Liquefied petroleum gas tanks feature a fill valve, vapor return valve, liquid withdrawal valve, relief valve and service valve. Along with the fixed liquid level and float gauges, all fittings are replaceable.
Also known as propane, LPG or LP gas, liquefied petroleum gas requires careful handling. The American Society of Mechanical Engineers regulates its storage and use, dictating the valve types and appearance for any tank labeled with the ASME designation. Those valves act as connectors and safety devices to control the flow of gas into and out of the unit.
The fill, vapor release and liquid withdrawal valves deal with adding and removing gas from the tank. The fill valve is the point where a service provider connects the delivery truck hose to the container, allowing fuel intake. The vapor return valve discharges pressure built up during filling. The liquid withdrawal valve pulls gas from the tank, usually when replacing, deactivating or moving the unit.
The relief valve releases liquid when pressure builds beyond safe levels due to excessive heat, vapor buildup or other circumstances. The service valve opens and closes gas from the tank, acting as the main shutoff for the system. It is also where liquid gas vaporizes as it travels out of the reservoir to appliances. A separate regulator manages the amount of gas flowing toward the target items.