'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
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Information about Fluid Power is also available on the National Fluid Power Association web-site nfpa.com
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USDA Research: Biodegradable Plant-Based Hydraulic Fluid
See also
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Dexron
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Hydraulics
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Hydraulic machinery
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Hydraulic brake
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Military Hydraulic FluidsTechnolube Products
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Osmosis