Always remove the tank from the model before filling ,A good thing to do is weigh the tank empty , It gives you a starting point ,And most gas tanks only take between1 and 5 ounces to fill, I find it better to have the gas tank colder than the one thats going to fill it, Also that can help having some silicone tubing on the end of the filling adaptor like rhavrane suggests in his video of filling a cheddar gas tank,Regarding leaving full tanks if youre not going to use for a long time i tend not to for some reason i have had a couple of instances of the tanks deforming , after filling i always let some gas out of the tank to make sure you have gas coming out and not liqueid as this would could be a problem lighting, Weigh the tank when full so you know its weight ,Sounds a bit dounting at first and it is but you will get the hang of it after several attempts ,regards Allan
To extend a bit more on this: It helps to first determine the volumetric capacity of the tank. I normally do this by removing the filling valve, then weigh the empty tank, fill it with water and weigh it again. Using metric, this should be pretty straightforward (every gramme of water is 1 ml of capacity) but imperial should give the same result, just different numbers.
Once you have those numbers, write them down and figure out how much liquid gas this volume CAN hold.
This will tell you the maximum possible weight of the gas-filled tank.
FWIW, LPG (30% propane, 70% Butane) has a density of roughly 0,55 g/ml but pure butane or propane are fairly similar in density.
Usually, the bottle you buy both has a net volume AND a net weight stated on the label, so it should be no problem to work out the actual density of the gas you are using.
Since liquid gas has a fairly large thermal expansion factor, I usually keep a 10% margin when fillling.
Leakage during filling is a matter of both having a decent filling adapter, and applying it as straight as possible to the filling valve. Takes a bit of practice, I guess. If I see/hear leakage. wiggling the bottle a bit usually solves that. If it doesn't, finmd a better adapter.
Never leave the filled tank in the model for reasons allready mentioned. Either run it completely empty, OR store it separately in a well ventilated place free from ignition sources.
