VISOCOMETER COMPARISON CHART

For Newtonian liquids 

Comparison chart for commonly used viscometers for Newtonian liquids:

Note: This chart is provided for informational purposes only and may not be applicable to all situations. The measuring ranges and accuracy listed may vary depending on the specific model and manufacturer of the viscometer.

Note : This chart is intended to be an aid in comparing viscometer measurements on Newtonian liquids by referencing to absolute and kinematic viscosity . (Centistrokes reference , Mobilmeter , Engler , Ford 4 , Ford 3 , Saybolt Universal , Redwood Standard , Ubbelohde , Gardner Holts , Zahn 5 , Zahn 3 )

References :

Centistoke (cSt) is a unit of kinematic viscosity commonly used to express the viscosity of fluids. It is defined as the ratio of the dynamic viscosity of a fluid to its density.

The viscosity of common liquids in centistokes at room temperature (25°C or 77°F) are as follows:

• Water: 1.003 cSt
• Ethanol: 1.20 cSt
• Motor oil (SAE 10W-30): 60 cSt
• Olive oil: 84 cSt
• Honey: 2,000-10,000 cSt
• Molasses: 5,000-10,000 cSt
• Tar: 1,000,000 cSt or higher

It is important to note that the viscosity of a fluid can vary with temperature, pressure, and shear rate, and may not remain constant even within a specified temperature range. Therefore, the above values are just reference values and actual viscosity values may differ depending on the specific conditions.

Viscosity is a measure of a fluid's resistance to flow, or its internal friction. It is the property that describes how thick or thin a fluid is, and how easily it flows. Viscosity is usually measured in units of dynamic viscosity, such as Pascal seconds (Pa.s) or Poise (P), or in kinematic viscosity units, such as centistokes (cSt). Dynamic viscosity is the ratio of the shear stress to the shear rate of a fluid, while kinematic viscosity is the ratio of dynamic viscosity to density. Viscosity plays an important role in many industrial processes, as it affects the flow behavior and performance of fluids in various applications, such as lubrication, mixing, pumping, and processing. Viscosity also determines the resistance of a fluid to deformation and the rate of energy dissipation, which can affect the heat transfer and pressure drop in a system. Different methods and instruments can be used to measure viscosity, depending on the type of fluid, the range of viscosity, and the required accuracy and precision. Some common types of viscometers include capillary viscometers, rotational viscometers, and falling ball viscometers.

Absolute viscosity and kinematic viscosity are two related but distinct properties that are used to describe the flow behavior of fluids.

Absolute viscosity, also known as dynamic viscosity, measures a fluid's resistance to shear or deformation under an applied force or stress. It is defined as the ratio of the shear stress (force per unit area) to the shear rate (velocity gradient) of a fluid. The unit of absolute viscosity is Pa.s or Poise (P), with 1 P = 0.1 Pa.s.

Kinematic viscosity, on the other hand, describes a fluid's resistance to flow due to its internal friction and its density. It is defined as the ratio of absolute viscosity to density, and represents the fluid's ability to flow under the influence of gravity. The unit of kinematic viscosity is usually expressed in centistokes (cSt) or square millimeters per second (mm²/s).

The relationship between absolute viscosity and kinematic viscosity can be expressed by the following equation:

kinematic viscosity (cSt or mm²/s) = absolute viscosity (P or Pa.s) / density (g/cm³)

Absolute viscosity and kinematic viscosity are important parameters for characterizing the flow properties of fluids in many industrial and scientific applications, such as lubrication, pumping, mixing, and processing of liquids and gases. The choice of viscosity measurement method and units depends on the type of fluid, its viscosity range, and the required accuracy and precision.

Saybolt Universal is a method for measuring the viscosity of petroleum products and other liquids. It measures the time required for a fixed volume of fluid to flow through a standard orifice at a specified temperature under gravity. The method is named after its inventor, American engineer and inventor Arthur Saybolt.

In the Saybolt Universal method, the sample is heated to a specified test temperature, usually 100°F (37.8°C) or 210°F (98.9°C), and then poured into a viscometer. The viscometer has a calibrated tube and a standard orifice at the bottom. The time it takes for a fixed volume of fluid to flow through the orifice is measured in seconds and reported as Saybolt Universal seconds (SUS). The higher the SUS value, the lower the viscosity of the fluid.

The Saybolt Universal viscosity test is widely used in the petroleum industry to measure the viscosity of crude oil, fuel oils, lubricating oils, and other petroleum products. It is also used for other liquids such as adhesives, varnishes, and paints. The test method is standardized by the American Society for Testing and Materials (ASTM) as ASTM D88. The Saybolt Universal seconds can be converted to kinematic viscosity in centistokes (cSt) using conversion tables or equations, but the conversion depends on the temperature and the specific type of fluid being tested.

The Redwood Standard method is a viscometry method used to measure the viscosity of petroleum products, such as fuel oils and lubricating oils. It is named after its inventor, Sir Boverton Redwood, a British chemist and civil engineer who developed the method in the late 1800s.

The Redwood Standard method measures the time taken by a fixed volume of fluid to flow through a standard orifice at a fixed temperature under gravity. The fluid is heated to the test temperature, which is usually 100°F (37.8°C) or 210°F (98.9°C), and then poured into a viscometer. The viscometer has a calibrated tube and a standard orifice at the bottom. The time it takes for the fluid to flow through the orifice is measured in seconds and reported as Redwood seconds (RS). The higher the RS value, the lower the viscosity of the fluid.

There are two types of Redwood viscometers, the Redwood Viscometer No. 1 for liquids with viscosities up to 2000 Redwood seconds, and the Redwood Viscometer No. 2 for liquids with viscosities between 2000 and 8000 Redwood seconds. The Redwood Standard method is widely used in the petroleum industry to measure the viscosity of various petroleum products, such as fuel oils, lubricating oils, and crude oil. The test method is standardized by the American Society for Testing and Materials (ASTM) as ASTM D445. The Redwood seconds can be converted to kinematic viscosity in centistokes (cSt) using conversion tables or equations, but the conversion depends on the temperature and the specific type of fluid being tested.

The Ubbelohde viscometer is a type of capillary viscometer used to measure the kinematic viscosity of liquids. It was developed by German physicist and chemist Max Ubbelohde in the early 1900s.

The Ubbelohde viscometer consists of a vertical glass tube with a bulb at the top and a capillary tube at the bottom. The liquid to be tested is placed in the bulb, and the time it takes for a fixed volume of the liquid to flow through the capillary tube is measured. The flow rate is determined by measuring the time required for the liquid to flow through a fixed length of the capillary tube, typically between 50 and 500 mm.

The Ubbelohde viscometer is widely used for measuring the kinematic viscosity of fluids, particularly oils, and is the preferred method for high-precision measurements. The test method is standardized by the American Society for Testing and Materials (ASTM) as ASTM D446.

The Ubbelohde viscometer is available in different sizes, with different capillary tube diameters, to accommodate different viscosities. The viscosity of the liquid can be calculated using the measured flow time and the dimensions of the viscometer, and the results are reported in centistokes (cSt).

Gardner-Holt viscosity cups are simple, low-cost, and portable viscometers used for measuring the viscosity of liquids. They consist of a tapered, cylindrical cup with a small orifice at the bottom and a handle for convenient use. The cup is dipped into the liquid to be tested, and the time taken for the liquid to flow out of the cup through the orifice is measured. The time is typically measured in seconds and is used to determine the viscosity of the liquid.

The viscosity measurement is based on the relationship between the viscosity of the liquid and the time taken for the liquid to flow out of the cup. The Gardner-Holt viscosity cup is designed to provide a specific outflow time for liquids with different viscosities. For example, the No. 2 cup is designed to provide a 25-30 second outflow time for liquids with viscosities between 25 and 80 centistokes (cSt).

Gardner-Holt viscosity cups are commonly used for measuring the viscosity of paints, lacquers, and other coatings. They are easy to use and require minimal setup, making them ideal for on-site testing. However, they are less precise than other types of viscometers, and the results may be affected by factors such as temperature and air pressure.

The Engler viscometer is a type of viscosity measurement instrument used for determining the viscosity of petroleum products, such as fuels and lubricants. It was developed by German chemist and engineer August Friedrich Wilhelm Engler in the late 1800s.

The Engler viscometer consists of a cylindrical container with a fixed volume of 200 ml, a water jacket to maintain a constant temperature, and a calibrated glass tube with a fixed diameter and length. The test sample is heated to a specified temperature and poured into the container. A specified volume of the sample is then allowed to flow out of the container through the calibrated tube. The time taken for the sample to flow through the tube is measured, and the viscosity of the sample is calculated based on this time and the calibration of the tube.

The Engler viscosity value is reported as the number of times that the sample would flow through the calibrated tube in the same time that a fixed volume of water would flow through the same tube at the same temperature. The Engler viscosity is dimensionless, and its value varies depending on the type of petroleum product being tested.

Although the Engler viscometer is widely used for testing petroleum products, it has some limitations. The test results may be affected by factors such as the sample temperature, the calibration of the glass tube, and the presence of impurities in the sample. In addition, the Engler viscometer is not suitable for measuring the viscosity of non-petroleum liquids or liquids with very low viscosities.

Zahn 5 is a type of viscosity cup that is used for measuring the viscosity of paints, lacquers, and other coatings. It is a small, cylindrical cup with a tiny orifice at the bottom, which is dipped into the liquid to be tested. The cup is then lifted out of the liquid, and the time taken for the liquid to flow out of the cup through the orifice is measured.

The Zahn 5 cup has a fixed orifice diameter of 0.9 mm and is designed to measure the viscosity of liquids with a range of 15 to 120 centistokes (cSt). The time taken for the liquid to flow through the cup is converted to viscosity using a standard conversion chart or formula.

Zahn 5 viscosity cups are easy to use and portable, making them popular for on-site testing. However, they are less precise than other types of viscometers, and the results may be affected by factors such as temperature, air pressure, and the level of the liquid in the cup. To obtain more accurate results, multiple tests are often performed and the average value is calculated.

Zahn 3 is a type of viscosity cup that is used for measuring the viscosity of liquids, especially those with low to medium viscosity, such as inks, oils, and solvents. It is a small, cylindrical cup with a tiny orifice at the bottom, which is dipped into the liquid to be tested. The cup is then lifted out of the liquid, and the time taken for the liquid to flow out of the cup through the orifice is measured.

The Zahn 3 cup has a fixed orifice diameter of 3.05 mm and is designed to measure the viscosity of liquids with a range of 28 to 231 centistokes (cSt). The time taken for the liquid to flow through the cup is converted to viscosity using a standard conversion chart or formula.

Zahn 3 viscosity cups are easy to use and portable, making them popular for on-site testing. However, they are less precise than other types of viscometers, and the results may be affected by factors such as temperature, air pressure, and the level of the liquid in the cup. To obtain more accurate results, multiple tests are often performed and the average value is calculated.

Ford 4 is a type of viscosity cup that is used for measuring the viscosity of paints, lacquers, and other coatings. It is a small, cylindrical cup with a tiny orifice at the bottom, which is dipped into the liquid to be tested. The cup is then lifted out of the liquid, and the time taken for the liquid to flow out of the cup through the orifice is measured.

The Ford 4 cup has a fixed orifice diameter of 4 mm and is designed to measure the viscosity of liquids with a range of 30 to 120 centistokes (cSt). The time taken for the liquid to flow through the cup is converted to viscosity using a standard conversion chart or formula.

Ford 4 viscosity cups are easy to use and portable, making them popular for on-site testing. However, they are less precise than other types of viscometers, and the results may be affected by factors such as temperature, air pressure, and the level of the liquid in the cup. To obtain more accurate results, multiple tests are often performed and the average value is calculated.