DanandDaphne
Senior Member
Respectfully, that's a common but incorrect misconception.
The OPD (Overfill Prevention Device) built-in to modern tanks serves to prevent overfilling of the tank but does not restrict gas flow if a regulator failure or 'open line' occurs.
Common 'portable' LPG tanks of the type we use in the RV environment lack an integral flow restricting device because there are some legitimate applications outside of our RV / BBQ experience which require very high flow rates.
However, a valve inside the 'green nut' of the pigtail between the tank and the regulator does serve as a safety device to severely restrict (but not necessarily completely stop) gas flow in the case of a regulator failure or 'open line' occurrence. It is this 'excess flow prevention valve', integral to the pigtail, which can 'block flow' sometimes when the tank main valve is opened too quickly, a phenomenon some folks have experienced much to their bewilderment.
But that doesn't explain why my propane tank shut itself down when it was 3/4 full. I didn't tip the tank over drop it or anything. The tank was being use on my home grill. It wouldn't let any gas out whether on the grill or not until I took it in and had it filled even though it was mostly full. After filling it it worked normally again.
So what happened then if there's not a flow stopping device in the tank valve?