When fully opened, which type of valve will have the highest head loss?

The globe valve is designed primarily for throttling and controlling flow. Its internal structure, which includes a disc or plug, creates a significant restriction even when it is fully opened compared to other valve types. This design results in a longer flow path and higher turbulence, leading to increased head loss.

In contrast, when a gate valve is fully open, it provides minimal resistance to flow, allowing water to move more freely. Ball valves also feature a design that allows for smooth passage when fully open, leading to lower head loss. Pressure relief valves are mainly concerned with maintaining system pressure and do not usually impose significant head losses in the open position. Therefore, among these options, the globe valve is the one associated with the highest head loss due to its construction and function.