Propane Tank Purging?

[Dreamscape]

Has anyone done this and if so how did you do it? I have free propane to fill two 40 lb. tanks and they are new. I'm cheap what can I say!

BTW, I have done a search on here, BNO and Google, just wanted some to the point opinions from the experts!

Thanks,

Paul

[Frank @ TX]

Hi Paul,
When my tank was new the propane station , at the first fill up , did the purge thing.
They put in a little bit of propane then let almost all of it come out.
Then added some alcohol in the hose to keep the tank dry.
Then filled the tank full.
I'm not sure it the alcohol is still in there any more.
That's how they did it with mine.
Not sure what kind of alcohol they used
Frank

[bobofthenorth]

My experience is with purging anhydrous ammonia tanks but the principle is the same.  Propane is heavier than air so it will fall to the bottom of the tank.  What you want to do is introduce gas into the bottom of the tank and let the air off the top of the tank.  Whether or not it is possible to do that will depend on the valve configuration on your tanks.  On tanks with multiple valves you introduce gas at the bottom of the tank (down the dip tube) and release air from the vapour valve at the top of the tank.  On portable tanks the only real option is to put some gas in the tank and then open the valve wide and let it blow off on the assumption that air will be expelled first. 

[boogiethecat]

I'm sure you already saw this but if you didn't:

http://home.earthlink.net/~derekgore/rvroadiervfulltimingwhatisitreallylike/id45.html

The easiest way to do it is, as mentioned above, fill with a small amount of propane and dump it a few times.  Not such a safe idea though.

The best way to do it is to pull a vacuum on the tank then fill it.  Could be easily done with an AC vacuum pump.

[JohnEd]

And Boogie for the WIN!  The vent valve takes its draw from the very TOP of the tank so if you put in some propane and vent at the VENT it should expell air first and completely purge the tank with a min of propane loss.  I wouldn't have to much of a green consideration here as every time they connect or disconnect they "spill" propane.

Boogie,

After you hear the correct answer it always seems so "simple".  Thanks.

John

[PADoug]

At U-Haul, we used both systems. We had a vacuum system; which occasionally played hell with the tank of first fill up because it would draw the gas in so quickly the valves would freeze up and stop the flow. Then you would have to wait a few minutes while the valves warmed up to normal. Also, you could only get about 90-95% air out of the tank, so I have to warn customers about "yellow flame" for the first few minutes of burn time.

The second way: Put a tenth of a gallon in, let it settle for about 5-10 seconds to form a "propane bubble", then open up the vent for 3/4 fill, then close and top to 80% way my preferred method.

We had a lot of repeat customers when the new T-Valve system came into place several years ago. (April 1 2001?? just in time for Summer cooking). I frequently asked how the tanks were performing; since I thought I would have to switch, but decided to stay with charcoal instead.

I never had one complaint about the second method. But the customers who I used the first method told me that they would get on and off yellow flame for 45 minutes to an hour, though it didn't significantly affect cooking performance.

HTH

Doug