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Propane tank overfill or regulator failure?

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Had something happen this afternoon I've not experienced in all my years bladesmithing. Just got the 100# tank filled up for my ChileForge and after dinner went out to do some forging. 

Fired up the forge and started doing the things you do in the shop while the forge heats up. Suddenly I hear the forge tone drop from the rushing sound of a well-mixed fire to the belching sound you get when you pour way too much fuel into the forge and way too little air. I glance quickly and see a wave of flame coming out of the forge mouth confirming this. 

After two seconds, it goes back to normal. Then about a minute later it happens again. The "burps" continue getting more rapid. I also notice that frost is forming on my regulator.

I turn the propane tank off at the main valve, and damnest thing was, the forge kept burning for a LONG time afterwards. I've got a lot of time in on this forge. I know how she's supposed to behave; this is not it.

I disconnected the tank and it's now sitting about fifty feet away from my house in the driveway.

So . . . Anyone have experience with this? I have a working hypothesis, but propane safety is not something with which I'm interested in experimenting.

My hypothesis is that the tank was overfilled. The guy at the gas station was geeking out over the fact I made blades and wasn't really paying attention. He put 22 gallons into the tank, and I'm pretty sure there was at least 2-3 gallons in there already. Is it possible that liquid propane was entering the regulator? That would explain why the fire didn't die out as quickly as it should (i.e. the liquid in the lines/regulator continued to expand into gaseous form).

Or is this the symptom of a regulator failure? I suspect it is the tank overfill just because the regulator was working dandy yesterday when the tank ran out of fuel.

Anyway, any thoughts on how not to die a horrible burny death would be appreciated.




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More data that seems to confirm the over-filled theory.

Looks like a full 100# tank is supposed to weigh 170 lbs. Just brought a scale out to the tank. 191 lbs! 

I'm slowly venting it by opening the valve and letting it off in the atmosphere every 10 minutes or so.

Sorry, environment, but I don't want to explode.


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Dave;  You might try putting your regulator on another bottle to see if the same issue pops up

that would eliminate one problem and give you a course of action from there..............My.02........;)

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Great minds, Clifford.  

I did that. Went out and robbed the little 20# tank from the BBQ and hooked it up. The forge worked normally. Guess that eliminates the regulator.

After venting the 100# bottle for about 2 hours (opening it for about 10 seconds every 15 minutes or so) I still have it at over 180lbs. 

I think the lesson here is don't tell the guy filling your propane tank that you're a bladesmith. He asked "is this for a forklift?" . . . next time I'll just say: "Yup."


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Liquid propane getting into the regulator, and boiling off from there would cause frost on the regulator and probably keep it from functioning properly.  Liquid in the line between the tank valve and the regulator would explain why the forge ran on after the valve was closed.

I'd buy your original hypothesis, but am not an expert on propane.

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reduce the regulator discharge pressure...when the propane tank was over filled it also created excess pressure inside the tank....

if you're normally running your forge at 8-10 psi on the discharge side adjust your regulator down to 5-6 psi to compensate for the increased tank pressure

as the volume in the tank decreases you can readjust your pressure back to what you would consider normal settings

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10 hours ago, Gerald Boggs said:

Not really my skill set, but might there be a problem with the bleeder valve?

Chances are good that Milton (the guy who filled the propane tank) forgot to open the bleeder valve while filling it. The "bladesmith story" happens all the time when I fill my 100# tanks. I gotta stop wearing that blacksmith hat.....

If you put the tank in a nice sunny spot, it will discharge through the PRV and operate normally.

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