What ensures that gas does not escape from a ruptured line upstream of storage containers?

The option that ensures gas does not escape from a ruptured line upstream of storage containers is the excess-flow check valve. This valve is designed to automatically shut off or significantly reduce the flow of gas if it detects flow rates that exceed predetermined levels, such as what might occur in the event of a rupture. By functioning in this way, the excess-flow check valve helps to protect storage containers from receiving too much gas and prevents potential hazards associated with leaks in the line.

This mechanism plays a crucial role in maintaining safety in the handling and transportation of compressed natural gas, as it minimizes the risks of gas escaping into the environment or causing explosions. Properly placed and maintained excess-flow check valves are vital components in natural gas systems, ensuring that safety protocols are followed and leak mitigations are in place.