Which valve is specifically designed to relieve excess pressure by fully opening?

The safety valve is specifically designed to relieve excess pressure by fully opening in response to a predetermined pressure level. This design allows the valve to quickly and effectively discharge fluid, thereby preventing pressure buildup that could lead to a dangerous situation or catastrophic failure in a pressure vessel or piping system. Unlike other types of valves, safety valves are engineered with a spring-loaded mechanism that ensures they open completely when the set pressure is reached, allowing for a rapid release of pressure.

In contrast, while relief valves also serve to manage excess pressure, their operation can vary depending on design and application. They might not always fully open instantly and can be designed for gradual release. The terms "sustainability valve" and "ball valve" do not relate to the specific function of relieving excess pressure. A ball valve is primarily used for on/off control of flow and does not inherently provide a fail-safe mechanism for pressure relief. Thus, the safety valve is recognized as the most appropriate choice for this particular function.