Need help calculating how much natural gas I have (not that kind of natural gas , I already have a good idea of how much of that I produce).

I have a 500 gallon CNG tank (it might even be LP). How can I calculate how much cubic feet of gas I have?

 

Depends on the pressure... As Natural gas compresses you get more... I do caculations for pipelines and and example (not accurate) for a 2" line at 30 pounds is about the same as a 3/4" at 75 pounds...

If it is a tank for your house it is probably LP. One way to tell is if the tank has one small regulator then it is probably LP.. If it has a HP reg to drop it to 30 pounds or so and then another to drop it to 1/3 pound or so in the house then it may be natural gas.

Natural gas use a guage (careful may be up to 3000 pounds or so).. LP weigh the tank (I know how the heck do you weigh a 500 gallon tank -- I dont know)..

Gerry

 

The tank isn't for residential service. Its for a generator at a remote communication site I maintain. The tank has a guage. The guage reads how much is in the tank as a percentage. The needle will point to 60 and the tank is 60% full. There is a regulator on it (not on the tank but on the service line to the generator) that look like this.

When the truck filled it the meter on the truck read liguid gallons and not pressure. The tank has liquid in it and the generator draws the from the gas layer on top of the liquid in the tank. If I knew how much cubic feet of gas it hold I can calculate how long the tank will last if the generator is run continuosly.

 

Try calling the company that filled it. They should know.

Since you are using vapor, and the tank is holding liquid...you will need some conversion from cu.ft of liquid to cu.ft of vapor for the specific contents of your tank. I'm sure I used to be able to solve such a problem, but the knowledge has been replaced by other, less usefull, things. It may be in some engineering handbook.

 

and it is propane, not natural gass.

 

Definatly propane......

I cant find my books right now...but if you know the pressure in the tank, and the pressure after the "let-down" regulator, then all you need too do is use gas laws, and find a table with the properties of propane.....a refrigerant table would doo nicely!!

 

You also also have some density calcualtions in there as well....

 

This place http://energy.growmark.com/propane/Chapter1.html

says that there is 36.39 cu ft of vapor at 60 deg F per gallon of liquid propane at the same temp.

http://energy.growmark.com/propane/index.html is the home page and has some topics that may be useful for your application. Have a read through it. I will too.

 

Thanks, SIOTWO. That gave me a good estimate of how long the generator will last on 500 gallons of LP. Generator draws 49 cu ft/hr at 1/2 load or 1176 cu ft per day. The 500 gallon tank has 18,000 cu ft in there at full capacity. So the generator will run approx 15 days continuous before the tank needs refilled.

 

my pleasure....you're located in Guam!? Wow.

 

Yep, Coast Guard transferred me here and I brought the truck too. Awesome place, really great if you are into scuba diving.