×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

viscosity

viscosity

viscosity

(OP)
SSU is a unit of viscosity. I believe it is unit for kinematic viscosity (centistokes) and not dynamic viscosity (centiPoise). The relationship between centistokes and SSU is something like logarithmic or exponential - I dont know, but that is what I am trying to find! Where can I find an equation relating the two? Does this equation change depending on the fluid and fluid properties (pressure, temperature etc.)

RE: viscosity

Common used units for viscosity are

CentiPoises (cp) = CentiStokes (cSt) x Density
SSU(Note1) = Centistokes (cSt) * 4.55
Degree Engler(Note1) * 7.45 = Centistokes (cSt)
Seconds Redwood(Note1) - 4.05 = Centistokes (cSt)

Note1 - centistokes greater than 50

There are two related measures of fluid viscosity - known as dynamic (or absolute) and kinematic viscosity.


I found this via google at:

http://www.engineeringtoolbox.com/dynamic-absolute-kinematic-viscosity-d_412.html

"Do not worry about your problems with mathematics, I assure you mine are far greater."   
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

RE: viscosity


From the brochure DG-400 by EXXON we can read:
"Many petroleum products are graded according to the ISO Viscosity Classification System, approved by the International Standards Organization (ISO). Each ISO viscosity grade number corresponds to the mid-point of a viscosity range expressed in centistokes (cSt) @ 40ºC. For example, a lubricant with an ISO grade of 32 has a viscosity within the range of 28.8-35.2, the mid-point of which is 32.

Rule-of-Thumb: the comparable ISO grade of a given product whose viscosity in SUS at 100ºF is known can be determined by using the following conversion formula:
SUS @100ºF + 5 = cSt @40ºC. "

RE: viscosity


Centistokes (Z), are estimated from SSU (S) as follows:

for S < 100:  Z = 0.226×S - 195÷S
for S > 100:  Z = 0.220×S - 135÷S

A similar thread in the past dealt with this subject, but I'm too lazy to look for it.

RE: viscosity

(OP)
25362:

For S values less than around 30 SSU, the value of Z calculated per your formula is -ve! Is that correct?

RE: viscosity

It was my understanding (I could be wrong) that Saybolt was one of the "obsolete" units though it wouldn't be surprising for it still to be in use along with Engler, Redwood and a few others.
Visit www.viscosity.com where Norcross maintains a nice set of conversions.
Go here for a converter: http://www.softslide.com/volumes/v3/t3/p1/
More tables here:
http://www.coleparmer.com/techinfo/techinfo.asp?openlist=II&htmlfile=ConversionViscosity.htm&Title=Viscosity+Conversion+Factors
not forgeting:
http://www.engineeringtoolbox.com/dynamic-absolute-kinematic-viscosity-d_412.html

JMW
www.ViscoAnalyser.com

RE: viscosity

There is an excellent free downloadable conversion program, Unconeer, at this website.

The author is a regular participant of Eng-Tips.

www.katmarsoftware.com

RE: viscosity

(OP)
There has to be some published peer-reviewed sources which describe this conversion. I am looking for those sources. Do not mean to imply that these website are no good, but they can change in the future!

RE: viscosity



To picasa, according to the approximate formulas I quoted from old argentine YPF tables, definitely yes. Tabulated values I have for 210oF are:

Z       S      Z by formula  % deviation

2.0    32.8       1.47          -26.5
2.5    34.6       2.18          -12.8
3.0    36.3       2.83          - 2.3
3.5    37.9       3.42          - 2.3
4.0    39.4       3.89          - 2.8
4.5    41.0       4.5             zero
5.0    42.6       5.05            1.0
10     59.2      10.08            0.8
20     98.2      20.2             1.0
50    233.0      51.8             3.6
70    325.7      73.0             4.3
90    418.7      94.1             4.6
100   465.2     104.7             4.7

Which shows the formulas are a gross approximation, and a graph would better serve for extrapolation at the lower end.
Also, please note that temperatures slightly affect the conversion.

Beside all that, the conversion factor above 70 cS is said to be constant, 4.62 for 100oF, and 4.652 for 210oF.

RE: viscosity

Actually, there is an ASTM standard somewhere that will be what you want: WK5950 Standard Practice for Conversion of Kinematic Viscosity to Saybolt Universal Viscosity or to Saybolt Furol Viscosity

JMW
www.ViscoAnalyser.com

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources