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Tips, Techniques, and Questions -- Technical questions or tips

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  #1  
Old 2006-11-01, 1:13pm
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Default Propane regultor goes down fast after 400psi

This is the second time this has happened and I am truly stumped. I use propane with an oxy concentrator. This morning my gas measured at 400 psi at the tank. My pressure to the torch was 5. ( I have a Betta torch). I have been using this tank for about 60 days and the gas has been usuage has been gradual.
A few moments ago the flame went out and in checking the tank the needle is at 0. Of course the needle gauge to the torch was also back down to zero.
From 400 to 0 in 3 hours? Do these things operate like a car gas gauge? It goes slow and then whammoo!

This is a brand new tank, I am the only person who has used it. This a brand new propane regulator . The first one I had(6 months ago) had the same thing happen but the needle on the gauge from the tank to the torch went way over to the other side and stuck. Generations figured it was broken and replaced it.

Could the hoses have a leak that I am unaware of? I got the whole set-up only six months ago and this is only my second tank of propane. The hoses are regulation grade from Generations. The propane is stationed outside and the hoses go up and out the wall.

I bled my torches last night but I didn't fiddle with the brass handle on the tank. The flame died down in very short order and went out. I then checked to make sure my tank valve are in the off position .

I turn the torch on as slowly as I can and release/open the gas as slowly as I can when firing up.
I am so frustrated and completely ignorant on this. I have no idea what to do . ...

Who do I call? What am I doing wrong??
Any help will be greatly appreciated.

Thanks for any help you can give.
Anne
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  #2  
Old 2006-11-01, 8:31pm
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Do you really mean 400 psi or is that a typo?

Me
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  #3  
Old 2006-11-02, 2:46am
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I'm sure there is some really fancy scientific explanation for this phenomenon ( I think it has to do with the volumes of gases and resulting pressures), but I do know that the only way to know how much propane you have left in a tank is to weigh it, not look at the pressures. The rate that the pressure drops after you get to 400 probably isn't detecting a leak or something. Mine also drops more rapidly at some point and I believe that everyone's does. Just to verify this....you might fill a tank weigh it.....weigh it as it starts appoaching this magic pressure and you'll see that it's nearly empty. (This same thing freaked me out one time as well).
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  #4  
Old 2006-11-02, 5:56am
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It's because the tank will hold a constant pressure when there's liquid propane in the tank. It only expands into gas until it hits a certain pressure... then the rest stays liquid. Once the liquid is used up, there's no more to replace the gas you've used... the pressure drops really fast from that point. Some tanks have a little heat thingy on the side, so you can see where the liquid level is. The pressure has nothing to do with how much liquid is left, so it can be confusing. It's perfectly normal and yes... it's a scientific dealy-doo. A compressed oxygen tank drops gradually, because there isn't any liquid involved... it's all gas. Hope this helps.
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  #5  
Old 2006-11-02, 6:11am
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There is something VERY wrong here. The maximum pressure on the tank side of the regulator should NEVER EVER read in excess of about 150 PSI on a full tank, and usually somewhere between 100 and 125 PSI, depending on the ambient temperature.

Are you absolutely sure it read four HUNDRED PSI??????

Is this the same tank that you previously had problems with?

It's my guess that you have a 2nd defective regulator.

Quote:
Originally Posted by anne225
This is the second time this has happened and I am truly stumped. I use propane with an oxy concentrator. This morning my gas measured at 400 psi at the tank. My pressure to the torch was 5. ( I have a Betta torch). I have been using this tank for about 60 days and the gas has been usuage has been gradual.
A few moments ago the flame went out and in checking the tank the needle is at 0. Of course the needle gauge to the torch was also back down to zero.
From 400 to 0 in 3 hours? Do these things operate like a car gas gauge? It goes slow and then whammoo!

This is a brand new tank, I am the only person who has used it. This a brand new propane regulator . The first one I had(6 months ago) had the same thing happen but the needle on the gauge from the tank to the torch went way over to the other side and stuck. Generations figured it was broken and replaced it.

Could the hoses have a leak that I am unaware of? I got the whole set-up only six months ago and this is only my second tank of propane. The hoses are regulation grade from Generations. The propane is stationed outside and the hoses go up and out the wall.

I bled my torches last night but I didn't fiddle with the brass handle on the tank. The flame died down in very short order and went out. I then checked to make sure my tank valve are in the off position .

I turn the torch on as slowly as I can and release/open the gas as slowly as I can when firing up.
I am so frustrated and completely ignorant on this. I have no idea what to do . ...

Who do I call? What am I doing wrong??
Any help will be greatly appreciated.

Thanks for any help you can give.
Anne
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  #6  
Old 2006-11-02, 6:31am
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I agree with Mike, Something is very wrong if you actually have 400lbs of preasure in the tank, On a warm summer day just filled it should only read about 125
Dave
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  #7  
Old 2006-11-02, 8:10am
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Anne,
Is it possible that you're reading the KPa instead of PSI on the guage? I think most regulators show both. 400 KPa is about 60 PSI. As others have said the pressure drops rapidly once the liquid phase is exhausted. Mine drops rapidly after about 60-70 PSI.
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  #8  
Old 2006-11-02, 9:10am
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60 PSI (pounds per square inch) translates into 413 KPa (kilopascal)...

For tank to read 400psi ambient temperature around tank would have to be about 140 - 160 F. degrees ........ Also there is a internal safety valve built into tank valve that blow off pressures at about 360psi, causing a pressure drop in tank to safe level...


As MR. S. states propane gas is in a liquid form in tank, and boils off a vapor that is sent out to torch... Its possible you finally reached the point (in the three hours of use) that there is no more liquid gas in tank to produce a vapor... In essence you may have a truly empty tank....

This site has pretty good chart for relationship of pressure to temperature in propane tank....

http://www.flameengineering.com/Propane_Info.html


I personally would weight tank and if it weighs in at 18 to 20 pounds it is a empty tank..... A full tank should weigh about 38-40 pounds.. The time factor you have used tank (2 months) makes me think its empty.

Dale
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Last edited by Dale M.; 2006-11-02 at 3:22pm.
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