23
1.0
Pressure Reducing Valve (PRV) Adjustment
1.1
The pressure reducing valves are “factory set” on
70E and 70M systems, therefore, change of setting
may be required. If needed, the following items
should be checked first before any attempt is made
to change the setting:
a) Does the desired system pressure correspond to
the pressure indicated on the nameplate?
b) Is the suction pressure equal to or higher than the
pressure indicated on the nameplate?
c) Is the demand (GPM) within the capacity indicated
on the nameplate?
d) Has the PRV been properly vented?
1.2
Any deviation from the above conditions will prevent
the unit from operating at the factory (nameplate)
settings.
1.3
To adjust the PRV place the pump in manual opera-
tion per paragraph 5.3. With the pump now running,
slowly close the main gate valve downstream of the
discharge header allowing a trickle of water to flow
through it. Read the system pressure on the display.
It should read 3 or 4 psi higher than the desired sys-
tem pressure. If not, remove the protective cap on
the pilot control valve and loosen the jam nut on the
adjusting stem of the PRV. Slowly turn the stem
clockwise to increase the delivery pressure and
counter clockwise to decrease pressure. (Note that a
pilot valve furnished for a 20 to 300 psi range will
change the main valve setting approximately 28 psi
for each full turn of the adjusting screw.) Set the
screw so the system display reads 3 to 4 psi higher
than the desired system pressure.
1.4
Open the gate valve fully. If feasible, draw between
50 to 80% of the designed pump capacity to recheck
valve setting. The display should now read the
desired system pressure. Tighten jam nut and replace
cap.
1.5
Repeat the above procedure for all pump and valve
combinations as required.
1.6
The CV Flow Control Valve (opening speed control)
may require field adjustment if pressure hunting
occurs. Normal setting of the valve is from 4 to 7
turns open. Never open more than 8 turns.
APPENDIX C
PROCEDURE FOR FIELD BALANCING 70E/70M PRV’S
