Groth 1401E - Manual (Page 6)

5
WARNING
The recommended set pressure range is stamped on
the nameplate. Never adjust a spring for a set
pressure beyond its upper or lower design limit as
specified on the nameplate and in Table 2.
Exceeding the upper limit may compress the spring
beyond its working height and the pilot valve may not
open fully. A valve set below the lower limit will
require excessive overpressure to open fully. In
either case, the pressure relief valve may not provide
sufficient capacity to prevent overpressure and
failure of the tank.
TABLE 2
SPRING TABLE
Spring
Range
Set
Pressure Color Part No.
1 2.0-4.0" WC Yellow 81631001
2 4.1-8.0" WC Green 81631002
3 8.1-16.0" WC Pink 81631003
4 16.1-28.0" WC Blue 81631004
5 1.1-2.0 PSI White 81631005
6 2.1-4.0 PSI Gray 81631006
7 4.1-8.0 PSI Black 81631007
8 8.1-15.0 PSI Red 81631008
The following are the normal operating phases of the
pilot valve:
Fig. 3 Closed Position
ATMOSPHERE
TANK
PRESSURE DOME
PRESSURE
BOOSTER
DIAPHRAGM
SENSE
DIAPHRAGM
BLOWDOWN
ORIFICE
The tank pressure is less than set pressure and the
pilot valve is closed. Since the pressure between the
diaphragms is equal to the pressure under the booster
diaphragm, the net force on the booster (larger)
diaphragm is zero. Therefore, the net effective
opening force is the tank pressure acting on the sense
(smaller) diaphragm and is insufficient to overcome
the spring force.
Tank pressure has filled the relief valve actuator
(dome) through the sense line and the adjustable
orifice. The relief valve is tightly closed. When the
tank pressure increases to the point that the net
opening force equals the spring force, the pilot valve
will begin to open.
Fig. 4 Open - Snap Action
T he pilot valve begins to open at set pressure with
the blowdown orifice set for snap action (minimum
area). The space between diaphragms exhausts to
atmosphere and the net effective lifting force is the
system pressure acting on the booster (larger)
diaphragm. The additional lifting force caused the
pilot to open fully. The actuator exhausts rapidly
through the fully open pilot valve. The relief valve
opens fully at approximately 10% overpressure and
system pressure begins decreasing immediately.
Fig. 5 Open - Modulating
The pilot valve begins to open at set pressure with
the blowdown orifice set for maximum modulating
action (increased orifice).