Everything about Hydraulic Oil totally explained
Hydraulic fluids are a large group of fluids used as the motive medium in
hydraulic machinery. Fluid types include synthetic compounds,
mineral oil, water, and water-based mixtures. The fluids are found in machinery and equipment ranging from
brakes,
power steering systems, and
transmissions to
backhoes,
excavators,
garbage trucks and industrial
shredders. Hydraulic systems are very common in
aircraft flight control systems.
Hydraulic systems like the ones mentioned above will work most efficiently if the hydraulic fluid used has low
compressibility.
Composition
Base stock
Base stock may be any of:
castor oil,
glycol,
esters,
ethers,
mineral oil,
organophosphate ester,
polyalphaolefin,
propylene glycol, or
silicone.
Other components
Hydraulic fluids can contain a wide range of chemical compounds, including:
oils,
butanol, esters (for example
phthalates, like
DEHP, and
adipates, like
bis(2-ethylhexyl) adipate),
polyalkylene glycols (PAG),
phosphate esters (for example
tributylphosphate), silicones, alkylated aromatic hydrocarbons, polyalphaolefins (PAO) (for example
polyisobutenes),
corrosion inhibitors, etc.
Biodegradable hydraulic fluids
Environmentally sensitive applications (for example
farm tractors and marine
dredging) may benefit from using biodegradable hydraulic fluids based upon
rapeseed (
Canola)
vegetable oil when there's 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.
Brake fluid
Brake fluid is a subtype of hydraulic fluid with high
boiling point and low
freezing point. It is intentionally hygroscopic, so that it'll absorb water which could otherwise cause corrosion of brake system components.
Safety
Because industrial hydraulic systems operate at hundreds to 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 hydraulic systems.
Fire resistance is a property available with specialized fluids.
Trade names
Some of the trade names for hydraulic fluids include Durad, Fyrquel, Houghton-Safe, Hydraunycoil, Lubritherm Enviro-Safe, Pydraul, Quintolubric, Reofos, Reolube, and
Skydrol.
Aircraft hydraulic systems
The use of hydraulic systems in aircraft almost certainly began with braking systems. As aircraft performance increased in mid-20th century, the amount of force required to operate mechanical flight controls became excessive, and hydraulic systems were introduced to reduce pilot effort. The hydraulic actuators are controlled by valves; these in turn are operated directly by input from the aircrew (hydro-mechanical) or by computers obeying control laws (fly by wire). See
flight controls.
Hydraulic power is used for other purposes. It can be stored in accumulators to start an auxiliary power unit (APU) for self-starting the aircraft's main engines. Many aircraft equipped with the
M61 family of cannon use hydraulic power to drive the gun system, permitting reliable high rates of fire.
The hydraulic power itself comes from pumps driven by the engines directly, or by electrically driven pumps. Electric pumps can provide both redundancy and the means of operating hydraulic systems without starting the engines, which can be very useful during maintenance.
Aircraft hydraulic fluids fall under various specifications:
Common petroleum-based:
- Mil-H-5606: Mineral base, flammable, fairly low flashpoint, usable from -65F to 275F, red color
- Mil-H-83282: Synthetic hydrocarbon base, higher flashpoint, self-extinguishing, backward compatible to -5606, red color
- Mil-H-87257: A development of -83282 fluid to improve its low temperature viscosity.
Phosphate-ester:
Skydrol - Typically light purple, not compatible with petroleum-based fluids, won't support combustion.
Special, stringent care is required when handling aircraft hydraulic fluid as it's critical to flight safety that it stay free from contamination. It is also necessary to strictly adhere to authorized references when servicing or repairing any aircraft system.
Further Information
Get more info on 'Hydraulic Oil'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://hydraulic_fluid.totallyexplained.com">Hydraulic fluid Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
