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  #1  
Old 07-02-2009, 05:45 AM
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Default Diesel oil over temperature

How do I go about compensating diesel fuel flow over temperature? Does the volume / flow change significantly over say 50C or is the change minimal? What figures do I need to do the calculation and can anyone suggest where these might be available? I am looking at MDO mainly, but am also interested in whatever grade is used in marine gas turbines - we have been quoted an SG of 0.922 for these if that helps!
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  #2  
Old 07-02-2009, 05:54 AM
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Default Re: Diesel oil over temperature

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Originally Posted by Unregistered View Post
How do I go about compensating diesel fuel flow over temperature? Does the volume / flow change significantly over say 50C or is the change minimal? What figures do I need to do the calculation and can anyone suggest where these might be available? I am looking at MDO mainly, but am also interested in whatever grade is used in marine gas turbines - we have been quoted an SG of 0.922 for these if that helps!
What kind of accuracy? It will change a few percent.

The API publishes (and sells) tables of volumetric factors for all kinds of petroleum products. Because they sell them, they jealously guard the numbers and it is hard to find a reliable number on the Internet.

The tables are based on SG at standard temperature, 60F,
and I don't even have approximate data for your SG. Sorry.
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Old 07-02-2009, 05:59 AM
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Default Re: Diesel oil over temperature

We are looking at preferably 1% accuracy over the entire flow range, 2% maximum. Any idea where we can get these numbers from in the UK? (Are the standards the same world-wide? I'd assume they'd be at least similar otherwise getting the right grade would be tricky)
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  #4  
Old 07-02-2009, 06:06 AM
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Default Re: Diesel oil over temperature

I believe the API tables are sold (and are applicable) worldwide. I don't have access to a set. I think they are laid out by basic fuel type, then specific gravity. I don't know if there are comparable ISO tables.

For your target accuracy, you should work from a recognized standard and not from approximate tempcos you may find on the Internet.

Edit: While I caution you not to rely on it, I found a number on the Internet; use it only for general scale of your problem. The coefficient of thermal expansion for diesel (probably automotive diesel, SG around 0.85, but not specified) of 0.00046/F. (x1.8 for C)

For a 50 C change from 15 C (roughly 60 F), the change is 0.0414, so 1 L at 15 C becomes 1.0414 L at at 65 C. Your heavier diesel should be a little less change.

Last edited by JohnS; 07-02-2009 at 06:14 AM.
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Old 07-02-2009, 06:13 AM
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Default Re: Diesel oil over temperature

Thanks a lot for that - will look these up and see where we can get hold of a set.
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Old 07-02-2009, 09:16 AM
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Default Re: Diesel oil over temperature

Check this link:
http://www.oiml.org/publications/R/R063-e94.pdf

From pages 3-5, it looks like API, ASTM, IP and ISO all publish the same tables, and they worked together on methodology. I think any would meet your need.

There is also software based on the tables.
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  #7  
Old 07-05-2009, 03:09 PM
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Default Re: Diesel oil over temperature

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Originally Posted by Unregistered View Post
How do I go about compensating diesel fuel flow over temperature? Does the volume / flow change significantly over say 50C or is the change minimal? What figures do I need to do the calculation and can anyone suggest where these might be available? I am looking at MDO mainly, but am also interested in whatever grade is used in marine gas turbines - we have been quoted an SG of 0.922 for these if that helps!
I think I found a decent FREE spreadsheet on the web (I'm still testing it).

Check this download page and the spreadsheet:
http://www.viscoanalyser.com/page8.html
http://www.viscoanalyser.com/Density%2012Mb.xls

I have tested it for automotive gasoline and diesel (730 kg/m and 840 kg/m) against Volume Correction Tables published by Measurement Canada. It works very well for those. However, instructions are pretty minimal.

If your SG = 0.922, it is probably specified at 60 F, and water density is 0.999 kg/L there, so true density is 0.921 kg/L or 921 kg/m at 60 F.

The spreadsheet uses standard temperature of 15 C (59 F), so using above as observed, density at standard is 921.38 kg/m. Then going forward in 10 increments:
15 C, 921.38 kg/m
25 C, 914.47 kg/m
35 C, 907.54 kg/m
45 C, 900.57 kg/m
55 C, 893.58 kg/m
65 C, 886.57 kg/m

Edit 2009-07-07: There is a slight error in the VCF factors calculated by this spreadsheet. They have deleted the version above, and replaced it by a new version:
http://www.viscoanalyser.com/Density%2012MD.xls
If you downloaded prior version, I suggest you delete it and download the new; it corrects the error. Some more discussion in posts below.

JohnS

Last edited by JohnS; 07-07-2009 at 06:38 AM.
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  #8  
Old 07-06-2009, 04:12 AM
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Default Re: Diesel oil over temperature

I must admit I can't fathom out how that spreadsheet works! We have a S.G. for the MDO of 0.82 to 0.86 but I can't work out where to put this in the spreadsheet or what else I need to do to get results from it!
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  #9  
Old 07-06-2009, 08:16 AM
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Default Re: Diesel oil over temperature

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I must admit I can't fathom out how that spreadsheet works! We have a S.G. for the MDO of 0.82 to 0.86 but I can't work out where to put this in the spreadsheet or what else I need to do to get results from it!

It's not obvious, is it? By the way, if you register, your threads will post immediately rather than after a moderator approves them. A brief tutorial:

Near top left are some grey selection boxes. Select:
#1: Select Auto(matic). Crudes and refined products use different formulas to calculate tempco from density; for refined products, different formulas are used in different density ranges. This setting does it correctly and automatically from density for refined products. Your other choice would be "Fuel Oil".

#2: Pick the choice to calculate observed density, no hydrometer correction

#3: Pick C

Scroll further down to user data. I'll explain why in a moment but use a density of 839.39 kg/m, and copy it into several boxes down the column for true density at 15 C. You must use units of kg/m. Most of us are more used to thinking kg/L, and I made that error initially; it WON'T work.


A couple of columns to right, enter desired temperatures at which you want density. Make one 15.56 C, and any others, say 25, 35, 45, 55, 65. Calculated densities at those temperatures will appear.
DON'T trust the Volume Correction Factor (VCF) column; there seems to be a problem. Calculate your own VCF from the calculated density divided by standard density.

Where did 839.39 come from; I didn't pull it out of my a**. Results will differ for different densities so I started with the middle of your SG range, 0.84. This is ratio of density to that of water, both at 60 F. AT 60 F density of water is 0.999 kg/L or 999 kg/m, so your SG corresponds to 839 kg/m at 60 F.

Unfortunately, the program needs density at 15 C (59 F); it corresponds to Table 54 of the Petroleum tables. I changed box 2 to calculate standard from observed and determined 839 kg/m at 60 F is 839.39 at 15 C (59 F). I suggested 15.56 C as one of your temperatures; you will see that you get 839 kg/m back.

Hope this helps; write back if you still have problems. If you wish, you can follow the example and work out for the endpoints of your SG range. By the way, Measurement Canada has on their website a table of Volume Correction Factors for diesel of density 840 kg/m. If you don't want to screw around with the spreadsheet, it would probably be close enough for your needs. I ran that value and compared to table as a check on the spreadsheet. One limit, it only goes to 30 C.
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  #10  
Old 07-07-2009, 12:05 AM
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Default Re: Diesel oil over temperature

Still having problems but I suspect it's my computer rather than anything else - I get an error message when I first load the spreadsheet telling me some data was lost. I get this whether I open it direct from their server or if I save it to my computer first. Then the grey button don't do anything - I did suspect at first I needed to click these to make a selection, but a single click does nothing and a double click returns the message that the sheet is locked... My suspicions are that it is in a newer version of Excel than I have access to and presumably any Excel viewers wouldn't let me input values so are no use either..

Anyway, those tables on the Measurement Canada website look quite useful - we do need to compensate up to 70C but I *think* that the responses are fairly linear so I should just be able to extrapolate upwards. The error requirement on this job is 2% so that should be fine.

Thanks for your efforts - much appreciated.
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