Lockdown batteries

Assuming you're looking to detect Calor gas or similar, you'll smell the gas long before you get to enough to go bang. All the same, it does make sense to have the detector as close to the bottom of the bilge as practicable, since that's where the gas will collect. But only if you have a dry bilge. Detectors don't like getting wet.
 
capnsensible said:
Dunno if anyone has heard of this accident:

https://assets.publishing.service.gov.uk/media/547c717be5274a429000013b/lord_trenchard.pdf

A friend of mine was onboard. Very unpleasant experience. Best not dik about with gas.......
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I own one of her sister ships - hence Paul’s reference to the case - and she has a particularly serious gas detector installed, with three detector heads, one under the cockpit and two more under the galley. That incident is no doubt why it is hard wired ‘On’. It is very sensitive and INCREDIBLY LOUD!

According to the MAIB report cited, a bottle had been changed incorrectly, leading to a leak into the locker, which in turn leaked into the under cockpit watertight compartment as there were imperfectly sealed penetrations into the bottle locker The skipper started the generator (which in our case we have not got) installed in the under cockpit space and the explosion followed.

The bottle locker is basically unchanged but the lower level penetrations are not there.
 
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Spirit (of Glenans) said:
IMHO there seems to be an inherent problem with that arrangement; if you go below and switch on the lighting breaker in order to activate the gas detector, the resulting spark will activate the gas, with disastrous results.
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My boat does not have remote deep bilges containing sources of ignition, while the battery master switch and breaker panel are around chest height, if I couldn't smell gas while reaching to operate them, the chances of setting off an explosion are remote. The Lord Trenchard is a salutary case, it would seem wise that the lowest penetration of the gas locker is the overboard "drain" while any other penetrations should be nearer to the top.

Camping Gas MSDS suggests the following:-
  • Odorisation allows a 0.5% gas content in the air to be detected
 
Spirit (of Glenans) said:
IMHO there seems to be an inherent problem with that arrangement; if you go below and switch on the lighting breaker in order to activate the gas detector, the resulting spark will activate the gas, with disastrous results.
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Of course not. You turn the gas off when you leave the boat. Upon arrival you turn the power on, then the gas.
 
rgarside said:
My boat does not have remote deep bilges containing sources of ignition, while the battery master switch and breaker panel are around chest height, if I couldn't smell gas while reaching to operate them, the chances of setting off an explosion are remote. The Lord Trenchard is a salutary case, it would seem wise that the lowest penetration of the gas locker is the overboard "drain" while any other penetrations should be nearer to the top.

Camping Gas MSDS suggests the following:-
  • Odorisation allows a 0.5% gas content in the air to be detected
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There should be no other penetrations of the gas locker into the accommodation.
The thing about gas, is that it's a gas, not a liquid.
It won't run out by gravity like water, it will diffuse through holes, even if they are high up.

Gas locker drains quite commonly block.
One boat I had, the outlet at the transom trapped water like the u-bend in a toilet.
I've seen them collect leaves over winter.
 
Stemar said:
Unfortunately that requires human intervention, far and away the least reliable part of most gas installations.
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It was that - the knowledge that I am an absent minded and scatterbrained individual - that kept me from wanting to learn to fly and kept me loyal to paraffin cookers on boats for the first half century of my sailing career.
 
Well, my house batts do indeed appear to be dead.

Assuming you can fit either, is there any reason for two batteries rather than one big one of similar capacity?
 
Stemar said:
Unfortunately that requires human intervention, far and away the least reliable part of most gas installations.
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If you can't remember to turn the gas off, you won't remember to turn the seacocks off, won't remember to turn the power off....

You have no business being on a boat :)
 
Kukri said:
It was that - the knowledge that I am an absent minded and scatterbrained individual - that kept me from wanting to learn to fly and kept me loyal to paraffin cookers on boats for the first half century of my sailing career.
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The alarm is there to warn you of gas in the bilge. If you turn the bottles off, it can't get there, there can't be a leak.

If you don't turn the bottles and the alarm off, like you didn't when the batteries went flat, and there was a leak, the bilges fill up with gas, the alarm runs the batteries flat, you arrive to a bilge full of gas. Oblivious to that, you start the engine to charge the batteries up BOOM
 
PaulRainbow said:
The alarm is there to warn you of gas in the bilge. If you turn the bottles off, it can't get there, there can't be a leak.

If you don't turn the bottles and the alarm off, like you didn't when the batteries went flat, and there was a leak, the bilges fill up with gas, the alarm runs the batteries flat, you arrive to a bilge full of gas. Oblivious to that, you start the engine to charge the batteries up BOOM
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“True, O King”, as Dorothy L Sayers would put it.

Alarm is hard wired, and I’ve just learned from JBJag27’s post 25, above, that this is because she was coded. The only way to turn it off is to pull the fuse. This I didn’t do because I was expecting to be back the next day, not six weeks later!

I always turn the bottle off.

On the ex boat, which had a seacock on the exhaust outlet, I used to hang the keys on the seacock. This made quite sure that I never started the engine with the seacock closed.
 
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Kukri said:
On the ex boat, which had a seacock on the exhaust outlet, I used to hang the keys on the seacock. This made quite sure that I never started the engine with the seacock closed.
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If like me you cannot get to the raw water and Exhaust seacocks you can fit an limit switch to the seacocks to disable the engine starter until the seacocks are open. This is the same as the neutral gear start interlock.
 
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