identifies methods that may be flawed. Such reevaluations have contributed to the development of standards and the addition of aids to the analyst.
An aid to the analyst may appear either as an addendum or as a precautionary statement in the main text. It indicates potential pitfalls that have been found to create bias and/or large scatter in the data. In 1957, the ASTM Cross-Check program for Gasoline Octane Determinations in the Rocky Mountain Regional Group of subcommittee 1, Combustion Characteristics found the determination of octanes at high-altitude laboratories to be quite a problem. The lab (at that time the U.S. Bureau of Mines Laboratory in Laramie, Wyo.) was 7,000 feet above sea level, accounting for significant differences in combustion air properties from a coastal laboratory. Cross-Check programs facilitated the revision of the test method to compensate for such differences, so that any laboratory, regardless of altitude, would report the same octane on samples from the same population.
Cross-Checks for the Engine Lubricant Performance Quality Classification system are considered so critical they are administered with greater orthodoxy within subcommittee B, in stark contrast to the voluntary participation allowed in the other programs like the in-service lubricant program(s). Specification D4485, for example, explicitly requires that “All bench tests are to be conducted in laboratories current in participation in the ASTM Interlaboratory Cross-Check Program for the particular tests.” Three elements in subcommittee B are instrumental to the success of the system: Test Monitoring Board (TMB), Surveillance Panels and the overall ASTM D.02 Cross-Check Program for New Lubricants.
Although any adequately equipped laboratory can perform the tests required for specification D4485, the activities of TMB provide the consumer with the assurance that the requirements for CH-4 or SJ designations have been met. For a laboratory to have test results (primarily bench engine tests) recognized as official, TMB personnel must inspect their facilities and verify that the technicians are competent to perform the tests and interpret the results. The TMB also sends samples to the laboratories to verify that correct results are achieved. Distinct Surveillance Panels exist for each test that monitor results on an ongoing basis.
What is CS-96?
The scope of CS-96: In-Service Lubricant Testing and Condition-Monitoring Service Industry Support is, “the formation of definitions, terminologies, recommended guidelines, practices and methods and the promotion of knowledge relating to services associated the evaluation of in-service lubricants. To coordinate with other ASTM committees and subcommittees as well as other organizations in support of the service industry evaluating in-service lubricants.” It is a primary forum for all those with an interest in the analysis and performance of in-service lubricants, including manufacturers and marketers of equipment, engines, lubricants and additives, equipment owners, and testing laboratories. The present focus is on lubricant and machinery condition.
While the subject of CS-96 is not new (D6224 - “Practice for In-service Monitoring of Lubricating Oil for Auxiliary Power Plant Equipment and D4387 - “Practice for In-service Monitoring of Mineral Turbine Oils for Steam and Gas Turbines” already existed), CS-96 aims to bring these practices into widespread use and extend them to all lubricants. A primary aspect of CS-96 will contain four sections whose interests are: viscosity and viscometrics, FTIR, wear and chemistry. The other aspect is what ASTM calls the support aspect. It is divided into a guidelines section and a miscellaneous section handling innovations and new issues.
For more information on the various Interlaboratory Cross-Check Programs (ILCPs) offered by ASTM International, including the In-Service Diesel Engine Lubricating Oil (ISDO) Program, go to www.ASTM.org and click on ILCP programs. A registration form can be easily downloaded to subscribe to this reasonably priced program that is conducted three times a year.
Further Reading
ASTM D4485, Performance Specification for Automotive Engine Oils.
