PRX Series
4
relieving or pressure-limiting devices to prevent
service conditions from exceeding those limits.
Also, be sure the installation is in compliance
with all applicable codes and regulations.
Additionally, physical damage to the
regulator could break the pilot off the
main valve, causing personal injury
and property damage due to bursting of
pressure-containing parts. To avoid such
injury and damage, install the regulator in a
safe location.
1. Use qualified personnel when installing, operating and
maintaining pilots. Before installing, inspect pilot and
tubing, for any shipment damage or foreign material that
may have collected during crating and shipment. Make
certain that body is clean and the pipelines are free of
foreign material.
!
WARNING
In hazardous or flammable gas service,
vented gas may accumulate and cause
personal injury, death or property damage
due to fire or explosion.
Vent a regulator in hazardous gas service to
a remote, safe location away from air intakes
or any hazardous location. The vent line or
stack opening must be protected against
condensation or clogging.
2. PRX Series pilots have a 1/4 NPT vent connection in the
spring case. To remotely vent gas from the spring case,
remove the screened vent and connect 1/4 in. / 6.4 mm
piping or tubing to the spring case connection. The
piping or tubing should vent to a safe location, have as
few elbows as possible and have a screened vent on its
exhaust. Install the regulator and any remote vent piping
or tubing so that the vent is protected from condensation,
freezing or substances that may clog it.
CAUTION
To avoid freeze up because of pressure drop
and moisture in the gas, use anti-freeze
practices, such as heating the supply gas or
adding a de-icing agent to the supply gas.
3. The PRX Series pilot connections are 1/4 NPT.
Connect a downstream control (sense) line to a
straight run of pipe 6 to 10 pipe diameters from the
regulator outlet, using 3/8 in. / 9.5 mm or larger outside
diameter tubing. If such a distance is not practical,
connect the control line away from elbows, swages,
nipples or any area where abnormal flow velocities
occur. Connect the other end of the control line to the
“A” port on the bottom of the PRX Series pilot.
4. Connect a downstream bleed line from the “S” port on
the PRX Series pilot to a straight run of pipe 6 to 10 pipe
diameters from the regulator outlet, using 3/8 in. /
9.5 mm or larger outside diameter tubing.
CAUTION
To prevent damage to the pilot during
startup, the sense and bleed lines should be
located on the same side of the downstream
block valve.
5. Install hand valves in the downstream sense and bleed
lines if desired. If hand valves are installed, they should
be full flow valves, such as a full port ball valve.
6. For optional remote pneumatic loading of a PRX Series
pilot, make the spring case piping connections just as
they would be made for remote venting.
Startup and Adjustment for
Types PRX/120 and PRX/125
Prestartup Considerations
Each regulator is factory-set for the outlet pressure specified
on the order. If no setting was specified, outlet pressure was
factory-set at the mid-range of the pilot control spring. Before
beginning the startup procedure in this section, make sure
the following conditions are in effect:
• Block valves isolate the regulator
• Vent valves are closed
• A bypass, if any, is in operation
In all cases, check the control spring setting to make sure it
is correct for the application.
CAUTION
Be sure to slowly introduce pressure into the
system to prevent downstream overpressure
due to potential rapid pressure increase.
Pressure gauges should always be used
to monitor downstream pressure during
startup. Procedures used in putting this
regulator into operation must be planned
accordingly if the downstream system is
pressurized by another regulator or by a
manual bypass.
Note
When using a Type SA/2 pilot supply filter
regulator, the differential pressure across the
regulator must be at least 45 psid / 3.1 bar d
for optimum regulator performance. The
Type SA/2 can be removed if differential
pressure across the regulator is less than
45 psid / 3.1 bar d and inlet pressure stays at
or below 200 psig / 13.8 bar.
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