Propane leak - Page 2 - SailNet Community
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post #11 of 35 Old 10-09-2007
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Quote:
Originally Posted by Sailormann View Post
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.

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post #12 of 35 Old 10-10-2007
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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.
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post #13 of 35 Old 10-10-2007
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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
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post #14 of 35 Old 10-10-2007
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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.
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post #15 of 35 Old 10-10-2007
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Propane does change pressure and volume with temperture changes. Just like Freons do.

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post #16 of 35 Old 10-10-2007
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a propane leak is nothing to mess with, I would have it off my boat in a nanosecond.
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post #17 of 35 Old 10-10-2007 Thread Starter
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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)
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post #18 of 35 Old 10-10-2007 Thread Starter
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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).
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post #19 of 35 Old 10-11-2007
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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.
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post #20 of 35 Old 10-11-2007
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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.

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