Machinery Lubrication


Machinery Lubrication magazine published by Noria Corporation

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Page 11 of 76 | September - October 2017 | 7 the Group V PAG lubricant. These are the typical contamination levels observed during a lubricant exchange. Visual Compatibility Visual compatibility was the first phase of the compatibility testing. The lubricants were observed after they were blended and stored for three to five days. ASTM D7155 describes how to study samples and provides an appear - ance guide for rating compatibility. Are the lubricants clear and bright or do they appear cloudy? To meet the compatibility criteria, the blended lubricants must be "absolutely bright." As seen in the photos on the right, the studied lubricants all passed the visual compatibility tests. If the two lubricants do not have good compatibility, three interactions are affected: liquid-air, measured by the lubricant's foaming proper ties (A S TM D892); liquid-solid, measured by the formation of insoluble solids (ASTM D7843); and liquid-liquid, measured by the lubricant's demulsibility (ASTM D1401). Foam The change in the liquid-air interaction is measured using the ASTM D892 foam test. This measurement looks for a negative change in performance after the lubricants are blended. The test reports three values: the amount of foam at the end of the 5-minute blowing period (foaming tendency), the amount of foam at the end of the settling time (foam stability), and the settling time. Most new lubricants have a foaming tendency ranging from 10-60 millili- ters and a foam stability of 0 milliliters. Results of the visual compatibility tests 90% PAG/10% Mineral Oil 1 90% PAG/10% Mineral Oil 2 BLENDED LUBRICANTS FOAMING TENDENCY FOAM STABILITY SETTLING TIME 90% PAG/10% Mineral Oil 1 60 mL 0 mL 39 minutes 90% PAG/10% Mineral Oil 2 50 mL 0 mL 33 minutes Foam test results

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