Sheet N ° 3 Definitions
Normal working pressures are between 10 and 350 bars.
Pneumatics : Part of physics which studies air and its industrial application, in the form of compressed air up to a pressure not exceeding 10 bars in general.
Hydrostatic : Part of hydraulics which studies the laws of liquids at rest. It is also the name given to the closed type circuit.
Hydrodynamics : Part of hydraulics that studies the laws of liquids in motion.
Atmospheric pressure : Pressure exerted by air on the earth's surface. (approximately 1 bar)
Absolute pressure : It is the addition of relative pressure and atmospheric pressure.
Cavitation : Phenomenon corresponding to the formation of gas bubbles which mainly occurs on pumps and hydraulic motors.
By creating a vacuum (example: pipe too small), the elongation of the oil drops causes the appearance of dissolved gas which implodes while recompressing.
Degassing : Phenomenon where the release of gas dissolved in the oil caused by a depression is observed. (between -0.4bar and -0.6 bar)
Diesel effect : Implosion and combustion of the oil (gunshot). Usually this phenomenon occurs locally at the cylinder seals. The destruction of the seals is caused by the compression of a large volume of air and a small volume of oil (example: poorly purged cylinder)
Emulsion : Mixture of two liquids (mayonnaise)
Foaming : Phenomenon observed in the hydraulic reservoirs caused by an air intake on the circuit.
Oil : viscous liquid with low compressibility used to transmit energy.
Viscosity : Resistance to flow.
TAN number : Acid number (neutral pH = 7).
Freezing point : Temperature at which the oil is frozen.
Pour point : The lowest temperature at which the oil still flows.
Flash Point : Temperature at which oil vapors ignite in the presence of a flame.
Point of fire : Temperature for which combustion is maintained over time.
Auto Ignition Point : The temperature at which an oil ignites spontaneously (approximately 500 °).
Aniline point : Temperature at which a hot solution, consisting of equal volumes of oil and aniline, during a test cooling, has a cloudy appearance by crystallization of aniline (between 90 ° and 110 °).
Low aniline point : Softening and swelling of elastomers.
Strong point of aniline : Hardening and shrinkage of elastomers.