IOM-POSR-2
4
bleed orifice. The reduced loading pres sure
on the upper side of the piston closes the main
valve’s plug enough to restore the down stream
(P
2
) pressure to the setpoint.
7. Pressure setpoint is adjusted by changing
the com pres sion of the pilot’s range spring by
turning the adjusting screw either clockwise
(CW) or counter-clock wise (CCW). Turning
the adjusting screw clockwise (CW) will
in crease the downstream (P
2
) pressure.
Turn ing the adjusting screw counter-clockwise
(CCW) will decrease the down stream (P
2
)
pressure.
SECTION IV
IV. START-UP
A. General
1. Start with the block valves closed.
2. Ensure that the needle valve(s) on the
sensing line is opened and downstream (P
2
)
pressure is in di cat ing on pressure gauge.
3. Relax the pilot valve range spring by turning
the adjusting screw counter clockwise
(CCW) (viewed from above) a minimum of
three (3) full revolutions. This reduces the
outlet (downstream) pressure setpoint.
4. Slowly open the bypass valve to preheat the
system piping and to allow slow expansion of
the piping. Assure proper steam trap op er a tion.
Closely monitor outlet (down stream) pressure
via gauge to assure not over-pres sur iz ing.
NOTE:
If no bypass valve is in stalled, extra
caution should be used in start ing up a cold
system; i.e. do everything slowly.
5. Slowly open the outlet (downstream) block
valve until fully open. Slightly close the by pass
valve at same time.
6. Slowly open the inlet (upstream) block valve
ob serv ing the outlet (downstream) pressure
gauge. De ter mine if the regulator is flowing.
If not, slightly close bypass valve, and then
slowly rotate the pilot valve adjusting screw
clockwise (CW) (viewed from above) until flow
begins.
7. Continue to alternate slowly closing the
by pass valve and then slowly opening the inlet
(upstream) block valve, especially when the
downstream piping sys tem isn’t pres sur ized.
If the outlet (downstream) pressure exceeds
the desired pressure, close the by pass
valve until fully closed. If outlet pressure still
re mains above desired level, rotate pilot’s
ad just ing screw CCW (viewed from above) in
1/2 revolution increments until outlet pressure
reaches desired level. If outlet pressure is
below desired level, rotate pilot’s adjusting
screw CW (viewed from above) until desired
level is reached.
8. When flow is established steady enough that
the inlet (upstream) block valve is fully open,
begin to slowly close the bypass valve and
continue until fully closed.
9. Develop system flow to a level near its
ex pect ed normal rate, and reset the regulator
setpoint by turning the pilot valve adjusting
screw CW (viewed from above) to increase
outlet pressure, or CCW to reduce outlet
pres sure.
10. Reduce system flow to a minimum level and
observe setpoint. Outlet pressure will rise from
the set point of Step 9. There should be no
more than a 10% variation in outlet pres sure
over the maximum to minimum flow range.
plug increases its opening, elevating the
loading pressure on the upper side of the main
valve’s piston. The combined actions increase
flow enough to restore the down stream (P
2
)
pressure to the setpoint.
6. If the downstream (P
2
) pressure rises above
the setpoint, the force developed by the
in creased pressure on the underside of the
piston instantly moves it upward and partially
closes the main valve’s plug. Simultaneously,
the pilot valve’s plug partially closes and al lows
the loading pressure to decay through the
CAUTION
Do not walk away and leave a bypassed regulator
unattended when on manual bypass!
