Page 4 / Bulletin 22-00 A
piston changes position, the pressure
on top of the piston changes also.
Th
erefore, a decrease in upstream
pressure will result in the range spring
pushing both the diaphragm and pilot
plug piston downward. Increasing
pressure on top of the piston causing
the valve to close, thereby decreasing
fl ow through the main valve as the
piston begins to regulate towards
a closed position. Conversely, an
increase in upstream pressure will
move the diaphragm up along with
the pilot plug. Resulting in a lower
pressure on top of the piston and
causing the valve to opening.
Note:
In the A4W port plate there are
two channels illustrated in the inlet
side cross sectional drawing. Th
e
internal channel running horizontally
from the gauge port, passage (H),
to the pilot plug is used for an R/S
outlet regulator, A4WO, variation and
is not required for a standard A4W
inlet regulator. A plug is installed at
the factory to prevent any pilot fl ow
through this channel.
A4WB Principle of Operation
Th
e port plate for the A4WB is a
slightly diff erent construction, shown
in the A4WB principle of operation
cross-section diagram, than the
standard A4W, but the regulating
portion of the valve works in the same
manner as described in the A4W
principles of operation.
Note:
Th
e passages in the A4WB port
plate are not in the same cross section
as shown in the diagram. Th
e upper
half of passage (N), passage (B),
passage (M), and the piston pressure
release passage (P) are all located
on diff erent cross-sections of the
port plate. Th
e cross-section shown
is to better illustrate how the valve
operates.
Th
e ‘B’ feature, electric wide open,
when energized will cause the
solenoid plug to lift and the valve will
fully open. Th
e pressure on top of the
piston is released through passage
(B) and into passage (T), lowering
the pressure. Th
e inlet pressure
acting on the bottom side of the
piston overcomes the outlet pressure,
therefore forcing the piston upward
A4WS Principle of Operation Cross Section (‘S’ Coil Energized)
A4WBS Principle of Operation Cross Section (‘B’ Coil De- Energized
and ‘S’ Coil Energized)
Electric
Shut-Of
f
N
P
T
B
M
N
Electric
Wide
Open
Manual
Bypass
Stem
T
P
N
P
T
B
M
N
Electric
Shut-Of
f
Manual
Bypass
Stem
T
P
Seal Cap
Passage
Description
N
Inlet Pressure
P
Piston Pressure, Top
T
Outlet Pressure
B
Electric Wide Open Bypass
S
Electric Shut-Off
M
Manual Opening Stem
A4W Port Plate Passage Table
