Bulletin 22-05 A / Page 3
A4WO Principle of Operation
Th
e outlet pressure enters the space
under the diaphragm through passage
(T), shown in the A4WO principle
of operation cross-section diagram,
fi lling the chamber underneath the
diaphragm. When force created by
this pressure acting on the underside
of the diaphragm exceeds the force
of the range spring acting on top of
the diaphragm, the diaphragm moves
upward. Th
is also results in an upward
movement of the spring loaded pilot
plug installed directly underneath the
diaphragm. Th
e upward movement
of the pilot plug forces the pilot
plug piston to close, preventing any
pressure above the piston to escape
through passage (P) and into passage
(T). Th
e pressure on top of the piston
is equalized to the pressure below,
inlet pressure, through the piston
bleed hole and the piston moves
downward, closing the valve due to
the weight of the piston and the spring
closing force. A piston seal ring
ensures that this bleed hole is the sole
source of equalization.
Note:
the inlet passage (N), shown
in the A4WO principle of operation
cross-section diagram, is blocked off at
the port plate. Th
is passage (N) is used
for the A4W inlet regulator variation
and is not required for a standard
A4WO outlet regulator. A plug is
installed at the factory to prevent any
pilot fl ow through this passage.
When the outlet pressure decreases,
such that the range spring overcomes
the pressure force underneath the
diaphragm, the diaphragm moves
downward forcing the pilot plug to
move downward opening passage
(P), releasing the pressure above the
piston through the pilot plug and into
passage (T). Th
is lowers the pressure
on top of the piston and the inlet
pressure underside the piston forces
the piston to open.
Note:
passage (P) and passage (T) in
the port plate use the same piping
system. Th
e pilot plug prevents both
passages from being utilized at the
same time.
A4WO Principle of Operation Cross Section
A4WOB Principle of Operation Cross Section (‘B’ Coil Energized)
system. (See Bulletin 00-20 for more
information)
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
N
T
B
M
B
Electric
Wide
Open
Manual
Bypass
Stem
Seal Cap
N
T
P
Pilot Plug
Piston
Seat
Diaphragm
Pilot
Spring
Manual
Bypass
Stem
Pilot Plug
Piston
T
P
P
P
