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Old 08-01-2018, 10:52   #31
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Re: Propane released when lighting burner

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Originally Posted by newhaul View Post
6500 btuh is 108.3 btum I was not quite awake when I did my earlier calcs.
Propane is somewhere around 715 btu per oz. So Brunner would run for about 6.5 min per oz of propane so you see how miniscule a couple seconds of propane from that theoretical
Burner.
Before addressing that, and more germane to the issue of safety, is what does it actually take to reach the Lower Explosive Level in the atmosphere of an enclosed boat cabin? Of course, this is totally dependent on the size of the boat. But let's take an example of a mythical cabin that has an average width of 6 feet, average height of 6 feet, and a length of 15 feet, for a volume of 540 cubic feet, it would take 11.34 cubic feet of propane to reach the 2.1% LEL. That is a LOT of propane, over 28,000 BTUs worth.

Of course, that's a worst case example, and if the entire cabin reached the LEL and was ignited, there likely wouldn't be much left of the boat, its occupants, or anybody unlucky enough to be in close proximity. But such explosions do happen.

A much more likely scenario is the few cubic feet of air surrounding the burner, and that COULD be caused by a typical burner left running but not burning. That is why all proper marine stoves have thermocouples which cut off the flow of gas until they are heated by the flame. That's why we have to push in the burner valve handle and hold it pushed in until the flame is lit.

The real danger with any gas fueled appliance is the slow leak, which is why flammable gas detectors are so important.

Newhaul, are we awake yet?
The 715 BTU value you used is per liquid ounce (91,502 BTU/gallon, divided by 128 ounces to a gallon). But it's more useful to use weight, not liquid volume, as propane cylinders are filled by weight. So that calc is 21,548 (BTU/lb) divided by 16 (which is ounces to a pound for those of a metric bent), giving us 13,347 BTUs per ounce. So that 6,500 BTUH will burn for more than two hours on one ounce (by weight) of propane. This is useful info for estimating how long you can cook on a given tank size.
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Old 08-01-2018, 11:32   #32
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Re: Propane released when lighting burner

Quote:
Originally Posted by Brewgyver View Post
Before addressing that, and more germane to the issue of safety, is what does it actually take to reach the Lower Explosive Level in the atmosphere of an enclosed boat cabin? Of course, this is totally dependent on the size of the boat. But let's take an example of a mythical cabin that has an average width of 6 feet, average height of 6 feet, and a length of 15 feet, for a volume of 540 cubic feet, it would take 11.34 cubic feet of propane to reach the 2.1% LEL. That is a LOT of propane, over 28,000 BTUs worth.

Of course, that's a worst case example, and if the entire cabin reached the LEL and was ignited, there likely wouldn't be much left of the boat, its occupants, or anybody unlucky enough to be in close proximity. But such explosions do happen.

A much more likely scenario is the few cubic feet of air surrounding the burner, and that COULD be caused by a typical burner left running but not burning. That is why all proper marine stoves have thermocouples which cut off the flow of gas until they are heated by the flame. That's why we have to push in the burner valve handle and hold it pushed in until the flame is lit.

The real danger with any gas fueled appliance is the slow leak, which is why flammable gas detectors are so important.

Newhaul, are we awake yet?
The 715 BTU value you used is per liquid ounce (91,502 BTU/gallon, divided by 128 ounces to a gallon). But it's more useful to use weight, not liquid volume, as propane cylinders are filled by weight. So that calc is 21,548 (BTU/lb) divided by 16 (which is ounces to a pound for those of a metric bent), giving us 13,347 BTUs per ounce. So that 6,500 BTUH will burn for more than two hours on one ounce (by weight) of propane. This is useful info for estimating how long you can cook on a given tank size.
ok several issues with your post
First I am a U.S. navy certified gas free engineer .
Second 21,584 btu per pound is 1,349 btu per oz.
Third LPG tanks are filled by the gallon not by weight. ( in the USA )
6,500 btuh would require just under 5 oz per hour.
( your calculator is not working right. )

used your numbers but I suspect them to also be a bit non standard.
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Old 08-01-2018, 11:52   #33
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Re: Propane released when lighting burner

Nitpick
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LPG tanks are filled by the gallon not by weight. ( in the USA )
Competely up to the vendor. Many quote pricing per gallon but actually measure on a scale - my preference, more accurate for small quantities.

Some just open the pressure valve and fill until it spits, have a fixed price per bottle size, my least favorite since it discourages you from keeping tanks full.
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Old 08-01-2018, 11:55   #34
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Re: Propane released when lighting burner

As for OP, the little bit gets diluted and dispersed enough if there's any ventilation to outside.

Which there should be anytime any unvented combustion is happening in an enclosed space.

Detectors as well, follow all ABYC specs.
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Old 08-01-2018, 12:10   #35
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Re: Propane released when lighting burner

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Actually, about 500 people a year in the USA alone die from fires and explosions involving cooking equipment.
When factored into the 125 million households in the usa, gives a death rate of 0.000006%. Still pretty safe, unless you're one of the 500.

Put another way, You are 2600 times more likely to die in a automobile crash then by stove (in the USA). 1.3million people a year die in automobile accidents in the USA.
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Old 08-01-2018, 12:21   #36
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Re: Propane released when lighting burner

That's 1.3 million worldwide.
Around 40,000 in the US last year.
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Old 08-01-2018, 12:42   #37
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Re: Propane released when lighting burner

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That's 1.3 million worldwide.
Around 40,000 in the US last year.
You are right so stoves are only 74 times as safe as cars. Darn blonde moments.
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Old 08-01-2018, 12:48   #38
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Re: Propane released when lighting burner

Rashly assuming any propane would be collecting in the semi-isolated bilge space, rather than in the entire cabin, I think you'd need a lot less gas to reach the explosive level, since it would only have to equalize out in the BILGE spaces to reach that level. It wouldn't really be mixing in the overall cabin, unless there was so much it was spilling out of the bilge.
And then when the bilge pump switched on routinely...Ooops. Or do they claim to be ignition protected too?
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Old 08-01-2018, 13:00   #39
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Re: Propane released when lighting burner

Yachting Monthly did a series of videos with a Crash test Boat. The last one was trying to blow it up with propane (LPG). It was much harder than they assumed...

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Old 08-01-2018, 13:08   #40
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Re: Propane released when lighting burner

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Originally Posted by john61ct View Post
Nitpick
Competely up to the vendor. Many quote pricing per gallon but actually measure on a scale - my preference, more accurate for small quantities.

Some just open the pressure valve and fill until it spits, have a fixed price per bottle size, my least favorite since it discourages you from keeping tanks full.
all of the vendors I have ever dealt with pump the liquid into the tank and it is measured by gallon.
https://www.eia.gov/dnav/pet/pet_pri...RS_dpgal_w.htm
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Old 08-01-2018, 13:11   #41
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Re: Propane released when lighting burner

Screenshot cut off the top of the page here it is.
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Old 08-01-2018, 13:33   #42
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Re: Propane released when lighting burner

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LPG tanks are filled by the gallon not by weight. ( in the USA )
Somewhere close to 30yrs. cruising between Toronto & Florida and have always carried two 20lb. tanks. I have never had those tanks filled by the gallon, always by weight in Canada, Bahamas and the US.
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Old 08-01-2018, 13:47   #43
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Re: Propane released when lighting burner

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Originally Posted by newhaul View Post
all of the vendors I have ever dealt with pump the liquid into the tank and it is measured by gallon.
https://www.eia.gov/dnav/pet/pet_pri...RS_dpgal_w.htm
In this part of the world, it is sold by the kg. ( Cylinders have their Tare weight stamped on them and the cylinder is filled sitting on scale).
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Old 08-01-2018, 14:40   #44
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Re: Propane released when lighting burner

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In this part of the world, it is sold by the kg. ( Cylinders have their Tare weight stamped on them and the cylinder is filled sitting on scale).
hence my statement in the U.S.
A 20# cylinder holds 4.7 gallons ( till old shuts the tank off from filling.)
used to be a 20 pound tank held 5 gallons. Ie 4 pounds to the gallon.
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Old 08-01-2018, 14:48   #45
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Re: Propane released when lighting burner

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Somewhere close to 30yrs. cruising between Toronto & Florida and have always carried two 20lb. tanks. I have never had those tanks filled by the gallon, always by weight in Canada, Bahamas and the US.
next time you fill in the states ask if its by weight or volume. ( check your receipts)
everything I can find on propane in Florida is listed as price per gallon
https://www.eia.gov/dnav/pet/hist/Le...RS_SFL_DPG&f=W
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