Filling empty propane cylinder from another full cylinder

[JumbleDuck]

Just a little bit of extra info: we now live with a buried cistern of gas, it only gets filled to 85%, the delivery man shrugged his shoulders, explaining that it was for safety reasons.

LPG tanks in cars only fill to 85% as well.

 

[vyv_cox]

LPG tanks in cars only fill to 85% as well.

And Gaslow bottles in motorhomes.

 

[Lon nan Gruagach]

Just a little bit of extra info: we now live with a buried cistern of gas, it only gets filled to 85%, the delivery man shrugged his shoulders, explaining that it was for safety reasons. This bears out previous mentions of limiting the fill.

Yes, liquid propane and butane arent that compressible compared to the gaseous state. Maintaining a decent volume of gas in the cylinder/tank ensures it wont pop if the temperature goes up a bit (as in just after filling [the expansion of the fluid as it moves from donor cylinder/tanker to the tank will cool it below ambient])

 

[Lon nan Gruagach]

I just turn off the top/donor bottle then wait half an hour before closing the valve on the lower/receiving bottle. All the liquid propane has drained out of the hose into the lower bottle by then and only a snift of gas escapes when disconnecting.

Good idea. However the fluid will drain pretty quickly, ever watched a refillable cigarette lighter with transparent sides?
Also the gas equivalent volume of the liquid in the pipe isnt all that huge, but still, no point just wasting it.