Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1080534
4 | January - February 2019 | www . machinerylubrication.com AS I SEE IT relatively low. is is because they will deposit in a concentrated zone, in the center of the blotter, providing more conspicuous viewing. This feature is more of a negative when particle concentrations are high, as they tend to pile on top of each other, which can obscure the view of some large particles. Examining Blotter Spot Particle Deposits The nature of solid particle deposits can be obser ved in the blotter samples shown on page 2 and below. ese particles, which are basically sediment, are largely constrained in the central deposit zone and slightly at the halo region of its periphery. In most cases, the central zone is deeply colored with a dense debris field, similar to what you might see in a patch test. In a few other instances, the core region of the central zone is distinctly Filter Paper I II III How the Blotter Spot Test Is Performed To perform the blotter spot test, sample the oil from an active live zone of the system, similar to conventional oil analysis. Next, using a disposable laboratory syringe, place a couple drops of oil in the center of the blotter paper (see the illustration below). e oil should not be too hot, as many of the target components become insoluble at lower temperatures and only then can contribute to the blotter's structure. Room temperature is best. If trending is performed, the blotters should be developed at roughly the same temperature. When trending, the current blotter is compared to blotters from previous samples. Allow the paper to sit in a horizontal position, such as on the rim of a beaker or drinking glass. Don't lay the card flat in direct contact with a table top or other flat surface, as this contact will interfere with the development of the structure. Next, let the oil develop or wick radially into the paper, creating a structured blotter spread. It will absorb outward from where the oil drops were applied by capillary action. e rate of absorptive movement and total travel is influenced by many physical (e.g., viscosity) and chemical (e.g., polarity) properties, including temperature. Typically, after an hour or so, the blotter is ready to be examined. Note that some blotters will continue to move even days later. For this reason, use a standard time interval, especially if images are taken for future comparison. This ISO VG 460 worm gear oil had 3,619 ppm iron and 291 ppm copper. Extremely fine metallic debris was observed, both iron and copper. Iron comes from the worm, and copper from the bronze ring gear. The pale center indicates very small particles of iron and copper. No base oil deg- radation was observed. This oil had 128 ppm silicon and 185 ppm iron. Silica may not be visible in this blotter, as it usually blends into the paper's color and texture. However, it is likely a significant contributing factor to the presence of iron from abrasion and surface fatigue. No base oil distress was observed. This is an ISO VG 680 gear oil with 273 ppm copper and 766 ppm iron. The higher viscosity of this gear oil appears to show evidence of coarse filtration and larger iron and copper particles, as indicated by the darker center zone. This gear oil has 870 ppm iron. A high value was reported from di- rect-reading ferrography (ferrous density). Large, concentrated ferro- magnetic particles were found by the lab. This is evident on the blotter from a small, tightly packed central zone. No particle mobility was observed.