What type of valve is used to isolate feedwater pumps?

The gate valve is specifically designed for the purpose of isolation in piping systems, making it the ideal choice for isolating feedwater pumps. Its primary function is to start or stop the flow of fluid in a system rather than to regulate flow, which is a key characteristic of other valve types.

Gate valves are typically used in applications where a straight-line flow of fluid and minimal pressure drop are necessary. They provide a tight seal when closed, preventing any leakage, which is crucial when isolating equipment like feedwater pumps, where ensuring no water flows through during maintenance or repairs is essential. Their ability to be fully opened or closed makes them efficient for use in isolation.

In contrast, globe valves are used primarily for regulating flow and are not as effective for complete isolation, while check valves allow fluid to flow one way and automatically prevent backflow, and pressure relief valves are safety devices used to relieve excess pressure in a system, rather than isolating parts of the system. Thus, the function and design of the gate valve make it the correct option for isolating feedwater pumps.