What does "hydraulic fluid hygroscopy" refer to?

Hydraulic fluid hygroscopy refers to the ability of hydraulic fluid to absorb moisture from the environment. This characteristic is important as the presence of moisture in hydraulic fluids can lead to various issues, including reduced lubrication effectiveness, corrosion of components, and decreased operational efficiency in hydraulic systems. Moisture contamination can also promote the growth of bacteria and fungi within the fluid, which can further degrade system performance and lead to potential failures. Therefore, understanding the hygroscopic nature of hydraulic fluids is key to maintaining hydraulic system integrity and performance.

The other choices present concepts unrelated to hygroscopy. Combustion properties, degradation over time, and filtration processes do not pertain to the absorption of moisture, thus highlighting the distinction between the behaviors of hydraulic fluids in the presence of environmental conditions versus their general performance characteristics.