Try a different tank. If you still have the leak, chances are that it isn't the tank. BTW, what kind of connections are you using. IMHO, you should be using propane hose with swaged fittings.

 

at this point I am using Xintex (spelling?) regulator and their pigtail hose. That is it, everything else was disconnected and removed, so it just does not matter.

Trying a different tank may be the thing to do except that properly sized tank is a long mail order away (only one kind of tank fits my propane locker). Oh well, guess there is no way out of that.

 

Could it be the tank itself?

Yes.

Also - make sure that you are using real propane fittings with the flared ends and "O" rings. The "Expert" I purchased some things from this year thought he would save me some money and sold me some journeyman stuff which did not work properly. Irritating. I don't skimp on my boat. Don't recommend others do either.

 

Anyone dealt with that before? Could it be the tank itself? How the hell do i find it? Soap and water failed miserably, perhaps because the leak is very slow (I get down from 175psi to 120psi or so in 24 hours). Ideas would be very welcome.

This is NOT a small leak. With a pressure drop like that there have to be bubbles in a soapy water test. Try submersing the entire tank in a bucket of water. If it is the tank you will see bubbles.

 

I thought about that, but it is a steel tank (and also it is pretty darn big - I don't have a bucket big enough for it). May be a tub would work?

 

The soap test should always work--it takes zilch to puff up a bubble. Grab some Dove, water a bristle brush and some beers and sit a spell. One fitting at a time.

Caution: This may entail a six pack or so---your drinking may vary........

 

most fittings are flare type, but some have to be pipe thread by necessity. those regulators they sell have a threaded 3/8" hole in the bottom without any specific sealing method recommended, and the only way it can be closed is by using pipe thread fitting (and special gas pipe compound, I suppose, at least thats what I got). Same goes for a solenoid - it has a flared fitting on one end but a regular NPT female on the other. This is the stuff those boating gas companies sell, in fact none of their own parts fit together without lots of connectors. Irritating.

 

That's what I use for my outboard testing........

You submerge your outboard in a big garbage can ??? Uhmm - not sure how to say this - but if you didn't "test" it so often you might find it runs with fewer problems.

You're welcome - always happy to help

 

"....and please remember to tip the hat girl on your way out............"

 

Those custom-sized tanks are damned expensive. I had the same symptoms; I could smell the leak every now and then but nothing showed on the soap test. Out it all came. I replaced the ten-pounder in the locker with a twenty hanging off the rail. It isn't marine-grade but you exchange it when empty so that isn't a problem.
As others have mentioned make sure you aren't mixing pipe-thread fittings(which must be sealed with PROPER gas tape-don't use plumbing tape) with compression fittings (which must NOT be sealed with tape) or you will have a leak. Also my regulator had to be mounted with the output facing down.

 

Bath tub, hot tub or small kiddie pool. Suspend a tarp from trees. Carry it to your lake and submerge it. You don't even need something that deep. Just roll the tank over. I have never been let down with submerging in water. Regular soap IMHO is to thin and a leak will blow away the soap without it foaming. I use a product called Big Blue when I soap test.

50 pound drop in 24 hours is small enough that you cannot hear it.

Compression fittings are bad. If they are not leaking now they will leak.

The gauge and fittings you are using to pressurize the system could also be the source.

Any Home Depot or Lowe's fittings should be discarded. Most of them are garbage.

Good Luck,

Jim

 

My understanding is that the pressure test is conducted over a 10-15 minute period. Normally you should see either no loss or at most a very slight loss of pressure (say <5lbs) or so during this period.

If you are testing over a 24 hour period, all bets are off. There are external variables that can affect the pressure, notably temperature fluctuations. And you have to maintain the same environmental conditions when testing, such as keeping the entire system in shade. I once had a precipitous INCREASE in pressure when the boat swung on the mooring, allowing direct summer sunlight to shine in the propane locker and heat up the hoses and other hardware. The opposite can happen if it's in sunlight to begin with and then moves to the shade.

I would not place much emphasis on pressure drops observed over a 24 hour period. If you follow the standard guidance and still have pressure loss, then by all means keep searching for the cause.

 

Propane does change pressure and volume with temperture changes. Just like Freons do.

 

a propane leak is nothing to mess with, I would have it off my boat in a nanosecond.

 

Ok, so soap tests did nothing at all. Water immersion test kinda worked and had shown that leaks are very very tiny. That is - there is no stream of bubbles or anything like that. However, once every few minutes (yes, I spent that long staring into the damn bucket) a bubble would roll off of the plastic cap (nut?) on the front of regulators (two different regulators, actually, by Trident marine). I have no idea what it does but it was not completely tightened ("assembled in Mexico"). Also, when testing the "quick assembly" pigtail (the one with plastic external nut that hand-tightens onto the tank valve, it would never completely seal. The other kind that screws into the tank valve seals fine. With that I finally got a non-leaking regulator and pigtail assembly.

The rest of connectors are done pretty well (I did a lot of work on my hydraulic steering system previously so I kinda got to learn about all the different thread types and all that fun stuff). At this point the system is being tested over 24 hours. I am pretty well aware of changes in pressure due to temperature differences, but I am accounting for that (as well as my physics knowledge allows anyway).

There is also an "internal leak" in the system - the solenoid (Xintex one) does not fully close, so even when closed, it will allow the gas to move from the tank side of the system to the stove side, though slowly. Not great, but I don't really know if any of their solenoids are better - they all look like junk.

That said, 15 minute test passed fine (the brand new Plastimo stove seems to be closing properly, thanks for that).

Will see what happens by tomorrow.

So far grades for products:

Trident - D- (I really wish there was another manufacturer of boat propane stuff, nothing they make matches anything else they make and everything looks like cheap junk. I really would like my propane regulator to be assembled in Japan, no offence to our neighbor to the south)
Xintex (spelling?) - B- (decent electronic system, crappy solenoid)
Plastimo - B (stove works but none of the gymbals match)

 

On fittings issue:

NPT thread can seal properly against same size regular thread (including thread inside any flare fitting), while using a proper pipe sealant (Lock-Tite makes a special white stuff for gas connections).

The reverse is, of course, not true - flare fittings need flare fittings (of the same angle too) to seal together. You can use pipe sealant compound on their threads too, but it won't be very useful and will likely lock them forever.

I am not a big fan of NPT fittings myself but they do seal reasonably well with proper care. A lot of boat propane items require them - Trident regulators have straight thread fitting on the bottom that can only be sealed with a 3/8 NPT male, same goes for both inlet and outlet of Trident solenoid. They don't even provide fittings - you have to get your own (local Cawliflowers is the best source of those things, as I found).

 

Brak,

I've never heard of a "24-hour" test for propane systems. I'm only aware of the 15 minute test. How are you accounting for changes in ambient temperature? If you are using a 24 hour test, do you have information on what kind of pressure drop should be expected during this period? If a 5lb drop is nominal for the 15 minute test, and you were to extrapolate that, I would expect a very substantial pressure drop over 24 hours.

As for the solenoid not closing completely, you should replace that immediately. It is the key safety component of the system, and it needs to close completely.

I have always used teflon tape to seal the propane fittings with good repeatable results. Make sure the tape wraps in the opposite direction of the threads.

 

Generally, I don't recommend using teflon tape for gas fittings. In many states it isn't allowed. You really should use pipe thread dope instead. IMHO, it is far safer. If you use teflon tape and the tape shreds, pieces of it can get in the gas line and cause leaks at valves and such, which isn't the case with pipe thread dope.

 

I've never had that problem, but I can see how it could happen. It's important to apply the tape to the threads only, with no overhang. Here's Don Casey's advice:

"When connecting the supply hose to the solenoid, an adapter is usually required. Wrap the threads of the solenoid end of the adapter with Teflon sealing tape. Do not use Teflon tape on the hose end. The rule is that when the threads form the seal, you need Teflon tape, but not when the seal is formed with a flare, O-ring, or other compression fitting."

The entire article can be found here: http://www.boatus.com/boattech/Casey/18.htm

 

Use nitrogen for the test and eliminate the temp variances. 1 lb loss in 15 minutes may not be able to be read on the gauge at 175 psi. The value you place on your life is the amount of time you allow for leak testing propane.

 

Charles Law

All gases will increase in volume with an increase in temperature, per Charles Law. Charles Law: V1/T1=V2/T2
V= volume
T= Temperature
Temperature must be in Kelvin.
To convert Farenheight to Kelvin.
K=(Fdeg+459.67)/1.8

 

Well, I am keeping it simple for now.
The system passes 15-30 minute tests ok, longer than that and temperature does play games with pressure, so I left that alone for now.

I will monitor the system as I am using it, see if it behaves any better or worse.

 

BTW, IMHO, the propane tanks need to have their valves closed unless you are using the propane. This was an issue with Ken Barnes...where he wasn't sure of what electrical equipment he could use after his knockdown, because he wasn't sure the propane system wasn't leaking.

 

I know, this is why my new propane locker was placed in the cockpit - for easy access, so that I won't have an excuse not to turn off the tank when done cooking or for the night.

I suppose the downside is that a tank is so close to everything, but on a boat it is kinda hard to keep things "far" anyway, what with limited space and all.

 

The 24 Hour period intrigues me. Does that mean you leave your gas valve open all the time ?

Asking the question of everyone else, how many of you don't close off your gas supply when you finish using the stove etc ?

I can't believe that anyone would leave a gas line open permanently. Seems terribly silly to me.

ps - Brak answered my first question while I was still typing.

 

Guys... something is not adding up here.
The pressure should not drop until the tank is exhausted. The propane is in liquid-gas equilibrium in the tank, and the guage pressure will monitor the vapour pressure of the gas on top of the liquid. The vapour pressure is dependent only on tank temperature, and not content (well, not until it is about to run out that is).
Measuring the content of the tank is normally done by weight, with a spring balance. Pressure does not tell us much.

 

In English, to be inert is to be in a state of doing little or nothing.

In chemistry, the term inert is used to describe something that is not chemically active. The noble gases were described as being inert because they did not react with the other elements or themselves. It is now understood that the reason that inert gases are completely inert to basic chemical reactions (such as combustion, for example), is because their outer valence shell is completely filled with electrons. With a filled outer valence shell, an inert atom is not easily able to acquire or lose an electron, and is therefore not able to participate in any chemical reactions. For inert atoms or molecules, a lot of energy is involved before it can combine with other elements to form compounds. A high temperature and pressure is necessary, and sometimes requires the presence of a catalyst. Wikipedia

Nitrogen is an inert gas and is not chemically active.

 

Nitrogen is not a noble gas, and as such is not inert. However, it is far less active than most other common gases.