A Simple Method for Monitoring Fire-Resistant Fluids Used in Electro-Hydraulic Governing Systems

ABSTRACT

Intact triaryl phosphate is essential for the reliable functioning of hydraulic controllers. In this study, a simple approach for monitoring the condition of triaryl phosphate using acid–base indicators was developed. The analytical determination of the products from the degradation of triaryl phosphate revealed acidic components (e.g., diaryl phosphoric acid) that permitted a clear visual test of degradation and digitization using acid–base indicators and spectrophotometry. Methyl red serves as a promising indicator for a wide range of degradation products from triaryl phosphate and was used to demonstrate that the measured lightness value decreased with increasing acid number. This rapid method requires minimal sample preparation and can assess early-stage degradation, thereby making on-site monitoring possible for optimising operational function.

KEYWORDS:

• Acidity
• basicity
• lubricant degradation
• hydraulic systems
• phosphate esters
• failure analysis

Acknowledgment

The authors are grateful to Hiroki Nagase of the Electric Power Engineering Systems Co. Ltd. for assistance with the color reactions of the degraded triaryl phosphate samples with acid–base indicators.