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Implementing a procedure to characterize lubricant contaminant particles and becoming proficient in this technique will require considerable study and practice. But there are aspects you can begin researching to progress the development and implementation of your oil analysis program.
First, you need to identify and establish your oil analysis goals. This can include aspects such as determining the particle size, the metal type, and the wear failure modes present in your lubrication.
Once you determine what you would like to measure and what you hope to learn from the analysis, the next step is to obtain the information. This information can be obtained from a particle characterization sample collected through ferrograms, filtergrams, patch tests, or lubricant monitoring software.
While each method is effective for performing an oil analysis, there are pros and cons to each option. It’s important to understand the differences between these sample-collecting methods in order to determine the best course of action for achieving your plant’s oil analysis goals.
With a ferrogram, wear particles, or the particles produced when machine surfaces begin to breakdown, are captured on a glass surface. These samples are then placed in a magnetic field to separate the wear debris from the lubricating oil, and further washed to remove any remaining lubricants. From here, the sample is ready to be examined.
Although ferrogram testing does capture non-ferrous particles, because the sample is placed into a magnetic field, it can have a bias towards ferromagnetic particles, such as iron or steel. This is frequently referred to as analytical ferrography, and equipment most likely to produce these magnetic wear particles include engines, gearboxes, rolling-element bearings, and most hydraulics.
For identification purposes, ferrograms are easy to heat-treat and have bottom light transmission, but the wear particles can begin to pile up and the preparation equipment is generally more expensive than other available options.
During a filtergram particle collection process, an oil sample is forced through a filter membrane where any particles larger than the pore size are randomly trapped on the membrane surface. From here, the sample is evaluated and analyzed using a bottom light.
Unlike its ferrogram counterpart, not only do filtergrams have no bias towards ferrous particles, but they are also easier to prepare and have more affordable hardware. However, despite this, it can be more difficult to distinguish between metal types and to prepare two membranes – one being ferrous and the other being non-ferrous – due to the opaqueness of the filter membrane. This opaqueness can cause the transmission of the bottom light to not be as effective.
Equipment with critical non-ferrous frictional surfaces includes worm gears, stainless-steel machinery, and turbomachinery with bronze or Babbitt bearings.
A patch test, also known as patch ferrography, an oil sample is diluted in a solvent and then pushed through a patch or paper membrane where particles larger than the membrane’s surface are captured for later inspection. With this method, there are no biases toward ferromagnetic elements or other metallic debris.
While other testing methods require the use of specialized tools or hardware, the patch test separates itself by being the low-cost, easy-to-operate option that allows on-site technicians to quickly identify abnormal levels of contamination.
After particle samples are taken and analyzed with a microscope, it is possible to heat the sample to observe color changes in the particles to help identify their metal type.
The final option to consider for particle counting during your oil analysis is to utilize a lubricant monitoring technology. These systems apply high-definition microscope lenses, cameras, LED lighting, and a digital processor to accurately identify and count particles, helping to determine the exact type of wear occurring in your equipment.
Not only will it count the wear particles in your lubrication, but it can effectively identify and remove bubbles from the count, giving you a more accurate picture of the health of your oils.
While there are initial costs to purchase and install the equipment, once in place, it can reveal an in-depth look at the state of your oil. Some monitoring programs also offer remote, real-time lubricant monitoring that can be accessed and evaluated anywhere, at any time.
No matter which particle characterization sample method you select, it’s important to ensure that the process fits seamlessly into your company’s current system while enhancing your lubrication culture. By evaluating your options and comparing them against the needs of your facility, you can begin to build an oil analysis program focused on the continued health and success of your lubricants.