Black or green connector knobs on Type 1 OPD service valves indicate?

The black or green connector knobs on Type 1 OPD (Overfill Prevention Device) service valves specifically indicate the flow rating of propane cylinders. The coloring helps in the quick identification of the type of connection allowable for the propane system being utilized. Each color corresponds to a specific safety standard and infrastructure design, which not only promotes uniformity but ensures safe handling and use.

While there are indeed safety mechanisms and specifications related to pressure and size compatibility in propane systems, the distinctive black or green knobs are primarily designated for indicating flow rates. By understanding this, users can effectively ensure they are using the correct equipment for their specific propane needs, thus enhancing operational safety and efficiency.