INSTALLATION, OPERATION AND MAINTENANCE MANUAL
IOM-3200
10-20
SECTION I
I. 3000 SERIES DESIGN AND FUNCTION
Model 3200
Pressure / Vacuum Relief Vent
w/ Pipeaway Connection
Models 3100 through 3600 Pressure and /or Vacuum
Vents are used for the normal venting requirements.
Normal venting is defined as venting required
because of operational requirements (i.e. filling and
emptying the tank) or atmospheric changes. Model
3700 Emergency Relief Vent is used to meet venting
required when an abnormal condition, such as an
external fire or such as ruptured internal heating
coils, exist either outside or inside the tank.
All of these devices are sized in accordance with API
Standard 2000. Improperly specified relief vents may
result in structural damage to the tank or system and
can cause severe personal injury or death.
Figure 1
illustrates the operation of the Pressure
Relief Vent under overpressure conditions. As the
tank pressure increases as a result of product being
pumped into the tank and/or because of thermal
expansion of the product and vapors, the pressure
pallet remains closed until the set pressure of the
vent is reached. When the tank pressure reaches the
pressure setting of the vent, the pressure pallet lifts
allowing the tank pressure to bleed off.
Figure 2
illustrates the operation of the Vacuum
Relief Vent under vacuum conditions. As the tank
pressure decreases as a result of product being
pumped out of the tank and/or because of thermal
contraction of the product and vapors, the vacuum
pallet remains closed until the set vacuum of the
vent is reached. When the tank vacuum reaches the
vacuum setting of the vent, the vacuum pallet lifts
allowing air to be drawn into the tank.
MODEL
P
V
DESCRIPTION
3100
P
V
Vent to Atmosphere
3200
P
V
Vent to Header
3300
V
Top Mounted
3400
P
Vent to Atmosphere
3500
P
Vent to Header
3600
V
Side Mounted
3700
P
Emergency/Manhole Cover
Figure 1 - Pressure Relief
Figure 2 - Vacuum Relief
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