gas bottle filling problem

The pressure in an lpg bottle is determined by the temperature, at least while there is liquid present. That is why when filling one bottle from another you maintain a small temperature differential, with the donor bottle the warmer of the two. The pressure wont fall until all the liquid has gone if the temperature is maintained.

You mentioned CNG , compressed natural gas, in an earlier post. That is a totally different matter. It is not liquefied. It is simply stored at a much higher pressure than butane or propane.

You also said there is not much difference in the pressures of butane and propane. Infact at 20C the vapour pressure of butane is only about 1.2 bar whereas the vp of propane is about 7.2 bar.

I said that in relation to the camping gaz bottle taking the pressure of propane it would be no problem in my view
 
I said that in relation to the camping gaz bottle taking the pressure of propane it would be no problem in my view

What matters is whether or not a camping gas bottle can be safely used at 5or 6 times the pressure of its intended use and withstand the pressure at the highest temperature it may normally encounter.

They are presumably pressure tested when made and periodically when returned for filling. At what pressure have they been tested?
 
The OP is probably refilling Camping Gaz cylinders from a large Calor butane cylinder. Its a well known trick if the gas locker wont take Calor cylinders and one does not want to pay the stupid price of C.G. refills.

Now I am sure I am going to be savaged by various old blokes for whom spending less money is a pleasure completely unrelated to the sum saved, but why would anybody do that for boating purposes (as opposed to LPG cars or whatever). We get 12 months of in season fry ups and out of season cuppas and FB pies out of one camping gas 907 which is 20 quid on exchange in the local camping shop, that's not a round of drinks at the bar. Life and definitely sailing opportunities are just too short.
 
Now I am sure I am going to be savaged by various old blokes for whom spending less money is a pleasure completely unrelated to the sum saved, but why would anybody do that for boating purposes (as opposed to LPG cars or whatever). We get 12 months of in season fry ups and out of season cuppas and FB pies out of one camping gas 907 which is 20 quid on exchange in the local camping shop, that's not a round of drinks at the bar. Life and definitely sailing opportunities are just too short.

We get through a lot more gas then that. In a season of light use we'll use two or three bottles. If we are able to use the boat more than usual we get through 5 or 6 bottles. Just cooking and hot water. Mind you I enjoy cooking on board.
 
Now I am sure I am going to be savaged by various old blokes for whom spending less money is a pleasure completely unrelated to the sum saved, but why would anybody do that for boating purposes (as opposed to LPG cars or whatever). We get 12 months of in season fry ups and out of season cuppas and FB pies out of one camping gas 907 which is 20 quid on exchange in the local camping shop, that's not a round of drinks at the bar. Life and definitely sailing opportunities are just too short.

I get through a 4.5Kg? calor bottle a week on holiday on average. The cost does build up over the year.
 
We get through a lot more gas then that. In a season of light use we'll use two or three bottles. If we are able to use the boat more than usual we get through 5 or 6 bottles. Just cooking and hot water. Mind you I enjoy cooking on board.

I wasn't thinking of hot water to be fair. But that's still only sixty quid for your average season. Do you just mean hot water for washing up? I'm not really bothered about hot water for anything on board so I admit I have less needs on that basis.

Cheers
 
We get through a lot more gas then that. In a season of light use we'll use two or three bottles. If we are able to use the boat more than usual we get through 5 or 6 bottles. Just cooking and hot water. Mind you I enjoy cooking on board.

Blimey! What are you cooking? In four months living aboard with four people this summer we only used three 907 cannisters.
 
The RRP of Camping Gaz 907 refills is £30 now - I paid £27 at Go Outdoors a few days ago, with my 10% discount card. As we use about 4 a year, thats £120, which is starting to get significant.
Having said that, I'm a Process Engineer working in the Oil & Gas industry, and have a very good understanding of the properties of LPG, and there's no way I would decant it from one cylinder to another on my drive in order to save what £60 or so!
 
Are you sniffing it? :) we livaboard, cooking every day and I like my tea. We get 20 days on average from a 3.4kg propane, £15 a refill, 75p/day.

Agreed we probably spend a month aboard during the season, seldom cook in the evenings (we sail locally and eat out) so there is plenty left in a 907 for cuppas for me while I am fiddling with the boat in winter. Sounds about the same rate of usage.

Of course there are liveaboards and people who cruise very extensively, but looking at the boats around me in Cardiff Bay, that's not the average user. Of course the OP may be one of the former so my generalization might not apply.

Cheers

Cheers
 
The RRP of Camping Gaz 907 refills is £30 now - I paid £27 at Go Outdoors a few days ago, with my 10% discount card. As we use about 4 a year, thats £120, which is starting to get significant.
Having said that, I'm a Process Engineer working in the Oil & Gas industry, and have a very good understanding of the properties of LPG, and there's no way I would decant it from one cylinder to another on my drive in order to save what £60 or so!

Still £19.95 at the local (small town) camping shop five minutes walk from home down our high street. Can well imagine its more at go outdoors.

Cheers
 
I wasn't thinking of hot water to be fair. But that's still only sixty quid for your average season. Do you just mean hot water for washing up? I'm not really bothered about hot water for anything on board so I admit I have less needs on that basis.

Cheers

Hot water for washing up and ourselves. TBH I've never stopped to consider whether we use a lot of gas or not but we eat on board most of the time and have only a few meals ashore. We do drink a lot of tea as well.

When I bought gas it's usually inevitably been somewhere boaty and a bottle has cost nearer £30 than £20.

In answer to Andrewbroadbent; I did work out the saving from filling my own bottles and, whilst I can't remember exactly what the saving was it was a lot more than 50%. An 80% saving rings a bell, but it's easy enough to work out for anyone who wants to.
 
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The OP is probably refilling Camping Gaz cylinders from a large Calor butane cylinder. Its a well known trick if the gas locker wont take Calor cylinders and one does not want to pay the stupid price of C.G. refills.

Exactly.

And to settle other questions I did the cylinders all at the same time and with the same conditions. All filled OK bar this one.
 
Then again those of us who've seen a boat explode and burn to the waterine after a snag with a gas bottle are happy to take precautions like one piece gas pipes, gas detectors with alarms and stumping up a few quid to have replacement bottles filled ! :rolleyes:

I guess that having seen a few cars burn out you take your car back to the makers to fill with fuel then.
 
Without making comment on the safety issues of gas filling of secondary cylinders by non-professionals, this sounds like an issue of partial pressures.

Each gas compound present within a vessel exerts its own partial pressure, and if more than one compound is present these add together to make up the total measurable pressure. When the overall pressure equals that of the source compound pressure, which would normally be warmer to create a higher local pressure and hence a flow, the flow stops.

Ideally the cylinder should only contain the gas compound being filled, and in the case of LPG this should condense and liquify. This will happen simply by keeping the receiving cylinder a few degrees cooler than the donor cylinder. If another gas of mixture of gases (e.g. air) is present in the cylinder then the partial pressures added by the air will add to that of the LPG compound's partial pressure, but the air won't liquify so the pressure simply increases to the point that the receiving cylinder pressure equals that in the donor cylinder, flow stops as does the increase in cylinder mass.

This is a basic and common fault found in fridge systems where air has been left in. In an LPG cylinder giving the cylinder a good vent blast should remove most of the air and the flow should be restored once the air has been blasted out by the boiling liquid LPG when the valve is opened and the cylinder pressure drops.

At last a likely and sensible suggestion. I will trade that bottle in for a replace
 
Now I am sure I am going to be savaged by various old blokes for whom spending less money is a pleasure completely unrelated to the sum saved, but why would anybody do that for boating purposes (as opposed to LPG cars or whatever). We get 12 months of in season fry ups and out of season cuppas and FB pies out of one camping gas 907 which is 20 quid on exchange in the local camping shop, that's not a round of drinks at the bar. Life and definitely sailing opportunities are just too short.

There's a real contradiction in your post. Why on earth would you throw away money on gas only then to eat muck like FB pies? I'd rather put cheap gas in my bottles than cheap food ( is it really food) in my guts.

" for whom spending less money is a pleasure completely unrelated to the sum saved"
Guilty as posted. But I am a Yorkshireman.
 
I run a large activity centre in the Midlands, and most of our motorised kit runs on LPG, all with portable gas tanks refillable from a 2000l autogas(propane) tank. I've looked in to refilling standard butane bottles and lpg bottles before and decided against. If you get it wrong and overfill/damage the take off valve, you stand a good chance of having liquid rather than vapour going to your cooker. If that happens you might get away with a small flare up, but more likely you'll have one of those new cabriolet style boats. It also freezes the piping potentially cracking it and potentially freezing the valve and safety valve (if it has one) open. The cheap standard regulators can also struggle with the pressure.

It's all safe when done properly, we have over pressure release valves etc on the cylinders and calibrated measuring for filling, tanks checked on regular basis etc.

I've actually taken the gas cooker off the boat and gone over to an Origo stove, due to the ambiguous regulations relating to boat lpg installations, and the potential for gas leaks/risk in confined space.

Not at our place, but I have seen LPG cylinders go up, and through concrete walls, so I'd suggest either buying a proper refillable cylinder- you can get quite nice 11l ones which are horizontal rather than vertical or paying the money and exchanging.

The quality and mix of LPG varies from UK supplier to supplier. One of the more well known suppliers a few years ago bought a load of cheap wholesale gas from Russia. It was shocking, full of rubbish that blocked everything up. Lost a lot of big customers, and legal action was taken against them. So that may not be helping if you have the full cylinder upside down and have disturbed the sediment. Depending on the type of cylinder the take off pipe location can vary within cylinders. Any yes there does need to be a temperature variation between bottles if you're not pumping the 'moonshine' through.

Good luck!
 
For long distance cruisers... how do you propose to refuel with butane/propane around the world ? I'm fairly sure that Calor fittings and bottles are only exchangeble in the UK with entirely different systems and rules in other countries... Do you propose to buy new cylinders in every country visited and trash the old ones ?? You'll probably have 15kg (ish) bottles so that's alot of money !
 
We get through a lot more gas then that. In a season of light use we'll use two or three bottles. If we are able to use the boat more than usual we get through 5 or 6 bottles. Just cooking and hot water. Mind you I enjoy cooking on board.

A boat I sail on used to get through gas at that sort of rate.
Mysteriously consumption was dramatically reduced after a winter refit, when cooker, regulator and all gas plumbing was replaced.
The old system had been inspected, professionally.
I found that a bit sobering at the time, the owner put it down to the cooker being more efficient, but I suspect leaks.

Also, I think this level of cost is definitely a good argument for a calorifier, although payback will still be a few years.
 
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