Rapid, Portable Voltammetric Techniques for Performing Antioxidant, Total AcidNumber (TAN) and Total Base Number (TBN) Measurements

摘要

This paper describes rapid voltammetric techniques for determining theantioxidant, total acid number (TAN), and total base number (TBN) measurements of a wide variety of oils and fluids. The voltammetric techniques require less than 1 milliliter (mL) of oil, 5 mL of acetone or ethanol solution, and less than 2 minutes for each analysis and can are performed in vials using inexpensive, portable instruments. In contrast to currently used TAN (ASTM Method 664) and TBN (ASTM Method 2896 or 4739) techniques, the voltammetric techniques do not involve titrations, and consequently, do not rely on endpoints which are operator dependent. Once prepared, the oil/analysis solution mixture can be analyzed several times (20 seconds per repeat analysis) to ensure the accuracy of the voltammetric analyses. The current ASTM methods require resampling followed by a new titration (requiring several minutes per titration) for duplicate analyses. This paper also presents results for the voltammetric and ASTM method (TAN and TBN) analyses of various new, laboratory stressed, and authentic used fluids obtained from different types of normally and abnormally operating equipment. The evaluated oils and fluids include diesel engine oils obtained from test stands, phosphate ester based hydraulic fluids obtained from commercial airliners, and ester based turbine engine lubricating oils obtained from military and commercial aircraft. The results presented herein demonstrate that combined knowledge of the antioxidant/TAN/TBN (if applicable) measurements improves the capability of the analyst or equipment operator to evaluate the remaining useful life of the tested fluid as well as the condition of the operating equipment. Interrelationships among the different voltammetric analyses and wear debris analyses of the used oils and fluids are demonstrated and discussed.