Hydraulic fluids sealing

Swelling of rubber (or other elastomer) gaskets, or seals, when exposed to petroleum, synthetic lubricants, or hydraulic fluids. Seal materials vary widely in their resistance to the effect of such fluids. Some seals are designed so that a moderate amount of swelling improves sealing action. Refer to Swell and Shrinkage Tests. 

Other Fire-Resistant Hydraulic Fluids. Phosphate and more recently polyol esters are marketed as fire-resistant compounds. They are formulated with additives to control wear, oxidation, corrosion, and misting. Seal compatibdity and solvency characteristics of these fluids may be quite different from those of mineral ods. 

Leather To 210 Good mechanical properties for sealing. Resistant to alcohol, gasobne, many oils and solvents, synthetic hydraulic fluids, water. 

The control and application of fluid power would be impossible without suitable means of transferring the hydraulic fluid between the reservoir, the power source, and the points of application. Fluid lines are used to transfer the hydraulic fluid, fittings are used to connect lines to system components, and seals are used in all components to prevent leakage. This chapter is devoted to these critical system components. 

Face-seal materials can be chosen from filled, molded or reinforced resins with which water, hydraulic fluids, mineral oils or synthetic oils are all compatible. Their maximum temperature in service depends on the brittle point of the resin but, generally, the range is from —50°C to 100°C (122°F to 212°F). Abrasion resistance is generally good but, as far as possible, resins are not used in the presence of foreign solids. 

Among important previous applications of PCB mixtures are hydraulic fluids, insulation dielectrics in transformers and condensers, plasticizers in plastics, outdoor paints and printer s ink and different sealing and construction products for building and mounting purposes. 

Over the years, detergents have found equally important usage in many other types of lubricants, including gear oils, farm tractor hydraulic fluids, automatic transmission fluids and industrial oils. The performance properties that detergents impart to these lubricating fluids include rust and corrosion prevention, improvement in lubricant elastomeric seal compatibility, enhancement of sludge control under oxidative conditions and improvement of wet clutch and wet brake friction level and stability. 

It is important to note that hydrocarbon-based fluids and phosphate ester-based fluids are not interchangeable as the materials that they may contact, e.g. seals, wiring insulation and paint must be carefully selected for whichever hydraulic fluid class is being used on the aircraft. Also, the two different types of fluid must never be mixed. 

Gschwender L, Snyder CE, Sharma SK, Idanagan S. (1998) US Air Force Research Laboratory Hydraulic Fluids and Seals Workshop Proceedings, 1998. MIL-PRF-23827 Fire Resistant Hydraulic Fluid. 

Fig. 7.4 A piston-cylinder high-pressure apparatus (a) the pressure frame, (b) a 100 tonne hydraulic ram, (c) the piston, (d) the bottom plug, (e) high-pressure seals, (f) a double-walled pressure vessel, (g) the pressurizing fluid, (g) a 500 bar hydraulic fluid for pressurization, (i) hydraulic pressure used for piston extraction, (j) the sample. (Reproduced by permission from PSIKA Ltd).

Because of its exceptional resistance to fuels and hydraulic fluids, Buna-N s major area of application is in the manufacture of aircraft hose, gasoline and oil hose, and self-sealing fuel tanks. Other applications include carburetor diaphragms, gaskets, cables, printing rolls, and machinery mountings. 

Uses Lubricant, EP agent for chem., aerospace, hydraulic fluids, metalworking, nuclear, pulp/paper, other industries chemical piping chem.-resist. seals/o-rings gaskets tank linings wire/cable insulation mold... 

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