Ion Exchange/Vacuum Dehydration Treatment of Phosphate Esters in Industrial Applications

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Phosphate esters are widely used in a variety of hydraulic systems in industrial applications. These fluids typically exhibit good lubricity and oxidative stability. The fire‐retarding characteristics of phosphate esters make them attractive for use in applications where petroleum‐based fluids would constitute a fire hazard. However, in the presence of water, these fluids hydrolyse and form acidic partial phosphates. Because this process accelerates in an acidic environment, the reaction is referred to as autocatalytic. Moreover, fluid degradation becomes extremely difficult to reverse once acidity reaches an acid number of I mg KOH/g. From that point on, it is increasingly hard to stabilise the fluid with conventional treatment methods such as fuller's earth or activated alumina. In contrast, fluid treatment based on a combined application of ion exchange and vacuum dehydration (IX/VD) was found to be highly effective in arresting fluid degradation and restoring fluid properties to within limits acceptable for continued operation. This paper presents data collected over a period of several years at a number of power plants throughout the USA and Europe. The data confirm that fluids that initially exceeded manufacturer specifications even by a wide margin were successfully stabilised through a combined treatment of IX/VD under normal operating conditions.