Page 4 / Bulletin 22-05 A
A4WOB Principle of Operation
Th
e port plate for the A4WOB is a
slightly diff erent construction, shown
in the A4WOB principle of operation
cross-section diagram, than the
standard A4WO, but the regulating
portion of the valve works in the same
manner as described in the A4WO
principles of operation.
Note:
the passages in the A4WOB port
plate are not in the same cross-section
as shown in the diagram. Th
e upper
half of 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
and fully opening the valve. Th
is
pressure does not feed back through
the pilot plug, because the pilot plug
piston is fully seated.
Simply de-energize the ‘B’ feature on
the valve to regulate.
A4WOS Principle of Operation
Th
e port plate for the A4WOS is the
same port plate used for the A4WOB.
Th
e only diff erence is that the seal
cap and coil assembly are located in
the opposite location, as shown in the
A4WOS principle of operation cross-
section.
Th
e ‘S’ feature, electric shut off , when
energized will cause the solenoid
plug to lift and allow the valve to
regulate. Th
e regulating portion of the
valve works in the same manner as
described in the A4WO principles of
operation.
When the ‘S’ feature is de-energized
passage (P) is blocked off and the inlet
pressure bleeds through the bleed hole
in the piston allowing for continuous
equalization of inlet pressure to the
A4WOS Principle of Operation Cross Section (‘S’ Coil Energized)
A4WOBS Principle of Operation Cross Section (‘S’ Coil Energized &
and ‘B’ Coil De-Energized)
Electric
Shut-Of
f
N
T
B
M
B
Manual
Bypass
Stem
Seal Cap
P
P
Electric
Wide
Open
Electric
Shut-Of
f
N
T
B
M
B
Manual
Bypass
Stem
P
P
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
A4WO Port Plate Passage Table
