What is known as the blowdown of a safety valve?

The blowdown of a safety valve refers specifically to the difference between the pressure at which the valve opens and the pressure at which it closes. This characteristic is crucial in ensuring that the safety valve can effectively relieve pressure from a system without constantly cycling open and closed. When the pressure in the system rises to the set point, the valve opens to relieve excess pressure and then reseals once the pressure drops to a lower predetermined level.

Understanding the blowdown is essential for proper safety valve operation, as it ensures that the valve does not continually open and close under fluctuating pressure conditions, which could potentially lead to equipment damage or safety hazards. This difference in pressure helps maintain system stability and safety during normal and emergency operations.