For fuel oil, we often see classifications such as 180cSt and 380cSt. Here we give a brief introduction to the indicators that are often used in all oil products.
cSt is the abbreviation of Centistoke (centistoke), cSt is one percent of the Kinetic Viscosity unit “Stoke”, abbreviated cSt.
Viscosity (VISCOSITY) is a characterization of the fluidity of oil products, which reflects the strength of the interaction of liquid molecules in the process of movement, the effect is strong (the viscosity is large), and the flow is difficult. Paraffin-based crude oil contains more alkane components, the effect of intermolecular force is relatively small, and the viscosity is low. But it should be noted that the fluidity of oil is not only determined by viscosity, it is also related to the pour point (or freezing point) of oil.
The viscosity of the fluid is significantly affected by the ambient temperature (the pressure also has a certain effect, but it is generally negligible), and this effect is also implemented through intermolecular interactions: the usual concept is that the temperature increases the volume of the fluid expands, and the distance between the molecules As the distance increases, the interaction weakens and the viscosity decreases; as the temperature decreases, the volume of the fluid decreases, the intermolecular distance shortens, the interaction strengthens, and the viscosity increases. Since viscosity is closely related to temperature, any viscosity data should indicate the temperature at which it was measured. The effect of temperature on viscosity is usually particularly pronounced in the low temperature region.
There are many methods for measuring viscosity. Redwood Viscosity is commonly used in the United Kingdom, Saybolt Viscosity is commonly used in the United States, and Engler Viscosity is often used in continental Europe, but countries are gradually using Kinemetic Viscosity more widely, because The accuracy of its determination is higher than the above-mentioned methods, and the sample consumption is small, and the determination is rapid. Conversions between various viscosities can usually be approximated using pre-made conversion tables.
Viscosity is an important parameter for various oils. The vaporization performance of internal combustion engine and jet engine fuel, and the quality of fuel atomization for boilers are directly related to the viscosity of each oil, and the transportation performance of oil is also closely related to viscosity. Due to the importance of viscosity in the practical application of oil products, many oil products, such as residual fuel oil and some lubricating oils, often use viscosity as the basis for their classification. In addition, the measurement of the viscosity of the lubricating oil during use can provide information on whether the oil has deteriorated and needs to be replaced.
KINEMETIC VICOSITY υ is the ratio of the dynamic viscosity (Dynamic Viscosity) η of the oil to the density ρ of the oil at the same temperature:
The unit, Stoke = centimeter 2/second, is usually expressed in one hundredth of it – centistoke cSt.
Specifically, it is to measure the time “seconds” required for a certain amount of sample to flow through the capillary of the kinematic viscometer at a specified temperature (such as 40°C, 50°C), and then multiply by the calibration constant of the viscometer to obtain the sample. Viscosity cSt.
The advantages of kinematic viscosity are that the sample dosage is small, the test speed is fast, and the accuracy is much higher than other determination methods (Reyborg, Saixu, etc.), so the application is becoming more and more common.
Dynamic viscosity is the internal frictional force produced when two layers of liquid with an area of 1 cm2 and a distance of 1 cm are moved relative to the other liquid at a speed of 1 cm/s. The unit is “poise” ( Poise), one percent of which is centipoise (CP).
SAYBOLT VISCOSITY is the time, in seconds, required for a certain amount of sample to flow out of 60 ml from a SAYBOLT viscometer at a specified temperature (such as 100OF, 122OF or 210OF).
Saybolt viscosity can be divided into Saybolt Universal viscosity (Saybolt Universal, commonly expressed as SSU) and Saybolt heavy oil viscosity (Saybolt Furol, commonly expressed as SSF). The hole diameter of the general viscometer is smaller, and the heavy oil viscometer is larger. Generally, when the outflow time measured by the Saybolt general viscometer exceeds 2000 seconds, the Saybolt heavy oil viscometer is used instead. Numerically, SSF is about ten times larger than SSU.
Saybolt viscosity is widely used in the United States and other places. Redwood viscosity (REDWOOD VISCOSITY) is the time required for a certain amount of sample to flow out 50 ml from a Redwood viscometer at a specified temperature (100OF), in seconds. Reinhardt viscosity is divided into Reinhardt 1, Redwood No.1 (abbreviated RWⅠ) and Reinhardt 2, Redwood NO.2 (abbreviated RWⅡ). When the measured RWI exceeds 2000 seconds, use RWII instead. Numerically, RWII is equal to 10 times of RWI.
Reid’s viscosity is widely used in the UK, and has been gradually replaced by Kinemetic Viscosity due to the poor accuracy of the regulations.