Correcting Specific Gravity to Standard Temp?

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Jun 19, 2006 | 11:49 AM

horsepuller

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Correcting Specific Gravity to Standard Temp?

I need to correct the specific gravity of a fluid to standard temperature, 60° F.

The specific gravity of the fluid is .994 and the temperature is 75° F.

Can anyone provide a link to a conversion table or have a book you can scan a page out of?

Scott

Jun 19, 2006 | 12:11 PM

bigdaddyII

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What type of fluid are you working with? Here is a basic table, hope it helps. It is the best I can do without more information. Hope it helps.

Jun 19, 2006 | 12:22 PM

seventyseven250

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Different fluids expand and contract different amounts with temperature. So there isn't an accurate conversion factor that can be used for all fluids.

What fluid do you need? I have some engineering data books around the office that would have some common industrial ones listed.
or just google the name of the fluid and "thermal expansion" and you may get lucky.

Jun 19, 2006 | 12:33 PM

sigma

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The formula is:

Correction (to add on to raw hydrometer reading) = 0.00000359 temp^2 + 0.00006971temp - 0.00151687

In temperatures between 0oC and 40oC you can approximate the SG by adding 0.001 for every 5 degrees the sample is above the hydrometer's calibrated temperature (normally 60F) and subtracting 0.001 for every 5 degrees the sample is below the hydrometer's calibrated temperature

Jun 19, 2006 | 01:39 PM

horsepuller

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Thanks for the quick response, guys!

The fluid is aqua ammonia. Sorry I didn't mention that. I didn't think it would matter because the temp conversion for API gravity uses the same conversion table for all petroleum fluids.

Quote:

Originally Posted by sigma

In temperatures between 0oC and 40oC you can approximate the SG by adding 0.001 for every 5 degrees the sample is above the hydrometer's calibrated temperature (normally 60F) and subtracting 0.001 for every 5 degrees the sample is below the hydrometer's calibrated temperature

So in the example I gave above, since the temp is 75° F, the corrected gravity would be 0.003+0.994=0.997?

Quote:

Originally Posted by sigma

Correction (to add on to raw hydrometer reading) = 0.00000359 temp^2 + 0.00006971temp - 0.00151687

I would like to be able to use that, but can you give the math for dummies translation of that? I'm having a hard time filling in the blanks.

0.00000359 (does what to) 75°F to the power of 2 plus 0.00006971 (does what to) 75°F, minus 0.00151687 plus 0.994 equals...

Thanks!

Jun 19, 2006 | 08:15 PM

Flash

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If you need any engineering values or processes, go here:

http://www.engineersedge.com/Design_Data.shtml

They have just about all of the bases covered.

Jun 20, 2006 | 08:21 AM

seventyseven250

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The reason I asked about they type of fluid is that it will make a difference. Even between different "petroleum fluids" they will each have different correlations. Also, Aqueous ammonnia isn't a petroleum fluid.

The way to get the exact answer would be to use the appropriate equation of state, but that's probably overkill.

You'll get 90% of the way there using the correlations that have been given above. Depending on what you are trying to do here, that's probably good enough.