Filtration Effects on Foam Inhibitors and Optically Detected Oil Cleanliness

Abstract

ABSTRACTFoam inhibitors (FIs) are effective at reducing foam in lubricants but can be detected by optical particle counters as contaminants. Filtration can decrease the particle counts but will also adversely affect foam performance because the additive is filtered out of the fluid. In this research, we explore the opposing effects of filtration on optically detected particle counts due to foam inhibitors and foam performance. A custom-built test rig is used to filter fluid consisting of polydimethylsiloxane foam inhibitors in base oil and to measure particle counts per ISO 4406. Foam tests are then performed per ASTM D892 on samples taken during filtration. In order to meet both particle count and foam performance specifications, we find that the following three variables must be carefully optimized: FI treat rate, filter pore size, and number of filtration passes.