What component must the fill line on a storage cylinder have?

The fill line on a storage cylinder must incorporate a backflow check valve to ensure safe operation. This component is critical as it prevents the reverse flow of gas from the storage cylinder back into the filling equipment or the connected system during the filling process. By doing this, the check valve helps to avoid potential back pressure situations which can otherwise lead to hazardous conditions, such as system contamination or over-pressurization, ensuring that the compressed natural gas flows in a single direction—into the storage cylinder only.

The integrity of the fill line is vital for maintaining safe filling practices, and incorporating a backflow check valve is a key aspect of this design. Thus, the check valve plays a crucial role in the overall safety and functionality of the filling operation.