What is a characteristic of plug valves?

A characteristic of plug valves is that they consist of a tapered or straight cylinder inserted into a valve body. This design allows for efficient on/off control of fluid flow. The cylindrical shape can rotate within the valve body, permitting or blocking flow based on its position. The tapered design often helps provide a better seal when the valve is closed, since it can make contact more thoroughly with the valve seat, minimizing leaks.

The other options do not accurately represent the design or operation of plug valves. For instance, while ball-shaped cores characterize ball valves, they are not a feature of plug valves. The mention of a horizontal disk pertains more to other types of valves, like gate or butterfly valves. Lastly, while some valves can be operated with pneumatic controls, plug valves can be actuated by various means, including manual, electric, or hydraulic methods, making the statement of exclusive pneumatic operation inaccurate.