Re: [mh] Monitoring liquid propane level & useage

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Thanks for the replies. I am not looking for anything as complicated as 
weighing the tank. The tank I am monitoring is 500 gal & has a percent 
gauge on it which I assume operates off of pressure. I realize it 
flucuates with temp, but that is all I really need, just something so I 
have an idea if I need to order more without going outside when it is 
-20 F or colder!! I would like to get a fairly accurate flow rate 
though. I will try googling. Thanks

sean mathews wrote:
>  Just how accurate do we need to be : c ) This may not be 100% correct
> but the concept should work to get a fairly accurate reading, and its
> less scary than putting a tank of flammable liquid on some moving
> platform as I am sure that violates some safety/sanity code.  
>
>  To calculate the weight of propane in your tank based upon ambient
> temperature and the liquid level in a tank.
>
>  Adjustments to this can be made based upon ambient temperatures by
> adjusting the specific gravity data ( formula below ).
>
>  Using warm water or something to tap with locate the liquid / vapor
> line and mark with chalk ( automate with a string of 1wire
> thermisters? ). 
>
>  Below mark is LP liquid. LP liquid specific gravity is 0.51 ( to
> water ) Above mark is LP Vapor beginning to liquefy or settle. LP vapor
> specific gravity is 1.5219 ( to air )
>
>  If your tank were a perfect cylinder you can then determine the volume.
>
>  Lets say your tank is 2 feet in diameter and 13 inches tall ( π  • r² )
> would be 452.38 cubic inches for every 1 inch of height in the tank.
>
>   WEIGHT = (SG OF LIQUID) * (WATER WEIGHT PER VOLUME MEASURE) * (VOLUME)
>   133.34 oz  =  .51 * 0.5779259 * 452.38896 (1 inch below the line)
>    8.3125lb @60 degrees and @10 degrees it will be 11.42 lb's
>   WEIGHT = (SG OF GAS)    * (AIR WEIGHT PER VOLUME MEASURE)   * (VOLUME)
>   68.82 oz   = 1.5219 * 0.00833 * 5428.66752 12 inches above the line
>
> Total weight @ 60 degrees is 12 lb or 202 oz
>
> Facts:
>
> Water is 0.5779259259259259259 oz per cubic inch.
> Air is 0.008333333333333333333 oz per cubic inch.
>
> Formula:
>
> Specific gravity correction formula to compensate for temperature.
>  correction = 1.313454 - 0.132674*T + 0.002057793*T*T -
> 0.000002627634*T*T*T
>  SG_corrected = SG + correction
>
>  Does this work for LP as well as water or was this based only upon
> water? Need to see the book "Handbook of Chemistry and Physics (CRC)"
> Anyone have it? 
>
>
> References:
>
> http://www.npga.org/i4a/pages/index.cfm?pageid=633
> http://www.gordonengland.co.uk/conversion/density.htm
> http://www.primetab.com/formulas.html
> http://brewery.org/library/HydromCorr0992.html
>
>
> Regards 
>  Sean Mathews
>
>
> On Wed, 2009-04-22 at 10:59 -0600, Randy Ridley wrote:
>   
>> LP has a tendency to change volume with temperature. The only reliable
>> way to determine tank level is with a weight sensor on the tank itself. 
>> When I had a 1000 gal tank, I used a truck spring with a linear
>> potentiometer. It had horrible reliability. If I were to do it again, I
>> think I would use a strain gauge on the truck spring.
>>
>> Randy
>>
>> On Wed, 2009-04-22 at 08:16 -0700, Sean Mathews wrote:
>>     
>>> Hay Rohn.
>>>
>>>  I am sure they make a flow meter for this. Just google "flow meter LP"
>>>
>>> http://www.sierrainstruments.com/products/pdf/boiler_trak.pdf
>>>
>>>  I expect that most you will find though will cost a pretty penny. If
>>> you do find any inexpensive ones let us know.
>>>
>>>  The level is trickier. I am sure it could be done with an array of
>>> thermisters to detect the temperature difference of the metal of the
>>> tank where the level of the liquid is.
>>>
>>> Re
>>> Sean M
>>>
>>>
>>>       
>>>> -----Original Message-----
>>>> From: Rohn Shearer [mailto:ro...@sh...]
>>>> Sent: Wednesday, April 22, 2009 4:38 AM
>>>> To: mis...@li...
>>>> Subject: [mh] Monitoring liquid propane level & useage
>>>>
>>>>
>>>> Is there any way to monitor the tank level or usage of LP? Thanks
>>>>
>>>>
>>>>         
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>
>
> ------------------------------------------------------------------------------
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> 300 plus technical and hands-on sessions. Register today. 
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