| Safety Valve |
A Safety Valve is an automatic pressure relief device designed to protect pressure vessels, pipelines, and process systems from overpressure. When the system pressure reaches the set pressure, the valve automatically opens to discharge excess fluid. Once the pressure decreases to the reseating pressure, the valve automatically closes and restores a tight seal. Safety Valve is primarily designed for compressible fluids such as steam and gases, opening rapidly to protect the system from overpressure. |
| Pressure Relief Valve |
A Pressure Relief Valve is primarily designed for liquid service and opens progressively as system pressure increases to relieve excess pressure. |
| Set Pressure |
The predetermined pressure at which a safety valve begins to open to protect the system from overpressure. |
| Commence-to-Blow Pressure |
The pressure at which the safety valve first begins to discharge fluid. At this point, the disc has just lifted from the seat but has not yet reached full lift. |
| Full Lift Pressure |
The pressure at which the valve reaches its rated lift and is capable of discharging its rated relieving capacity. |
| Rated Relieving Pressure |
The pressure used to determine the valve's rated relieving capacity during performance testing. |
| Reseating Pressure |
The pressure at which the safety valve closes and re-establishes a tight seal after system pressure decreases. |
| Blowdown |
The difference between the set pressure and the reseating pressure, usually expressed as a percentage of the set pressure. |
| Lift |
The maximum vertical distance that the valve disc travels away from the valve seat during operation.
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| Rated Relieving Capacity |
The maximum flow rate that a safety valve can discharge under specified operating conditions. |
| Rated Coefficient of Discharge |
The ratio of the actual discharge capacity to the theoretical discharge capacity, used for valve sizing and capacity calculations. |
| Valve Seat Bore |
The inside diameter of the valve seat that forms the primary sealing surface and flow passage. |
| Discharge Area |
The effective flow area through which the fluid is discharged when the valve is open. |
| Nozzle Throat Diameter |
The minimum internal diameter of the nozzle flow passage, which directly affects the valve's discharge capacity. |
| Back Pressure |
The pressure existing at the outlet side of the safety valve, which may affect valve performance and relieving capacity. |
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| 1.Chattering |
Rapid and repeated opening and closing of a safety valve during discharge, preventing stable operation and potentially causing damage to the valve disc and seat |
| 2.Hunting |
Repeated small oscillations of the valve near the set pressure without maintaining a stable relieving condition. |
| 3.Fluttering |
Continuous vibration of the valve disc within a small lift range that may affect sealing performance and valve operation. |
| 4.Flashing |
The instantaneous vaporization of a liquid when its pressure is reduced below its saturation pressure. |
