Data Sheet

Bulletin 74.2:T208
5
Figure 4. Body and Vent Position
be used as part of a gas blanketing system to control outow of
blanketing gas under normal conditions and collect tank vapors
for the vapor disposal or reclamation system. Provide alternate
methods of emergency overpressure protection.
Universal NACE Compliance
Optional materials are available for applications handling
sour gases. These constructions comply with the
recommendations of National Association of Corrosion
Engineers (NACE) sour service standards.
The manufacturing processes and materials used by
Emerson™ assure that all products specied for sour gas
service comply with the chemical, physical and metallurgical
requirements of NACE MR0175-2002. Customers have the
responsibility to specify correct materials. Environmental
limitations may apply and shall be determined by the user.
Sizing Blanketing Systems
When sizing a gas vapor recovery regulator system,
consider the volume of blanketing gas that must be
displaced from the vessel when either lling the vessel with
liquid (pump-in) or the expansion of vapors inside the vessel
during atmospheric thermal heating.
Using the established procedures from American Petroleum
Institute Standard 2000 (API 2000), determine the ow rate
for outbreathing:
Q
total
= Q
pump
+ Q
thermal
where,
Q
total
: Required Flow Rate
Q
pump
: Required Flow Rate due to pump in
Q
thermal
: Required Flow Rate due to thermal heating
Capacity Information
Table 5 shows the T208 Series C
v
coefcient and ow
capacities of air at selected set pressure. Flows are in SCFH
(at 60°F and 14.7 psia) and Nm
3
/h (at 0°C and 1.01325 bar)
of 1.0 specic gravity air. For gases of other specic
gravities, divide the given capacity of air by the square root
of the appropriate specic gravity of the gas required. To
determine regulating capacities at pressure settings not
given or to determine wide-open ow capacities, use the
following formula:
Q = C
g
P
1
SIN
520
GT
3417
C
1
∆P
P
1
DEG
where:
Q = ow rate, SCFH
G = gas specic gravity
T = absolute temperature of gas at inlet, °Rankine
C
g
= gas sizing coefcient, Table 4
P
1
= absolute inlet pressure, psia
C
1
= C
g
/C
v
, ow coefcient, Table 4
ΔP = pressure drop across the regulator, psi
B
C
D
VENT POSITION
POSITION 1 (STANDARD)
A (STANDARD)
POSITION 2 POSITION 3 POSITION 4
BODY POSITION
B
C
D
VENT POSITION
POSITION 1 (STANDARD)
A (STANDARD)
POSITION 2 POSITION 3 POSITION 4
BODY POSITION
B
C
D
VENT POSITION
POSITION 1 (STANDARD)
A (STANDARD)
POSITION 2 POSITION 3 POSITION 4
BODY POSITION
BODY POSITION
VENT POSITION
POSITION 1 (STANDARD) POSITION 2
POSITION 3 POSITION 4