Bleed valve.......Fix Liquid Level Gauge
The only proper means of confirming tank is not overfilled (above the 80% liquid level)
OPD is NOT to be use as Primary ----Fixed Liquid Level Gauge IS
*Attendant cracks open 'bleeder valve' when filling
Vapor vents out until 80% liquid level is reached ---then spews Liquid Propane
Stop filling/close bleeder valve
Fixed Liquid Level Gauge
Valve that screws into tank wall and is connected to a Stand Pipe which has an open end at the 80% level
NOT something one just Adds....built in during manufacturing
LP Tanks are under the jurisdiction of the American Society of Mechanical Engineers & National Fire Prevention Association
*ASME/NFPA
Tank Internal components----Left to Right
Level gauge...magnetic float assembly
Pressure Relief Valve/Stand Pipe......open end in Vapor Zone
Fill Valve/OPD
Fixed Liquid Level Gauge/Bleeder Valve---open end at 80% level
Service Valve/Stand Pipe.....open end in Vapor Zone