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Units
of Viscosity Measurements Table of Contents Physical & Chemical Properties The unit of absolute or dynamic viscosity is Force/Area X Time. The basic SI unit is Pascal X second Pa s (or Ns m-2). Mineral oils are typically 0.02 to 0.05 Pa.s at 40 degree C. 1 mPa.s = 1 Centipoise (cP) cP is commonly used for absolute viscosity. The symbol for viscosity is usually u. When gravity is used to cause flow for the viscosity measurement, the density p of the oil is involved and kinematic viscosity is reported =u/p. The basic SI unit is meter2/second (m2 s-1). Also 1 cm2 s-1 = 1 Stoke (St) and 1 mm2 s-1 = 1 centiStoke (cSt) cSt is commonly used for kinematic viscosity. Viscosity of industrial lubricants is commonly classified using the International Standard Organization Viscosity Grade (ISOVG) system, which is the average viscosity in centiStokes (cSt) at 40 degree C. For example, ISOVG 32 is assigned to oils with viscosity between 28.8 and 35.2 cSt at 40 degree C. The viscosity of oils is dependent upon temperature, pressure, and shear rate. Viscosity decreases as temperature increases because the molecules vibrate more and interact less. Conversely, the viscosity of oil increases as temperature decreases and can become grease-like at very low temperatures. For more information call 1-888-HERGUTH (437-4884) |
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