Which valve type provides the best sealing capability for isolation purposes?

The ball valve is designed for quick shut-off and provides an excellent sealing capability for isolation purposes due to its construction. It features a spherical disc or "ball" with a hole in the center; when the valve is closed, the ball rotates to block the flow completely. This design ensures minimal leakage when the valve is in the closed position, making it particularly effective for isolating sections of a system.

The tight seal offered by ball valves makes them ideal for applications where preventing backflow or leaks is critical. Additionally, they require only a quarter turn to operate, allowing for quick and easy shut-off.

In contrast, other valve types, such as gate valves and globe valves, may not achieve the same level of sealing efficiency under pressure or may experience wear over time, reducing their effectiveness in isolation applications. Butterfly valves, while useful for regulating flow, often allow some leakage when fully closed due to their design.