What is a characteristic of a relief valve?

A relief valve is designed to maintain safe operating pressures in a system by automatically releasing excess pressure. One of its key characteristics is that it functions without adjusting for decreasing pressure; rather, it responds primarily to exceedances of set pressure levels. This means the valve opens when pressure exceeds a predetermined limit to allow fluid to escape, preventing potential damage or failure in the system.

In contrast, a relief valve does not actively compensate for pressure drops. Instead, its role is reactive, maintaining pressure balance by releasing fluid when necessary, rather than adjusting to varying conditions within the system.

The other options mischaracterize the functionality and application of relief valves. Relief valves are not limited to high pressure scenarios, can work effectively across varying draft conditions, and are not restricted to use with diesel engines, making the selected answer the most accurate representation of a relief valve's characteristics.