The Model 3800 does not provide vacuum relief and therefore vacuum relief must be supplied by the normal operating vent. For vacuum relief see Valve Concepts Models 3100, 3200, 3300 and 3600 series vents.
The emergency vent provides an effective vapor-tight seal when the tank is not under emergency conditions. If the tank outbreathing requirements exceeds the capability of the normal pressure relief vent, under emergency conditions, the pallet will raise to allow vapors to escape, preventing damage to the tank due to excess pressure. The emergency vent pallet is top guided so that when the excess pressure is relieved the pallet will reseat to again provide a vapor-tight seal.
The Model 3800 top guided emergency pressure vents provide emergency pressure relief beyond that furnished by the normal pressure vent for atmospheric and low pressure tanks, as well as providing a convenient access for tank cleaning, inspection and repair. Emergency relief vents provide relief from excessive internal pressure which may be caused by an abnormal condition, such as ruptured internal heating coils or an external fire.