Machinery Lubrication

Machinery Lubrication January - February 2019

Machinery Lubrication magazine published by Noria Corporation

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O il Analysis AS I SEE IT Jim Fitch | Noria Corporation Blotter Spot Testing for Metallic and Other Solid Particles e blotter spot test has been discussed numerous times in the pages of Machinery Lubrication magazine. It not only is one of the oldest oil analysis tests (mid-19th century) but endures as one of the most effective at detecting and even quantifying certain lubri- cant abnormalities. However, the blotter spot test is not commonly known as a test for detecting and examining particles in oil such as wear debris and dirt. As a practical matter, its ability to reveal normal and even slightly abnormal amounts of solid particles is limited, especially without the aid of a microscope. is generally is true with other applications of blotter spot testing. In other words, the lack of a visible structure (rings, starbursts, pasty center, etc.) is an indication of the absence of the target condition. Because of this, the blotter spot test is less likely to produce a false negative compared to other more advanced analytical methods. While each method has its own unique interferences and lower sensi- tivity limits, the ability of blotter spot testing to provide a reliable alert to abnormal particle concentrations is undisputable. Of course, this depends on the alarm limit. Such particles would be invisible in the oil as viewed with the unaided eye. Other methods such as patch testing, ferrography, particle counting and elemental anal- ysis (for small particles only) could detect particles in this same range of concentration and particle type. "Like most condition monitoring methods, blotter spot testing adds information or data to help answer questions about machine health and lubricant condition." 2 | January - February 2019 | www . This blotter shows rust from a lubricant con- taminated with water. Oil analysis found 397 parts per million (ppm) iron. Water is not generally observable on non-engine blotters. The base oil properties looked normal. Oil analysis reported 1,257 ppm lead. Other trace insolubles in a band around the central pat- tern were observed. This band could be varnish potential, dead additives or contamination. This is an ISO VG 220 gear oil. The 870 ppm iron was mostly silt-sized wear debris and rust. The lubricant was probably heavily filtered. The base oil and other properties appeared normal. This ISO VG 68 bearing oil had an acid number of 2.25, 1,257 ppm lead and 119 ppm copper. The oil appeared to have been previously contaminated with water. Babbitt distress from thrust bearing pads or radial plain bearings was observed.

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