PRX Series
5
Pilot Adjustment for
Types PRX/120 and PRX/125
Loosen locknut (key 2) and turn the adjusting screw into
the spring case to increase (or out of the spring case to
decrease) the downstream pressure. When the desired
setpoint adjustment is completed and verified, tighten the
locknut to lock the adjusting screw in position.
PRX Series Pilot Restrictor and Damper
Screw Adjustment
Note
The Type PRX/125 (upstream monitor pilot in
working monitor installations) does not have
a restrictor screw.
The Restrictor and Damper screws on the PRX Series pilot
control the regulator’s proportional band (droop) and speed
of response.
1. Start with the restrictor screw 1 turn counterclockwise
from fully seated (turn restrictor fully clockwise then
1 turn counterclockwise) and the damper screw
fully counterclockwise.
2. Turn damper screw clockwise until desired performance
is achieved. This reduces the flow path of the damper.
If the damper becomes fully seated (no longer able to
turn clockwise) and the desired performance has not
been achieved, return the damper screw to the fully
counterclockwise position.
!
WARNING
The damper screw should not be left in
the fully seated position, as it will lock the
regulator in last position which could cause
incorrect pressure regulation.
3. Turn the restrictor screw an additional turn
counterclockwise from fully seated. This increases
the flow path of the restrictor. If additional tuning is
required, repeat step 2. Follow this method until desired
performance is achieved.
Shutdown
CAUTION
If the pilot bleed control line pressure is
shutdown first, the downstream system may
be subjected to full inlet pressure.
SERIES
CAP SCREW (KEY 5)
OPEN END WRENCH
ALLEN WRENCH
FT-LBS
N•m
mm
mm
PRX
7.5 to 9.2
10.2 to 12.4
10, 17
5
Table 3.
Torque Recommendation and Request Tools
1. If the pilot setting must be disturbed, be sure to keep
some tension on the spring. This will prevent trapping inlet
pressure during blow down.
2. Slowly close the valves in the following order:
a. Inlet block valve
b. Outlet block valve
c. Control line valve(s), if used.
3. Open the vent valves to depressurize the system.
Maintenance for Types PRX/120
and PRX/125
Pilot parts are subject to normal wear and must be inspected
and replaced as necessary. The frequency of inspection and
replacement of parts depends upon the severity of service
conditions or the requirements of local, state and federal
regulations. Due to the care Emerson™ takes in meeting
all manufacturing requirements (heat treating, dimensional
tolerances, etc.), use only replacement parts manufactured
or furnished by Emerson.
All O-rings, gaskets and seals should be lubricated with a
good grade of general-purpose grease and installed gently
rather than forced into position. Also, apply an anti-seize
compound to the adjusting screw threads and other areas
as needed. Be certain that the nameplates are updated
to accurately indicate any field changes in equipment,
materials, service conditions or pressure settings.
!
WARNING
To avoid personal injury resulting from
sudden release of pressure, isolate the pilot
from all pressure and cautiously release
trapped pressure from the pilot before
attempting disassembly.
CAUTION
Always remove spring (key 7) tension before
performing maintenance on this unit. To
remove spring tension, loosen locknut (key 2)
and back out adjusting screw (key 1) until
compression is removed from the spring.
Lower Case Maintenance
1. Disconnect pilot and remove from the line.
2. Remove machine screws (key 10) and washers (key 11)
from lower cover (key 21) and the separate lower cover
from the body (key 16).
