What is it about?

Critical applications such as electro-hydraulic control (EHC) systems in steam turbine uses phosphate ester fluids. Electro-hydraulic control valves regulate the flow of steam in a steam turbine and hence maintain the efficiency of the turbine. These fluids undergo degradation during its lifecycle, the primary degradation mode being hydrolysis. This paper describes the hydrolysis reactions of phosphate ester fluids, hydrolysis by-products, and the measurement of the species involved, i.e., alkylphenols. Hydrolysis by-products 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.

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Why is it important?

The paper address unique technique to monitoring phosphate ester degradation. Monitoring hydrolysis process in the field is challenging and linear sweep voltammetry helps with onsite analysis.


Fire-resistant used in steam turbine EHC are critical components of the system Maintaining the health of the fluid ensures relaible operation of the EHC system.

Jatin Mehta

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This page is a summary of: Understanding and Measuring the Decomposition Products in Phosphate Ester Fluids Using Linear Sweep Voltammetry (Remaining Useful Life Evaluation Routine), Journal of Testing and Evaluation, May 2019, ASTM International,
DOI: 10.1520/jte20180376.
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