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Posts: 87
Reply with quote  #1 
I've read of the problems some have when using a new tank for an engine fuel source.  I admit I have never had a new tank used for engine fuel but I have had tanks that had been opened or inerted (with carbon dioxide) that had no problem whatsoever.  Maybe it was the method used for filling.

Long ago I would get a 20 pound tank filled at the local welding supply for use with a propane torch.  They would set a platform scale to the total full weight of the tank and then pump the fuel until the scale beam tripped at which point they stopped pumping.  They never opened the bleeder.  I can see if this method was used that air in a new tank would be trapped.

On the other hand, every bulk plant I used would ALWAYS open the 80% bleed valve, regardless of the tank size, and then fill until there was a liquid discharge from the bleeder and then cease pumping.  Since propane is heavier than air, and a liquid when filling the tank it seems logical to me that the air in a new tank would be forced to the top of the tank and vented as the liquid level rose.  Then, what little air was left would be displaced by propane vapor boiling off from the liquid propane and since the propane vapor is heavier than the air it would, as it boiled, push all (or at least most) of the air out the bleeder.

The second filling, since there was still some liquid in the tank and the entire non-liquid portion of the tank filled with propane vapor should eliminate any remaining air when the bleeder is first opened.

Where is the flaw in my logic?  Does the propane vapor mix that intimately with the air as to create a mixed gas rather than two layers of discrete gas?

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Posts: 732
Reply with quote  #2 
Yes if the propane tank has a bleeder valve that would work. Propane is heavier than the air in the tank so the air will stay at the top of the tank.
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Senior Technician
USCarburetion, Inc.
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