Browse durable internal valves at F.W. Webb. Double-flanged internal valves are commonly used in propane equipment including storage tanks and containers. This valve provides excess flow protection by shutting off when propane is not being withdrawn. Made in durable steel, sturdy double-flanged valves can withstand the normal daily use of an LPG or NH3 container. Explore high-quality internal valves from trusted maker Cavagna to find the best fit for your containers.