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Old 10-08-2007, 23:19   #1
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Another way to detect a propane leak

I thought I would post a description of my recent propane leak for other people who are as interested in failure modes as I am.

The pigtail from the tank to the pressure gauge has a swivel joint in it. I think this is supposed to relieve torque on the fitting as you move the hose around to attach your propane tank.

A few days ago, we were out of propane, so I went out to change the tank. I was surprised that we were out of propane so soon. When I got into the propane locker, I noticed that the pressure remaining was zero, which seemed a littler lower than usual for an "empty" tank on a hot day.

Ok, so maybe we were cooking longer than usual or something, right?

The propane locker is too small for two full-size tanks (no matter what Beneteau says), so we keep a few 1 pound tanks to use until we re-fill the big tank. When I attached one, propane started spraying out of the swivel joint in the pigtail. It looked just like spray coming out of a spray can - only a spray can makes a narrow spray, and this spray was going everywhere.

Naturally, I disconnected it as fast as I could, so I only got about 1 second of spray, but it was quite an impressive display. While disconnecting the tank, I noticed that the amount of spray varied a lot as the hose wiggled about.

My hypothesis is that this is what happened:

This swivel joint has probably been going bad for some time. The big tank was empty so soon because it was slowly leaking and the gas was running overboard through the vent. Normally, you would turn off the solenoid when the stove goes out, leaving some pressure in the tank. Because there was a constant leak, this time the tank pressure got down all the way to ambient. Because of varying temperature, I might even have sucked some air into that tank when temperatures dropped overnight, so I'm going to have it purged.

When I worked on the system, I moved the swivel joint. That made a bigger gap for the leak, which made a more impressive display. I couldn't hold the hose perfectly still while attaching and removing the small tank, and that motion explains why the leak varied some. The metal around the leak got very cold, and I could see condensation there.

It seems unlikely that the big tank leaked out in a catastrophic event similar to what I saw when I attached the new tank. It was very noisy, and even just leaking for a few seconds made a distinctive smell over a large area. I can't be sure, though, because it might have happened when nobody was around.

One thing that bothers me is that the system passed the leak tests last time I bought propane. I'm surprised that it could go this bad in such a short time. Obviously, replacing the bad fitting isn't enough -- I'll have to do a thorough inspection of the system before I start using it again.

I don't think I want a swivel in the replacement pig tail.

One thing I have thought of to do differently: Wear gloves while changing propane tanks. If the leak had been in a fitting closer to my hands, the spray might have been too cold to either turn off a valve or unscrew the smaller tank.

Depending how you want to look at it, you could say this is a demonstration of how dangerous propane is, or you could say it is a demonstration of how important it is to use proper safety systems. In this case, the vented locker performed it's function quite well.
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Old 11-08-2007, 00:54   #2
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How old was the system and how many tank changes was there and how many sea miles on it?
How far away was the support to the swivel?

Just looking at wear issues and when should one replace one.
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Old 12-08-2007, 10:57   #3
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The boat is only about 5 years old now. It was part of the dealer's inventory for about 6 months. After that, we lived aboard full time. I would guess we filled the tank maybe 2 or 3 times a year. Sea miles are insignificant -- thousands of miles, but still under ten thousand.

Here is a picture of the hose. The threaded part screws in to the regulator. The two arrows point at a joint that rotates. That is where the gas came out.

It is actually a pretty tight joint. It doesn't turn when I twist it by hand, but if I use a wrench to hold the nut part it turns easily. It also turned easily when it was still installed and I moved the hose/tank at all.

I suspect it swivels here so that moving the hose doesn't unscrew the threaded joint.

This hose is only about 2 feet (60 cm), so you can't move the tank (e.g. to disconnect it from the hose) without putting a bending force as well as a twisting force on this joint. I wonder if that contributed to the leak.

For repairs, I found an assembly that has the tank adapter, pressure gauge, and regulator as a single rigid module. The advantage is that there is no hose containing high pressure. It does not have any joint similar to the one on the old hose.
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Old 12-08-2007, 11:02   #4
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Ok, how do you attach a picture? Click on the paper clip, enter the file name in the popup, then click "Upload", right? It says "Uploading File(s)"...

It looks like the forum server stops acknowleding the packets after the picture is partly uploaded. I'll try again later.
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Old 12-08-2007, 21:25   #5
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Even though you are working on the outside of the boat, be vary careful Mark. You don't want to have this happen.
ARTICLE: Man injured when sailboat explodes in Ocean View marina (The Virginian-Pilot - HamptonRoads.com/PilotOnline.com)
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Old 13-08-2007, 04:59   #6
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I have a small canary in a cane cage I take to the boat with me. If he were to stop singing I know to get in the dingy and paddle as fast as I can.
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Old 13-08-2007, 13:58   #7
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Old 28-09-2007, 13:35   #8
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Propane = BOOM
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Old 28-09-2007, 14:55   #9
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Yikes, I know boats can be difficult to sell but you think he would run it offshore and sink it like everyone else does.
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Old 28-09-2007, 18:33   #10
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Thanks for sharing this story.

I just installed the propane system on my "land boat" and was taking a long look at that pigtail myself.

One thing you mention that is contrary to my installation is that you have a pigtail BETWEEN the tank and the regulator. The regulator's function is to drop the high pressure in the tank down to about 11 inches water column. If you have the pigtail between the tank and the regulator, you are putting enormous pressures into that pigtail line.

A safer installation would be to get a regulator that screws directly onto the tank, then run a pigtail from the regulator to the beginning of your lpg system. This way, there is no part of the system (or pigtail) subjected to the raw high pressure gas from the tank. It will only get a few PSI and will allow your pigtail/supply lines to have less stress.

PS: I'm still scared sh*tl*ss about having lpg gas. No leaks so far, but it's just not comforting to have an lpg refer with a flame always on and the potential to have a leak and end up like that boat in the link. My setup is regulator, then pigtail to a "t" flare fitting, then copper lines to the refer and stove, all with flare fittings. So far so good...

One scary part is this: When you smell a leak, you are supposed to vacate the area, open windows and not touch anything electrical that could arc. Funny thing - the propane shutoff switch is electrical and uses a solenoid. Yikes! How is that safe?

I think once you have a leak, you're either lucky or you're dead. Man, I hate this stuff.
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Old 28-09-2007, 22:19   #11
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Quote:
Originally Posted by ssullivan View Post
One thing you mention that is contrary to my installation is that you have a pigtail BETWEEN the tank and the regulator. The regulator's function is to drop the high pressure in the tank down to about 11 inches water column. If you have the pigtail between the tank and the regulator, you are putting enormous pressures into that pigtail line.
Before buying this boat, I looked at a lot of other boats, which meant looking in a lot of propane lockers. The pigtail between the tank and regulator appears to be a pretty standard configuration.

The good news is that the hose is rated for 350 psi. If I remember correctly, that is a safe working load pressure, not a failure limit. I usually see about 170 psi on a hot day. I think the pressure gauge only goes up to 200 or 250.

Quote:
A safer installation would be to get a regulator that screws directly onto the tank, then run a pigtail from the regulator to the beginning of your lpg system. This way, there is no part of the system (or pigtail) subjected to the raw high pressure gas from the tank. It will only get a few PSI and will allow your pigtail/supply lines to have less stress.
I wanted to do that. I was not concerned about the high pressure in the hose, but that the same failure mode would occur in the new hose.

In fact, I found out that there just isn't a good way to retro-fit that into my system. I would need way too many adapters. There are just too many sizes and types of connectors that don't go together, and some of the adapters are difficult or impossible to obtain. (e.g. I believe one propane distributor I called has some of them, but they will only sell fittings to licensed plumbers.)

I ended up just replacing the pigtail.

Quote:
One scary part is this: When you smell a leak, you are supposed to vacate the area, open windows and not touch anything electrical that could arc. Funny thing - the propane shutoff switch is electrical and uses a solenoid. Yikes! How is that safe?
I think the point of the solenoid valve is that the gas is turned off when you are not using it. That means that the stove can't leak when nobody is around, for example. This is a net gain because you will turn off the switch when you are done cooking, but you will not go out in the rain, open the propane locker, and turn the knob on the tank every time you make a cup of tea.

If you have a serious leak in the cabin, you don't want to turn off a switch in the cabin. On the other hand, if you break a knob off the stove, you can still turn off the switch.

Quote:
I think once you have a leak, you're either lucky or you're dead. Man, I hate this stuff.
I don't look at it that way at all. I had a leak, but I am not dead and I don't consider myself particularly lucky. The system worked exactly as intended: There are many joints in the propane system, but most are in the propane locker. One of them leaked, and the propane was only able to escape the locker by pouring overboard through the vent, where it would disperse into the environment and not be so dangerous.

Most things in the world are dangerous in some way or another. You just have to understand the danger and build your systems appropriately. I was careful when working on the propane system, but then I am careful when I put gasoline in my car too.
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Old 28-09-2007, 22:43   #12
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Sort of related but 99% of all houses and apartments in Asia use bottled LPG for their house cooking. The bottles usually sit on a cement pad out back of the kitchen. We have two full bottles right now. Certainly putting LPG or propane in an enclosed space on a boat is a different set of circumstances but like all things it is a manageable exercise.

Keep the equipment in good shape and rely on the built in failsafe, venting and warning systems. When installing a new system don't cut corners on the install thinking, "it can't happen to me."

There's lot's of ways to die on a boat, gas systems are just another one of them.

Did I mention keep the equipment in good shape?
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Old 29-09-2007, 05:07   #13
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Originally Posted by coot View Post

If you have a serious leak in the cabin, you don't want to turn off a switch in the cabin. On the other hand, if you break a knob off the stove, you can still turn off the switch.

He he... I should have known better than to suggest propane was scary. I know it's a passionate topic. But the above snippet is important. Thanks for sharing that too. I was not sure what the safety factor was in having the remote electric solenoid shutoff.

My imagination was seeing an lpg leak INSIDE the cabin, filling it up with gas while I wasn't there. I have a Norcold refer/freezer that runs on lpg, meaning it has a flame on 24/7. If say, my stove were to leak lpg, it would fill up the room and once it hit the flame for the refer- BOOM! I can't see that I could shut it off with a solenoid, since it would create a spark (potentially). I also can't see running out to shut off the propane at the tank. All I can see is running as fast and as far away as possible.

Or... should I just not be so concerned about my flare fittings coming loose after being jostled around for years?
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Old 29-09-2007, 08:10   #14
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Six flown to hospital after boat explosion

9:50AM Saturday September 29, 2007


Six people, including four children, were flown to hospital today after an explosion on board a boat off the Coromandel Peninsula.
The two adults on the 10m catamaran were the most badly injured, suffering serious burns, Coromandel Senior Constable John Morrissey said.............

Six flown to hospital after boat explosion - 29 Sep 2007 - NZ Herald: New Zealand National news
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Old 30-09-2007, 14:24   #15
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"I can't see that I could shut it off with a solenoid, since it would create a spark (potentially)."
Look behind you. [g] AFAIK you don't turn the power ON to shut a gas solenoid, you turn the power OFF. So, there's no spark to shut the valve, it shuts when the power to it is cut off. I've seen those solenoids set up on timers, so you can turn them "on" before you start cooking, and then they will shut the gas off automatically in an hour whether you remember it or not.

I thought those lpg reefers had to run on gimbals, or be kept level, and that they were unsuitable for marine use because of that?

Don't worry, every year a couple of homes and businesses blow up from gas explosions in the US alone. And nother couple of gasoline stations--usually from the folks who stop there to buy and light cigarettes while they are fueling. Um.
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