Mineral oil and Ester-based hydraulic fluid spectra
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The FTIR analysis showed that three of the six systems contained pure mineral oil — in other words, our customer’s maintenance department never changed over to ester-based fluid as they claimed. Elemental analysis by X-Ray spectroscopy showed that all three contained zinc dithiophosphate additive, which is used in mineral oils but not in esters. The other three systems did contain ester fluid, but contaminated with mineral oil ranging from 9 to 18%, probably from inadequate draining during change-over. Because 5% mineral oil contamination is considered the maximum level for safe use, all six of the systems were out of specification.
I informed our customer that three of his systems still contained mineral oil in spite of the incorrect conclusions from his contract laboratory, and that the other three were considered too contaminated for safe use. If the contract lab had used FTIR, or had analyzed for zinc and sulfur in addition to phosphorus, or had simply checked specific gravity, they should have recognized that these samples were not ester-based fluid. Unfortunately, they did not have the capability of recognizing that completely wrong fluid was in the systems, rather than “improperly blended” material, a potentially deadly conclusion.
Because we offer free testing, we suggested they send system samples to us for periodic analysis.
Robert Johnston is group leader, Analytical Services for Houghton International. Contact Johnston at (610) 666-4114 or via email [email protected]