Data Sheet

Bulletin 71.2:299H
10
Wide-Open Monitor
The control line of the upstream regulator is connected
downstream of the second regulator (Figure 6), so
that during normal operation the monitoring regulator
is standing wide open with the reduction to distribution
pressure being taken across the working regulator. Only
in case of open failure of the working regulator does the
wide-open monitoring regulator take control at its slightly
higher setting. A pressure build-up above the monitor set
pressure is required for the monitor to take control in the
event of an overpressure situation. Installing a pilot supply
regulator on the monitor will minimize the pressure build-
up. The pilot supply regulator should be set to
3 psig / 0.21 bar above the monitor setpoint.
The minimum set pressure difference between
the worker and monitor should be greater than the
proportional band. Small set pressure differences may
cause the worker and monitor to function independently.
The upstream regulator can easily be eld converted
or ordered with screws and O-rings in the throat
(Figure 6). This seals off the path that otherwise would
let line pressure ahead of the working regulator inlet
and try to close the wide-open monitoring regulator.
No Downstream Bleed Monitor
The no bleed monitor is a wide-open upstream
monitor which works like a conventional wide-open
upstream monitor except for registration. The no bleed
monitor utilizes a dual registration construction as
opposed to the external registration construction of the
conventional monitor. This ensures that the lockup of
the monitor system is the lockup of the downstream
working monitor at zero ow during normal operation.
Installation
Although the actuator and pilot can be mounted in
90° increments relative to the body, the normal installation
is with the body in a horizontal run of pipe and the pilot
hanging vertically from the bottom of the actuator.
Control and vent lines necessary for installation are not
supplied with a Type 299H regulator. Control and vent
connection locations are shown in Figures 8 and 9.
In many instances good piping practice will require
that outlet piping be swaged up above the body size
to prevent excessive pressure drop along the outlet
line. The piping should be expanded as close to the
regulator outlet as possible.
Capacity Information
Tables 5 through 10 give the 299H Series natural gas
regulating capacities at selected inlet pressures and
outlet pressure settings. Flows are in SCFH (60°F and
14.7 psig) and Nm³/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.
For critical ow:
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
1(abs)
(C
g
)(1.29)
For subcritical ow:
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 3)
C
g
= Gas sizing coefcient (see Table 3)
G = Gas specic gravity (air = 1.0)
P
1
= Regulator inlet pressure, psia
∆P = Pressure drop across regulator, psi
Q = Gas ow rate, SCFH
T = Absolute temperature of gas at
inlet, °Rankine
Note
Due to boost, the above formulas
cannot be used to obtain correct
regulating capacities for regulators with
internal registration.
The published capacities were obtained using inlet and
outlet piping the same size as the regulator body size.