Kinamatic Viscosity !


Thread Starter

Manohar Joshi

One of the Automation projects we have to measure kinematics viscosity.

The kinematics viscosity is arrived by the formula = Absolute viscosity / density. Any body is aware or experience in measuring Kinematics viscosity with following arrangement. Please explain.

I heard that kinematics viscosity can be measured by installing DP transmitter across corilios mass flow meter (for measuring density).

Manohar Joshi
ABB Automation
Bangalore India

Michael Johnson

This may be possible theoretically if the Reynolds number for the type of flow through the mass flow meter is known, then if the flow is laminar, then the pressure drop reading from the DP transmitter and the density reading from the mass flow meter can be used to calculate the velocity through the pipe using the Darcy equation ( with the friction factor = 64/Reynolds number ). Then with the known Reynolds number,
diameter of pipe, measured density and calculated velocity, the viscosity can be calculated. Which will lead immediately to the kinematic viscosity.
If the flow is turbulent, then the friction factor is a little more complex. However, there are plots available that graph friction factor against the Reynolds number and relative roughness of the pipe. Hence, calculations can still be done. There are such things as viscosity meters. This may be a little more easier and more accurate.
If you could consult the Chemical Engineering magazine, in the 'Process Control reprint june 1969' section 12 is an excellent primer on viscosity and consistency.

Has it been updated ? I think so. My son consults regularly on their web site.
The instrument company Fisher & Porter have rotameters designed for measuring viscosty in-line.

Also, consult the ISA directory, via their chapter nearest to you.
See also the Bela Liptak Instrument Bible.
New technologies are being introduced all the time.
Pressure drop measurement across a coriolis mass flowmeter compared to using a process capillary viscometer has the advantages: (1)speed of
response.... it is real time which enables closed loop control (2) at process conditions... of limited application in hydrocarbon processes unless supported by some means of finding the kinematic viscosity at the reference temperature against which quality is determined). is a useful reference site for Brunswick Research Inc. who market viscosity solutions with the MicroMotion Mass flowmeter.

However, new technologies (Vibrational, electromagnetic piston, and ultrasonic; see sites: ; ; ; ; ; ; ; ) offer real time continuous measurement at process conditions. Some measure dynamic viscosity only, some measure density as well so can offer kinematic viscosity (potential with the mass flow meter solution).
These offer closed loop control in simple behavioural applications (controlling the viscosity at process temperature for spraying, coating, dipping atomising etc.) Hydrocarbons viscosity is a product quality measurement i.e. the viscosity required is the viscosity at a one or more reference temperatures e.g. to find molecular weight in polymerisation control as per ASTM D2502 - 02, or BS MA 100 which defines the quality of heavy fuel oils by the viscosity at
100degC. Thus hydrocarbon viscosity measurement depends on either controlling the temperature of the sample stream to be the reference temperature (as does the process capillary, but with consequent long response times) or by calculation.
Precise temperature control is difficult with variable process conditions and calculation requires a method which can use a temperature viscosity relationship (e.g. ASTM D341) and requires an instrument which is sufficiently accurate. Only some of the new technologies have the necessary capabilities but they are beginning to replace the process capillary with significant success using direct (control of temperature) or indirect (calculation) methods. Successful applications include meter correction, fuel oil blending, quench oil control, asphalt blending, crude oil pipe line viscosity control, bitumen blending, polymerisation control etc.
See "Direct Measurement of viscosity at high temperature" by Mark Shelly (Fluor) and J
Watson (Solartron) given at the Texas A&M 2000 instrument symposium and an article in Hydrocarbon Engineering 2000 (January issue).