A 12-inch nonlubricated plug valve will have what type of operator?

A 12-inch nonlubricated plug valve typically requires a worm gear operator due to its size and the operational demands associated with nonlubricated valves. Worm gear operators are particularly well-suited for large valves as they provide a mechanical advantage when opening and closing the valve, allowing the operator to manage the force required to rotate the valve stem with greater ease. The worm gear's design transforms rotational movement into linear movement efficiently, which is essential for larger valves that can be more difficult to operate manually.

In contrast, lever operators may require excessive manual force for larger valves, which could lead to operator fatigue or difficulties in operation. Chain operators might be more appropriate for configurations that require larger reach or are positioned at height, but they are less common for plug valves. Wrench operators may provide a basic mechanism to turn the valve but lack the mechanical advantage needed for a nonlubricated 12-inch valve. Thus, the worm gear operator is the most effective choice for maintaining control and ease of operation in this scenario.