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[Geoff]

Whilst operating steam engines with the refillable gas container I have often experienced difficulty in getting the gas in without excessive wastage and or getting the tank to fill properly.
One of my tanks seems to fill quite readily but the other is very difficult and whilst I have replaced the filler valve it is not much better.
A friend showed me a different way to fill the gas tanks which works extremely well with very little wastage.
Basically instead of using the adaptor probe to fill the tank you connect a pipe from the gas supply canister direct to the outlet valve of the refillable container so no modification is needed. Note that another valve is required at the filling canister.
(My first Cheddar model unit came with a screw on adaptor and valve to connect the burner direct to the gas canister (small size which is no longer available). This is used on the gas canister with a short rubber gas hose to a screw on adaptor to the refillable gas tank).
If the filling canister is held vertically (nozzle downwards) and its valve opened then the tank outlet valve is opened liquid gas flows into the tank, this can be heard gurgling in.
On the first couple of efforts I also depressed the original filler valve to vent gas out so liquid can flow in. Subsequent try I didn’t do this and the liquid gas still flowed until there was a balance of gas and liquid in the receiving vessel.
Both valves are then closed tightly and the pipe removed. The only loss of gas is that contained in the pipework which is a lot less than the usual filling method. The shorter the pipework the less gas is lost.
There would seem to be some considerable advantages to this method:
1)      Very easy to fill
2)      Very little gas leakage, which can be a safety issue
3)      Very efficient use of gas
4)      No modifications needed to the tank
I’m still experimenting with this method but I would say I can now get the tank 80%/90% full every time which is the maximum you want. Simply opening the valve briefly will confirm gas rather than any liquid comes out.
Geoff
 

[kiwimodeller]

Geoff, I use disposable cannisters of various sizes in my boats but I became really annoyed with my (only) local shop when the 125g smallest cannister went from $6 to $9 to $14 and now to almost $17 in about 18 months. Their excuse was that they dont sell a lot of this size so they dont buy in large quantities. At the same time the 230g cannister has gone from $6 to $7.50. I now buy a 450g cannister for $9 and using a soldered tube and two taps I fill the small cannisters from the inverted large one. I use a small set of 500g dieters scales and write on each cartridge the full and empty weights so I can tell how much they have left in them at any time. Depending on ambient temperature I can usually get the small ones 95% full, often up to 120g. I then use the left over gas in the big cannister to bring the boiler up to pressure before changing to the small cannister to go sailing. If the price of the 230g ones goes up I will start doing them also. I already have full and empty weights for these worked out. I see no reason why this system would not work with the commercially available refillable tanks and as you have found there is no need to have a vent pipe unless you want to get the last drop in. We are after all just refilling and repressurising them to the original volume and pressure or slightly less. Cheers, Ian.

[steamboatmodel]

When refilling any tank make sure that you never fill a tank completely. You need some space above the liquid to allow for expansion of the liquid. There was a problem with some of the small gauge one trains in that the fuel tanks were designed without expansion space and they had problems with tanks splitting.
Regards,
Gerald.

[mrsgoggins]

Overfilling gas tanks is potentially a dangerous occupation. The higher the fill ratio the more rapidly the pressure rises with temperature and since a freshly filled tank will be cold the change in temperature will be significant.
From memory commercial fills are generally 66%, ie 66g per 100ml of container volume.
Insurers would, I'm sure, take a dim view of a tank failure resulting from overfilling and would pack-up and go home if a "non-refillable" container was involved.

Keith

[Circlip]

Same effect should be noted when hydraulically testing a boiler. By virtue that the boiler must be completely filled with water and the pressure increased, it may be necessary to release some pressure to maintain the test figure due to the contents expanding if the ambient temperature rises.
 
  Regards  Ian.

[Jerry C]

Specific gravity of butane approx 0.6 so 1 liter weighs 600 grams so those tanks must be full. The vapour pressure of butane at 15°C is approx 2Bar or 30psi. The ronson type filler valve protrudes into the tank on my gas tank so there is always vapour above the liquid. Adding a small quantity of propane does not increase vapour pressure to that of pure propane. If you use things for what they were designed to do you will usually be ok but you must know what you are doing when you go outside the box.
Jerry.

[Liverbudgie2]

 You don't state which tank you are trying to fill.

I have an MHB Opal. The way I was shown to fill the gas tank was to hold the tank in the palm of your hand, after first slacking off the valve at the discharge end. Hold with your thumb and fore finger the valve control wheel and then begin filling the tank at the sprung valve end by pushing the canister and filling tube downwards, while holding the tank at an angle of around 45 degrees, so that the discharge valve is facing downwards, until the gas starts escaping out of the valve. At that point nip the valve shut with your thumb and fore finger and remove the filling tank.

Using this method gives me a running time of about twenty minutes with a full boiler.
LB