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Old 06-07-2016, 11:25 AM   #1
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Purge LP Tanks?

Hi all.

I was looking for some info about something else in the AS guide book and came across an item that recommended purging the LP tanks every so often. Has anyone done this? Is it really necessary and I am guessing that this is something that the LP refill place does.

Thanks for your help.

Jonathan
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Old 06-07-2016, 11:30 AM   #2
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Purging propane cylinders is not necessary, unless you somehow got air into them.
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Old 06-07-2016, 11:33 AM   #3
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Wow. that was quick! Thanks Protagonist for that info. I thought it might be because condensation builds up somehow, but I guess not.
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Old 06-07-2016, 11:41 AM   #4
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Wow. that was quick! Thanks Protagonist for that info. I thought it might be because condensation builds up somehow, but I guess not.
If the cylinders were purged the first time they were filled, and haven't been left open while empty since, they shouldn't contain anything but propane liquid and propane vapor. So no water vapor is present to condense.
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Old 06-07-2016, 09:01 PM   #5
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What can happen -- and does relatively often up here (8400 feet) -- is that a very large change in elevation combined with warm weather will cause pressure build-up within the cylinder, altering the boiling point of the liquid propane within. A nearly full cylinder acting like it is empty.

To handle this, i merely release some of the propane vapor from the top of the cylinder, lowering the pressure and allowing the liquid propane to boil. Sometime i wind up not pumping any propane at all into the cylinder afterwards. Lower the pressure and tell them to have a nice day. Not worth it for just a gallon oir less of liquid. Free service. (If you do right by customers, they'll be back to purchase propane at some later time.)

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Old 06-07-2016, 10:12 PM   #6
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I changed the valves & CW purged both when they re-filled them.

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Old 06-07-2016, 11:25 PM   #7
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Originally Posted by crazylev View Post
Hi all.

I was looking for some info about something else in the AS guide book and came across an item that recommended purging the LP tanks every so often. Has anyone done this? Is it really necessary and I am guessing that this is something that the LP refill place does.

Thanks for your help.

Jonathan
Propane gas contamination can occur, which could cause problems with the refrigerator and water heater, as documented in "A little trouble at Sylvan Lake."

... and further detailed in "Rallying in Fort Collins, CO": "The leading theory is that oil and heavy hydrocarbon contamination (from a variety of sources during processing, transportation, and storage) has formed a gooey clog in the line."
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Old 06-08-2016, 06:15 AM   #8
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I'm having trouble figuring this out.

1. Contamination with noncondensing gases (air, nitrogen) should not accumulate in the tank. They would go out with the propane. If they don't accumulate in the tank there would be no need to purge the tank on an every-so-often schedule.

2. If you have contamination with condensable gases (water, high boiling gases) they will accumulate in the bottom of the tank. Purging will not get rid of these. You would need to remove the valve and invert the tank to drain these out. Purging will make the problem worse because removing the propane will cool the liquid in the tank and lead to more condensation inside the tank.

3. Contamination with oils and waxes, such as ethyl mercaptan or compressor oils will also accumulate in the bottom of the tank and not come out with purging. Again you would need to remove the valve and clean the tank.

Routine purging of the tanks doesn't sound like a requirement to me. If you have a problem with contaminated propane you should complain to the supplier. Accidents happen. But I don't think scheduled purging of the tanks is required.

I think the only reason to purge the tank is if you are replacing the valve, recertifying, welding on it, or turning it into a barbeque smoker.
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Old 06-08-2016, 06:20 AM   #9
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Quote:
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I'm having trouble figuring this out.

1. Contamination with noncondensing gases (air, nitrogen) should not accumulate in the tank. They would go out with the propane. If they don't accumulate in the tank there would be no need to purge the tank on an every-so-often schedule.

2. If you have contamination with condensable gases (water, high boiling gases) they will accumulate in the bottom of the tank. Purging will not get rid of these. You would need to remove the valve and invert the tank to drain these out. Purging will make the problem worse because removing the propane will cool the liquid in the tank and lead to more condensation inside the tank.

3. Contamination with oils and waxes, such as ethyl mercaptan or compressor oils will also accumulate in the bottom of the tank and not come out with purging. Again you would need to remove the valve and clean the tank.

Routine purging of the tanks doesn't sound like a requirement to me. If you have a problem with contaminated propane you should complain to the supplier. Accidents happen. But I don't think scheduled purging of the tanks is required.

I think the only reason to purge the tank is if you are replacing the valve, recertifying, welding on it, or turning it into a barbeque smoker.
YEP.....I change valves at 10yrs.


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Old 06-08-2016, 08:05 AM   #10
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Just had filled and recert. 40 lb aluminum tanks that are 40 yrs. old, had valves changed they recert. then and this is only 2nd. time recert. Plant operator stated as long as no visual damage or welding they are good to go. Also my 30 lb. aluminum is 50 yrs. old done at same time same story about them and they look like new, to lazy to polish 30 or 40. tanks
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Old 06-12-2016, 12:15 PM   #11
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Thanks guys! More information here than I ever expected!
Best to you!

JL
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Old 06-21-2016, 11:34 PM   #12
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Propane gas contamination can occur, which could cause problems with the refrigerator and water heater, as documented in "A little trouble at Sylvan Lake."

... and further detailed in "Rallying in Fort Collins, CO": "The leading theory is that oil and heavy hydrocarbon contamination (from a variety of sources during processing, transportation, and storage) has formed a gooey clog in the line."
Contaminated propane theory proved correct:

A teaspoon of dark brown oil was collected after blowing out the gas lines running from the refrigerator to the propane regulator per:

Repairs in Jackson Center and beyond
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Old 06-22-2016, 12:09 AM   #13
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Just had filled and recert. 40 lb aluminum tanks that are 40 yrs. old, had valves changed they recert. then and this is only 2nd. time recert. Plant operator stated as long as no visual damage or welding they are good to go. Also my 30 lb. aluminum is 50 yrs. old done at same time same story about them and they look like new, to lazy to polish 30 or 40. tanks
When you have your tanks recerted, This is where you can get air into the propane tank, or if they find they need to change the valve. Then it takes a couple tanks to get the air out of the propane tank. Your stove will burn orange. Some of the liquid you might find could be from the nasty Odorant they put in the propane so you can smell it. Seems logical that after a few years there could be a bit of liquid from that nasty stuff.
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Old 06-22-2016, 05:07 AM   #14
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In homes that use propane for heating and/or cooking the lines from the tank to the appliances can fill up with oily stuff to a point where the propane can't get through. The call center we just sold and retired from used to get that kind of call - not often - but once or twice a month. The owners would almost invariably say that they thought they were out of propane because they couldn't hear it "bubbling in the line". And the tech would get into the crawl space and clean out a couple of cups of dirty old oil that had finally gotten so bad that the propane couldn't get through. They tried to be very careful not to spill it because it did carry so much smell from the odorant. The house probably would have been unlivable for several days if that had all drained onto the ground.

But I agree - if you're changing the valves it might make sense to drain the stuff from the bottom of the tank, otherwise, why bother?

Paula
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