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Catalina/Capri 25/250 Sailor's Forums

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What causes icing up of a propane cylinder?

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Initially Posted - 11/04/2006 : 10:06:41

While we were cooking last night the propane cylinder iced up in a big way, and we went through two cylinders in one night. Now I understand the ideal gas law http://en.wikipedia.org/wiki/Ideal_gas_law or at least I used to when I went through nuke school in the USN. The cylinders were fairly cold when we started using them, they'd been outside in the fuel locker on the boat in some below freezing weather a few days ago, and the air temp outside last night was around 50 degrees. What I don't understand was that a couple of weeks ago I was cooking on our new SS grill for about 90 minutes straight at a party, and I had fuel left at the end of the night from the one pound bottle I was using, but we went through two bottles in about an hour last night, and both iced up. I found that if I ran water over them to warm them, they seemed to have better pressure.

Do I need to keep the propane cylinders somewhere warmer before I use them? Anybody have some wisdom to impart?

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

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wmeinert@kconline.com
Past Commodore

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USA
353 Posts

Response Posted - 11/04/2006 : 11:41:27

It's called the dew point! That is how much humidity is in the air and at what tempature will it turn into water drops. Yes keeping you cylinders warm will help, try wrapping them in a towel, to much water can cause corrosion. Also when the vaulve is lowered or laying down will also lead to icy conditions, even in the summer.

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 11/04/2006 : 13:15:51

I'm suspicious you have a leak. That would explain the faster-than-normal consumption of the gas, which in turn would explain the bottle getting colder than normal. (As you learned, the faster the gas escapes, the faster the liquid "boils" in the tank, and the colder the liquid gets.) Since the gas is heavier than air, it won't necessarily float up to your nose. Give it the soap-and-water test, and check that you have the proper gasket at the connection.

Edited by - Dave Bristle on 11/04/2006 13:20:40

Champipple
Master Marine Consultant

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USA
6855 Posts

Response Posted - 11/04/2006 : 13:56:17

This guy here has a cylinder that ices up; he doesn't seem to have a problem with it

http://www.asciimation.co.nz/beer/

Edited by - Champipple on 11/04/2006 14:04:44

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 11/04/2006 : 17:30:54

Watching the shrink wrappers do their work in colder weather, I noticed that more than a few of them will warm the tanks with the flame thrower when pressure starts to drop.

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Gloss
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Response Posted - 11/04/2006 : 18:52:59

Cylinders ice up due to the latent heat of vaporization needed to turn the liquid gas to a vapor

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Leon Sisson
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Response Posted - 11/05/2006 : 08:24:02

I agree with Dave. I think you had a propane leak the time the tanks emptied fast and iced up.

-- Leon Sisson

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 11/05/2006 : 10:04:07

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by dlucier
 Watching the shrink wrappers do their work in colder weather, I noticed that more than a few of them will warm the tanks with the flame thrower when pressure starts to drop.
<hr height="1" noshade id="quote"></blockquote id="quote">

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 11/05/2006 : 11:25:01

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave Bristle
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by dlucier
 Watching the shrink wrappers do their work in colder weather, I noticed that more than a few of them will warm the tanks with the flame thrower when pressure starts to drop.
<hr height="1" noshade id="quote"></blockquote id="quote">

<hr height="1" noshade id="quote"></blockquote id="quote">

My thoughts exactly!

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Arlyn Stewart
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2980 Posts

Response Posted - 11/05/2006 : 20:33:37

Coleman cartriges are a hybrid of propane and butane and thus are subject to some degrees of the issues of butane boiling temperature.

It could be that the actual formula on the batch used leaned towards the butane spectrum and therefore was affected much more by the lower temperatures. Pure butane is not very effective below freezing temps and close to it's boiling point.

Or, what I wonder is if the hybrid mixture can seperate by aging... and allowed the propane to boil off while the butane portion remains beneath the boiling threshold because of the cannister temperature.

Were the cannisters very old?

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 11/05/2006 : 23:16:33

Two of the canisters were brand new, a third was of unknown origin, it came with the boat and was expended quickly.

I wasn't aware of the butane mixing, is that only with Coleman canisters, or is that across the board?

We initially thought we had a leak as well, but were unable to smell any escaping gas, or locate any obvious leak. I noticed that shaking the bottle helped keep pressure up, but warming it with water from the sink seemed to be the best way to keep the gas flowing. I think the next time I do this, I'll keep the propane bottle in the truck with us on the way to the launch to keep it warm, then wrap it in a towel or something to insulate it while it's in the fuel locker.

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 11/06/2006 : 12:10:54

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by delliottg
 ...I think the next time I do this, I'll keep the propane bottle in the truck with us on the way to the launch to keep it warm, then wrap it in a towel or something to insulate it while it's in the fuel locker.
<hr height="1" noshade id="quote"></blockquote id="quote">
If the outside temp is around 50 or above, insulating the cannister while using it could have the wrong effect. The frost you saw shows how the depressurization causes cooling... All things being relative, 50-degree air will actually add warmth in that circumstance, while a towel will allow the cannister to get colder as the gas is expelled, further reducing the pressure.

Arlyn: Coleman calls them "propane cylinders"... Sounds like propane to me.

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glivs
Admiral

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USA
836 Posts

Response Posted - 11/06/2006 : 18:57:24

David,
I agree with Dave B. and Leon...it is almost certain you had a leak to go through that much gas so quickly. Propane will flash to a vapor at atmospheric pressure so condensation is not a surprise. Did you try painting a little dish soap/water mixture on the joint? Even the slightest leak should blow bubbles.

Dave B....they are nominally "propane cylinders" but yes they contain a fair percentage of butane and a few other hydrocarbons. In fact the mixture is often varied slightly depending upon latitude, thus cylinders sold in the warmer climes actually have higher concentrations of butane than those sold in cooler areas...and especially so outside the U.S.

And Arlyn...your thoughts about the gases separating or layering inside a cylinder over time are right on....but the cylinders would have to be quite physically and thermally stable. In my research days, we had to regularly roll our calibration gas cylinders or we would see systematic shifts in the concentrations pulled from the top.

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oldsalt
Admiral

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USA
578 Posts

Response Posted - 11/07/2006 : 08:40:12

If the cylinder is discharging faster than it should, icing could be the result, especially in cool damp ambient conditions.

I don't believe that the icing of the cylinder was the problem, but rather the result of a leak in the system which would also explain the faster than normal depletion of the cylinders.

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delliottg
Former Mainsheet C250 Tech Editor

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4479 Posts

Response Posted - 11/11/2006 : 13:32:58

I got a chance to look into the icing thing today, especially after so many folks suspected a leak. I was confident that there was no leak, but I've learned to listen to the voices of experience a long time ago. It turns out the little cork gasket on the regulator isn't making a good seal, I get bubbles when I spray the neck joint with the regulator/bottle with soapy water. I soaked the gasket with water for a while to plump it up a bit, and it was definitely a better seal, but not enough that I'd want to chance it.

<ul><li> First question, and this is the big one. How is it possible that four people couldn't smell the leak from the bottle? We noticed a definite smell of propane at first, but after removing and reattaching the bottle a couple of times, the smell seemed to go away, although the hissing & icing did not. Even with my nose up against the bottle/regulator joint I was unable to smell anything nor were my wife and friends. Does your nose get "tired" of the smell and simply not notice it any more? Admittedly three of us were having cocktails, but the fourth was not, and it was early into the evening, so I think alcohol had little to do with the loss of smell. Anyone have any insight on this? It's a troubling thought that you might become insensitive to the smell of propane and not notice it. </li><li> Second question, does anyone know where I can get a replacement gasket? The manufacturing company doesn't even list propane regulators on their site, and only has propane detectors. I've searched the web unsuccessfully for a gasket, so I'm tending towards making my own. Any suggestions on the material? I have a Coleman heater on board as well, and it's gasket material looks like rubber or some synthetic which would seem to be a better material assuming that you can find something that's propane resistant.</li><li> Would oiling the gasket make any difference in the short term? On my white gas camping stove, you have to oil the pressure rod gasket a couple of times annually to keep it happy.</li></ul>

Thanks to everyone who offered advice, especially those who counselled that I had a leak.

Edited by - delliottg on 11/11/2006 13:35:09

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 11/12/2006 : 11:02:15

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by delliottg
 Thanks to everyone who offered advice, especially those who counselled that I had a leak.
<hr height="1" noshade id="quote"></blockquote id="quote">
You're very welcome! It feels good to be right for once!

(Of course when Leon agrees with you, you're definitely right!)

On smelling a leak, a very slight breeze could be carrying the gas away very quickly, especially if it's on the leeward side. Also, propane flows downward in air--especially when it's very cold (as it gets when it's expanding rapidly at the point of the leak).

Edited by - Dave Bristle on 11/12/2006 11:06:58

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 11/12/2006 : 20:40:16

It turns out the leak around the neck of the cylinder was just the tip of the iceberg. I cupped some water around the joint in the line from the regulator to the stove, and got some bubbles there. I noticed that the joints had little in the way of PTFE tape on them so I took the whole assembly apart, retaped all the joints, and snugged them back up. Surely this would fix it I thought, but I still had the same hissing and icing up behavior. I had presumed that the hose connection to the stove itself was sound, as it turns out, it was all but falling off the threads, it wasn't even hand tight, it was literally about a thread & a half away from falling off, and had no PTFE tape at all. I taped that joint and tightened it up, and voila, no more hissing sound, nice steady flame on the stove, and a normally cool to the touch cylinder, not a block of ice. That also answered the question about how the four of us couldn't smell the gas, it was falling straight down into the galley cabinet and oozing it's way to our bilge. I got the chills just thinking about the possible outcomes had I not investigated this further. I need to research how long it takes for propane to dissipate, it's quite likely there was a fair amount of gas in my bilge from last weekend. Anyone have any data?

The PO said they rarely used the stove, it's probably a good thing, it was a disaster waiting to happen. I feel quite relieved to have gotten to the bottom of the mystery.

Of course now I've got another series of questions which I'll post in a different thread.

Thanks again to everyone who offered insight, you've helped avert a possible disaster.

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