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Author Topic: Question on my propane tank size and how is propane measured. Gallons or pounds  (Read 9860 times)

jbkoonse

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Tank in my class A is cylindrical and horizontally mounted. About 34" long by 14" wide. Any idea as to capacity? Are they measured in gallons or pounds? ???

DonTom

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Gallons. At least that's how it is sold. Full is at 80% of tank capacity.

-Don-
-Don-   AA6GA

2000 Fleetwood Tioga 24D, 7.4L

SSF, CA    or   Reno, NV

jbkoonse

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Thanks!

Ned

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A 34"x14" cylindrical tank holds about 22.6 gallons, so at 80% full is 18 gallons of propane.  ASME tanks are measured in gallons, bottles are in pounds as they are filled by weight.
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John From Detroit

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Most places I have seen Propane sold they sell by the gallon now days,, you can take a tank that's 1/2 full and they will top it off to 80 percent for you and charge by the gallon.

In the old days (Say 40 years ago) We bought it by the pound when we ran out and the gas man was not due so we had to cart the bottle to the re-fill station and get a refill.

We put the bottle on the scale. They hooked the hose up, balanced the beam,  put the 100 pound weight on the hook and filled till the scale balanced.. At many propane stations you will still see that old beam balance sitting there.  (Usually seriously neglected and weathered)

However that is kind of dangerous,, Because if the bottle still has 20 pounds in it. then adding 100 will overfill it.   So not they fill by the gallon and use the spitter valve to tell when it's full or use the internal auto-cut off.
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Gary RV Roamer

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The legal measurement for a DOT spec tank seems a bit bizarre. DOT bottles are actually measured in their water capacity (WC) in lbs. That's because water is not compressible, whereas propane is, so they use water rather than water as the legal standard. You will see the WC weight and Tare Weight (TW) stamped into the metal on the bottle. TW is the weight of the empty bottle, while WC is the weight of water that would fill the tank. Convert the water weight to gallons by dividing by 8.35. If you want [liquid] propane weight, multiple the gallons by 4.23

LP gas can be sold by weight or liquid volume. When the propane is dispensed, it is in liquid form and so gallons can be measured as it passes through the pump. In the DOT bottle, it will be mostly liquid and some gas, but the quantity is the same.
Gary
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Gary Brinck
2004 American Tradition
2007 GMC Acadia
Homebase: Ocala National Forest, FL

lavarock1210

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I suspect one reason they used to fill by lbs and not gallons was the flow meters.  Years ago a flow meter that was certified was probably very expensive where a certified scale was not.  Today it is probably the opposite.  A certified flow meter may cost less than a certified scale.  Doing it with a flow meter is much easier.  When I have purchased propane with the old valves they always filled until liquid escapes from the 80% bleeder.  With the new valves it will not let you fill past the 80% level.

John From Detroit

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I don't know about that Lavarock.. I know the tank truck that delivered Fuel to the farm had flow meters. as did the pump we used to fill the tractors and such.

But I do not know how much they cost.
The meter at Parker's Propane looks very much like the one on the gasoline truck. (It is the oldest of the propane meters I've seen, they have been in business a long time)

But you may well have a point.. Scales of the kind I still see at some propane pump stations are fairly inexpensive.

Nothing adds excitement like something that is none of your business
My Home is where I park it.

jbkoonse

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The legal measurement for a DOT spec tank seems a bit bizarre. DOT bottles are actually measured in their water capacity (WC) in lbs. That's because water is not compressible, whereas propane is, so they use water rather than water as the legal standard. You will see the WC weight and Tare Weight (TW) stamped into the metal on the bottle. TW is the weight of the empty bottle, while WC is the weight of water that would fill the tank. Convert the water weight to gallons by dividing by 8.35. If you want [liquid] propane weight, multiple the gallons by 4.23

LP gas can be sold by weight or liquid volume. When the propane is dispensed, it is in liquid form and so gallons can be measured as it passes through the pump. In the DOT bottle, it will be mostly liquid and some gas, but the quantity is the same.

Harder than I thought,  but at least armed with information.  ::)
Edit: Fixed quote.
« Last Edit: December 17, 2010, 11:12:41 AM by Tom »

boatbuilder

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The flow meters for gasoline, fuel oil, and propane are all temperature compensated to a specified temperature by the ANSI, I believe.  That way you get basically the same weight of liquid whether it is hot or cold.  Since combustion is a mass process this insures that you are getting the same amount of BTU's irregardless of the liquid expansion or contraction.  I worked for an oil company for a while and had to calibrate meters on our delivery trucks.  On the ships and barges it is all in tons.
Charlie

saddletramp1200

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Also I have found that taking the bottles or coach to the propane dealer is sometimes much cheaper than filling up from one of the service trucks that come to rv parks and such.
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Lou Schneider

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Quote
You will see the WC weight and Tare Weight (TW) stamped into the metal on the bottle. TW is the weight of the empty bottle, while WC is the weight of water that would fill the tank. Convert the water weight to gallons by dividing by 8.35. If you want [liquid] propane weight, multiple the gallons by 4.23

Don't forget to multiply the end result - propane gallons or poundage - by 0.8.  That's how much fuel the tank actually holds, since it's never filled beyond the 80% level.


Gary RV Roamer

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Lou is right. The WC weight is for a full tank of water, but the propane quantity will be only 80% full.
Gary
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Gary Brinck
2004 American Tradition
2007 GMC Acadia
Homebase: Ocala National Forest, FL