Which one of the following describes the operation of a safety valve installed on a high pressure steam system?
A. A safety valve is initially lifted off its seat by system pressure, then is forced fully open by an air-operated piston.
B. As system pressure increases to the safety valve setpoint, the pressure overcomes spring force on the valve operator, causing the valve to open.
C. A safety valve will remain open until system pressure has been reduced to the pilot valve actuation setpoint.
D. When the open safety valve has returned system pressure to the lifting set point, a combination of air and steam pressure above the valve disk closes the valve.
Share your understanding of this question with the correct explanation.