Generalized products density correction algorythms?? 1

[antoil]

Hi!!

I am looking for an algorythm which corrects the density of petroleum products from physical temperature to 15oC.

I have heard that such thing is written in ASTM petroleum measurement tables volume X which I do not have.

I want to automate a process by entering in an excel file the volume and density of petroleum,without looking each time to the correction tables (ASTM tables53b-54b) in order to calculate the real volume in 15oC??

Any help would be appreciated!!

Thank you!!

 

[jmw]

Incidentally, density at 15degC is one of the calculations necessary in fuel oil blending so you can also ask the marine fuel oil companies for copies of their free calculators. e.g. Shell Marine Fuels, Exxon Mobil Marine Fuels. You can download a calculator from

http://www.steamesteen.com

which i think also does this.

 

[25362]

A short note: knowledge of liquid density often in combination with other properties is also used as a guide for chemical composition to characterize a fraction or a mixture of fractions.

In general, paraffinic hydrocarbons have comparatively low densities, naphthenic and olefinic hydrocarbons intermediate densities, and aromatic hydrocarbons comparatively high densities.

Pure hydrocarbons happen to also have differing coefficients of cubic thermal expansion at the same temperature.
For example, at 25 deg C: benzene, 1.14; paraxylene, 1.0; pentane, 1.64; hexane, 1.41; cyclohexane, 1.15; heptane, 1.26; octane, 1.16; nonane, 1.08 x 10[sup]-3[/sup]/[sup]o[/sup]C.
For the paraffins it continues in dropping down with increasing molecular masses, as follows: C[sub]10[/sub], 1.02; C[sub]11[/sub], 0.97; C[sub]12[/sub], 0.93; C[sub]13[/sub], 0.90; C[sub]14[/sub], 0.87. Compare with water: 0.256 x 10[sup]-3[/sup]/[sup]o[/sup]C.

The coefficient increases with temperature in a different manner, for example, toluene at 20[sup]o[/sup]C, 1.05, and at 50[sup]o[/sup]C, 1.13x10[sup]-3[/sup]/[sup]o[/sup]C; hexane at 25[sup]o[/sup]C, 1.41, whilst at 45[sup]o[/sup]C its coefficient rises to 1.52x10[sup]-3[/sup]/[sup]o[/sup]C.

For these light hydrocarbons as well as for mixtures under pressure of propane and butane, see PERRY VI Chapter 3.

 

[jmw]

25362, good point.
There is also a factor called the viscosity gravity constant (VGC) that will help identify if a hydrocarbon is parrafinic or kerosene based (as i recall).
See ASTM D2501-91(2000) where there is also an equation for this.

 

[antoil]

Thanks jmw!!
This file helped allot!!

Right now I've managed to combine the use of table 53B and 54B in an excel ,so when entering:

-real volume & temperature of fluid in tank
-observed density and observed temperature in hydrometer cylinder

I have the volume in 15 degrees C.

The only problem is when dealing with floating roofs , where I need to exclude from the total volume, the volume that occupies the roof;
which comes by dividing (the actual weight of the roof) by (the corrected density to the tank temperature).

How should I convert the observed density in the hydrometer , to density of fluid in the tank ????
Thank you all again for your precious time!!!

 

[jmw]

Ah! now there is a question. A lot depends on your hydrometer (they come in all sorts and standards) and on someone who understands this bit better than i do contributing a comment!

 

[25362]

Densities at various temperatures can be interconverted by the use of relevant tables. Besides, the hydrometer could be made to measure the density at the tank's temperature.

Actual volumes should consider the tank volume changes in L/mm at temperatures differing from 15 deg C, a temperature normally used for reference in calibration.

When dealing with heavy fuels, sometimes even with crude oils, sampling for density measurements should be "representative" of the tank contents, otherwise errors due to "layering" may occur. Often, samples are taken at different (top, middle, bottom) elevations to that end.

 

[Moggc1]

Would any of you be able to point me in the direction of an excel version of table 54b???

 

[athomas236]

I have used the calculator in

http://www.steamesteen.com/

to plot graphs of density vs temperature for densities at 15C from 900 to 1100kg/m^3 and found that basically they are straight lines but at different slopes.

I then fitted a polynomial to the slopes and now have a method of calculating density at any temperature for temps upto 400C and densities at 15C ranging from 900 to 1100kg/m^3, which seems good enough for fuel oils.

athomas236

 

[jmw]

You could download this spreadsheet I created which is based on the API equation and uses the default values from it but take care, I got lazy and didn't include the pressure corrections.

http://www.viscoanalyser.com/downloads.html

JMW

http://www.viscoanalyser.com

Eng-Tips: Pro bono publico, by engineers, for engineers.

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Moggc1]

The Link

http://www.steamesteen.com/

doesnt apear to work for me? and the table on

http://www.viscoanalyser.com/downloads.html

seems to be 53b?
but thanks for your help anyway guys...

I am after Table 54B Genral products correction of volume to 15'C against density at 15'C.
I wish to convert measured litres in our storage tanks to standard (at 15'C) liters.