Data Sheet

Bulletin 71.1:1301
4


Tables 2 and 3 give regulating capacities at selected
pressuresandoutletpressureowsinSCFH (at 60°F and
14.7 psia) and Nm
3
/h (at 0°C and 1.01325 bar) of air. To
determine the equivalent capacities for other gases, multiply
the table capacities by the following appropriate conversion
factors:1.29for0.6specicgravitynaturalgas,0.808for
propane, 0.707 for butane, or 1.018 for nitrogen. For gases
ofotherspecicgravities,dividebythesquarerootofthe
appropriatespecicgravity.
Todeterminewide-openowcapacityforreliefvalvesizing,
use one of the following equations:
For Critical Pressure Drops
Use this equation for critical pressure drops (absolute outlet
pressure equal to one-half or less than one-half the absolute
inlet pressure).
Q = P
1(abs)
C
g
where,
 Q  = gasowrate,SCFH
C
g
 = gassizingcoefcient
P
1
= absolute inlet pressure, psia
For Non-Critical Pressure Drops
Use this equation for pressure drops lower than critical
(absolute outlet pressure greater than one-half of absolute
inlet pressure).
Q = C
g
P
1
SIN DEG
520
GT
3417
C
1
ΔP
P
1
where,
 Q  = gasowrate,SCFH
 G  = specicgravityofthegas
T = absolute temperature of gas
at inlet, °Rankine
C
g
  = gassizingcoefcient
P
1
  = absoluteinletpressure,psia
C
1
  = owcoefcient
ΔP = pressure drop across the
regulator, psi
Then, if capacity is desired in normal cubic meters per hour
at 0°C and 1.01325 bar, multiply SCFH by 0.0268.

Tables 5 and 6 give regulating capacities in U.S. gallons per
minute and liters per minute of water.
To determine regulating capacities at pressure settings
not given in Tables 5 and 6, or to determine wide-open
capacities for relief sizing at any inlet pressure, use the
following equation.
Q = C
V
ΔP
G
where,
 Q = liquidowrate,GPM
ΔP = pressure drop across the
regulator, psi
C
v
= regulating or wide-open
  owcoefcient
 G  = specicgravityoftheliquid
Figure 2. Type 1301F Operational Schematic







M1015
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
Type 1301F
M1015
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
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