A hydraulic fluid or hydraulic fluid is the medium in which power is transferred in a hydraulic machine. The common hydraulic fluid is based on mineral oil or water. Examples of equipment that may use hydraulic fluids are excavators and backhoes, hydraulic brakes, power steering systems, transmission, garbage trucks, aircraft control systems, elevators, and industrial machinery.
The hydraulic system as mentioned above will work most efficiently if the hydraulic fluid used does not have zero compressibility.
Video Hydraulic fluid
Functions and properties
The main function of hydraulic fluid is to convey strength. However, in use, there are other important functions of hydraulic fluids such as the protection of hydraulic machine components. The table below lists the main functions of hydraulic fluid and fluid properties that affect its ability to perform the function:
Maps Hydraulic fluid
Composition
Stock base
The original hydraulic fluid, dating back to ancient Egypt, was water. Beginning in 1920, mineral oil began to be used more than water as a base stock because of its inherent lubrication properties and the ability to be used at temperatures above the boiling point of water. Currently most hydraulic fluids are based on mineral oil source stock.
Natural oils such as rapeseed (also called canola oil) are used as a base stock for liquids in which biodegradability and renewable sources are considered important.
Other base stocks are used for special applications, such as for fire resistance and extreme temperature applications. Some examples include: glycols, esters, organophosphate esters, polyalphaolefins, propylene glycols, and silicone oils.
NaK-77, an eutectic sodium-potassium alloy, can be used as a hydraulic fluid in high-temperature and high-temperature environments, for temperature ranges from 10 to 1400 ° F (-12 to 760 ° C). The bulk modulus at 1000 Â ° F (538 Â ° C) is 310,000 psi (2.14 GPa), higher than hydraulic oil at room temperature. The lubrication is bad, so the positive-displacement pump is not suitable and the centrifugal pump should be used. The addition of cesium shifts useful temperature ranges up to -95 to 1300 ° F (-70 to 704 ° C). The NaK-77 compound was tested in a hydraulic and fluid system for Low Supersonic Low Altitude.
Other components
Hydraulic fluids may contain various chemical compounds, including: oils, butanols, esters (eg phthalates, such as DEHP, and adipates, such as bis (2-ethylhexyl) adipate), polyalkylene glycol (PAG), organophosphates (eg tributylphosphate), silicones, alkylated aromatic hydrocarbons, polyalphaolefins (PAOs) (eg polyisobutenes), corrosion inhibitors (including acid scavengers), anti-erosion additives, etc.-
Biodegradable hydraulic fluid
Environmentally sensitive applications (eg agricultural tractors and marine dredging) can benefit from the use of biodegradable hydraulic fluids based on rapeseed vegetable oils (Canola) when there is a risk of oil spills from cracked oil channels. Usually these oils are available as ISO 32, ISO 46, and ISO 68 oil specifications. ASTM Standard ASTM-D-6006, Guide for Assessing Hydraulic Fluids Destruction and ASTM-D-6046, Classification of Hydraulic Fluid Standards for Relevant Environmental Impacts.
Brake fluid
Brake fluid is a subtype of hydraulic fluid with high boiling point, both when new (determined by the equilibrium boiling point) and after absorption of water vapor (determined by wet boiling point). Under braking heat, both free water and moisture in the braking system can boil into compressed vapor, resulting in brake failure. Glycol-ether based fluids are hygroscopic, and the absorbed moisture will greatly reduce the boiling point over time. The oil and silicone based fluids are not hygroscopic.
Power steering fluid
Power steering fluid is a sub-type of hydraulic fluid. Most are liquid or silicon-based mineral oil, while some use automatic transmission fluids, made from synthetic base oils.
The use of the wrong type of fluid can cause power steering pump failure.
Security
Because industrial hydraulic systems operate on hundreds to thousands of PSIs and temperatures reach hundreds of degrees Celsius, severe injuries and deaths can be caused by component failure and maintenance should always be done while performing treatment on the hydraulic system.
Flame retardant is a property available with a special liquid. Water-gycol and polyol-ester are some special liquids that contain excellent thermal and hydrolytic properties, which helps in fire resistance.
Aircraft hydraulic system
As aircraft performance increased during the mid-20th century, the amount of power required to operate mechanical flight controls became excessive, and the hydraulic system was introduced to reduce demonstration efforts. The hydraulic actuator is controlled by the valve; this is in turn operated directly by input from aircrew (hydro-mechanical) or by a computer that comply with the control law (fly by wire).
Hydraulic power is used for other purposes. It can be stored in the accumulator to start an additional power unit (APU) to start the aircraft's own main engine. Many aircraft equipped with the M61 cannon family use hydraulic power to move the weapon system, allowing for a high level of fire that can be relied upon.
The hydraulic power itself comes from a pump that is driven by the engine directly, or by an electrically driven pump. In modern commercial aircraft this is an electrically driven pump; If all engines fail in flight, the pilot will deploy an electric generator driven by a propeller called Ram Air Turbine (RAT) hidden beneath the plane. It provides electrical power for hydraulic pumps and control systems because power is no longer available from the machine. In such and such systems, electric pumps can provide redundancy and operate hydraulic systems without machine operation, which can be very useful during maintenance.
Specifications
Mineral oil base:
- Mil-PRF-5606 (original Mil-H-5606): Mineral base, flash point, low flash point, usable from -65 Â ° F (-54 Â ° C) to 275 Â ° F (135 Â ° C) Ã, Â ° C), red color, developed in the 1940s
- MIL-PRF-6083: Can be used from -54Ã, Â ° C to 135Ã, Â ° C "where corrosion protection is required and it has been determined that MIL-PRF-46170 (FRH) hydraulic fluid is unusable. used in reverse mechanisms and hydraulic systems to rotate weapons or target tactical and support armament equipment, except for combat armored vehicles/equipment requiring FRH Hydraulic fluid is also used as a preservative for aircraft hydraulic systems and components in which MIL-H - 5606 (OHA) or MIL-PRF-87257 is used as an operating fluid. "
Synthetic hydrocarbon base: This synthetic liquid is compatible with mineral-based hydraulic fluids and was developed to overcome the low point of hydraulic mineral-based recall.
- Mil-H-83282: Synthetic hydrocarbon base, higher flashpoint, self-extinguishing, 5660 compatible, red color, with degrees -40 Â ° F (-40 Â ° C).
- Mil-H-87257: Development of liquids -83282 to increase its low temperature viscosity.
Bases of phosphates-esters:
- US/NATO Military Specification - MIL-H-8446
- Boeing Seattle - BMS3-11
- Boeing Long Beach - DMS2014
- Boeing Long Island - CDS5478
- Lockheed - LAC C-34-1224
- Airbus Industrie - NSA307110
- British Aerospace - BAC M.333.B
- Bombardier - BAMS 564-003
- SAE - Ac974
- SAE - AS1241
- Skydrol
Contamination
Special and rigorous care is required when handling aircraft hydraulic fluid as it is essential for aviation safety to remain free from contamination. It is also necessary to strictly comply with official reference when serving or repairing any aircraft systems. Samples of the aircraft hydraulic system were taken during heavy aircraft maintenance checks (mainly C and D checks) to check for contamination.
Military Spec 1246C is one of the specifications of fluid contamination.
The ISO liquid contamination scales provide the category of contamination based on the number of particle size and distribution.
Other Use
The hydraulic oil properties of HLP 32 make it ideal for lubricating machine tools.
See also
- Dexron
- Hydraulic brakes
- Hydraulic fuse
- International Hydraulics, INC.
- Hydroponics suspension - car app
- Oleo strut - an airplane app
- Osmosis
- Skydrol
References
External links
- Information and purchase of military specifications (mil-spec) hydraulic fluid
- Information on Fluid Power is also available on the National Fluid Power Association nfpa.com website
- USDA Research. Hydrolegegradable Hydraulic Fluid
- Biodegradable Hydraulic Oil
- Industrial Hydraulic Oil
- flight hydraulic fluid
Source of the article : Wikipedia
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