Originally Posted by RnRollie
I imagine the nrv sits in the flying saucer pressure regulator and that any nrv valve in the cylinder/flask head is actually depending on pressure. iow for refill they use brute force pressure to force open the nrv. Unfortuantely, much more pressure as you can generate
There is no pressure regulator with the clip on adapter I've bought its all for the high pressure side....the adapter I've got is simply a clip on mechanism, ball valve and sadly nrv mechanism.
I'm not sure if there is a non return valve built into gas cylinder/flask heads.....the mechanism for the clip on type is a bit of an unknown as far as I'm concerned, and what I've seen of the screw valve fittings there is no nrv in the valve and can't be any in the flask head as it simply a tapered screw fitting.....so it should be alright with that type......if there is a pressurized nrv in the cylinder/flask head then I'm out......as you say I'd not generate the pressure to open that.....But having said that there can't be a pressurized nrv in there...if you think it out....it would be closed all the time unless as you say brute force opend by pressure from outside....but it would in normal operation be closed and not let gas passed for normal use...surely?.....I've been making a few phone calls to see if I can get a definitive answer on this, while I wasn't able to get that I did find out that often when cyliders are returned to the deport for refilling they are full of water, that sort of negates the idea of their being a nvr that requires pressure to override it.
Originally Posted by RnRollie
So, screw safety features:
Put a brass T with ballvalve between the cylinder & the tap (with non-return valve).
Butane will still get to the chamber, but will have to return using a secondary line (hence the ballvalve & T)
Problem is the clip on and nrv are all in one solid unit which clips directly onto the cylinder.....so can't put a "T" section in there before the nrv.
Okay just found this video on youtube....kind of proof this can be done...at least with the screw valve propane type cylinder.....so no non return valve present there.
The valve he is releasing is the overpressure safety valve so he is basically allowing gas to be released and replaced by liquid.....so that's proof that these cylinders can be refilled by this sort of means ie no nrv.
But obviously he is doing it differently by releasing the safety overpressure valve to allow the vapor to be replaced by liquid.
Here's another video to show sort of proof of concept for doing it as I intend via a temperature pressure differential.
So it does all seem like this is doable....I'm a little concerned about the figures quoted in the end of this last video of what temp differential is required to get an optimal 80-90% fill.....that temp differential equates to about a 50psi filling pressure...no way I could do that...I'm looking at 8psi as just about a maximum...but again...if the tube is open and there is a pressure differential...then it will refill....surely?....of course what may be hampering their refill potential is that the small canister is actually being warmed by the incoming liquid propane which is at ambient temps...and the refill process they are using does generate an amount of heat via reversed phase change in the smaller bottle.....I'm guessing in the setup I'm using where the bottle is held at -20c in the freezer then fluid movement will go to completion.Edited by technogiant - 8/22/13 at 7:46am