I.
MANUALLY SET PRESSURE REDUCING VALVE
1.
INTRODUCTION
The PRV-71H (manually operated) is a normally open, spring loaded, diaphragm type, self actuating pressure
reducing valve. Its purpose is to reduce and control downstream pressure between 15 to 45 psig by the manual
adjustment of the adjustment screw. The valve will close if downstream pressure exceeds the set pressure.
The upper valve body is provided with a
1
⁄
4
" FNPT vent connection. If the diaphragm fails, the pressurized gas
can be directed to an appropriate location by use of the vent connection.
The PRV-71H design incorporates a removable trim capsule assembly, allowing for easy maintenance and
cleaning.
2.
INSTALLATION
Because of its weight, the PRV-71H (manually operated) should always be supported. An optional wall-
mounting bracket is available and includes four
3
⁄
8
" x 1" wall mounting slots. The PRV should be installed in
the upright position.
Inlet and outlet connections are
3
⁄
4
" or 1" female NPT depending on the model chosen. A label is provided
to show the direction of fl ow and help identify the inlet and outlet. Note that the outlet connection and vent
connection are on the same side of the valve. There is also a
1
⁄
4
" FNPT vent connection on the top body of the
PRV in case of diaphragm failure. The vent line should be
1
⁄
2
" schedule 80 carbon steel pipe and slope at least 2
degrees downward to prevent water/moisture entry. An insect screen must also be installed on the outlet of the
vent piping to prevent insects from blocking the pipeline.
The valve should be installed downstream of the chlorine fi lter and liquid traps (drip legs).
A pressure gauge should always be installed in the downstream piping to indicate the reduced pressure.
3.
OPERATION
The outlet pressure is adjustable by means of the Adjustment Screw (PRH-396G-8000). By rotating the
Upper End Cap (PRH-378U-8000) the user can access the adjustment screw. Turning the Adjustment Screw
allows the user to increase (clockwise) or decrease (counterclockwise) the compression on the Loading
Spring (SPH-424A-8000) thus controlling how much the valve opens. Turning the Adjustment Screw
clockwise will increase the tension on the loading spring, thus increasing the outlet pressure and turning it
counterclockwise will decrease the outlet pressure. Adjustments should be made slowly and carefully, while
monitoring the pressure with a pressure gauge installed on the downstream side of the pressure reducing valve.
4.
MAINTENANCE
The frequency of required cleaning or maintenance will depend on the quality of the gas supply and the gas
fl ow rate. However, it is recommended that that the valve be serviced at least once per year.
Parts/Maintenance Kits are offered and contain the parts necessary to accomplish the recommended mainte-
nance as well as a parts diagram.
Note: Please refer to the parts diagram for those items included in the Part & Maintenance Kits.
Maximum Discharge Pressure Settings to Prevent Liquifaction
Cl
2
Service: 40 psig (275 kPa guage)
SO
2
Service: 15 psig (103 kPa guage)
NH
3
service: 40 psig (275 kPa guage)
3
