In which type of piping systems are butterfly valves commonly used as final control elements?

Butterfly valves are favored in air and water piping systems due to their design and operational characteristics. They are lightweight, compact, and offer quick operation with minimal seating and unseating force required to open and close the valve. In systems involving air and water, which typically operate at lower pressures and flow rates compared to other mediums, butterfly valves can effectively manage flow with lower pressure drops.

Their ability to provide throttling capability makes them ideal for controlling flow in air and water applications, where the precise regulation of flow rates is often needed. Furthermore, butterfly valves can handle a wide range of temperatures, making them versatile within these systems.

In the context of other options, while butterfly valves can be used in gas, oil, steam, sludge, chemicals, and food applications, they are most competitively operational in air and water systems where the requirements align well with the performance characteristics of butterfly valves.