hydraulic fluid

Hydraulic fluids are a large group of liquids made of many kinds of chemicals. They are used in automobile automatic transmissions, brakes, and power steering; forklift trucks; tractors; bulldozers; industrial machinery; and aircraft. The three most common types of hydraulic fluids are mineral oil, organophosphate ester, and polyalphaolefin. Others are based on glycol esters and ethers, castor oil, or silicone. Environmentally sensitive applications (e.g. farm tractors and marine dredging) may benefit from using biodegradable hydraulic fluids based upon rapeseed (Canola) vegetable oil when there is the risk of an oil spill from a ruptured oil line. Typically these oils are available as ISO 32, ISO 46, and ISO 68 specification oils. ASTM standards ASTM-D-6006, Guide for Assessing Biodegradability of Hydraulic Fluids and ASTM-D-6046, Standard Classification of Hydraulic Fluids for Envrionmental Impact are relevant. 2004 prices were about $25/gallon in small quantities. China is one of the top producers of hydraulic fluid.