Bulletin 71.3:Y692VB
5
Note
To determine ow capacities for the Y692VB Series
vacuum breakers, use the following formula:
where,
Q = ow capacity in SCFH (60°F, 14.7 psia) of air
P
1abs
= absolute inlet pressure, psia (P
1
psig + 14.7)
C
g
= ow coefcient (from Table 3)
C
1
= 35 (from Table 3)
P = pressure drop across the vacuum breaker
If the actual change in control pressure (from the
service conditions) is less than the change in control
pressure required to reach wide-open (Table 2), the C
g
in the formula must be reduced accordingly. To obtain
the correct reduced C
g
, multiply the C
g
(Table 3) by the
ratio of the actual change in control pressure to the
change in control pressure to reach wide-open.
Q
=
P
1abs
C
g
sin
deg
)
)
P
1abs
P
3415
C
1
3
1 to 3-inches w.c.
1.5 to 5-inches w.c.
3 to 8-inches w.c.
(2 to 7 mbar)
(4 to 12 mbar)
(7 to 20 mbar)
2-inches w.c.
4-inches w.c.
7-inches w.c.
(5 mbar)
(10 mbar)
(17 mbar)
1-inch w.c.
1-inch w.c.
1-inch w.c.
(2 mbar)
(2 mbar)
(2 mbar)
8 psig
(0,55 bar)
500
700
900
(13,4)
(18,8)
(24,1)
1000
1400
1800
(26,8)
(37,5)
(48,2)
8 to 16-inches w.c.
16 to 32-inches w.c.
0.25 to 3 psig
(20 to 40 mbar)
(40 to 80 mbar)
(17 to 207 mbar)
14-inches w.c.
28-inches w.c.
2 psig
(35 mbar)
(70 mbar)
(138 mbar)
2-inches w.c.
6-inches w.c.
0.4 psig
(5 mbar)
(15 mbar)
(28 mbar)
900
1000
1300
(24,1)
(26,8)
(34,8)
1800
1900
2500
(48,2)
(50,9)
(67,0)
Table 5. Y692VB Series Capacities (based on atmospheric inlet pressure)
To determine equivalent capacities of 0.6 specic
gravity natural gas, propane, butane, or nitrogen,
multiply the calculated capacity by the following
appropriate conversion factor: 1.29 for 0.6 natural
gas, 0.810 for propane, 0.707 for butane, or 1.018 for
nitrogen. For gases of other specic gravities, divide
by the square root of the appropriate specic gravity.
When ordering, specify:
1. Composition and specic gravity of gas (including
chemical analysis if possible)
2. Temperature range
3. Inlet pressures (maximum, minimum, nominal)
4. Pressure drops
5. Desired pressure setting or range
6. Flow rates (minimum, maximum, normal)
7. Piping size(s)
Refer to the Specications section and to each
referenced table; specify the desired selection
whenever there is a choice to be made. Be sure to
specify spring case port location from Figure 4.
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