Pumps - Bürkle GmbH

Viscosity of liquidsThe right pump for each liquidPumps are used in widely different fields of application. Bürkle offersa large number of different versions. However, when choosing asuitable pump several criteria must be considered. The most importantare the viscosity, structure and density of the liquid.How the liquid behaves under the influence of external influences,e.g. variations in temperature and pressure, is also important.We would be pleased to help you make certain that you choose thecorrect pump for your application.Viscosity using motor oil as an exampleEveryone has heard of the viscosity terms for motor oil. This classificationis based on the flow behavior of the motor oil as a function ofthe temperature. In Winter low-viscosity oils are required. In Summerthe oil becomes hotter, but it must still remain sufficiently thick.For example: SAE 5W-40. The first number defines the viscosity at0 °F (-18 °C), the second for a temperature of 210 °F (99 °C). An oilwith the classification 5W (W=Winter) is therefore thinner than a15W motor oil under cold conditions.Viscosity – what actually is viscosity?The viscosity characterizes the flow behavior of a liquid. Highviscosityliquids are thick, low-viscosity liquids thin. This viscosityresults from intermolecular forces; these are also known as theinternal friction. This internal friction decreases as the temperatureincreases and increases as the temperature decreases.The dynamic viscosity is given in Pas, for low-viscosity liquids in mPas.It is defined as the force in newtons that is necessary to displace aliquid layer of 1 m 2 and 1 m height along a boundary parallel to asecond layer at a speed of 1 m·s -1 .Typical viscosity values in mPas at 20 °CKerosine 0,65Coffee cream ~ 10Hydraulic oil ~ 120Water 1,0Glycol 40Motor oil 15W40 390Grape juice 2 – 5Olive oil ~ 100Honey ~ 10 00041