It is a measure of kinematic viscosity based on comparing a flow of the substance under test to the flow of water. For example:ĭegree Engler is still occasionally used in the UK. These have often been named after the viscosity meter used to measure viscosity. Occasionally other units of viscosity are quoted. Rotary Viscometer - used to measure dynamic viscosityĬone & Plate - a variance on the rotary viscometer This is perhaps the most common method of viscosity measurement There are three main types of rheometer Ĭapillary Tube - sometimes referred to as a viscosity bath, is used to measure kinematic viscosity. Viscosity measurement can not be measured inline - it is performed in the laboratory using a rheometer. Therefore for a dynamic or kinematic viscosity to be meaningful a reference temperature must be quoted. Viscosity is temperature dependent, generally the warmer a liquid the less viscous it is whereas the warmer a gas the higher the viscosity. To convert Kinematic viscosity in SSU to centiStokesĬentiStokes = 0.226 x SSU - (195/SSU) for SSU values less than 100, andĬentiStokes = 0.22 x SSU - (135/SSU) for SSU values greater than 100 Kinematic vicosity (SSU) = 4.63 x dynamic viscosity (cP) / SG This practice establishes the official equations relating SUS and SFS to the SI kinematic viscosity units, mm 2/s. The kinematic viscosity of a fluid can be calculated from its dynamic viscosity by dividing it by the fluid's density e.g.ĬentiPoises (cP) = centiStokes (cSt) / DensityĪ rough conversion of Redwood Seconds to centistokes is given by the formula:Ĭentistokes (cSt) = 0.260t - (0.0188/t), where t is the time in Redwood SecondsĪSTM D2161 - 05e1 Standard Practice for Conversion of Kinematic Viscosity to Saybolt Universal Viscosity or to Saybolt Furol Viscosity. Imperial units are square foot per second. In practice the centiStoke is used since the Stoke is a large unit. The metric units of kinematic viscosity are square centimetre per second, called a Stoke (called after Irish scientist George Gabriel Stokes). Most pipe friction charts and pump correction charts used by engineers refer to kinematic viscosity. Again, the larger the molecules, the greater resistance, the higher the kinematic viscosity. Kinematic viscosity on the other hand is a measure of a fluid's resistance to flow and shear under the forces of gravity. Imperial units are either slugs per foot-second, or the equivalent pound-seconds per square foot. In practice the centiPoise is used since the Poise is a large unit. The metric unit for dynamic viscosity is dyne-second per square centimetre (or sometimes the numerically equivalent gram per centimetre-second is used) called a Poise (named after French physician and physiologist Jean Louis Marie Poiseuille). The larger the molecules, the higher the internal resistance and consequently the higher the dynamic viscosity. This internal friction is caused by the resistance of the fluid's molecules moving relative to each other. The dynamic viscosity (sometimes called absolute viscosity) of a fluid can be defined as the resistance to flow and shear under the forces of internal friction.

Kinematic viscosity units