In the event of losing feed water pressure, which valve will automatically close?

When feed water pressure is lost, the check valve is designed to automatically close in order to prevent backflow. Check valves are specifically engineered to allow fluid to flow in one direction and automatically shut when the flow reverses or falls below a certain threshold, such as in the event of a drop in feed water pressure. This function is vital in maintaining the system's integrity and preventing potential damage from reverse flow.

In contrasting this with the other options, safety valves are typically responsive to pressure conditions and open to relieve excess pressure; they do not close automatically in response to a loss of feed water pressure. Stop valves are manually operated devices used to isolate sections of a system and do not act automatically; they require manual intervention to function. Pressure relief valves are similar to safety valves in that they are designed to open to relieve pressure but are also not intended to close automatically based on feed water pressure loss. Therefore, the closure of the check valve is the appropriate response to a loss of feed water pressure, maintaining proper operational safety in the system.