SYMPOSIA PAPER Published: 01 December 2022
STP163420200082

Particle Count Testing and Its Impact on True Oil Cleanliness

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Oil contamination with solid particles causes abrasive wear and can restrict lubricant flow to areas with tight clearances, resulting in unplanned outages and shorter equipment life. Ensuring that clean oil enters a system and remains clean throughout its life is critical. Clean oil supports longer oil and equipment life with less maintenance and downtime. The most common way to measure oil cleanliness is by utilizing a light-extinction method to count particulates. In this method, a lubricant passes by a light source; particles within the lubricant interact with the light and are measured and counted. Alternatively, particles may be physically isolated from a lubricant by means of fine filtration and then measured and counted with the aid of a microscope. Because the number of particles counted are usually high, utilizing a reporting code system such as ISO 4406 is common. Light-extinction testing apparatuses for counting particles are ubiquitous, affordable, fast, and economical. Particle counting using a microscope can be labor-intensive, even when using an automatic microscope to count particles. Automatic particle counting (APC) by light-extinction methods can have drawbacks that influence determining the true cleanliness of a lubricant. APCs cannot differentiate “soft particles” such as air, water, or dispersed additives (such as antifoamants) from solid abrasive particles. Solvent dilution helps to dissolve and dissipate contributions from water and air droplets as well as dissolve (at least partially) dispersed additives. The degree to which soft particles contribute to the overall particle count results may vary depending on the equipment and procedure. This paper reviews multiple particle counting techniques as well as considerations to take into account when utilizing or comparing the different methods. The impact that antifoam additives have on particle counting and the efficacy of solvent dilution to remove antifoam contribution to particle count results are also investigated.

Author Information

Hartlen, Kurtis
Imperial Oil, Sarnia, CA
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Pages: 85–102
DOI: 10.1520/STP163420200082
ISBN-EB: 978-0-8031-7715-4
ISBN-13: 978-0-8031-7714-7