Why do dimensions of 250 gallon propane tank calculate to more gallons?

[Gasifier]

Using a tank volume calculator for gallons, (www.greertank.com/tankcalc.htm), the dimension for a 250 gallon propane tank calculates to more than 250 gallons. Why is this. My guess whould be the tank holds 250 gallons of liquid propane and there is more room for the gas portion? I don't know. If I buy a 250 gallon propane tank for storage is it going to hold more than that in hot water for me? Hopefully so. I know, shut up and buy the tank already. Right? Can you fill me in. Again, novice at work here. But looking to learn something new everyday.

 

[jimbom]

How did you handle the thickness of the shell and the rounded ends of the tank?

 

[Gasifier]

I didn't. I figured the thickness of the shell must only be 3/8" at the most. The rounded ends would only add more volume. I must be missing something here.

 

[woodsmaster]

you must not be subtracting for the dome ends. I figured A 31" diam. 94 length tank subtracted 9" off each end to compensate for the dome and got 248. I dont think you will fit any more than 250 gal. in a 250 gallon tank. Propane is also measured in pounds.

 

[ewdudley]

Using a tank volume calculator for gallons, (www.greertank.com/tankcalc.htm), the dimension for a 250 gallon propane tank calculates to more than 250 gallons. Why is this. My guess whould be the tank holds 250 gallons of liquid propane and there is more room for the gas portion? I don't know. If I buy a 250 gallon propane tank for storage is it going to hold more than that in hot water for me? Hopefully so. I know, shut up and buy the tank already. Right? Can you fill me in. Again, novice at work here. But looking to learn something new everyday.

Assuming wall thickness of 5 mm / 0.200 inch and perfect hemisphere on each end, using dimensions from

http://www.missiongas.com/lpgastankdimensions.htm

You have: in^3*(((86.5-31.5)*((31.5-0.4)/2.0)^2*pi)+((4.0/3.0)*pi*((31.5-0.4)/2.0)^3))
You want: gallon
   249.04954

You have: in^3*(((94.0-31.0)*((31.0-0.4)/2.0)^2*pi)+((4.0/3.0)*pi*((31.0-0.4)/2.0)^3))
You want: gallon
   265.51362

You have: in^3*(((94.0-30.0)*((30.0-0.4)/2.0)^2*pi)+((4.0/3.0)*pi*((30.0-0.4)/2.0)^3))
You want: gallon
   249.43633

You have: in^3*(((92.0-30.0)*((30.0-0.4)/2.0)^2*pi)+((4.0/3.0)*pi*((30.0-0.4)/2.0)^3))
You want: gallon
   243.47845

But the ends are flatter than a hemisphere, so these numbers might be a little low.

--ewd

 

[Willman]

Propane tanks aren't overfilled. If they are when the sun hits em they flare off the excess pressure. I witnessed this once on a refill at my house.
Will