Which valve is best suited to relieve excess pressure without needing to fully open?

The relief valve is specifically designed to relieve excess pressure in a system without requiring full opening. This is crucial in preventing potential damage to equipment and maintaining the safety and integrity of the system. Relief valves operate by automatically releasing pressure once it exceeds a predetermined set point, and they can modulate the flow to maintain a safe operating level without opening all the way.

Control valves, on the other hand, are primarily used for regulating flow or pressure within a system, but they are not designed to provide relief from excess pressure specifically. Safety valves serve a similar function to relief valves but are typically used in specific applications, such as steam or gas pressure containment. Shutoff valves are used to isolate sections of piping or equipment but do not serve to relieve pressure, as they require full closure to function. Therefore, the relief valve is the best choice for the requirement of relieving excess pressure without needing to fully open.