Propane Tank Pressure Gauge Meaning - Page 2 - SailNet Community
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post #11 of 19 Old 05-27-2008
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Quote:
Originally Posted by sailingdog View Post
Believe that you should have said: "This means that at 70 deg F the pressure gauge should never read LOWER than 110...." since if there is any amount of liquid propane, the pressure should be 110 PSI.
Assuming that he intended to send me out with a fully equipped boat, then yes, the guage should not have been lower than 110PSI. That's an assumption that I didn't make. (As I remember, the dock hand looked at it and said; "100 pounds, that should hold you for a week." )

The guage can not read higher that 110 PSI if the tank only contains liquid propane. The guage could read lower, however, if there was no liquid fuel remaining in the tank, and the vapor was being used up.
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post #12 of 19 Old 05-27-2008
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The guage will indicate the vapour pressure of the propane at the then tank temperature. It does not vary much, unless you cool it out of sight. Someone said that it boils at -41 degF, so the guage would cease reading at that moment. If you took the top off the tank at that moment, then in theory the propane would just puddle there and would not come out.

At sane temperatures, the moment that the pressure begins dropping sharply, you will have very little indeed in the tank. Indeed, if the pressure dropped to (say) 100 psi, you would only have about 100/14.5 = 6.89 times the volume of the tank, and you have to leave one volume behind, all measured in standard volume units (typ cubic feet).
Would approx 5.69 times the tank volume in standard cubic feet last a week?
I doubt it.
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post #13 of 19 Old 05-27-2008
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The guage will indicate the vapour pressure of the propane at the then tank temperature. It does not vary much, unless you cool it out of sight. Someone said that it boils at -41 degF, so the guage would cease reading at that moment.

At sane temperatures, the moment that the pressure begins dropping sharply, you will have very little indeed in the tank. Indeed, if the pressure dropped to (say) 100 psi, you would only have about 100/14.5 = 6.89 times the volume of the tank, and you have to leave one volume behind, measured in standard volume units (typ cubic feet).
Would approx 5.69 times the tank volume in standard cubic feet last a week, with the pressure dropping all the time?
I doubt it.

Last edited by Rockter; 05-27-2008 at 06:52 PM.
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post #14 of 19 Old 05-27-2008
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The only reliable way to avoid running out of propane is a back up supply. That 100 psi tank would probably be gone before the water bolils for your coffee, so either take the tank off the boat and weigh it before your trip, or provide a back up! The suggestion was made to use a couple of those little green coleman bottles, but if you have room a second 10 pound bottle is less expensive in the long run because it can be refilled. My Endeavour is blessed with two propane lockers, one in each side cockpit coaming. One of them has the stove feed and solenoid, the port one is only a storage site. Trust me, there is a full gas tank strapped inside! For a liveaboard it would seem practical to purchase (or build) a second propane locker and vent it, because with daily gas usage you will run out and use those disposable bottles often!

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post #15 of 19 Old 05-27-2008
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I don't know. Mine's been reading about 75 PSI lately and we cooked five meals and had coffee for four mornings with that level. It's now down to around 60 PSI. I did notice the flame is lower though so I imagine it's running out.
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post #16 of 19 Old 05-27-2008
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Did anyone see the write up PS did on this little guy?

[IMG]Photobucket[/IMG]

You can see how much propane you have left. They are DOT approved and made by two different manufacturers. One is slightly larger than a typical 20lb-er and the other slightly smaller.

PS had nothing bad to say about them.
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post #17 of 19 Old 05-27-2008
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The composite propane tanks are pretty cool...available in 10, 20 and 30 lb. sizes. The 10/20 lb. tanks are about $100, but not legal for use in many countries, including Canada IIRC.

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post #18 of 19 Old 05-30-2008 Thread Starter
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Kudos for all!

Sailors.

Well, a big THANK YOU for all the propane tank info. Previously I always used alcohol.

It was all very interesting and enlightening, and complete.

I really appreciate the knowledge sharing on this site.

Also nice is the feeling of a sailing community with a positive social impact - for example, I have seen very few mean messages posted among participants. You can usually log off sailnet feeling a little better about the world.

Thanks again, SaltyPat
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post #19 of 19 Old 05-30-2008
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I have the fiberglass tanks and I'm here to tell you being able to look and see the liquid level is the best way and only reliable way to tell how much is left. I've got a guage and it is absolutely meaningless.
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