Understanding and Measuring the Decomposition Products in Phosphate Ester Fluids Using Linear Sweep Voltammetry (Remaining Useful Life Evaluation Routine)

Abstract

Abstract Critical applications such as electrohydraulic control (EHC) systems in steam turbines use phosphate ester fluids. EHC valves regulate the flow of steam in a steam turbine and hence maintain the efficiency of the turbine. These fluids undergo degradation during their life cycle, the primary degradation mode being hydrolysis. This article describes the hydrolysis reactions of phosphate ester fluids, hydrolysis byproducts, and the measurement of the species involved (i.e., alkylphenols). Hydrolysis byproducts affect the fluid’s performance, and, hence, their analysis is critical for proper condition monitoring of the phosphate ester fluid. An electroanalytical method, linear sweep voltammetry, is described to measure the alkylphenols generated during the decomposition process. Monitoring the alkylphenols serves as a leading indicator tool for monitoring the hydrolysis extent and as a leading indicator for the varnish potential of the in-service phosphate ester fluid.