Data Sheet

Bulletin 71.1:CS400
12
Refer to Figures 6 and 7. If the primary regulator ceases
to control downstream pressure, outlet pressure will rise
underneath the diaphragm of the integral monitor, which
will assume control of the downstream pressure.
Table 5 shows a comparison between the integral
True-Monitor™ protection and the protection offered
by an backup orice device, which seals on a
secondary seating surface should the primary orice
seating surface or disk become damaged.
Pressure Registration
The Integral True-Monitor has the options for internal
pressure registration and external registration, denoted
by the “I” and “E” in the type number, respectively. The
method of pressure registration is dependent on the
registration of the primary regulator, see Figures 6 and 7.
The wide-open monitor’s registration should match
the registration of the primary regulator, if the primary
regulator’s registration is internal, then the wide-open
monitor regulator’s registration must also be internal, if
the primary regulator is external, then the monitor must
also be external.
Refer to the relief sizing coefcients and the Capacity
Information section to determine the required relief
valve capacity.

The Type VSX4 slam-shut module on the Type CS404
regulator is a fast acting shut-off device that provides
overpressure (OPSO) or over and underpressure
(OPSO/UPSO) protection by shutting off the ow of
gas to the downstream system. The Type VSX4’s
actions are independent of the CS404 Series regulator
and of variations to the inlet pressure. The Type VSX4
provides the option of internal or external downstream
pressure registration dependent on the registration of
the primary regulator, see Figures 8 and 9. External
registration requires a downstream sensing line.
Refer to the relief sizing coefcients and the Capacity
Information section to determine the required relief
valve capacity.

Tables 9, 11, 12, 14, 15, 16, 17, 19, 20, 21, 22, 24, 25,
26, 27, 29 through 71 provide natural gas regulating
capacities at selected inlet pressures, outlet pressure
settings and body outlet sizes. Tables 70 and 71
provide capacities specically for Pressure Factor
Measurement applications. Flows are in
SCFH (60°F and 14.7 psia) and Nm
3
/h (0°C and
1.01325 bar) of 0.6 specic gravity natural gas. To
determine equivalent capacities for air, propane,
butane or nitrogen, multiply the capacity number in
the tables by the following appropriate conversion
factor: 0.775 for air, 0.628 for propane, 0.548 for
butane or 0.789 for nitrogen. For gases of other
specic gravities, multiply the given capacity by 0.775
and divide by the square root of the appropriate
specic gravity.


To determine wide-open ow capacities for relief
sizing of 0.6 specic gravity natural gas at 60°F at
critical pressure drops (absolute outlet pressure equal
to approximately one-half or less than one-half of the
absolute inlet pressure), use the following formula:
Q=P
1abs
(C
g
)(1.29)

If pressure drops are lower than critical (absolute
outlet pressure greater than approximately one-half
the absolute inlet pressure), use the following formula
and convert according to the factors in the preceding
paragraph if necessary:
Q
= C
g
P
1
SIN
520
GT
3417
C
1
∆P
P
1
DEG
where:
C
1
= C
g
/C
v
(see Table 2)
C
g
= Gas sizing coefcient (see Table 2)
G = Gas specic gravity (air = 1.0)
P
1
= Regulator inlet pressure, psi a
∆P = Pressure drop across regulator, psig
Q = Gas ow rate, SCFH
T = Absolute temperature of gas at inlet, °Rankine
Note



internal registration.
The following capacities tables were obtained using inlet
and outlet piping the same size as the regulator body
size. The body size indicated in the tables refers to the
outlet side of the body.