Which type of valve allows the flow of feedwater in one direction only?

The check valve is designed specifically to allow fluid to flow in one direction while preventing backflow. This is achieved through the use of a movable disc or ball within the valve that opens when fluid is flowing in the intended direction and closes when there is a reverse flow. This function is critical in systems such as feedwater lines in boilers, where it is essential to maintain a consistent flow direction to avoid any backflow that could damage the system or lead to operational inefficiencies.

In contrast, the other types of valves listed serve different purposes. Ball and butterfly valves are typically used for regulating flow; they can be opened or closed to control the passage of fluid but do not inherently prevent backflow. Globe valves, while excellent for throttling flow and providing a constant flow rate, also do not offer the same one-way flow protection as a check valve. Thus, the check valve is the only option that fulfills the requirement of only allowing flow in one direction.