DJE
Well-Known Member
The point is that what you have in a gas bottle is liquid butane. Shake the bottle and listen. It vapourises when you let it out and a small amount of liquid makes a lot of vapour.
Explosive Mix
- Thread starter Das_Boot
- Start date
Das_Boot
Well-Known Member
I know that just look at a ciggarette lighter. However if a lighter failed it would hardly blow up the boat.
I was trying to find out the minimum size of cannister that in the worst case scenario (a complete leak) would still be safe.
I was trying to find out the minimum size of cannister that in the worst case scenario (a complete leak) would still be safe.
snowleopard
Well-Known Member
[ QUOTE ]
It is realy counter intuitive to believe such a small amount of gas could be so dangerous.
[/ QUOTE ]
look at it another way. assume a car with a 2 litre petrol engine, running at 2000 rpm, will go for 1 hour on a gallon of petrol. at 2000 rpm, the engine is burning 1000 x 2 litres of explosive mixture per minute i.e. 120,000 litres in an hour.
1/4 litre, the amount of liquid in your gas cartridge, will produce 7000 litres of mixture. doesn't look so unlikely does it?
It is realy counter intuitive to believe such a small amount of gas could be so dangerous.
[/ QUOTE ]
look at it another way. assume a car with a 2 litre petrol engine, running at 2000 rpm, will go for 1 hour on a gallon of petrol. at 2000 rpm, the engine is burning 1000 x 2 litres of explosive mixture per minute i.e. 120,000 litres in an hour.
1/4 litre, the amount of liquid in your gas cartridge, will produce 7000 litres of mixture. doesn't look so unlikely does it?
Das_Boot
Well-Known Member
I would say the rough volumn of my boat is 60 meters cubed therefor if I am not mistaken 1 meter cubed contains 1000 litres that would make 60000 litres therefore if the mix is 2% I would need 1200 litres of gas mix. It doesnt look good. or maybe my math is bad.
Thistle
Well-Known Member
Have a look at a safety data sheet (eg the one from BOC at http://www1.boc.com/uk/sds/special%5Cbutane.pdf).
They may be non-toxic but, as well as the danger of explosion, there are other dangers, eg "Inhalation In low concentrations may cause narcotic effects. Symptoms may include dizziness, headache, nausea and loss of co-ordination. In high concentrations may cause asphyxiation. Symptoms may include loss of mobility/consciousness. Victim may not be aware of asphyxiation."
I think I'd prefer to treat them as though they were toxic.
They may be non-toxic but, as well as the danger of explosion, there are other dangers, eg "Inhalation In low concentrations may cause narcotic effects. Symptoms may include dizziness, headache, nausea and loss of co-ordination. In high concentrations may cause asphyxiation. Symptoms may include loss of mobility/consciousness. Victim may not be aware of asphyxiation."
I think I'd prefer to treat them as though they were toxic.
Das_Boot
Well-Known Member
I dont believe he meant it (non-toxic) he was just trying to have a back handed dig not very christian but hey.
VicS
Well-Known Member
Re: Explosive Mix ... problem with the arithmetic
I think there is a problem with the arithmetic there.
If the butane cannister holds 220g and the RMM of butane is 58 then the canister holds 220/58 = 3.79 moles.
1mole occupies 22.4 litres at STP so 3.79 moles occupy 84.9 litres! (not about 1000 litres)
If the LEL is 2% then that quantity of gas can just create an explosive mixture of 84.9 X 100/2 = 4245 litres or about 4¼ cubic metres, not 50.
In fact the LEL of butane is 1.5% and as the LEL is quoted at 20C we can also take a figure of 24 litres as the volume of one mole of gas.
Repeating the calculation with these figures gives a final answer of 6 cubic metres (at 20C)
Not relating to your post, but to others in the thread, it must be remembered that although butane is more dense than air (about double in fact) if released into the cabin it will not drain into the bilges like a liquid will or even sink to form a permanent layer at floor level. It will, after initially sinking, in a short space of time, diffuse throughout the volume of the cabin and eventually the concentration will be the same every where. Inevitably some will find its way into lockers and the bilges though.
BTW the LEL for propane is 2.1% and the RMM is 44 should anyone feel like doing the sums for it.
I think there is a problem with the arithmetic there.
If the butane cannister holds 220g and the RMM of butane is 58 then the canister holds 220/58 = 3.79 moles.
1mole occupies 22.4 litres at STP so 3.79 moles occupy 84.9 litres! (not about 1000 litres)
If the LEL is 2% then that quantity of gas can just create an explosive mixture of 84.9 X 100/2 = 4245 litres or about 4¼ cubic metres, not 50.
In fact the LEL of butane is 1.5% and as the LEL is quoted at 20C we can also take a figure of 24 litres as the volume of one mole of gas.
Repeating the calculation with these figures gives a final answer of 6 cubic metres (at 20C)
Not relating to your post, but to others in the thread, it must be remembered that although butane is more dense than air (about double in fact) if released into the cabin it will not drain into the bilges like a liquid will or even sink to form a permanent layer at floor level. It will, after initially sinking, in a short space of time, diffuse throughout the volume of the cabin and eventually the concentration will be the same every where. Inevitably some will find its way into lockers and the bilges though.
BTW the LEL for propane is 2.1% and the RMM is 44 should anyone feel like doing the sums for it.
Das_Boot
Well-Known Member
Re: Explosive Mix ... problem with the arithmetic
So what you are saying that the small canister wont cause an explosion in a 12ish x 3.5 x 2 meter space or am I getting you wrong.
I know this works out at 84 and I said 60 meters cubed but I was taking into account the curve of the boat. Maybe I should say 40 cubic meters just to be safe.
So what you are saying that the small canister wont cause an explosion in a 12ish x 3.5 x 2 meter space or am I getting you wrong.
I know this works out at 84 and I said 60 meters cubed but I was taking into account the curve of the boat. Maybe I should say 40 cubic meters just to be safe.
snowleopard
Well-Known Member
Re: Explosive Mix ... problem with the arithmetic
if the gas is evenly mixed throughout the boat the concentration will be too low to explode. if however it flows down into the bilges it will be more concentrated there and at least some of it will be in the required concentration range.
if the gas is evenly mixed throughout the boat the concentration will be too low to explode. if however it flows down into the bilges it will be more concentrated there and at least some of it will be in the required concentration range.
Das_Boot
Well-Known Member
Re: Explosive Mix ... problem with the arithmetic
'''''''Not relating to your post, but to others in the thread, it must be remembered that although butane is more dense than air (about double in fact) if released into the cabin it will not drain into the bilges like a liquid will or even sink to form a permanent layer at floor level. It will, after initially sinking, in a short space of time, diffuse throughout the volume of the cabin and eventually the concentration will be the same every where. Inevitably some will find its way into lockers and the bilges though. '''''''
I think you forgot to read this part of his post!!!!
'''''''Not relating to your post, but to others in the thread, it must be remembered that although butane is more dense than air (about double in fact) if released into the cabin it will not drain into the bilges like a liquid will or even sink to form a permanent layer at floor level. It will, after initially sinking, in a short space of time, diffuse throughout the volume of the cabin and eventually the concentration will be the same every where. Inevitably some will find its way into lockers and the bilges though. '''''''
I think you forgot to read this part of his post!!!!
VicS
Well-Known Member
Re: Explosive Mix ... problem with the arithmetic
Despite my pedantic correction of arithmetic. Any signiicant leakage of gas into a confined space must be regarded as potentially dangerous.
You or I would look pretty stupid standing at the Pearly Gates, calculator in hand saying "According to my calculations it shouln't have exploded"
Despite my pedantic correction of arithmetic. Any signiicant leakage of gas into a confined space must be regarded as potentially dangerous.
You or I would look pretty stupid standing at the Pearly Gates, calculator in hand saying "According to my calculations it shouln't have exploded"
BSSOffice
Well-Known Member
This is a snippet of the Boat Safety Scheme information on the nature of LPG
<<LPG liquid is colourless and its density as a liquid is approximately half that of water. If LPG liquid is spilt onto water, it will float on the surface before vapourising. One volume of liquid produces approximately 250 volumes of gas and thus a leak of liquid poses a considerable hazard.
LPG vapour is heavier than air, butane about twice as heavy and propane about one and a half times heavier. Because of this, LPG vapour will tend to fall to low level and flow along cockpit floors, bilges and other low lying places. LPG vapour may travel some distance and in poorly ventilated places the vapour may persist for some time.
A mixture of LPG and air at a concentration of LPG between 2% and 10% is a flammable mix. Outside of this range the mixture is either too weak or too rich to ignite. If vapour within the flammable range is present in a confined space an explosion will result from ignition.
It is also possible for vapour/air mixtures arising from leaks or other causes to be ignited some distance from the point of escape and the flame travel back to the source.
[Source Boat Safety Scheme Technical Manual]
A mixture of LPG and air is flammable within certain concentrations, known as the flammable range. This range is 1.8% to 9.0% for BUTANE and 2.2% to 10% for PROPANE. These are approximate values at atmospheric pressure. At higher pressures, or with oxygen, the flammability limits are different.
An accidental release of LPG will be too rich to burn until it has mixed with air and will tend to settle in low places. On the fringe the gas cloud will mix with air and if the resultant combustible mixture reaches an ignition source, it will ignite. Heat generated by the burning gas causes turbulence and further mixing results such that, eventually, most of the gas will become mixed within the flammable range. A serious hazard may then result. [Source, LPG Association, LPG Fundamentals]>>
There are huge numbers of boats on UK inland waters operating with LPG on board very safely. The gas is stored in safe conditions and the LPG supply systems are well built and well maintained. Of 45 fires/explosions we recorded on boats last year, 11% were related to LPG although 22% of causes are unconfirmed.
Our advice is to treat portable cylinders (including 'empties') as you would a large gas bottle, store in drained, LPG-tight lockers or somewhere that escaping gas will drain overboard rather than into the interior of the craft.
If it helps, we have a leaflet called Avoiding Fire Afloat - Safe use of LPG. We can send it out in print or email.
<<LPG liquid is colourless and its density as a liquid is approximately half that of water. If LPG liquid is spilt onto water, it will float on the surface before vapourising. One volume of liquid produces approximately 250 volumes of gas and thus a leak of liquid poses a considerable hazard.
LPG vapour is heavier than air, butane about twice as heavy and propane about one and a half times heavier. Because of this, LPG vapour will tend to fall to low level and flow along cockpit floors, bilges and other low lying places. LPG vapour may travel some distance and in poorly ventilated places the vapour may persist for some time.
A mixture of LPG and air at a concentration of LPG between 2% and 10% is a flammable mix. Outside of this range the mixture is either too weak or too rich to ignite. If vapour within the flammable range is present in a confined space an explosion will result from ignition.
It is also possible for vapour/air mixtures arising from leaks or other causes to be ignited some distance from the point of escape and the flame travel back to the source.
[Source Boat Safety Scheme Technical Manual]
A mixture of LPG and air is flammable within certain concentrations, known as the flammable range. This range is 1.8% to 9.0% for BUTANE and 2.2% to 10% for PROPANE. These are approximate values at atmospheric pressure. At higher pressures, or with oxygen, the flammability limits are different.
An accidental release of LPG will be too rich to burn until it has mixed with air and will tend to settle in low places. On the fringe the gas cloud will mix with air and if the resultant combustible mixture reaches an ignition source, it will ignite. Heat generated by the burning gas causes turbulence and further mixing results such that, eventually, most of the gas will become mixed within the flammable range. A serious hazard may then result. [Source, LPG Association, LPG Fundamentals]>>
There are huge numbers of boats on UK inland waters operating with LPG on board very safely. The gas is stored in safe conditions and the LPG supply systems are well built and well maintained. Of 45 fires/explosions we recorded on boats last year, 11% were related to LPG although 22% of causes are unconfirmed.
Our advice is to treat portable cylinders (including 'empties') as you would a large gas bottle, store in drained, LPG-tight lockers or somewhere that escaping gas will drain overboard rather than into the interior of the craft.
If it helps, we have a leaflet called Avoiding Fire Afloat - Safe use of LPG. We can send it out in print or email.
Thistle
Well-Known Member
"LPG vapour is heavier than air, butane about twice as heavy and propane about one and a half times heavier."
[begin rant]
When will people learn that there is a difference between "weight" and "density" and start to use these, and associated terms like "heavier", correctly? A chunk of lead weighing a kilogram and a chunk of balsa weighing a kilogram lying beside each other have the same weight; neither is heavier than the other. The chunk of lead will sink if it is put into water because it is more dense than water; the balsa will float on water because it is less dense than water.
I find that incorrect and / or careless use of terms like these in a document (or post) leads me to doubt the value of the rest of the document (or post).
[end rant]
(Ex-)schoolteacher!
[begin rant]
When will people learn that there is a difference between "weight" and "density" and start to use these, and associated terms like "heavier", correctly? A chunk of lead weighing a kilogram and a chunk of balsa weighing a kilogram lying beside each other have the same weight; neither is heavier than the other. The chunk of lead will sink if it is put into water because it is more dense than water; the balsa will float on water because it is less dense than water.
I find that incorrect and / or careless use of terms like these in a document (or post) leads me to doubt the value of the rest of the document (or post).
[end rant]
(Ex-)schoolteacher!
stephenh
Well-Known Member
When charging your batteries an amount of Hydrogen will escape...
Static electricity ( from artificial fibres ?) has been known to spark an explosion..
So shouldn't you chuck your batteries, fleeces, oilies and indeed sails and halyards, overboard with your gas cylinders ???!!!
Then you will be really safe....
Static electricity ( from artificial fibres ?) has been known to spark an explosion..
So shouldn't you chuck your batteries, fleeces, oilies and indeed sails and halyards, overboard with your gas cylinders ???!!!
Then you will be really safe....
iangrant
Well-Known Member
Stop worrying booty - there is no danger - you won't get blown up - honest!
Ian
Ian
G
Guest
Guest
there are many other items on board that are dangerous - so suggest you get rid of :
Petrol cans for outboard
Bunk cushions if not latest fire retardent foam and covers
Books and charts that are easily set fire
Timber bulkheads that are not cased in fire retardent caoting etc.
shall we go on ...
Boats for many years have sailed with calor gas etc. and not that many have actually gone BOOM ... yes there have been some spectacular ones .... it really does take the top of the boat !! But not many considering how many are fitted with gas.
I like Calor gas ... ballon is sited in locker aft end of cockpit - I turn off gas when not using - not trusting hoses / connectors etc. I prefer this to a Camping Gaz fitted cooker with cylinders suspended under it .... and having seen many a flair up with spirit stoves .... I'll stick to my eggs and bacon coming off the gas thanks !
Petrol cans for outboard
Bunk cushions if not latest fire retardent foam and covers
Books and charts that are easily set fire
Timber bulkheads that are not cased in fire retardent caoting etc.
shall we go on ...
Boats for many years have sailed with calor gas etc. and not that many have actually gone BOOM ... yes there have been some spectacular ones .... it really does take the top of the boat !! But not many considering how many are fitted with gas.
I like Calor gas ... ballon is sited in locker aft end of cockpit - I turn off gas when not using - not trusting hoses / connectors etc. I prefer this to a Camping Gaz fitted cooker with cylinders suspended under it .... and having seen many a flair up with spirit stoves .... I'll stick to my eggs and bacon coming off the gas thanks !
VicS
Well-Known Member
Re: Weight, density and mass...another (mini) rant
If you are going to have a rant about the use of the terms "weight" and "density" you really must get your other terms and units correct.
You talk about about weight but use the kilogram as the unit!
The KILOGRAM is the unit of MASS. The unit of WEIGHT is the unit of force, the NEWTON.
A lump of lead can have a mass of 1kg and it will be 1 kg where ever you take it be that the surface of the earth, the moon, any of the other planets or even outer space. Similarly for 1kg of balsa wood, although that will be a much bigger lump.
However the weight of the lump of lead is the product of gravity and mass. On earth the 1kg of lead will weigh 9.8 N but if you take it to the moon it will still be 1kg but it will weigh very much less, only about 1.6 N in fact because gravity is that much less. Go to Jupiter, where gravity is much greater, and your 1kg of lead will weigh 22.4 N.
/forums/images/graemlins/confused.gif Confused..never heard of a newton or thought it was a variety of apple? In fact a small apple weghs about 1N (on earth) /forums/images/graemlins/wink.gif A school teacher , at least a science teacher, should know all this
If you are going to have a rant about the use of the terms "weight" and "density" you really must get your other terms and units correct.
You talk about about weight but use the kilogram as the unit!
The KILOGRAM is the unit of MASS. The unit of WEIGHT is the unit of force, the NEWTON.
A lump of lead can have a mass of 1kg and it will be 1 kg where ever you take it be that the surface of the earth, the moon, any of the other planets or even outer space. Similarly for 1kg of balsa wood, although that will be a much bigger lump.
However the weight of the lump of lead is the product of gravity and mass. On earth the 1kg of lead will weigh 9.8 N but if you take it to the moon it will still be 1kg but it will weigh very much less, only about 1.6 N in fact because gravity is that much less. Go to Jupiter, where gravity is much greater, and your 1kg of lead will weigh 22.4 N.
/forums/images/graemlins/confused.gif Confused..never heard of a newton or thought it was a variety of apple? In fact a small apple weghs about 1N (on earth) /forums/images/graemlins/wink.gif A school teacher , at least a science teacher, should know all this
scarlett
Well-Known Member
Re: Easy Answer
For various reasons, the answer to the origional question is 'Yes, it could ignite'.
ps I couldn't be bothered to read any more after the first two rants.
For various reasons, the answer to the origional question is 'Yes, it could ignite'.
ps I couldn't be bothered to read any more after the first two rants.
Heckler
Well-Known Member
the LEL as i remember for coal gas is about 13% lpg about 10%. used to work in pit and going to the tech at night we were taught about explosive limits and used to experiment, get a biscuit tin, put hole in lid, fill with gas from bunsen burner, light gas coming from the hole in the lid, gas would gently burn until explosive limit was reached and KAABOOM.
thought it would be good to show the fitters in the surface workshop, no bunsen burner gas so used ACETYLENE from the welding set and HEY why not use oxy as well to get a good mix. apply light to hole, KAAAFLIPPINGOBSMACKINGEARDRUMBURSTINGBOOM, thought ohmygod are we ok is this going to hurt, we were just ok.
any plonker that thinks that loosing gas in bilges to experiment is a good idea wants their brains feeling
thought it would be good to show the fitters in the surface workshop, no bunsen burner gas so used ACETYLENE from the welding set and HEY why not use oxy as well to get a good mix. apply light to hole, KAAAFLIPPINGOBSMACKINGEARDRUMBURSTINGBOOM, thought ohmygod are we ok is this going to hurt, we were just ok.
any plonker that thinks that loosing gas in bilges to experiment is a good idea wants their brains feeling
BrendanS
Well-Known Member
It depends on what you think is a plonker
I've made explosives, and survived. Not for everyone though.
I've made explosives, and survived. Not for everyone though.