Cashco 3700 User Manual
Model 3700
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
IOM-3700
05-11
SECTION I
I. 3000 SERIES DESIGN AND FUNCTION
Model 3700
BOTTOM GUIDED
Emergency Relief Vent
Models 3100 thru 3600 Pressure and /or Vacuum
Vents are used for the normal venting requirements.
Normal venting is defi ned as venting required
because of operational requirements (i.e. fi lling and
emptying the tank) or atmospheric changes. The
Models 3700 thru 3900 Emergency Relief Vents are
used to meet venting required when an abnormal
condition, such as an external fi re 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 specifi ed 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/
Vacuum 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 Pressure/
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/Bottom Guided Relief
3800
P
Emergency/Top Guided Relief
3900
P
Hinged Emergency Relief
Figure 1 - Pressure Relief
Figure 2 - Vacuum Relief