Jump to content

And Now For Something Controversial


Biggles

Featured Posts

Temperature has nothing to do with it.

 

LPG is liquefied by being pressurised.

 

 

Temperature still has a lot to do with it for LPG (and even more to do with whether it's water or steam, which is what I think Innisfree meant). Propane or Butane is normally liquefied at room temperature by applying the appropriate pressure, and that is why it is liquid in typical gas bottles. If the gas is cooled down though it will liquefy at a lower pressure. If you cool Propane/Butane gas it enough it will liquefy and then go solid at normal atmospheric pressures.

 

N

Link to comment
Share on other sites

What is the equivalent weight of 22 litres of LPG at 6 bar?

 

 

 

Since the propane is liquid in the bottle the pressure doesn't matter except that sufficient is necessary to keep it liquid.

 

I am interested to know what mass of gas you bought. We pay about £23 for a standard 13kg bottle.

 

 

N

Link to comment
Share on other sites

Much talk about propane and butane freezing. Just to be pedantic neither do. What happens at low ambient temperatures is that they stop boiling off from liquid to gas. For butane this is not much less than 0degC. Propane boils at a much lower temperature.

 

They boil when the saturated vapour pressure is higher than the pressure on the gas. In the bottle the pressure is kept high so they don't boil until you open the tap. This reduces the pressure so the required amount of gas boils off. I am a little mystified about why butane and propane would be mixed because with my rather limited knowledge of such matters I would have thought that all the propane would boil off first and you would be left with something like pure butane by a fractional distillation process. If they boil off together then the mix would give you lower operating temperatures but why not just use propane?

 

I am sure that someone will come along and enlighten me.

 

N

Link to comment
Share on other sites

Much talk about propane and butane freezing. Just to be pedantic neither do. What happens at low ambient temperatures is that they stop boiling off from liquid to gas. For butane this is not much less than 0degC. Propane boils at a much lower temperature.

 

They boil when the saturated vapour pressure is higher than the pressure on the gas. In the bottle the pressure is kept high so they don't boil until you open the tap. This reduces the pressure so the required amount of gas boils off. I am a little mystified about why butane and propane would be mixed because with my rather limited knowledge of such matters I would have thought that all the propane would boil off first and you would be left with something like pure butane by a fractional distillation process. If they boil off together then the mix would give you lower operating temperatures but why not just use propane?

 

I am sure that someone will come along and enlighten me.

 

N

 

According to our old friend Google propane freezes at minus 190c and boils at minus 42c. If we ever get down to those temperatures we are sure in trouble!

 

Regards

Ditchdabbler

 

 

 

Link to comment
Share on other sites

Much talk about propane and butane freezing. Just to be pedantic neither do. What happens at low ambient temperatures is that they stop boiling off from liquid to gas. For butane this is not much less than 0degC. Propane boils at a much lower temperature.

 

They boil when the saturated vapour pressure is higher than the pressure on the gas. In the bottle the pressure is kept high so they don't boil until you open the tap. This reduces the pressure so the required amount of gas boils off. I am a little mystified about why butane and propane would be mixed because with my rather limited knowledge of such matters I would have thought that all the propane would boil off first and you would be left with something like pure butane by a fractional distillation process. If they boil off together then the mix would give you lower operating temperatures but why not just use propane?

 

I am sure that someone will come along and enlighten me.

 

N

 

A pinch of Dilithium crystals are added to warp the molecules together.

Link to comment
Share on other sites

And if LPG is a mix of propane and butane, am I right in thinking that propane has a better freezing point for our colder winters? Probably wouldn't really be an issue as I think propane freezes at -40 :cheers:

 

 

 

LPG is Liquid Petroleum Gas, not specifically edither type or a mix.

 

Butane is LPG (Blue Calor Cylinders)

Propane is LPG (Red Calor Cylinders)

A Butane/Propane mix is still LPG (Some "Patio" gases, I think)

 

AFAIK what is sold on forecourts is Propane, but I'm happy to be corrected if it has any Butane content.

 

Alan's pretty much spot on, LPG as sold as Autogas at petrol stations, is 100% (or near as matters) propane in the UK and Ireland. On the continent, they use propane/butane mixes. Patio gas is a mix of propane/butane.

Link to comment
Share on other sites

Copied from Wisegeek;

 

 

Characteristics of Propane

Propane is used in North America as fuel for heating houses, and is also available in smaller portable tanks. Gas barbecues, camping stoves, and lanterns frequently can be used with propanefuel. Mixed with small amounts of other substances like butylene, propylene, and butane, it can be used as an automobile fuel known as liquefied petroleum gas (LPG). The odorless gas will often have ethanethiol, which has a strong odor, added to it so any leaks can be more easily detected.

 

If the gas needs to be stored for a long time or in variable weather conditions, propane is usually a better choice than butane. It is relatively easy to liquify and compress, and has a boiling point of -44°F (-42°C), which means that it turns into a gas as soon as it comes out of the tank at any temperature above this. Propane can easily be stored outside in almost all environments, since temperatures below freezing don't affect how it is stored or used.

 

 

Characteristics of Butane

Butane, while not as easy to find in many places, is nonetheless a popular fuel for lighters, torches, and some camping stoves. Aerosols may also use the gas as a propellant. Although butane is generally less expensive than propane, it can be also be more difficult to use; because it is not as common, many devices are not designed to work with butane tanks.

 

This gas also has a boiling point right around freezing — 32°F (0°C) — so it does not work well at very low temperatures. Below its boiling point, butane stays a liquid, and there is no pressure change to force it out of its container. Butane is rarely used to heat homes or buildings in places where it gets very cold because it cannot be stored outside and still work effectively.

 

One of the advantages of butane is its improved fuel efficiency. If similar volumes of both substances are burned at temperatures above freezing, butane will provide about 12% more energy. This advantage makes butane a good choice for those trying to pack light, such as backpackers or campers. As long as access to an adequate supply is available, the energy efficiencyand price advantage can make butane a better deal in many, but not all, circumstances.

 

 

Mixed Fuels

Propane and butane are often combined in mixed fuels, which provide some of the advantages of each. Such mixes are popular for camping stoves in particular. Because propane has a lower boiling point, it can be used to force the butane out of the container, even at temperatures at or below freezing. Pure propane needs a strong steel container to hold it under pressure; combining it withbutane means that the pressure can be lower, and the container lighter, which is important for campers and backpackers.

 

 

 

 

Regards

 

Ditchdabbler

Link to comment
Share on other sites

  • 7 months later...

I am still amazed at the huge brainstores of knowledge out there in the nb world...pity we can't bottle it but it is still a joy to read this forum :-) and sometimes irritating lol

 

Well bottle only 80% of it, the other 20% is what methane is made from. biggrin.png

Link to comment
Share on other sites

 

£20 for 6kg http://www.canalworld.net/forums/public/style_emoticons/#EMO_DIR#/ohmy.gif That is extracting the urine!

 

Just exchanged a 13kg one for £25ish.

Ours is even worse!

 

About £22 depending on where you go for a 2.75kg bottle. Camping Gaz is a rip off but the small calor bottles don't fit in our gas locker.

 

Luckily we don't use much gas!

Link to comment
Share on other sites

According to our old friend Google propane freezes at minus 190c and boils at minus 42c. If we ever get down to those temperatures we are sure in trouble!

 

Regards

Ditchdabbler

 

that will be at normal atomospheric pressure presumably (which is why it needs to be under pressure to be liquid at normal temperatures)

 

The real problem is that the water vapour that is inevitably present, freezes in the small aperatures of the valves and regulators and on more than one occasion I've had to warm up a propane regulator with hot water (and in dire circumstances by peeing on it !). this used to be a regular winter morning ritual on a bulk tank we had (taking a kettle of hot water to the tank regulator) to get the gas cooker to work ! Nowadays Calor put some additive in the gas in winter to prevent this happening.

Link to comment
Share on other sites

I'd have to be usuing a lot of gas to make it worth my bother.

 

Can I be arsed to carry an empty bottle to the car, drive to a petrol station that does LPG, fill it up, return back to the boat and then lug the full bottle back to the boat for a saving of about £5

 

......... life's to short

Link to comment
Share on other sites

I was at our local Shell garage the other day and a chap was filling one of the refillable bottles, it was sat in the back of his estate and his misses was sat in the front which I didn't think was a great idea.

He had trouble filling it and a lady came out and told him how to do it, I expected her to say something about it being in the car while he did it. What she did say was that she came out a couple of days earlier because someone was trying to fill one in the back of a motor and because it was not a pucker refillable cylinder she refused to serve him.

 

Yes its not a good idea to refill in an enclosed space. Oh read what happened to a guy when his valve failed in Yachting monthly (May issue). Not funny

Link to comment
Share on other sites

I'd have to be usuing a lot of gas to make it worth my bother.

 

Can I be arsed to carry an empty bottle to the car, drive to a petrol station that does LPG, fill it up, return back to the boat and then lug the full bottle back to the boat for a saving of about £5

 

......... life's to short

 

How did you work out the saving was £5?

Link to comment
Share on other sites

Yes its not a good idea to refill in an enclosed space. Oh read what happened to a guy when his valve failed in Yachting monthly (May issue). Not funny

That is why the BSC doesn't allow them. I watched a chap filling one at the garage, it was in the back of his estate car, his wife was in the front.

Link to comment
Share on other sites

That is why the BSC doesn't allow them. I watched a chap filling one at the garage, it was in the back of his estate car, his wife was in the front.

 

What do you mean BSC doesn't allow them? The adapter is screwed onto the gas bottle, its taken to a garage to fill it, then the adapter is unscrewed and the normal regulator put onto the bottle. The BSS exam is done on the boat, so all you need to do is not leave the adapter permanently on the bottle.

Link to comment
Share on other sites

What do you mean BSC doesn't allow them? The adapter is screwed onto the gas bottle, its taken to a garage to fill it, then the adapter is unscrewed and the normal regulator put onto the bottle. The BSS exam is done on the boat, so all you need to do is not leave the adapter permanently on the bottle.

Sorry, misunderstood, I thought we were talking refillable bottles. The garage I mentioned will not allow the refilling of standard bottles only ones designed for refilling.

How do you know when the cylinder id 80% full ?

Link to comment
Share on other sites

Sorry, misunderstood, I thought we were talking refillable bottles. The garage I mentioned will not allow the refilling of standard bottles only ones designed for refilling.

How do you know when the cylinder id 80% full ?

 

I looked quite deeply into the regulations, the rules are basically: a garage shouldn't allow the filling unless there's a device which ensures the filler cuts out once its 80% full (ie same situation as fuel tanks on LPG cars), but they can't refuse you if you have this, simply because they don't like you. And anecdotally, (see above in this thread) people have used the adapters and filled LPG bottles at autogas stations....

 

Personally I'd be interested in saving the £15 or so you'd save by doing this, I don't have an adapter but if I can be reassured its reasonably safe, then I'd certainly go for it.

 

I can think of a few simple ways to achieve the 80% full, but they'd rely on common sense, not a device to automatically do it for you.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.