lockie wrote:Gotta chime in here as I design electrical installations for areas that have flammable gases and vapours (oil and gas plants, offshore platforms and the like).
SNIP
Keep the petrol containbers out where they are freely ventilated and the vapours can drain away easily. Lashed somewhere on deck is best unless you have a purpose designed ventilated locker, like some bigger boats do for LPG cylinders.
Cheers, lockie
Thanks Lockie, good insight. One of our Members here, Mark works in the refinery business, and one of his colleages is a good friend of mine. So, I asked him the question.
His simple answer was, if you can smell it, it's a problem.
Our in depth discussion was around how fuel vapours dissipate, and that whilst an oil rig or refinery have extremely strict protocols, the way we have (and he's seen my boat) our boats set up would present a minimal risk. The point at which a fuel/air mixture would explode has to be fairly precise, as in somewhere between 94% to 99% air to fuel ratio. Less air and it won't ignite, less fuel and it won't ignite. His reasoning for believing we are OK is as follows.
The hard plastic and metal fuel tanks have a breather in the cap, this is to allow the space once occupied by petrol to be replaced by air, not to vent expansion and contraction. If this is closed when you shut down, there should be no escape of vapours.
He also then said that any vapour that does escape into the bilges would still eventually dissipate into the atmosphere, it won't sit there indefinitely. The time this would take would depend on moisture, air flow and temperature, but again, if you stick your head in the bilge and smell petrol switch off the electricity and don't light your stove....
In essence, whilst having petrol in your cockpit locker isn't the perfect solution, it is better than having a sealed fuel container in the sun for weeks, months at a time. Just keep the cabin and the bilge aired as best you can, and keep a nostril out for smells.
To the original post. The electricity in very near proximity to the fuel tank is a limiting factor to all the above, it is something that really should be rectified as quickly as possible and for the trip north you're going to have to either lash the tanks to the deck, or move the battery and wiring.
Oh, and one other thing. Dulcamara is 30 years old this year, so a young'un compared to other Top Hats out there. She's had this set up for as long as the previous owner had her, and possibly before that, so whilst I will take extra care to check venting and airation, I'm confident it is quite safe for our purposes.