Propane leak into the bilge. What to do? - SailNet Community
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post #1 of 25 Old 04-03-2013 Thread Starter
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Propane leak into the bilge. What to do?

Ideally, I like to think of disasters and make plans for how to cope with them, before they happen. Sadly, this is not always the case, but when it has been, is sure is nice to have a plan (or plans) of action to try. That said, there is no propane leak on my boat right now. But what if there was?

We all know propane + enclosed boat hull = bad. We can buy sniffers to alert us to the presence of propane, but what if we did blow a seal and we leaked a bunch of the explosive stuff into the bilge. How do we get it out?

I've heard that a manual diaphragm bilge pump can be used, but I'm a bit skeptical. What about an electric (ignition protected of course) bilge pump? I may have to pick up a colored smoke bomb this 4th of July and see if I can figure out how to get rid of all the colored smoke to test any theories we come up with.

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post #2 of 25 Old 04-03-2013
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Re: Propane leak into the bilge. What to do?

Light a match?!? ..sorry, couldn't resist!

I, personally, haven't come across a manual bilge pump that was very good at sucking air, but I guess that's better than nothing. See how you go with the coloured smoke - and do take video, please.



(AFAIK, the usual course of action if an alarm goes off is to turn off all electrics, lift up the boards, open all hatches, and go sit on the beach for a while.)

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post #3 of 25 Old 04-03-2013
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Re: Propane leak into the bilge. What to do?

If you have a gasoline engine, like an atomic 4, they must have an ignition protected bilge blower installed. It pulls air out of the boat into the atmosphere and should clear out an enclosed boat in 5 minutes.
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post #4 of 25 Old 04-03-2013 Thread Starter
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Re: Propane leak into the bilge. What to do?

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If you have a gasoline engine, like an atomic 4, they must have an ignition protected bilge blower installed. It pulls air out of the boat into the atmosphere and should clear out an enclosed boat in 5 minutes.
Hmmm.... I have a blower for my diesel engine. I completely forgot I had one, because I never use it. It's bloody noisy and designed to feed cool air to the engine compartment. I wonder if I could rig up a switch to reverse the + and - and it would suck air (or propane) out of the bilge... Hmmm.... Thanks for the reminder that I have one of those things!

As for opening up all the hatches and sitting on the beach, not such a great plan if you're not near a beach. Even underway near land it would be nerve racking to be in a boat full of propane.... I hear it's 8 times heavier than air, so it seems like opening the hatches might not be enough.

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post #5 of 25 Old 04-03-2013
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Re: Propane leak into the bilge. What to do?

The propane sniffers are designed to alarm at a fraction of the explosive concentration, so hopefully you were on board to hear the alarm and responded by turning the gas off at the bottle.

If you weren't on board, the propane has no business being on at the bottle.

Although propane is heavier than air, I would have thought there would still be diffusion going on so it will eventually dissipate from the bilge, given ventilation but not forced ventilation.

Which is a long winded way of saying : open all the windows and hatches, and access hatches into the bilge. Go away from the boat and wait an hour. Let the breeze do it's work.

I would have thought this is safer than operating any electrical switches for fans. What if the propane has filled the cabin too and the spark from the switch sets it off?

The advice for home gas leaks is open some windows and do not touch any switches. Get away.

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post #6 of 25 Old 04-03-2013
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Re: Propane leak into the bilge. What to do?

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Hmmm.... I have a blower for my diesel engine. I completely forgot I had one, because I never use it. It's bloody noisy and designed to feed cool air to the engine compartment. I wonder if I could rig up a switch to reverse the + and - and it would suck air (or propane) out of the bilge... Hmmm.... Thanks for the reminder that I have one of those things!

As for opening up all the hatches and sitting on the beach, not such a great plan if you're not near a beach. Even underway near land it would be nerve racking to be in a boat full of propane.... I hear it's 8 times heavier than air, so it seems like opening the hatches might not be enough.

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Better be good and sure that diesel blower is safe for explosive gases....

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post #7 of 25 Old 04-03-2013
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Re: Propane leak into the bilge. What to do?

Med, a blower is a good idea, and if you have one already you could always physically mount it around the other way if swapping the wires doesn't work. Just make sure you can get plenty of air in at bilge level and that the engine (preferably) isn't running at the time. Diesels run just fine on gas..

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As for opening up all the hatches and sitting on the beach, not such a great plan if you're not near a beach. Even underway near land it would be nerve racking to be in a boat full of propane.... I hear it's 8 times heavier than air, so it seems like opening the hatches might not be enough.
Well, there's always the dinghy.

Actually, what you have to be careful of is maintaining the air/fuel ratio within the explosion limits (between 2.4% and 9.6% roughly) for long periods of time and, as MarkSF pointed out, the alarm will go off well before then. The stuff might be heavier than air, but with an SG of 1.52 (air=1), 8 times heavier it isn't. If the wind is blowing, it's surprising how much you can move through a boat if you need to.

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post #8 of 25 Old 04-03-2013
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Re: Propane leak into the bilge. What to do?

Diesels run just fine on gas..

That is only if by (fine) you mean they rev right up and run to destruction...

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post #9 of 25 Old 04-03-2013
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Re: Propane leak into the bilge. What to do?

I don't think any electrical air handler would be safe in that circumstance. I might think about having a CO2 or Halon extinguisher to fill the bilge with a non-combustible gas. If the bilge was filled with a mixture of CO2/Halon and Propane, it SHOULD act to prevent any explosion to allow you to then turn on a blower.
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post #10 of 25 Old 04-03-2013
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Re: Propane leak into the bilge. What to do?

I served on submarines where evacuating toxic/explosive gases and replacing them with clean air is a daily part of life. There is a factor called the "half-life". The half-life is the time that it takes to replace HALF of the atmosphere on the entire vessel.

A recreational sailboat (even a serious cruiser) is much smaller than a submarine, so the half-life is considerably shorter.

In your scenario of a catastrophic hose or seal failure, yes, an ignition proof blower like the one for gasoline marine engines is a good idea. Obviously, open all hatches and ports if weather conditions are calm enough. The diaphram bilge pump will not move a significant amount of gas.

If you disperse CO2 into the bilge, you could displace the propane from the bilge, into the main cabin.

To calculate your half-life, estimate the volume of your cabin (or bilge if you prefer), and the CFM rating of your ignition-proof blower, then calculate how long it will take the blower to move HALF of the volume of the bilge.

This will help you determine how long you need to run the blower, in order to clear the bilge of propane.

Hope this helps.

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