Viscosity Chart for SAE 30 Oil 4

[KimWonGun]

I am seeking a good estimate of the viscosities for straight SAE 30 oil at temperatures slightly below 32 F. The only reference material I have comes from a 1940s engineering handbook, which I used to estimate a best-fit curve. However, I wish to check my result against another source if possible.

I am using this oil as a baseline for a test rig and need to sample different oils at approximately the same low-temperature viscosity.

Can anyone help?

 

[MiketheEngineer]

Have you googled SAE 30 - I got over 2,000,000 hits. I am sure the info is in there somewhere

 

[jmw]

Go to

http://viscoanalyser.com/page8.html

and download the RMI ASTM D341 rev 01.xls spreadsheet.
If you have the actual viscosity at two temperatures, then you can calculate the viscosity at any other temperature (within reason).
Plugging in the oils nominal viscosities will get you some way but because of the tolerances, you will find some errors.
This spreadsheet is based on the ASTM D341 equation which compares with Castrol's Blend 42 calculations (for lubricants) very well.

JMW

http://www.ViscoAnalyser.com

 

[Latexman]

My Crane Technical Paper 410 has a graph of Viscosity of Water and Liquid Petroleum Products on page A-3. Data was extracted from the Oil and Gas Journal. I've seen this graph in several other references too. It has a curve for "SAE 30 Lube (100 V.I.)" that ends at 90 F but is extrapolated (dashed line) to 40 F. At 40 F it is about 1300 cP. If I extrapolate this curve further to 30 F, it is about 2500 cP.

Good luck,
Latexman

 

[ione]

I suggest you to download the spreadsheet Lubricant properties calculator.xls from the link below

http://www.xlrotor.com/resources/files.shtml

Many oils (SAE 30 included of course) properties vs temperature

 

[jmw]

Well Ione, I like the spreadsheet but why the funny density units?

Also,there is a huge difference between the viscosity calculations based on Va and Vb compared to ASTM D341.
at 60[°]F this gives 283cSt and ASTM D341, (using the 120[°]F and 220[°]F viscosities from the lubricants spreadsheet as the two values in the ASTM D341 spreadsheet i.e. at these temperatures they agree) 432.73cst.
That's a big error, all things considered.
at 120 we get 79.25cst and 62.78cst....
Now that's a puzzle so I'd suggest caution using ASTM D341 until this can be clarified.
Its not like an easy correction for density either.
The calculation for density is available on the viscoanalyser.com web site with the option for lubricant as a commodity.... I think I am going to cross compare the densities (if I can get past snails - anyone got a conversion between snails and kg/m3 handy?)

JMW

http://www.ViscoAnalyser.com

 

[jmw]

I haven't found a conversion for the density units yet but if I take 817kg/m³(i.e. numerically equivalent to 8.17 x 10^-5sn/in³ at 60[°]F (817.35kg/m³at 15[°]C)I get 756.6kg/m³ at 230[°]F while the number in the Xrotor spreadsheet is 7.62 x 10^-5....?

So, can anyone explain why the temperature density and temperature viscosity relationships for lubricants should be different to other hydrocarbons? I'll know more if I can convert those weird density units... but I can't think why using numerical equivalents in kg/m³ should give different answers of such significance at 230[°]F....
I an understand a significant viscosity at at much lower temperatures than the reference temperatures in an ASTM D341 equation, but not the significant errors between the temperatures...this would suppose than not only has the slope been adjusted but the entire temperature viscosity relationship.... and that means I have to explain why the Castrol Blend 42 equation for lubricants tested out against ASTM D341 in process measurements.... unless (and it's a long time ago) we only compared at common temperatures and not calculated values.... I need to delve into my records for that report.

So I'll have to do some research on this and for the moment withdraw the comment that ASTM D341workss for lubricants.

JMW

http://www.ViscoAnalyser.com

 

[jmw]

Well, I've been looking around (Bob's the Oil Guy etc.) and find this link:

http://www.tribology-abc.com/abc/viscosity.htm

This site seems to think ASTM D341 does describe the viscosity of lubricants..... I think it is time to approach Xrotor for a comment...

JMW

http://www.ViscoAnalyser.com

 

[jmw]

Boy, what a can of worms!
ASTM D341 is the Ubbelohde Walther Equation.
It was adopted in Gemrnay and opposed by Prof Riemschneider who points to the limitation of this "empirically" derived equation and also points out the limitations of the various (Lots of them) different Viscosity Index methods (leaving me wondering which one is used).
There are other papers which point to the limitations of ASTM D341....
Not sure yet where this is going....

JMW

http://www.ViscoAnalyser.com

 

[ione]

The unit used for density is definitely odd (I’ve not built the spreadsheet)

The conversion should be

sn/inch^3 = lbf*s^2/inch^4 = 4.44822 kg*m/s^2 *s^2/(4.1623*10^(-7) m^4) = 10686927.9 kg/m^3

kinematic viscosity values seem to be all right to me.

 

[jmw]

Thanks ione, I've posted a query in the tribology forum and been doing some research (googling).
There is a lot of weight behind the ASTM D341 equation. and there is a very significant difference between the ASTM D341 calculations (cross checked with a number of other ASTM calculators on the internet) and the xlrotor calculation; more than simply the difference between different models of the same behaviour.
I have queried xlrotor and look forward to their reply.

Regarding density, thanks for the conversion, I'll run some exact value checks but I would favour the industry standard in this case, if there remains an apparent error, which is the calculations defined in the Manual of Petroleum Measurement Standards.

JMW

http://www.ViscoAnalyser.com

 

[jmw]

I have received a reply from Brian Murphy which is satisfactory to me.
He says:

The formula used to compute viscosity can be seen in the cells of the
viscosity column. I believe some refer to this formula as "Reynolds
viscosity equation" and it is often used in the analysis of journal bearings
because it is computationally convenient. It is of course based on giving
it two temperature/visc points as a baseline. It is entirely adequate for
the temperature ranges that bearing lubricants typically operate in.
Adequate results for Reynolds formulation can be obtained if the known
temperature/viscosity points are
chosen at the oil inlet temperature and below the maximum film temperature

My emphasis.... this is a very important caveat and is equally applicable to the ASTM D341 equation - under some conditions it is an excellent method but under others it can act like a random number generator.
The big risk is deviating to far away from the reference temperatures used to establish the equation (usually the viscosity at 4o[°]C and at 100[°]C) and in extrapolating outside these values, especially when extrapolating to significantly lower temperatures.
Also, one should note that the values used in the xlrotor equation are the nominal values for the lubricants. Manufacturers can supply lubricants with significant tolerances (e.g. 10%) and these will certainly turn any calculations to mush.


JMW

http://www.ViscoAnalyser.com

 

[jmw]

I have a further comment from Brian:

The Reynolds formula is fine for its intended use, but using it outside that
temperature range one should not count on it without prior validation.

Lubricants used in industrial bearings typically do have their viscosity
drop significantly as they get hotter. The Reynolds formula is best used
between two known v/T points, and it assumes a linear variation in the
log(v) versus T. This assumption may or may not work well for other types
of fluids

I think the point here, relative to KimWonGung's original enquiry, is that pretty well any equation where the reference viscosities are at temperatures much above the target temperature at which you wish to know the viscosity, will give out unreliable results.
Thus, if you wish to use the Reynolds or ASTM D341 equations to find the viscosity of an oil at around 32[°]F(?) then you need to c calibrate the equations with viscosities appropriate to that temperature which the standard viscosities at 40[°]C and 100[°]C are not.
These should also be values taken from the oil to be tested rather than the typical values given for the oil grade.
When working to higher temperatures the problems are less.

JMW

http://www.ViscoAnalyser.com

 

[SNORGY]

I think you could probably get a reasonably reliable viscosity correction with temperature for SAE-30 oil with the De Guzman-Andrade correlation:

m = A x e^(B/T)

Take two known points, take logs on both sides of the equation and solve for constants A and B. After determining A and B, you can just enter the absolute temperature to get the viscosity.

This seems to work well for Newtonian fluids. At least, it has for me in the past. I haven't used it and verified it for a while, but I recall getting good results with it.

Regards,

SNORGY.

 

[ione]

Have found a couple of papers discussing temperature dependence of SAE 30 viscosity

http://rothfus.cheme.cmu.edu/tlab/visc/projects/t1_s86/t1_s86.pdf

http://rothfus.cheme.cmu.edu/tlab/visc/projects/t6_s87/t6_s87.pdf