Propane fill question
OK I am officially confused. I took one of my 40lb. propane cylinders out of my new RV to have it filled. A note on the door of the propane compartment said do not fill over 80%, could cause fire,e...
Forum Discussion
dougrainer wrote:wnjj wrote:
If you have a full container of liquid under pressure, the second you open the valve there is an increase in volume (the hose) which will drop the pressure rapidly. The first liquid to enter the hose will immediately boil off to gas. Now if the cylinder was at such a high pressure that adding the hose volume doesn't drop it below vapor pressure then liquid could flow to the regulator.
NOT TRUE. PERIOD. Doug (35 years as an RV Tech and 35 years Licensed by the Texas Railroad Commission, which trains and license LP service and fillers). Liquid also will into the piping even at 80% fill by the sloshing while driving. NOT so much a problem on DOT tanks but a common problem on Motorhome ASME tanks. Since the standard of auto cut off valves years ago this type problem has been minimized.
I'm not trying to be argumentative or "right" but really want to understand how this works.
Do you still think what I wrote above is not true if you consider a cylinder that's just sitting full with the valve closed, not one in motion with it open?
I may be remembering my college thermodynamics wrong but why would opening a valve on a full tank cause liquid to expel when it would turn to gas as soon as it hits the low pressure area? Please help me to understand by explaining the physics behind it.
Also consider that I only jumped into this mess when it was claimed that a 100% full cylinder wouldn't allow anything to flow out of it.
I get that in the real world, there is sloshing and valves aren't left closed while travelling.
