Propane versus Butane

[PeteE]

While we're on the subject of liquid gas entering the piping, I came across a 'yachtblog' type site the other day where a guy was using his Camping Gaz cylinders upside down (i.e. liquid take off) because they fitted better in the locker that way He reported no problems - EEK!

As an ex-hot air balloonist I can't see any problem - so long as you don't mind scorched flesh and singed eyebrows (and anything else within a couple of yards radius). Without the proper kit the effect of an unregulated liquid discharge at the nozzle is likely to be a large (uncontrolled) flame - just what you want when plummeting at speed in a balloon (where circumstances require a "silent burn") but not particularly desirable in a confined space.

In ballooning it is common practice to fill slave bottles from a master (propane) but the slaves are fitted with vent valves which prevent overfilling. If you are thinking of doing it always wear heavy gloves and preferably goggles.

As far as use in cold temperatures goes - I have used propane in temperatures of around 16 deg of frost (when my 5 gal water container was a solid block of ice) - as previous posts have noted, butane gives up long before this.

 

[VicS]

It might be controlling the downstream pressure but of what? Vapour or liquid? The liquid may pass thro the reg at 28/30/37mbar but as it warms to ambient temp against a closed valve it will rise to 2-5 bar! Far in excess of your appliance ratings. Then when you open an appliance valve, that 2-5 bar of liquid will rush out expanding as it goes. If I see SV Sarah I'd certainly be mooring well away from her!

If the down stream pressure is correct you wont have liquid only gas unless the temp is below the BPt for that pressure.

If the hose etc cools below the boiling point then there will be trouble.
We used to use a high pressure stove (no regulator) when camping and had to be very careful to avoid gas condensing in the hose etc as the temp fell during the evening. Normal routine became to always turn off at the bottle and burn off the gas left in the pipework!

If I get around to trying it I'll report back. If all goes quiet you'll know it was a disaster!

 

[VicS]

is propane, being lighter than butane (though still heavier than air), more likely to disperse from any build up in the bilge?

Yes I think it will disperse a bit more quickly than butane It'll diffuse more quickly being a smaller lighter molecule.

 

[snowleopard]

The biggest danger of overfilling a gas cylinder is that if there is no gas space at the top of the cylinder, i.e. it is totally filled with liquid, then it warms up, there is nowhere for the expanded liquid to go. Instead of gas pressure of a few Bar, you get hydraulic pressure of a few hundred bar. Enough to blow a safety valve if there is one, blow the tap out of the bottle or even split the bottle. Any of those result in liquid gas being discharged.

Propane has to be kept at a much higher pressure to keep it liquid than Butane does so the bottles have to be stronger. You must never get a Butane bottle refilled with Propane but Propane bottles are good for either.

When ehading south the first place outside the UK where we cold get our own bottles filled was Gran Canaria. Fortunately 2 x 13kg lasted over 3 months.

For UK waters I'd use Calor Butane unless expecting to live aboard in winter. For long stays on the continent, the largest Camping Gaz and if going transatlantic, Calor Propane.

 

[Sam_Steele]

thanks for all your help.....though I won't be filling my own bottles....
Regards
Sam

 

[dratsea]

Highly dangerous to fill your own cylinders unless you know what you're doing. [/QUOTE

Just fill to the specified weight i.e. 3.9kg in a 3.9kg cylinder. Tare weights are stamped on each cylinder and repeated on the aluminium disk beneath the valve at each cylinder re-test/re-valving. Apply common sense and it is totally without drama.

And the widely advertised "weigh your luggage" digital scales are perfect and unlike most others seem boatproof. Sam: If in Kent happy to demonstrate.

 

[Mandarin331]

Often wondered about that. Provided the regulator continues to control the downstream pressure I can see it working Ok.
I was actually thinking of trying it to see what happens (not on the boat ... in the garden with the camping stove )

But all the vaporisation will take place in the regulator, its going to get pretty cool around there maybe to the detriment of its insides.

Is this really a problem - I've seen many gas powered fork lift trucks with a propane tank strapped on the back lying down, and ths is how they're designed.

 

[vyv_cox]

Is this really a problem - I've seen many gas powered fork lift trucks with a propane tank strapped on the back lying down, and ths is how they're designed.

Additional to the possibility that liquids will be fed directly to the stove, there has been a quite widely reported problem of liquids in the supply hose. Over a bit of time the hydrocarbon dissolves some components of the hose, which can then deposit in the regulator and/or burners of the appliance. I believe this can be quite a serious problem. In my camper I use only stainless steel hoses to avoid this problem.

 

[Ubergeekian]

I think you may find they are specially designed cylinders with an internal gas take off tube. The cylinder has to be positioned so that the tube takes gas from the space above the liquid.

Surely forklifts will, like my car, run on liquid propane?

 

[VicS]

Surely forklifts will, like my car, run on liquid propane?

Yes you are right they do. I dont think gas stoves are designed to though

But how can you run a car on propane, What to you do when the bottle is MT. Do you have to carry a spare with you?

 

[Ubergeekian]

But how can you run a car on propane, What to you do when the bottle is MT. Do you have to carry a spare with you?

No, you just refill it. It's a proper Autogas conversions, which means a filler under the back number plate (Ah, Mr Bond. I've been expecting you.), an 85 litre tank in the boot, a vaporiser under the bonnet, a venturi mixer on the carb and a changeover switch on the dashboard.

In days gone by people used to use standard propane cylinders, mounted upside down, in cars, but that sort of fiddling around isn't needd now, thank goodness.

 

[theguerns]

butane verses propane

You want to check before you go abroad. Here in France it is elegal to use propane on a yacht or motorboat and I have been told that this may be the case in other eu countries

 

[saltylegs]

Surely forklifts will, like my car, run on liquid propane?

forklifts use liquid offtake cylinders these feed vapourisers in the engine bay where the engine coolant heats the liquid to help it vapourise.
the most up to date autogas instalations use direct injection of the LPG and also about 5% of petrol at the same time.

(boiling point of propane -42 deg C Butane -4 deg C but as the liquid boils it will lower the temp in the gas locker)

 

[saltylegs]

You want to check before you go abroad. Here in France it is elegal to use propane on a yacht or motorboat and I have been told that this may be the case in other eu countries

For very hot climates i would use Butane because as the pressure increases so does cylinder pressure eg. 30 deg C ambient butane will double to 4 bar and propane to 14 bar take it up to 35deg and your are at the blowoff point for some of the pressure relief valves (time to make sure that gas locker is properly constructed and vented).

 

[VicS]

No, you just refill it

But where?

I've never seen a propane pump on a filling station forecourt, although I guess they'd be sited away from the petrol and diesel pumps. Even so I've never noticed any indication of any facility to refill with propane.

Fine I guess if you have your own propane tank and can fill from there provided you don't want to do high mileages, or do you get so many miles per tankful that you can always get home again.

85 litre tank in the boot sounds a bit of a nuisance too. Even with my largish estate car there have been times when there's not been more that about 0.85 litres of spare space. Don't fancy an LPG tank in the car with me anyway... you would put it in a special locker on a boat!

Why cant it go where the petrol tank is normally fitted? Although I must admit mine's not as big as 85 litres.

 

[Ubergeekian]

But where?

I've never seen a propane pump on a filling station forecourt, although I guess they'd be sited away from the petrol and diesel pumps. Even so I've never noticed any indication of any facility to refill with propane.

There are quite a few around. It's normally sold as "Autogas" which is actually a mixture: mainly propane with some butane. The butane content varies year round as the average temperature changes. The pumps look very similar to standard petrol pumps, and are normally lined up with them. The tank will be above ground somewhere within a hundred yards or so.

Once you know where the LPG stations are in your area it's generally quite easy to plan fuelling accordingly - though I carry a few gallons as petrol as well, just in case. The hassle is, for me, more than made up for by the price ... around half the cost of petrol, per litre. You get slightly worse fuel economy, but overall the running costs on LPG are still around half of those on petrol.

I had my DS converted immediately I bought it. It cost a thousand quid to have done, and I have now done about 40,000 miles on LPG, which has paid back the conversion cost many times.

85 litre tank in the boot sounds a bit of a nuisance too. Even with my largish estate car there have been times when there's not been more that about 0.85 litres of spare space. Don't fancy an LPG tank in the car with me anyway... you would put it in a special locker on a boat!

Why cant it go where the petrol tank is normally fitted? Although I must admit mine's not as big as 85 litres.

Unless you're very confident, it's generally sensible to keep petrol too. Some companies will make an LPG tank (or an LPG tank with a small petrol section) to match and existing tank, but that's very expensive. Big 4x4's generally sling the LPG tanks underneath. For cars you either stick them in the boot (the DS boot is huge) or use a toroidal tank in the spare wheel well.

All the connections to the tank are in a gas type enclosure which vents "overboard" and there is also a safety valve to vent the tank in case of overpressure. Overall it's probably about as safe as petrol: the downside is that it's pressurised but the upside is that if there was a leak it would rapidly diffuse or be blown away, and not hang around to go Bang! as long as petrol does.

 

[Ubergeekian]

forklifts use liquid offtake cylinders these feed vapourisers in the engine bay where the engine coolant heats the liquid to help it vapourise.

Same as my car then. Vaporising propane takes about 1% of its heat content, which means about 3% of the engine's output, so with my 120 French horses the vaporising can be demanding 4hp in hot water. Which is why I can't start from cold and leave home on gas - whatever way I go involves a steep climb and the vaporiser will freeze within a mile.

 

[saltylegs]

Same as my car then. Vaporising propane takes about 1% of its heat content, which means about 3% of the engine's output, so with my 120 French horses the vaporising can be demanding 4hp in hot water. Which is why I can't start from cold and leave home on gas - whatever way I go involves a steep climb and the vaporiser will freeze within a mile.

should be able to cold start ok as coolant at 0 deg will still vapourise the LPG (sometimes needs a timing adjustment if you want to start on LPG) but if vapouriser is freezing this is due to high rate of vapourising and can be solved with a major upgrade of the antifreeze/coolant

ps not all LPG autogas forecourt tanks are above ground as some can also be buried i think shell did a few of those

 

[Bobobolinsky]

Don't worry about pressures in cylinders anymore, gas companies stopped using different rated cylinders decades ago, as it is cheaper to design and manufacture one cylinder and just paint it a differnt colour and change the valving. Most butane and propane supplied is BS(certainly in the UK unless you have a brickworks) and this allows for a mix of gases as lpg is a waste gas from the petroleum production. In some countries butane is supplied "dead" and won't vapourise if the temperature comes any where near zero. LPG may be supplied in anywhere from 10-50% mixes in the rest of the world.
Upside down cylinders are not a good idea, (unless you are decanting) as it relies on small diameter pipe to vapourise the gas.
Fork truck cylinders have a dip tube and supply liquid offtake. Vehicle supply tanks also have a dip tube and are liquid offtake.
30mB regs will run propane or butane appliances with no modification.
Propane is a slightly lighter gas than butane, but the bilge dissipation differences in practice are negligible as the explosive limits are also slightly different and you still get an explosive mixture.

 

[Deleted member 36384]

Stainless Steel Hoses

...... In my camper I use only stainless steel hoses .....

Could you elaborate please? Is this a standard hose with a stainless cover or some special metal hose? I would be interested in the latter as I am planning and outside run of hose on my boat.

If its the former I don't understand how it would prevent degradation of the hose by contact with liquid hydrocarbon.