the bear II wrote:
To fill the tank the attendant will open the over-pressure valve .....
the over pressure valve is held closed by a spring the pump jockey can not open it.
What he opens is called the visual overfill indicator valve.
I see a lot of mis-information about this valve in the forums.
The purpose of the valve. It is located at the 80% full point, if the valve is venting GAS (Propane not air) then the tank can hold more liquid propanem when the valve starts venting liquid propane that turns to vapor the instant it contacts open causing a white cloud to form. That means "Tank full" shut off pump close all valves and disconnect in accordance with standard procedure.
It is not an over pressure valve
It is not "To let the air out" for there is no air after the tank is properly purged at initial fill.
It spits liquid propane with the tank is full. It is a back up to the over fill protection device inside the tank,. and it worjks as designed,.