Hydraulic fluids lubricating power

The bulk of hydrauhc fluids is specified and purchased on bid. Specifications and approval fists are issued by some manufacturers of hydraulic pumps and system components that require lubrication as well as power for control signal transmission. U.S. government military specifications for hydraulic fluids are fisted ia Table 12, and ASTM tests that are applicable to hydraulic fluids iaclude the foUowiag ... 

Selection and care of the hydraulic fluid for a machine will have an important effect on how it performs and on the life of the hydraulic components. During the design of equipment that requires fluid power, many factors are considered in selecting the type of system to be used-hydraulic, pneumatic, or a combination of the two. Some of the factors required are speed and accuracy of operation, surrounding atmospheric conditions, economic conditions, availability of replacement fluid, required pressure level, operating temperature range, contamination possibilities, cost of transmission lines, limitations of the equipment, lubricity, safety to the operators, and expected service life of the equipment. 

Paraffinic and naphthenic (cycloparaffinic) stocks may be used for the formulation of lubricating oils, each with favorable characteristics for particular uses. Paraffinic stocks are generally preferred for their superior lubricating power and oxidation resistance. Naphthenic stocks, on the other hand, have naturally lower pour points, i.e, they maintain flow characteristics at lower pour-points than paraffinics (Table 18.8) and are better solvents, features which are more important for applications such as heat transfer, metal working, and fire-resistant hydraulic fluids [33]. Any residual aromatics in the lubricating base stock will have been removed before formulation by solvent extraction, using N-methylpyrrolidone, furfural, or less frequently today, phenol (Eq. 18.39). 

In addition to lubricating the engines, turbine lubricants are also required to lubricate a number of associated systems such as auxiliary power units and constant speed drive units and to act as hydraulic fluids, for instance, in the propeller pitch control units of some turbo-props. 

Eleftherakis, J., A Proven Approach to Hydraulic and Lubrication System Contamination Control , Lubr. Fluid Power J. 2, 13-20, Aug 2001. 

A hydraulic system uses an oil-type liquid called hydraulic fluid. This fluid is typically made from petroleum products. The advantages of hydraulics include the fact that liquids are more difficult to compress than gases, so the hydraulic system can transfer greater amounts of power. The hydraulic fluid also helps lubricate the system s components. However, if the hydraulic fluid leaks, it may present a problem. Elevators, dentists chairs, heavy equipment operations, and automobile braking systems use hydraulics. Hydraulic fluid pressure can easily be controlled. 

Automatic transmission fluid (ATF) performs many functions including lubrication, power transfer, hydraulic control, and cooling [73], This fluid is extremely complex consisting of a base mineral oil (consisting of paraffinic, naphthenic, and aromatic hydrocarbons) and an additive package. Newer ATF compositions consist of synthetic base materials. The additives prevent fluid oxidation, corrosion, loss of lubricity, and foaming. Even though antioxidants, inhibitors, and stabilizers are added to the ATF, the base oil... 

ISO/DIS 4548-12 Methods of Test for Full-Flow Lubricating Oil Filters for Internal Combustion Engines - Part 12 Particle Retention Ability and Contaminant Holding Capacity Using Particle Counting ISO/DIS 11171 Hydraulic Fluid Power - Calibration of Liquid Automatic Particle Counters... 

It may be helpful to express the change of viscosity of a silicone oil in a different manner. If we compare a typical silicone oil with a standard hydrocarbon oil of viscosity index 100, the two having the same viscosity at 100° F., we find that after cooling to —35° F. the silicone oil has seven times the viscosity it had, whereas the hydrocarbon oil has increased 1,800-fold in viscosity. This relative constancy of viscosity of the silicone oil makes it particularly suitable for use as a fluid in hydraulic systems for the transmission of power. Silicone oils do not react with the common metals of construction, and they are so inert that even at 300° F. they do not discolor r become acid or form sludge. They are satisfactory lubricants in hydraulic pumps and in any other device where conditions of hydrodynamic lubrication prevail. When used as lubricants, methyl silicone oils do not suffer loss of viscosity through shear breakdown under continuous load at high speed. 

Power Transmission Hydraulic systems utilize lubricating oils to serve all of the above listed functions plus the transfer of force and motion based on the fluids with general incompressibility. 

The lower cost dialkyl benzenes are used in a wide variety of industrial and metalworking products. In particular, their sulphur-free chemistry has led to extensive use as rolling and drawing oils for copper. The synthesised alkyl benzenes, even when their chemistry is optimised, generally exhibit poorer properties than PAOs. However, their excellent solvency and low pour point make them suitable for lubricants designed for extremely low-temperature operations in arctic greases, gear oils, hydraulic and power transmission fluids. 

The HH, HL, HM, HR, HV and HG hydraulic lubricants are the most important and widely used. As viscosity is one of their most important properties, they are produced in a wide range of viscosities, ISO VG 10-100. For a given application, viscosity should be as low as possible to give a rapid response for the hydraulic system, meaning that the oil should be sufficiently fluid for efficient power transmission. A minimum viscosity level is necessary to eliminate or minimize leakage losses and ensure lubrication of all tribological elements of the hydraulic system. 

High performance anti-wear hydraulic oils that are universally acknowledged as the market leader in the field of industrial hydraulic and fluid power lubrication. 

Hydraulic power was first based on water. The development of the oil industry meant the ready availability of power transmission fluids with improved characteristics compared to water. Oil has better lubrication ability and increased viscosity which allowed 5 much higher contact loads to be achieved in the machinery as well as lower leakage rates. 

Of this family of products, triaryl phosphates (TAP) and alkyl diaryl phosphates (ADP) are the two important categories of FR plasticizers for PVC. Trialkyl phosphates are considered too volatile for most vinyl processes, and are more commonly found in other applications, such as leveling agents or antifoam additives. In vinyl, TAP and ADP plasticizers are used to flame-retard thin films and laminates for articles such as wall covering, tarpaulins (transportation), and vinyl-coated furniture fabric. Another major application area is in vinyl for electrical insulation in wire and cable. In addition to these applications, phosphate esters are used as functional fluids for hydraulic equipment (metal industries, power generation, and aircraft hydraulic systems) and as additives in formulated lubricant systems. As flexible vinyl composites are usually defined by their additives, when formulated correctly, phosphate esters can help produce a very cost-efficient vinyl composite capable of very low smoke and flammabihty. In nearly all markets, phosphate esters are valued primarily for their FR properties, and the distinction from function and plasticization is sometimes obscured. 

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