Hydraulic fluid

Hydraulic fluids are a large group of mineral oil, water or water-based fluids used as the medium in hydraulic systems. These fluids are found in machinery and equipment ranging from brakes, power steering, and transmissions to backhoes, excavators, garbage trucks and industrial shredders.

Base stock may be any of: castor oil, glycol, esters, ethers, mineral oil, organophosphate ester, Chutte and polyalphaolefin, propylene glycol, or silicone. Some of the trade names for hydraulic fluids include Durad®, Fyrquel®, Houghton-Safe®, Hydraunycoil®, Lubritherm® Enviro-Safe, Pydraul®, Quintolubric®, Reofos®, Reolube®, and Skydrol®.

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 Environmental Impact are relevant. 2004 prices were about $6/liter in small quantities.

Brake fluid is a subtype of hydraulic fluid with high boiling point and low freezing point.

Hydraulic systems like the ones mentioned above will work efficiently if the hydraulic fluid used has low compressibility.

Fire resistance is a property available with specialized fluids.

Hydraulic fluids can contain a wide range of various chemical compounds; oils, butanol, esters (e.g. phthalates, like DEHP, and adipates, like bis(2-ethylhexyl) adipate), polyalkylene glycols (PAG), phosphate esters (e.g. tributylphosphate), silicones, alkylated aromatic hydrocarbons, polyalphaolefins (PAO) (e.g. polyisobutenes), corrosion inhibitors, etc.

Because industrial hydraulic systems operate at thousands of PSI and temperatures reaching hundreds of degrees Celsius, severe injuries and death can result from component failures and care must always be taken when performing maintenance on hydraulics.

External links

• Hydraulic press manufacturer
• Information about Fluid Power is also available on the National Fluid Power Association web-site nfpa.com
• USDA Research: Biodegradable Plant-Based Hydraulic Fluid

See also

• Dexron
• Hydraulics
• Hydraulic machinery
• Hydraulic brake
• Military Hydraulic FluidsTechnolube Products

• Osmosis