HFDU fluids, or hardly flammable fluids, are used in hydraulic systems that have a high risk of fire due to exposure to high temperatures, incandescent surfaces, open flames, etc.
The purpose of analyzing these products for predictive maintenance is to periodically check their efficiency, degree of aging, and pollution by foreign elements (water, dust, etc.).
The control of these fluids is essential because the ester base (often of vegetable origin) used in their formulation, in addition to the advantage of having a higher flash point than that of classic mineral hydraulic oils, also has disadvantages linked to the product chemistry - often sensitive to the presence of humidity in connection with high temperatures.
The need to avoid the formation of sludge and lacquers that could lead to valve blockage, and machinery interruption in general, requires close monitoring of these fluids by an expert laboratory.