Bilge blowers

Lady Campanula said:
OK, OK, you win! I'll just go on betting on the statistics to get me by....

Now, another leetl question. What about the highly flammable, volatile, almost explosive, vapours that constitute those 'Easy Start' sprays one sometimes uses to start the donk?

Much of that stuff is not drawn into the air filter, then the pre-chamber, and combusted, but misses and is squirted down alongside the engine block. What happens to it? Is it lighter than air, and so dissipates like hydrogen? Or otherwise....?

I'm beginning to think I should do something safer - like EOD!

:)
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'Otherwise' - it's mainly ether.
 
Ether has a density of 1.97 g/L, so much lighter than air, but as it evaporates, the stoichiometric ratio can become critical, and BOOM given any encouragement. Most Easy Start formulations (ins StartYa******* !) are about 25% ether and e.g. propane.

It is also an anaesthetic, and quite addictive, officer. :D

I concur with my experienced friend that all the inflammables on board should be kept well outwith the main body of the boat. Looks as if the stern locker is due for a clear out and redefinition of use ?
 
It is questionable whether you should be using starting fluid sprays. You can become addicted to it! Some say engines do as well.
Problem with it is said to be that you cannot control the ignition timing in a diesel ... you do in a petrol engine because it is still ignited by the spark.

It's ether as far as I know so about 2.5 times the density of air.
Very easily ignited .. That's why it's good as a starting aid. It will ignite with a weak spark in a petrol engine or with poor compression in a diesel engine
 
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sarabande said:
I concur with my experienced friend that all the inflammables on board should be kept well outwith the main body of the boat. Looks as if the stern locker is due for a clear out and redefinition of use ?
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Fortunately my (sealed, vented) gas locker is quite unnecessarily large for its intended purpose, which means that as well as the bottle and spare it can also hold a can of spare diesel, a good season's worth of lamp oil, and the refill can of butane for the stove lighter and rope-end-sealer.

Apart from said small butane items (which I assume have too little gas in to do major harm), the most flammable thing outside that locker is probably the gin :-)

Pete
 
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sarabande said:
Ether has a density of 1.97 g/L, so much lighter than air ...
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I remember reading about explosions from the (historical) use of diethyl ether in operating theatres - vapours creeping along the floor and igniting 'next door', as it were - so I've always considered ether as being heavier than air. And sure enough, my can of Easy-Start cautions that it produces 'inflammable heavy vapour'.

So - onto http://www.inchem.org/documents/icsc/icsc/eics0355.htm - which reads:
"DIETHYL ETHER - PHYSICAL DANGERS: The vapour is heavier than air and may travel along the ground; distant ignition possible. As a result of flow, agitation, etc., electrostatic charges can be generated."

Relative vapour density (air = 1): 2.6
Relative density of the vapour/air-mixture at 20°C (air = 1): 1.9
 
Make up your minds :-)
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Ether is C2H5OC2H5 So RMM is approx 74

1 mole, ie 74g has a volume of approx 25 litres at ambient temps and pressures

Air is 1/5 oxygen (RMM = 32) 4/5 nitrogen (RMM = 28) so average RMM is just a tad under 29.

So 29 g air has a volume of 25 litres

74/29 = 2.55 so ether vapour approx 2½ times as heavy as air
 
Vapour fires

Almost without exception there is a major boat fire here every year sometimes more. Perhaps there are more petrol powered inboard boats although sometimes it is the gas system. Certainly injury occurs and the boat is destroyed.
Danger times are at refueling or initial start up. For gas explosions it is after a period of non use. Petrol engines with carburettors are susceptible to flooding of the cab if the engine doesn't start immediately.
Fortunately outboards are becoming the preference over inboard petrol engines so we will see less modified car engines in boats. O/bs tending to be less inclined to leak fuel and are out board anyway so away from bilge.
It requires serious ventilation and patience to get rid of the vapour.

If you choose a fan not designed for bilge ventilation you need to look seriously at the motor. Most computer type very flat fans have a brushless design so are safe. But may be too small. I have not heard of static build up as a concern. Sucking air from the bilge enables you to lead a duct right to the bottom whereas pressurising the area means air leaves from areas near the vents. ie difficult to get it to leave from low down.

Yes vapour/gas fire is a real concern. Ventilation and gas detectors all help to minimise the danger.
Don't imagine a fire extinguisher will help.
A tall mast good sails no engine and alcahol stove can help even more. olewill
 
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