Viscosity hydraulic fluids

The silicone oils and silicone resins find application as (i) lubricants (their change of viscosity with temperature is small), (ii) hydraulic fluids (they are unusually compressible), (iii) dielectric fluids, (iv) for the pro duction of water-repellant surfaces, and (v) in the electrical industry (because of their high insulating properties). 

Metal- Working and Hydraulic Fluids. In the preparation of fluids for metal-working and hydrauflcs, the trend has been to replace organic-based materials with aqueous-based materials. Neodecanoic acid has found apphcation in these newer fluids as a corrosion inhibitor and a viscosity improver. For example, neodecanoic acid is used in an aqueous hydrauflc fluid concentrate for corrosion inhibition and improved antiwear properties (101), in the preparation of a thickened aqueous hydrauflc fluid to reduce viscosity loss (102), and in a water-soluble metal working oil to reduce corrosion (103). In a similar vein, neodecanoic acid has been used in antifreeze concentrates for corrosion inhibition (104). 

Viscosity is one of the most important properties of hydraulic fluids. It is a measure of a fluid s resistance to flow. A liquid such as gasoline which flows easily has a low viscosity, and a liquid such as tar which flows slowly has a high viscosity. The viscosity of a liquid is affected by changes in temperature and pressure. As the temperature of liquid increases, its viscosity decreases. That is, a liquid flows more easily when it is hot than when it is cold. The viscosity of a liquid will increase as the pressure on the liquid increases. 

For most practical purposes, it will serve to know the relative viscosity of the fluid. Relative viscosity is determined by timing the flow of a given quantity of the hydraulic fluid through a standard orifice at a given temperature. There are several methods in use. The most acceptable method in the United States is the Saybolt viscosimeter. Figure 40.17. 

For industrial applications, hydraulic oil viscosity is typically approximately 150 SUS at 100°F. It is a general rule that the viscosity should never go below 45 SUS or above 4000 SUS, regardless of temperature. Where temperature extremes are encountered, the fluid should have a high viscosity index. 

Another example of the importance of the VI is the need for a high viscosity index hydraulic oil for military aircraft, since hydraulic control systems may be exposed to temperatures ranging from below — 65°F at high altitudes to over 100°F on the ground. For the proper operation of the hydraulic control system, the hydraulic fluid must have a sufficiently high VI to perform its functions at the extremes of the expected temperature range. 

Typical BW antifoam emulsion products include SAG 10 and SAG 30 (10 and 30% milky white emulsions, each with a viscosity of 2,000 cS at 25 °C) from Union Carbide Corporation. These same products also are used for food processing (under FDA 21CFR 173.340), for petroleum processing (as amine scrubbers, gas-oil separators, etc.), and as functional chemicals (antifreezes, hydraulic fluids, cutting oils, etc.). 

Naturally occurring polysaccharides and their derivatives form the predominant group of water-soluble species generally used as thickeners to impart viscosity to treating fluids [1092]. Other synthetic polymers and biopolymers have found ancillary applications. Polymers increase the viscosity of the fi ac-turing fluid in comparatively small amounts. The increase in fluid viscosity of hydraulic fracturing fluids serves for improved proppant placement and fluid loss control. Table 17 summarizes polymers suitable for fracturing fluids. 

The physical properties important for the projected use of hydraulic fluids are viscosity, density, foaming behavior, and fire resistance. There is no generally recognized test method for measuring flammability of hydraulic fluids, although various test methods maybe utilized (Moller 1989). 

Saturation (v) is the volume fraction of the total void volume occupied by a specific fluid at a point. Saturation values can vary from zero to 1 with the saturation of all fluids equal to 1. Residual saturation (Sr) is the saturation at which the NAPL becomes discontinuous and immobile due to capillary forces. Residual saturation is dependent upon many factors, including pore size distribution, wettability, fluid viscosity and density ratios, interfacial surface tension, gravity and buoyancy forces, and hydraulic gradients. 

Hydraulic fluid a fluid supplied for use in hydraulic systems. Low viscosity and low pour point are desirable characteristics. Hydraulic fluids may be of petroleum or nonpetroleum origin. 

The maximum thickness that can be achieved by hydraulic fracturing is dependent on the fracture fluid viscosity, fracture containment pressure, and ground stiffness. The formation... 

The improvements have come by way of petroleum oils with viscosity index improvers, or synthetics with naturally high viscosity index. The problem of packing deterioration, or rusting, is chiefly a chemical matter. Hydraulic fluids for the various applications include those made from petroleum, synthetic oils, and aqueous solutions containing antifreeze and rust inhibitors. Antifoam agents are necessary in some hydraulic fluids. 

Because pore sizes in the cake and filter plate are small and the liquid velocity through the pores is low, the flow of filtrate may be considered laminar and Poiseuille s law is applicable. Filtration rate is directly proportional to the difference in pressure and inversely proportional to the fluid viscosity, as well as to the hydraulic resistance of the cake and filter plate. Because the pressure and hydraulic resistances of the cake and filter plate change with time, the variable rate of filtration may be expressed as ... 

Lubricants, Fuels, and Petroleum. The adipate and azelate diesters of C.. through Cn alcohols, as well as those of tridecyl alcohol, are used as synthetic lubricants, hydraulic fluids, and brake fluids. Phosphate esters are utilized as industrial and aviation functional fluids and to a small extent as additives in other lubricants. A number of alcohols, particularly the Cg materials, are employed to produce zinc dialkyldithiophosphates as lubricant antiwear additives. A small amount is used to make viscosity index improvers for lubricating oils. 2-Ethylhexyl nitrate [24247-96-7] serves as a cetane improver for diesel fuels and liexanol is used as an additive to fuel oil or other fuels (57). Various enhanced oil recovery processes utilize formulations containing liexanol or heptanol to displace oil from undeiground reservoirs (58) the alcohols and derivatives are also used as defoamers in oil production. 

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