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Old 08-22-2012, 08:04 PM   #1
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Here's the problem, what's the diagnosis: propane flow

Here's a tickler for you:

The water heater and the stove work fine during the later evenings, nights, and mornings, but during the hot afternoons the flow of propane is very anemic, practically impossible to use. (Yesterday afternoon, quite a hot one here in Santa Fe, I was completely unable to make my afternoon shot of espresso!)

I have my own hypothesis about what's happening, but I'd like to hear your opinions about it ...


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Old 08-22-2012, 08:22 PM   #2
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Have you drained the water out of your LP lines lately?
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Old 08-22-2012, 08:27 PM   #3
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Nope, haven't tried that yet, Terry, though I may try it when I get home. I kind of wonder if it's a major problem, though, because it stays relatively cool under the Airstream where the propane lines are. (This is Santa Fe heat, where the highs are in the 80s.)

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Old 08-22-2012, 08:33 PM   #4
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I mention the water because I had two Airstreams recently with intermittent function of the LP system. I undid a connection under each trailer, and got a bath of foul-smelling water, I assume from condensation.
Even if it doesn't work, it costs nothing to crack open a line underneath, and see if anything pours out.
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Old 08-22-2012, 08:44 PM   #5
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I am going to guess a bad regulator. Of course that is how I usually fix things. Start replacing parts until it works again!
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Old 08-22-2012, 08:49 PM   #6
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Isn't it funny how that replacing parts thing goes? It's always the last thing you change that was the problem.
Is it just my bad luck that this happens? LOL
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Old 08-22-2012, 08:52 PM   #7
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I am going to guess a bad regulator. Of course that is how I usually fix things. Start replacing parts until it works again!
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Isn't it funny how that replacing parts thing goes? It's always the last thing you change that was the problem.
Is it just my bad luck that this happens? LOL
I've found you can fix anything, if you throw enough parts and money at it.
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Old 08-22-2012, 09:00 PM   #8
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I mention the water because I had two Airstreams recently with intermittent function of the LP system. I undid a connection under each trailer, and got a bath of foul-smelling water, I assume from condensation.
Even if it doesn't work, it costs nothing to crack open a line underneath, and see if anything pours out.
I once helped a neighbor when I lived in the Texas Hill Country. She had a space heater connected to a propane tank in the yard. I got really cold, and nothing worked.

My hint was when she said, "I could hear it bubbling through the line before."

I took the line loose and we heated it with a hair drier. Sure enough, the ice melted and ran out. Heat worked again.

Although I'm not sure why water in the line would get worse in the heat. Like Terry said, it doesn't cost anything to try and if you do have condensation in the line, it needs to be removed.
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Old 08-22-2012, 09:15 PM   #9
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Ok, I'm going to throw out my hypothesis. It has to do with the vapor/air gaseous mixture at the top of the propane tank, above the liquid propane in the bottom.

Liquid propane turns to vapor at a certain temperature at sea level. Easy enough to look up. It's the sea level part that caught my eye: This involves air pressure. Obviously, if you dramatically lower air pressure, then vaporization occurs readily. If you dramatically raise the air pressure, then vaporization occurs far less readily.

Now consider that vapor/air mixture at the top of the tank, which is under pressure. In effect, what we have is an artificial environment of air pressure, pressing down on the liquid propane below it. If that artificial enviroment is heated, it expands, altering the pressure on the liquid propane below it.

I think you may get the picture here: Propane flow is reduced just in the afternoon heat because of the heat-enhanced pressure exerted on the liquid propane by the vapor/air mixture at the top of the tank.


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Old 08-22-2012, 09:25 PM   #10
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Isn't it funny how that replacing parts thing goes? It's always the last thing you change that was the problem.
Is it just my bad luck that this happens? LOL
Of coarse it's the last thing that you replace that fixes the problem. Only a moron would keep replacing more things after the problem was fixed!!
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Old 08-22-2012, 09:32 PM   #11
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Ok, I'm going to throw out my hypothesis. It has to do with the vapor/air gaseous mixture at the top of the propane tank, above the liquid propane in the bottom.

Two things:

First, your propane tank should have liquid propane below the liquid level and gaseous propane above the liquid level. There shouldn't be any air in the tank. If there is, at certain temperatures the propane/air mixture above the liquid would fall within the explosive limits, a most dangerous situation.

Second, the vapor pressure of a gas over a liquid in a closed container at equilibrium is independent of the partial pressure of any other gases in the closed container. (Dalton's Law)

I dunno what the problem is. The idea of draining the lines sounds to see if there's any liquid in them sounds worthwhile--and doesn't cost anything--and if that doesn't do it I think I'd replace the regulator on general principles. (otherwise known as eliminative analysis )
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Old 08-22-2012, 09:32 PM   #12
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It's related to cattle mutilations and those pesky chupacabras that frequent NM.
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Old 08-22-2012, 10:01 PM   #13
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I was told that problems can happen in old (or 'vintage', as we call them) trailers because the stinky stuff they include in the Liquid Propane (Ethyl mercaptan) pools in the supply pipes.

You can imagine the pooling that would be going on for 40 years or more in lots of trailers!

Apparently, the pooled Ethyl mercaptan can reach a point where certain fittings suffer reduced flow capacity, and potentially even blockage, so, all this to say, it is a Bad Thing to have this going on in your TT.

I was also told that the way to get rid of the problem is to renew the supply pipes to your furnace and heater.

Hearing Terry's tale of a few TTs with water in those pipes surprised me. Doesn't something have to be leaking, like say, the distribution valve, for that to be able to happen?
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Old 08-22-2012, 10:31 PM   #14
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Actually, what I've found when filling cylinders is that the pressure-sensitive pump I use will operate only very slowly for some cylinders, especially in the summertime. When I check those cylinders for pressure, I find that those that won't allow the pump to operate normally have tremendous pressure build-up inside.

In one fairly extreme instance, some folks staying over in Eagle Nest in July brought by their recently filled cylinders from their brand-new rig, saying that they couldn't get them to run the stovetop or anything else at all. I weighed the cylinders, determined that they were indeed fairly full, but then cracked one of the cylinders and found it to be VERY pressurized. No way would one have been able to pump any more propane into them. I simply released some of the pressure and sent them on their way. Happy campers.

It's now after 9:00 pm here and much cooler. The water heater didn't still want to work well at around 7:00 pm (though I did manage to get enough heat out of the weak flow at the stovetop to fix up a cup of espresso). The water heater started up like a champ just a few minutes ago.

Oh, one other thing. Since arrival here, I found that the fridge just won't cut the mustard on propane; does great on electricity. Odd because it seemed to work great on propane just before I left for Santa Fe from Angel Fire, where heat is rarely an issue. It's a fairly new fridge, a European Dometic, which was a better fit for the replacement of the old, dead one. Reading the documentation, I found that I probably need to do a clean-up of orfice area, etc. But now I'm wondering. Maybe I'll get to the bottom of the heat-related propane flow issue, then see if the fridge doesn't start acting right after all.

This still could be some kind of expanding non-propane liquid in the lines, and I plan to check it once I get the rig back home in early September. Wish I could check it all out here, though, because testing for heat-related flow decrease is kind of hard to do in Angel Fire. By early September, it's time to winterize up there.


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Old 08-22-2012, 10:49 PM   #15
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Ventport: I guess you missed the humor in my comment.
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Old 08-22-2012, 11:10 PM   #16
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Actually, what I've found when filling cylinders is that the pressure-sensitive pump I use will operate only very slowly for some cylinders, especially in the summertime. When I check those cylinders for pressure, I find that those that won't allow the pump to operate normally have tremendous pressure build-up inside.

In one fairly extreme instance, some folks staying over in Eagle Nest in July brought by their recently filled cylinders from their brand-new rig, saying that they couldn't get them to run the stovetop or anything else at all. I weighed the cylinders, determined that they were indeed fairly full, but then cracked one of the cylinders and found it to be VERY pressurized. No way would one have been able to pump any more propane into them. I simply released some of the pressure and sent them on their way. Happy campers.
In this example I suspect the "recently filled cylinders from their brand-new rig" did have air in them as a result of the new cylinders not being properly purged when they were initially filled. This is a Bad Thing.

See, for example, http://propane.tx.gov/training/custo...g-bulletin.pdf .

It would be handy to have a gauge showing the gas pressure at the inlet to the regulator. This should be the vapor pressure of the LP gas at the tank temperature, no more and no less. If it's higher then there might be something else in the tank.

Have you tried just venting a little gas out of your tanks like you did theirs? Might solve the problem.
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Old 08-23-2012, 07:27 AM   #17
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I plan to check for some excess pressure when back in Angel Fire, a more controlled environment. When you open a valve, you do get vapor, and it's not undangerous if variables are not controlled. Here in Santa Fe I'm unable to control nearby variables.

The link you sent is a handy one. It also illustrates the funky location of the propane safety business across states. In Texas, it's the railroad commission. Duh. In NM, it's the construction industries division. Duh. Now the big surprise. In AZ, it's the ... ah, woops, ain't none. Duh.

As far as air in cylinders is concerned, I suspect it happens a lot. Lots of folks wind up leaving valves open for extended periods after the cylinder is "empty" (won't run appliances); lack of purging is common (though the modern pre-purged tanks sure help).


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Old 08-23-2012, 11:45 AM   #18
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I plan to check for some excess pressure when back in Angel Fire, a more controlled environment. When you open a valve, you do get vapor, and it's not undangerous if variables are not controlled. Here in Santa Fe I'm unable to control nearby variables.
"Nearby variables?" You mean like your neighbor lighting his grill just as you vent a little propane? Well, yeah, you might have a point. . .

Quote:
The link you sent is a handy one. It also illustrates the funky location of the propane safety business across states. In Texas, it's the railroad commission. Duh. In NM, it's the construction industries division. Duh. Now the big surprise. In AZ, it's the ... ah, woops, ain't none. Duh.
The whole business is covered by DOT regulations, 18 United States Code something-or-other* , 50 different state laws, and God only knows how many local laws. And, the law is interpreted by the guy who is going to fill your tank, who knows what somebody told him, who in turn knows what somebody else told him, so there's a lot of variation. . .

* The actual USC reference is cited somewhere here on the forums. . . I looked it up once and even bookmarked it, but can't find it right at the moment. The federal law is undecipherable by nonspecialists, anyway.
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Old 08-23-2012, 01:23 PM   #19
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"Nearby variables?" You mean like your neighbor lighting his grill just as you vent a little propane? Well, yeah, you might have a point. . .
Precisely!

Quote:
The whole business is covered by DOT regulations, 18 United States Code something-or-other* , 50 different state laws, and God only knows how many local laws. And, the law is interpreted by the guy who is going to fill your tank, who knows what somebody told him, who in turn knows what somebody else told him, so there's a lot of variation. . .
Here's a page that has links to some of this stuff. Note that it basically involves transportation and hazmat; not a lot there on, e.g., filling.
Regulatory Affairs - National Propane Gas Association

A couple of years ago, I was dreaming about selling myself (and my NM filler's license, if possible) to some park or another in the desert, away from the white-out blizzard conditions of Angel Fire in the winter. What I was trying to determine was whether AZ and NM might have some kind of reciprocal agreement on licenses so that I could simply look for someplace down there without having to apply for an AZ filler's license. And I looked and looked and looked ... and finally decided I'd simply email whatever agency might be involved and ask. And I looked and looked and looked and couldn't find any such agency. So finally I wrote an email to the AZ propane dealers association. The person there wrote back to explain that there is no license in AZ.

So maybe I should not have wondered about my elderly dad's tale of the old fellow near Quartzsite who had the best price on propane. The best price, I guess, was based on the fact that the old guy would fill bottles with a lighted cigarette in his mouth.


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Old 08-23-2012, 02:11 PM   #20
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...

So maybe I should not have wondered about my elderly dad's tale of the old fellow near Quartzsite who had the best price on propane. The best price, I guess, was based on the fact that the old guy would fill bottles with a lighted cigarette in his mouth.


Lynn
And my guess is that if you could go back in time and ask him why he did such a dangerous thing, his answer would be something on the order of "Well, I ain't blowed up yet!"

He was probably a cousin of my grandfather who fixed and rigged all sorts of things with rubber bands and string. He was already a creature of habit by the time duct tape came into wide use or he might have changed his technique.
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