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After you identify your equipment lubrication requirements and match the types of lubricants for your applications and operating environments, you must choose from the different brands of lubricants or even the different types of lubricants from your supplier. For example, should you buy the best synthetic or semi-synthetic, since you've heard that synthetics are better? How do you decide what is best for your business, not necessarily what's best for your supplier?
You see that the equipment manufacturer has an array of lubricant performance test results and that they specify the recommended lubricant for your equipment. You also note that there is a list of specifications with test results indicated for the lubricant brand and type you are considering. How do you navigate your way through all this test data to determine what is right for your needs, and why are there are so many different performance tests for lubricating oils? Some of these tests even appear to measure the same properties. All of the tests and the resulting data actually serve several different purposes and have very good reasons as to why there are all in use.
A lubricant performance test, on its own, contributes to assessing a specific property of a lubricating oil being evaluated. In the proper combination with other tests, they collectively define the performance profile desired or the actual performance of a specific lubricating oil. There are a number of reasons why so many tests exist and why combinations of tests are appropriate for evaluating distinct types of lubricants.
Lubricants in general go through maturation processes as additive chemistry continues to change and improve. If a specific additive in an additive package is modified or replaced because of a newer chemistry becoming more effective or less costly, the balance of the entire additive package then must be re-evaluated for its performance. Specific performance tests apply to the additive being replaced, say for example, an antioxidant, to measure its effectiveness. Other tests then measure the effect that the change may have on other properties, like rust or corrosion protection. A finely balanced additive package that satisfies all the desired properties for a lubricant must be re-examined with the appropriate performance tests whenever any change is made to that additive package, even if that change starts with a single additive component.
Original equipment manufacturers (OEMs) design and build equipment for specific purposes, with very clearly defined standards for performance characteristics and operating parameters. For example, the equipment will have specifications identified for load, speed, operating temperature, etc. Similarly, the OEM will specify lubricants for use in the equipment that meet specific performance standards. The machine was designed not only for use in specific environments and applications, but also to be operated with the correct lubricant to maximize the performance, efficiency and lifespan of that equipment. The lubricating oil is identified and described as meeting certain performance levels in the tests defined by the OEM. The specific tests indicated are the ones determined by the OEM to be critical to the operation and performance of that machine as it was designed.
Not unlike how OEMs specify requirements for lubricants to be put in service into specific pieces of equipment, lubricant types and brands that meet those specifications can be identified by their reported performance test results from the lubricant manufacturers. A lubricant must be of the proper viscosity and meet the minimum performance hurdles for the tests indicated for a prospective lubricant in that application. Typical among these are requirements for viscosity index, flash point, pour point, rust prevention, oxidation, load performance, air release and foaming, to name a few.
While testing the impact on additive chemistry in new formula development, specifying lubricant properties by OEMs and selecting lubricants based upon performance test data are all important parts of lubricant application, what all the testing does to some extent is provide an indication of the finished lubricant's predicted performance in the field. A strong battery of carefully selected performance tests can reasonably predict how well a lubricant will perform when it is put in service under the conditions for which it was designed. This may seem somewhat obvious, but careful and specific selection of the best performance tests that will become predictors of actual field performance is neither simple nor insignificant.
Once the proper lubricant has been identified, selected and put into service, it must be monitored to assure that it stays in a condition suitable for continued use and is effectively protecting the equipment in which it is operating. This is where oil sampling comes into play to evaluate the key properties for the lubricant in that application. Viscosity will of course always be important to a lubricating oil, and it is measured to assure that the oil is staying within grade. Depending upon the equipment, application and environment, other lubricant properties will also be critical, with the appropriate performance tests selected so that they are reflective of those key characteristics. In the case of a turbine oil, for example, oxidation is always a critical factor and should be monitored closely.
Now that you understand why all these tests exist and what their contributions are to evaluating lubricating oils, you can begin by identifying your goals for your maintenance program. If your goal is to save on lubricant purchase price, your evaluation is simple. Call the suppliers in your area and ask for their price on anti-wear hydraulic oil, industrial extreme-pressure (EP) gear oil, turbine oil, compressor oil and multipurpose grease. Choose the lowest priced lubricants and then refresh your resumé because you won't have your maintenance manager job for much longer.
Obviously, that is not your maintenance goal. More realistically, your goal is to maximize equipment life and reliability. You may also want to extend oil life, increase equipment uptime or productivity, and minimize lubrication tasks with automated or centralized lubrication systems, both of which will have unique lubricant performance requirements.