Search Results

There is an ongoing interest in biodegradable hydraulic fluids. Biodegradable fluids are often considered to include only vegetable oils, polyol esters and diester base stocks. However, other fluid base stocks including highly refined mineral oils, poly(alpha olefins) and fire-resistant fluids such as water-glycol hydraulic fluids are also biodegradable fluid alternatives. This paper will provide an overview of the international literature on biodegradable fluids, various international testing protocol, fluid base stocks, effect of oxidative stability, material compatibility and pump performance.

Because of on-board fire problems during World War II, the us Navy initiated a program to develop hydraulic fluids that were more fire-resistant than the mineral oils that were in use at that time. Water-glycol hydraulic fluids were subsequently developed and first commercialized in 1947 which offered vastly improved fire resistance relative to mineral oils. Since 1947, in addition to formulation changes, there is significantly greater understanding of the impact of these changes on pump wear performance. This paper will present a selected overview of water-glycol formulation chemistry, some of the fluid formulation issues that have been encountered and the evolutionary improvement of hydraulic pump wear performance.

The importance of minimizing air entrainment and enhancing air release in hydraulic fluids has been recognized for over 40 years. These properties are dependent on the composition of hydraulic fluids, especially on the presence of contaminants which inhibit air release and additives which promote it. One objective of this paper is to present an overview of this critically important technology as it has unfolded over the last 40 years. The second objective of this paper is to integrate into this summary recent research results on the impact of additives on air release properties.