Model 3700
Bottom Guided Emergency
Relief Manhole Cover
OBJECTIVE
The Model 3700 manhole and 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 valves provide relief
from excessive internal pressure which may be caused by an abnormal condition,
such as ruptured internal heating coils or an external fi re. The Model 3700
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.
TECHNIQUE
The manhole/emergency vent pallert 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 vapor to escape, preventing damage
to the tank due to excess pressure. The manhole/emergency vent pallet is bottom
guided so that when the excess pressure is relieved the pallet will reseat to
again provide a vapor-tight seal. A restraining cable connects the
manhole/emergency vent weather hood to the flanged base and also provides electrical
grounding to eliminate static discharge.
BODY SIZE: 20", 24"
MODEL 3700 EMERGENCY VENTS