PRX Series
3
Available Configurations
Type PRX/120
: Outlet pressure range of 14.5 to 435 psig /
1.00 to 30.0 bar. The Type PRX/120 can be used as the pilot
on single stage pressure reducing regulators, as the monitor
or working pilot in wide-open monitor systems or as the
working pilots in working monitor systems.
Type PRX/120-AP
: Outlet pressure range of 435 to
1160 psig / 30.0 to 80.0 bar. The Type PRX/120-AP can
be used as the pilot on single stage pressure reducing
regulators, as the monitor or working pilot in wide-open
monitor systems or as the working pilots in working
monitor systems.
Type PRX/125
: Identical to the Type PRX/120 except
the restriction screw is removed. The Type PRX/125 can
only be used as the monitor override pilot on working
monitor applications.
Type PRX/125-AP
: Identical to the Type PRX/120-AP except
the restriction screw is removed. The Type PRX/125-AP
can only be used as the monitor override pilot on working
monitor applications.
Type PRX/131:
Outlet pressure range of 14.5 to 435 psig /
1.00 to 30.0 bar. Type PRX/131 is used as a booster or quick
dump pilot with another PRX Series pilot on a single stage
pressure reducing regulator or with the monitor pilot on the
monitor regulator in wide-open monitor systems.
Type PRX-AP/131:
Outlet pressure range of 435 to
1160 psig / 30.0 to 80.0 bar. This pilot is used as a booster
or quick dump pilot with another PRX Series pilot on a single
stage pressure reducing regulator or with a monitor pilot on
the monitor regulator in wide-open monitor systems.
Type PRX/182:
Outlet pressure range of 29 to 609 psig /
2.0 to 42.0 bar. This pilot is used in relief valve or backpressure
regulator situations.
Type PRX-AP/182:
Outlet pressure range of 435 to
1160 psig / 30.0 to 80.0 bar. This pilot is used in relief valve
or backpressure regulator situations.
Principle of Operation
Types PRX/120 and PRX/125
Pilot-operated regulators use inlet pressure as the operating
medium, which is reduced through pilot operation to load the
actuator diaphragm. Outlet or downstream pressure opposes
loading pressure in the actuator and also opposes the pilot
control spring.
When outlet pressure drops below the setting of the
pilot control spring, pilot control spring force on the pilot
diaphragm thus opens the pilot valve plug, providing
additional loading pressure to the actuator diaphragm. This
diaphragm loading pressure opens the main valve plug,
supplying the required flow to the downstream system. Any
excess loading pressure on the actuator diaphragm escapes
downstream through the bleed restriction in the pilot.
When the gas demand in the downstream system has been
satisfied, the outlet pressure increases. The increased
pressure is transmitted through the downstream control line
and acts on the pilot diaphragm. This pressure exceeds the
pilot spring setting and moves the diaphragm, closing the
orifice. The loading pressure acting on the main diaphragm
bleeds to the downstream system through a bleed restriction
in the pilot.
Type PRX/131 Pilot
The Type PRX/131 pilot is often referred to as a quick dump
pilot or a booster pilot, as it helps to boost the pressure
release. This pilot is used with another PRX Series pilot on a
single stage pressure reducing regulator or with the monitor
pilot when two regulators are set up in a Working Monitor or
Wide-Open Monitor system. The Type PRX/131 is always
attached to the Monitor regulator and allows the regulator to
operate faster. If the downstream pressure (P
2
) increases,
the Type PRX/131 opens and the loading pressure to the
regulator drops, allowing the regulator to release pressure off
the downstream side of the diaphragm so it closes faster.
Type PRX/182 Pilot
The Type PRX/182 pilot is used in relief valve or
backpressure regulator configurations. The pilot bleeds
constantly while the relief valve is in operation. The pilot
does not bleed when inlet pressure is below set pressure.
The pilot exhaust can be connected directly to the main
valve exhaust pipe if the pilot connection and the exhaust
pipe are designed to prevent significant backpressure
buildup during full flow conditions.
Adjustment
The adjustment of the regulator is performed by means
of the pilot adjusting screw, which varies the compression
of the control spring. Adjustment is performed while the
regulator is in operation with the aid of a pressure gauge to
monitor downstream pressure; loosen the locknut and turn
the adjusting screw slowly to adjust outlet pressure.
Installation
!
WARNING
Personal injury or equipment damage, due
to bursting of pressure-containing parts may
result if this regulator is overpressured or
is installed where service conditions could
exceed the limits given in the Specification
section and on the appropriate nameplate or
where conditions exceed any rating of the
adjacent piping or piping connections. To
avoid such injury or damage, provide pressure-
