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Old 31 August 2010, 17:46   #31
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Originally Posted by Nos4r2 View Post
It is-that's why fuel stores have vents in the doors next to the floor.

It's not online but when I did the ADR course, they show a video of petrol vapour being poured a good few feet down a piece of guttering to a flame and the flame backtracking to the can.
One of the curious things I remembered whilst reinvigorating my interest in chemistry whilst tutoring my son for his intermediates (just a fave subject for me) was that a 'vapour' is a curious state of a liquid moving to a gas (or vice versa), and is highly dependant on a number of factors.

Whilst in a transitional phase.. petrol vapour may in bulk may be heavier than air ... but its made up of quite a few volatile and aromatic hyrdocarbons, like benzenes in particular, which all have different rates of evaporation dependant on ambient temperature for example.. so that suggests, that whilst you may smell their presence immediately, once their concentration has diminished, there may be less aromatic vapour present, and thus residual vapour is less detectable, but no less flammable.. particularly in an open boat but in an enclosed space with dodgy electrics, its got to be trouble.

This we all know, but the risk of not being able to detect the stuff when its a confined vapour next to electrics is I think what would be helpful to know how to detect/avoid..and infact something most of us if we are honest, is a part of normal boating we just live with unless you only use external tanks .. which on a 5m+ RIB is not common,.. so thats pretty much many of us

Merlin .. I think because of the violence of this incident it would be very helpful if at least you could give us a layout plan/sketch of your boat.

The ignition would be a subject for debate, but a plan of where evrything was might be helpful to us all, and to you, to help shed some light here
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Old 31 August 2010, 17:58   #32
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Whilst in a transitional phase.. petrol vapour may in bulk may be heavier than air ... but its made up of quite a few volatile and aromatic hyrdocarbons, like benzenes in particular, which all have different rates of evaporation dependant on ambient temperature for example.. so that suggests, that whilst you may smell their presence immediately, once their concentration has diminished, there may be less aromatic vapour present, and thus residual vapour is less detectable, but no less flammable..
Well I'm Wiki'd, I'd always had you down as thick as mince.
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Old 31 August 2010, 18:10   #33
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Well I'm Wiki'd, I'd always had you down as thick as mince.
I dont need Wiki to find your credentials fella

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you might want some constructive comment rather than Mollers' pish.
give me another go ?
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Old 31 August 2010, 18:20   #34
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Only teasin'.
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Old 31 August 2010, 18:32   #35
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Only teasin'.
Aye .. ... next time I might not be so subtle ..






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. away and make some pasties tosser
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Old 01 September 2010, 02:43   #36
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. away and make some pasties tosser
I would, if I could only remember how to make 'em.
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Old 01 September 2010, 07:39   #37
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Sorry to hear about your issues, glad you are all OK. Might be worth reporting it to the MAIB as if there is a "lesson to be learned by everyone" then they should investigate and share that - even if its just a preliminary examination. I'd hope that they would take it seriously enough to come up with a likely cause (possibly with some sort of fire investigation expert) rather than speculation. I for one will be examining the condition of the main battery cables where they leave the console as clearly any chaffing causing a short here is a likely suspect that I've probably ignored. That's after my "isolator switch" - but I don't fancy getting to the switch if the console is alight! So thanks for sharing.
We have just had a misfiring fault diagnosed on a 2 year old 175 opti with 70 hrs as a wire to the compressor chafing through causing a short. Certainly worth checking wiring as Polwart says on any areas where chafing can occur. Considering this occurred within the engine where the design is mass produced, the likelihood of other wires retro fitted when putting consoles together would be much higher imho.

Glad you are all OK.

I'm very curious to look further in to the likelihood of fire when there is a console with 150l of fuel underneath and a bulkhead to separate the batteries, isolators etc from it.
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Old 09 September 2010, 06:09   #38
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What to look out for

The good old Recreational Craft Directive calls up various standards to prevent this sort of situation. When purchasing a RIB with fuel tanks under the deck - or where fuel could get into the bilges - its worth checking these points with the manufacturer:

- larger boats must have a permanently installed fuel system
- spaces with fuel tanks must be vented, with rules about the area of the vents
- electrics in spaces which could get fuel vapour in should be ignition protected to ISO8846
- fuel filling points should ensure no uncontained fuel can get below deck
- fuel filling points should be more than 400mm from any vents
- there must be a means of preventing siphoning from the tank(s) if the fuel system fails
- metal tanks must be earthed

These are just the main points - there are lots of others. In practice this means all the components below deck, like bilge pumps, fuel valves, switches etc should meet ISO8846. All other electrics, including the battery, must be completely separate from any spaces that can collect fuel vapour. If split fuel can get onto the deck, any deck plates should be completely water-tight. The space vents should be big enough to prevent fuel vapour accumulating.

As far as I can see, if a RIB meets the rules then an explosion can't happen.
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Old 09 September 2010, 18:30   #39
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The good old Recreational Craft Directive calls up various standards to prevent this sort of situation. When purchasing a RIB with fuel tanks under the deck - or where fuel could get into the bilges - its worth checking these points with the manufacturer:

- larger boats must have a permanently installed fuel system
- spaces with fuel tanks must be vented, with rules about the area of the vents
- electrics in spaces which could get fuel vapour in should be ignition protected to ISO8846
- fuel filling points should ensure no uncontained fuel can get below deck
- fuel filling points should be more than 400mm from any vents
- there must be a means of preventing siphoning from the tank(s) if the fuel system fails
- metal tanks must be earthed

These are just the main points - there are lots of others. In practice this means all the components below deck, like bilge pumps, fuel valves, switches etc should meet ISO8846. All other electrics, including the battery, must be completely separate from any spaces that can collect fuel vapour. If split fuel can get onto the deck, any deck plates should be completely water-tight. The space vents should be big enough to prevent fuel vapour accumulating.

As far as I can see, if a RIB meets the rules then an explosion can't happen.
I cant think of many that would meet those rules
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Old 09 September 2010, 18:37   #40
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I cant think of many that would meet those rules
on investigation my electronics (blue sea panel, battery switch etc are all ISO 8864 rated. The rule about the fuel filler and vent is an interesting one as I have a perko filler that has the vent built into the fitting as well.

THe tank in my rib is under deck and there are no vents or holes into the deck to vent it. Can't see how that would work?
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