Biodegradable hydraulic fluids

Engineers from Union Carbide Corp. and Caterpillar provide an overview of international literature on biodegradable fluids, various international testing protocol, fluid base stocks, stability effects, and material compatibility.

Hydraulic fluid leakage has been identified as a potential source of ground water contamination. Such concerns have led companies such as Union Carbide Corp. and Caterpillar to a worldwide search for hydraulic fluids with reduced environmental and toxicological impact. Specific industries with a high interest in such fluids include agricultural, forestry, and other off-highway applications.

The most common basestocks used for environmentally friendly hydraulic fluids are either vegetable oils or synthetic esters. Polyalphaolefin basestock also has been shown to be biodegradable. The most common vegetable oils for hydraulic fluid formulations are canola, soybean, rapeseed, and high oleic sunflower oils. Canola oil-derived hydraulic fluids have been used successfully in Germany when bulk fluid temperatures were kept below 60°C (140°F). Soybean oil, because it is readily available in the U.S., also is being evaluated as a basestock for hydraulic fluid. Studies have shown that soybean oil-derived hydraulic fluids exhibit good performance in various commercial and agricultural applications.