Companies invest in some form of on-site oil analysis with the understanding that any information is good information. But the reality is that most facilities have little or no idea what to do with the information revealed by the analysis.
Companies considering some level of on-site oil analysis frequently have trouble with the concept of on-site vs. off-site analysis. Many believe that you can replace off-site oil analysis with your on-site program. This may be the case for a few on-site labs with highly sophisticated facilities. But for the remaining 99 percent of on-site setups I have seen, these would be considered screening operations meant to provide go/no-go results that may prompt some further action which may include actual laboratory testing and analysis.
Even in the world of on-site oil analysis screening, there are certainly levels of sophistication and many opportunities for choice of test, ease of use and accuracy among others. All provide valuable information when given the knowledge on how to apply it. Because on-site screening and analysis is a broad subject, and there are many different systems, all-in-ones, single-use and magic boxes on the market, I have identified three screening tools that I've found to be very popular in the plant and easy to use, providing valuable feedback.
Viscosity is the most important property of the lubricant. For this reason, it makes perfect sense to include viscosity as an on-site test for new, incoming and in-service lubricants. One of the more popular tools for testing viscosity on-site is the viscosity comparator. Comparators equate a known reference viscosity to the oil sample in question. Once both oils are stabilized to the same temperature, testing can begin. Unit accuracy can be up to 95 percent, depending on the experience of the user.
Water seems to be the ever-present contaminant that eludes most efforts to exclude and remove it. Water is one of the most destructive contaminants in oil, and it would serve you well to monitor it on a consistent basis when dealing with sensitive or critical equipment. Water can be easily detected with some low-tech equipment. The lowest tech in the area of water detection in oil is the hot plate to perform a crackle test. Any kind of heated surface that can reach the predetermined temperature without baking the oil will usually suffice. A few drops of oil are dropped onto the plate, and the formation of bubbles and the audible crackle of moisture being heated correspond to a range of water amounts. Though this test is considered to be a pass/fail type test, good information can be gained. In most cases, if water is detected, regardless of knowing the exact volume of oil in water, the action taken must be to find and fix the source of the water ingression.
There also are some chemical tests available that are specifically designed for the plant or field environment. Acid number (AN) and base number (BN) testing kits are available that come with premeasured reagents. This allows the user to utilize testing methods once considered "wet chemistry fit for a lab environment" in the field at reasonable costs per test.
On-site tools for oil analysis can provide a wealth of almost instant information on which you can make immediate maintenance decisions. However, keep in mind that even though on-site tools can produce results worthy of scheduling maintenance or some other action, you can't accurately compare lab results to on-site results for the same test. Different methods will provide different results.
There are many other tests and kits available for use in the field and in the plant. Before you embark on the journey to on-site testing, you need to first ask yourself, "What will I do when I get this information?" In today's tough economy, you must embrace technology that adds value. No matter if the oil analysis data you receive is from a field kit or a commercial lab, if you don't use it to make sound maintenance decisions (and just tuck the report away), then it really is a wasteful activity. Start by focusing on what information you need, then research the on-site options that are available.
References
Aaron Black, Noria Corporation. "Integrating On-site Oil Analysis With Laboratory Analysis", Practicing Oil Analysis magazine, September 2007.