IIAR Tech Tip: Introduction to Oil Analysis – Part 1
A Crash-course In Understanding Used Oil Analysis
By: Jared Kantar, Isel - August 29, 2016
There are countless stories of individuals going in for blood work thinking they are perfectly healthy only to later find out they had an undiagnosed, symptomless condition. The use of blood analysis techniques helps to point out these life-threatening conditions before they escalate into something more serious. The lubricant in your machinery is just like the blood in your body – and it, too, can be analyzed to give an indication of the health of equipment. This process is called used oil analysis, or UOA for short.
So, what does oil analysis tell us? To start, it helps to determine the operating condition of the equipment by interpreting clues in the analysis results. It also can determine the condition of the oil, determining whether it’s suitable for continued use or has reached a condemning limit. This can help to maximize the investment in a lubricant and alert operators of potential equipment failures before they actually occur.
The first step to oil analysis is to collect the lubricant sample. When drawing lubricant samples for analysis, it is good to keep in mind a few basic best practices:
Ensure the equipment is at operating temperature and (if possible) running when sampling
- Flush sampling valves and devices to remove any outside contaminants
- Thoroughly clean sampling bottles (water or dust can skew oil analysis results) and use only approved sample containers
- Draw the sample from an active flow zone to ensure sample replicates bulk lubricant
- Draw the sample upstream of filters and downstream of machine components
- Sample at a consistent frequency at consistent locations
- Record the information that is requested by the lab accurately and clearly
- Forward collected samples to an analysis laboratory as quickly as possible
There are various methods that can be used to collect the sample, such as permanent sampling valves, suction pumps, drain plugs, or simply dipping the sampling container into the vessel of lubricant. Permanent sampling valves and suction pumps are the best methods for collecting lubricant samples due to their ease of use, ability to keep control of outside contaminants, and the repeatability of the sampling location. Samples pulled from drain plugs are also acceptable, but the operator must be aware of the potential to skew the results due to sediment settling in the sump near the plug. The dip method is not recommended due to the potential to skew results from dirt and contaminants on the outside of the container.
Once a sampling method has been determined, the operator should try to locate an active flow zone to collect the sample from. The active flow zone is the area in the flow of lubricant that promotes agitation and velocity. This flow prevents the sample from containing a large quantity of settled sludge or particulates. These settled particulates of sludge can skew oil analysis results and hamper proper predictive maintenance programs.
When beginning a predictive maintenance program, initial sampling intervals must be determined in order to build a trend of data. As the program continues forward, the operator will be able to determine their own ideal sampling interval based on the historical oil analysis results. Ideally, the samples would be pulled as frequently as possible while not overburdening personnel and costs. The more frequent samples are collected, the higher the resolution of the trending results will be. For most equipment, sampling can begin as a monthly process. For some machinery, this interval could slowly be pushed out to quarterly if the results remain consistent and trend well. However, if there is inconsistent trending, or the machinery is heavily abused in operation, the sampling may have to be decreased to a period that allows for reasonable resolution in the trending.
Every oil analysis lab will present their results in a different format, but the same information will almost always be presented.
In part two, we will discuss how UOA results can be one of the most powerful, and often overlooked, tools in a maintenance program.