Emergency Depressuring Vents

If column metal overheats beyond its safe working temperature, the column may burst at the overheated area at pressures lower than the relieving pressure. Overheating may occur when the column wall is 

Water spray and deluge systems, as well as fire insulation, are common techniques for overheating protection. Various techniques are also used for preventing the initiation and spread of fire. These constitute a portion of the plant fire prevention system, and are outside the scope of this book. Some discussion is available in API s standards (9, 10). 

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Process facilities pose severe risks with respect to fire, explosions, and vessel ruptures. Among the prime methods to prevent and limit the loss potential from such incidents are the provisions of inventory isolation and removal systems. These systems are commonly referred to in the process industry as BSD (emergency shutdown), venting, depressuring, or blowdown.Their objective is to prevent and limit the loss potential from system overpressure events that could lead to the loss of system integrity (i.e., ruptures, BLEVEs, etc.). 

NFPA 57 recommends that LNG dispensers be protected from collisions with vehicles and that they incorporate an emergency shut-down system. The maximum delivery pressure of the dispenser shall not exceed the operating pressure of the LNG tanks on the vehicle being refueled, and the LNG delivery hoses must have a shut-off valve at the end and a breakaway valve in the event a vehicle drives off with the refueling hoses attached. Bleed and vent valve must be incorporated into the dispensing lines to allow them to be drained and depressurized prior to disconnection if necessary. 

The System 80+ Standard Design utilizes the Shutdown Cooling System (SCS), the Reactor Coolant Gas Vent System (RCGV), the Safety Depressurization System (SDS), the Atmospheric Dump Valves (ADV), and the Emergency Feedwater Systems (EFW) as the preferred means to bring the reactor plant from hot standby to a cold shutdown condition within a reasonable period of time. These safety-related systems are normally operated from the control room and are described in CESSAR-DC, Sections 5.4.7, 10.1, and... 

The second emergency system is an automatic depressurization system. In the event of an uncontrolled reaction, the reaction can be safely limited by depressurizing the reactor to the vent system. The heat of vaporization of the boiling reaction mass safely removes heat from the reactor. The emergency vent system will be sized to handle the peak venting needs of the reactor system. 

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