Analysis of Microbial Tolerance and Physicochemical Properties of HFA‑E Hydraulic Fluids Used in Mechanized Mine Roof Supports.

This study presents a comparative analysis of microbial tolerance and physicochemical properties of HFA-E (fire-resistant hydraulic fluid, aqueous-based, emulsion type) hydraulic fluids based on commercial "Hydrotol-ITCh HFAE" and "Fimitol P87 AF" concentrates used in mining hydraulic roof support systems. Metagenomic analysis revealed distinct microbial community structures in the two fluids. The Hydrotol-ITCh HFAE-based fluid microbiota consisted predominantly of Bacteria (99.77%), especially Proteobacteria, while the Fimitol P87 AF-based fluid exhibited a more complex and taxonomically diverse community, including a significant proportion of Archaea (47.09%) and Bacteria (52.92%) from groups such as methanogens (Methanobacteriaceae) and sulfate-reducing bacteria (Desulfovibrionaceae), respectively. In vitro tests confirmed the inherent antimicrobial activity of the fluids, which significantly reduced planktonic microbial viability and eradicated the majority of bacteria. The physicochemical properties of the fluids remained stable even under high initial bacterial load, confirming their reliability during microbial contamination. However, under industrial conditions, the Hydrotol-ITCh HFAE-based fluid demonstrated lower contamination and higher emulsion stability (pH reduced to 8.5 after one year of operation versus 6.5 for "Fimitol P87 AF"), which reduced the risk of biocorrosion and the need for additional treatments. This study emphasizes the importance of comprehensive monitoring of microbial diversity and physicochemical parameters for predicting the service life of hydraulic systems, developing effective biocides, and minimizing risks to equipment and personnel. The obtained data can be used to optimize hydraulic fluid compositions and their operational strategies.