Can you depend on an OPD valve for the accurate filling of a DOT cylinder?

The correct choice is that an OPD (Overfill Prevention Device) valve is not approved for filling DOT cylinders. OPD valves serve a critical safety function by preventing the overfilling of propane cylinders beyond their maximum capacity, but they do not provide a method for accurately measuring the amount of gas being filled.

When dealing with propane cylinders, the filling process typically involves other systems and gauges that ensure proper measurement and safety during filling. The OPD itself is designed primarily to prevent overfilling, not to confirm the precise volume of gas inside the cylinder.

Furthermore, relying exclusively on an OPD for filling could lead to situations where the cylinder might be filled without adequately assessing the actual volume of propane, which could cause safety hazards. Proper procedures and equipment are required to ensure that cylinders are filled accurately and safely in accordance with regulations.