The performance of pressure relief valves is affected by several key factors, including the valve’s set pressure, overpressure, and blowdown. The set pressure is the pressure at which the valve opens, while overpressure is the amount by which the system pressure exceeds the set pressure. Blowdown, on the other hand, is the difference between the set pressure and the pressure at which the valve reseats. Other factors that can impact performance include the valve’s flow coefficient, valve size, and the properties of the fluid being relieved.