Is the gas bottle empty?

snowleopard

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I need some kind of indicator to remind me which gas bottle is in use, empty or full. Trying to think of something that is simple, reliable and easy to make but for the moment it eludes me. Anyone have a solution?

I've tried googling but all I find is things you stick to the bottle to indicate the level. I want something I can stick to the hatch coaming of the locker.
 
If you use one of those luggage weighing spring balance thingies you can then weigh the bottle and subtract the gross weight from the tare weight (both stamped on the bottle) to work out how much gas is within.

Or nick one of those "Do Not Disturb" labels from a hotel and hang that on the bottle in use.
 
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from a plastic milk bottle, cut three label sized pieces, and thread some string through each one. Label the labels in a manner which suits the use, then tie to the neck of the appropriate bottle.

See Ashley's Knots, p 146 for the traditional Cornish "Lugyard" knot which is ideal for this purpose.
 
Stick of old fashioned blackboard chalk?

Old some little labels to hang round the tops like those that label the decanters in your tantalus
 
As long as there is free liquid in the cylinder the pressure remains the same. I don't need any sort of measurement, just a reminder of Full - In Use - Empty.

Not strictly true in practice.

Changed a bottle a couple of days ago, oven and cooker-the only gas equipment on board-would not light.

Everything back to normal with a new bottle, but a little free liquid sloshing about in the bottom of the old one.

Big weight difference though, just by feeling the weight of each.
 
As to a physical indication of which cylinder has been turned on - you could have a coloured ribbon attached to the top of each cylinder.. just long enough that when you turn that cylinder on, you drape the ribbon out of the locker and it would be just visible from outside the locker.. Easy to tell when you've got the gas on then...
 
Not strictly true in practice.

Changed a bottle a couple of days ago, oven and cooker-the only gas equipment on board-would not light.

Everything back to normal with a new bottle, but a little free liquid sloshing about in the bottom of the old one.

I've experienced this on several occasions with different bottles but don't understand why. As SL says, any amount of liquid should create the same vapour pressure. Without wanting to thread drift can anyone explain? My only hypothesis is that water had got in the cylinders but it seems unlikely.

I would go with the chalk option, myself, for cylinder marking.
 
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My only hypothesis is that water had got in the cylinders but it seems unlikely.

I was going to say water as well. I assume it comes in with the gas, as a small proportion of H2O molecules along with the C4H10, and then settles out at the bottom. After a few damp fills, quite a lot could build up, since it doesn't empty out.

This is all conjecture though, I don't know for sure.

As for identifying the in-use cylinder, could the changeover valve handle be arranged to point at it? Or point at the other one? Attach a plastic arrow to it if you like, saying "IN USE" or "DISCONNECTED" as applicable.

I arranged Kindred Spirit's fuel filter valves so that the in-use filter had a handle in front of it, blocking its removal. The not-in-use filter had the handle swung out of the way. I got the idea from a photo of a dual water-intake system on a lifeboat, where the changeover valve handle blocked the lid of the in-use strainer and revealed the isolated one for removal and clearing. Probably not so feasible with big gas cylinders and small butane valves, though.

Pete
 
I have a handy way of telling the contents:
take a kettle of boiling water, and dribble it over the side of the cylinder such that it rund down the length. Only a width of 2-5cm need be covered, not the entire circumference.
Drain all the water out of the kettle.
The hot water will heat the steel of the cylinder where its got gas on the inside, but not the steel where there's liquid inside.
The result is that after a few second, a liquid line appears on the outside of the cylinder. Wet below the line where the steel didn't heat (due to liquid gas inside), and dry above the line where the steel heated up and caused the water to evaporate.
 
I had a similar problem with our water tanks, we have two, each with its own on/off switch. I needed a visual indicator to tell me whether the "other" tank was full or empty. So I got a cheap set of plastic coat hooks, there are 5 moulded to a plastic backplate, and a large keyring. The coat hooks are mounted under the tank switches. When both tanks are full the keyring lives on the centre hook, when we switch tanks because the first tank is now empty we move the keyring to the outer hook appropriate for that tank (so to the far left if the port tank is now empty). So now when we're getting low on water a quick look at the "tank indicator" tells me whether the other tank is full or empty.

Perhaps something similar for you gas bottles?
 
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