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The ASTM D1169-11 test method is currently used to determine the continued functionality of operational, fire-resistant phosphate ester (PE) fluids. The theory behind this is that greater resistance will reduce the propensity of lubricating fluids to cause streaming-current corrosion; however, to the average PE fluid user, the method provides a quantitative value that describes the overall general cleanliness of PE fluids. Specific PE contamination, such as by acids and water, negatively affects (lowers) the bulk volume specific resistance. The specific resistance can potentially fall below the condemning limit set by the PE fluid provider(s) and the original equipment manufacturer (5 GΩ · cm) if such contamination levels are high. Conversely, there is contamination that will increase the resistance of operational PE fluids; this contamination is in the form of extremely small, abrasive, dielectric aluminosilicate particles. This contamination comes from the manufacturer-recommended PE purification media Selexsorb GT. The dielectric nature of the particulate gives the user, and ASTM D1169-11, the appearance of resistance improvement, but particle abrasiveness is concomitantly catalyzing fluid degradation and causing undue mechanical wear. Data documenting the misleading PE fluid resistance improvement induced by aluminosilicate contamination are described. Novel methods to improve specific resistance without any deleterious side effects also are presented to help PE fluid users avoid condemning entire reservoirs as a result of low specific resistance.
resistivity, contamination, fluid treatment
Hobbs, Matthew G.
EPT, Calgary, AB
Dufresne, Peter T.
EPT, Calgary, AB