Data Sheet

Bulletin 71.4:1808
6
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
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
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
 

Figure 3. Dimensions
1808
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1. To determine capacities at set pressures or
buildups not given in Tables 4 and 5, use one
of the following formulas, and convert according
to the factors in the preceding paragraph
if necessary:
Q = (P
1
+ buildup)
abs
C
g
520
GT
2. For pressure drops lower than critical (absolute
outlet pressure greater than one-half of absolute
inlet pressure), use the following formula:
Q = C
g
(P
1
+ buildup)
abs
SIN
Deg.
520
GT
ΔP
(P
1
+ buildup)
abs
3417
C
1
where,
Q = ow capacity in SCFH
G = specic gravity of gas
T = absolute temperature of gas at inlet in °Rankine
(°Rankine = °F + 460)
C
g
= sizing coefcient from Table 3
(P
1
+ buildup)
abs
= absolute inlet pressure
= P
1
+ P
atm
+ buildup
= P
1
+ 14.7 + buildup
C
1
= C
g
/C
v
(See Table 3)
ΔP = pressure drop across the valve in psig

To determine relief capacities in U.S. gallons per
minute, use the Catalog 10 liquid sizing procedures
in conjunction with the appropriate liquid sizing
coefcient (C
v
) and recovery coefcient (K
m
) from the
Specications section. Then, if capacity is desired in
Nm
3
/h, multiply U.S. gallons per minute by 0.2271.

Refer to the Specications section on page 2. Fill
out the order guide on page 7, carefully review the
description of each specication. Always specify the
type numbers of other desired equipment as well as
the main valve and pilot.