System and lubricant cleanliness is one of the most critical factors for an effective lubricant program. But as every fleet manager, mechanic, driver and business owner can tell you, maintaining system and lubricant cleanliness isn’t easy because of tiny particles you can’t see. These microscopic particles can reduce the effectiveness of your lubricants, damage your equipment and lead to increased maintenance or even equipment failure. It’s why particle contamination has been the downfall of many lubricant programs.
How does particle contamination occur? It can happen at almost any time in the lubrication process. During manufacturing, transport or storage, it’s easy for microscopic particles to contaminate a lubricant supply. That’s why fleet managers, business owners and mechanics must take steps to prevent particle contamination from derailing their lubrication program by investing in oil analysis programs. These programs can help figure out how contaminated their supplies and equipment are. In addition, particle counting is a big part of the oil analysis process.
Particle counting is an effective tool for catching contamination. This process involves measuring the number and size of particles in lubricants and engine samples. The theory behind particle counting is that by identifying the size and number of different particles within the sample, you can determine how contaminated it may be. This idea is why most oil analysis programs use particle counting as a part of their analysis efforts. It’s especially effective for hydraulic, compressors, turbines, transmissions, bearing and gear systems. Most of these components or machinery have target cleanliness codes that indicate an acceptable level of particles to maintain efficiency. Particle counting is also used to measure how effective a filter is.
So if particle counting is so effective, how is it done? In a recent whitepaper, Chevron outlined a few standard methods for measuring particle size. Let’s examine their outlined methods and how they measure particle count from samples from your lubricants and machinery.
Microscopy
This is one of the most used methods for determining particle count. It involves taking a sample and then examining it under a microscope. The observer then manually counts the number of particles in the sample, which would be used to determine the overall cleanliness of the lubricant. It’s a cumbersome method, but still widely in use in many oil analysis labs as experienced technicians can provide very accurate results.
Light Extinction
The idea behind this method is to use a tool (typically a laser particle counter) to pass light through a sample onto a photocell. As the light passes through the sample, the particles block the light and the photoreceptors experience a voltage change that is the same size as the particle. This change is then measured as the size of the particle. It’s a very common method for measuring particle size in a sample because it’s relatively easy and inexpensive. Still, it can be ineffective because it counts any voltage change as a particle. This makes it difficult to differentiate between water, air and additives in a sample size.
Direct Imaging
This method is a lot like getting an X-ray. Again, light is passed through a liquid sample onto a photocell, but instead of counting the voltage change, a direct image captures an image of the particles. The captured image is then analyzed using computer algorithms for particle aspect ratio, perimeter length and circularity. These algorithms are so sophisticated they can differentiate between air, water, bubbles, fibers and more, which makes this method very effective. The only downside is that additives in lubricants are often still classified with other particulates, which can throw off the overall count.
Microscope Particle Counts
This particular method doesn’t rely on imaging or light tools. Instead, the sample is filtered through a membrane. It’s like when you drain pasta out of a pot using a strainer. Once the water is gone, you can see how much pasta is left. This method uses the same type of principle, except a little more sophisticated. Technicians use different size membranes to catch the particles. Then, they manually count the number of particles per millimeter or they might use image analysis. It’s a very effective process because it removes ‘soft particles’ like water, air and other liquids that can often be counted in different methods. But it’s also time-consuming, so it’s not commonly used.
Patch Comparison Tests
This test is almost a simpler version of the microscopic particle count. Again, the sample is filtered through the membrane, but this time it’s allowed to dry. Once the membrane has dried, the technicians take a picture and compare it to different reference patch image. It’s not an exact process that gives you an accurate particle count, but experienced technicians can use this process to determine lubricant cleanliness quickly. It’s very effective as a screening tool.
Pore Blockage
Like the microscopic particle count and patch tests, this method relies on a mesh membrane to filter the sample. But instead of visually assessing the size or number of particles left, the particle count is obtained by measuring the amount of pressure exerted on the mesh. This method is also not a very common method as it can be unreliable.
This overview gives you a quick sense of some of the most common measurement types. Each of the above-described test methods can be used to determine the size and count of particles in a lubricant or system sample. Particle counting sounds tedious and challenging, but it can be beneficial for ensuring your lubricants and machinery are clean and working correctly. Clean lubricants and machinery free of microscopic particles perform more efficiently and require less maintenance and downtime.
If you want to make the most of your lubrication program, we recommend joining our oil analysis program. This program utilizes several analysis tools, including particle counting, to determine how clean your lubricants and machinery are. As a member of this program, you will get customized data and maintenance recommendations for your equipment based on the findings from the samples you provide. It’s a highly effective tool that can save your business a lot of money in lubricant supplies and equipment maintenance. So if you have questions about the methods our oil analysis lab uses, feel free to contact your sales representative and they can provide a more detailed explanation of your analysis results.