Refrigerating Specialties Division
5
A4AO OUTLET REGULATOR
OPERATION
The outlet pressure is sensed under the
diaphragm through the sensing tube, which is part
of the Flange Ring-tube assembly. When the force
created by the outlet pressure acting under the
diaphragm is less than the force of the range
spring, the pilot is open, allowing pressure to enter
on top of the piston. This causes the power piston
to force the throttling plug to open to maintain
constant outlet pressure. Decrease in the outlet
pressure allows the range spring to open the pilot
further, allowing more pressure on top of the piston
and opening the throttling plug further. An increase
in the outlet pressure will lift the diaphragm against
the force of the range spring, allowing the pilot
plug to start closing. The pressure on top of the
power piston is decreased and the closing spring acts to reduce the opening
of the throttling plug and the flow of fluid through the regulator. The pressure
on top of the power piston is controlled by the flow through the pilot seat
and the bleed through a bleed hole in the power piston and through the
clearance between the piston and the cylinder. A maximum of 0.14 bar
(2 psi) pressure drop across the regulator is required to open it fully.
ADJUSTMENT
Install a pressure gauge at the regulator gauge port in the A4AO Adapter
next to the sensing tube. Back the adjusting stem all the way out to stop
(counter-clockwise). This will reduce the set-point to its lowest level and
cause the valve to close. Operate the system until the outlet pressure is
lower than desired. Slowly turn in the adjusting stem (clockwise) until the
desired outlet pressure is reached.
A4AO OUTLET PRESSURE SETTING RANGES
Set Point Ranges
Approx. Pressure Change
per Turn of Adjusting Screw
V: 500 mm hg to 8 bar
1.8 bar
(25 psi)
(20 in Hg to 120 psig)
D: 5 to 20 bar
(75 to 280 psig)
3.7 bar (53 psi)
A4AOE OUTLET PRESSURE REGULATOR,
REMOTE SENSING CONNECTION
This regulator allows control of downstream pressure at a point remote
from the outlet of the regulator. The pressure from the desired sensing
point is connected directly to the A4AOE adapter at Fitting 7A in place of
the Flange Ring-tube Assembly 20 shown for the A4AO. Thus the regulator
will control the pressure at the sensing point. The regulator operation and
adjustment is the same as for A4AO.
A4AOS OUTLET PRESSURE REGULATOR
WITH ELECTRIC SHUT-OFF
The A4AOS Pressure Regulator controls outlet
pressure when the modular solenoid pilot is
energized, and closes when the solenoid pilot
is de-energized regardless of the pressure
setting or pressure in the regulator. The
Modudapter® (Fig. 5) is used for this regulator.
The pilot solenoid valve is mounted in the
location shown for A4AS on page 7.
Adjustment - With the solenoid energized,
proceed as with the A4AO.
A4AOT REVERSE ACTING
TEMPERATURE REGULATOR
The A4AOT Regulator modulates flow in
response to the temperature variations sensed
by its thermal bulb. A special temperature pilot
replaces the standard A4AO pilot. A drop in
temperature will cause the valve to open; a rise
will cause it to close. This valve responds only
to temperature changes and is not a pressure
regulator.
Operation - Temperature change of the
controlled medium is sensed by the thermal bulb
of the pilot. As the bulb is warmed, the charge in the thermal element
expands. The resulting force is transmitted to the pilot plug by a push rod,
causing the pilot to close. This in turn causes the main valve to close. A
drop in the temperature at the thermal bulb causes the opposite to happen,
thus allowing the main valve to open. Standard range is -30°C to +30°C
(-20°F to 80°F). Also available 20°C to 60°C (60°F to 140°F). Maximum
temperature to which thermal bulb can be exposed is 65°C (150°F).
The A4AOTS Regulator combines the Reverse Acting Temperature
Regulator with Electric Shut-Off. It operates the same as the A4AOT when
the solenoid pilot is energized, and closes when the solenoid pilot is
de-energized regardless of the temperature setting or pressure in the
regulator.
A4AOM ELECTRICALLY COMPENSATED
OUTLET PRESSURE REGULATOR
This pressure regulator modulates the outlet pressure in accordance to
load requirements as sensed by an electric thermostat or humidistat which
varies an electric signal applied to a motor mounted on the regulator pilot.
The motor operation is as described on Page 9 for A4AM, except the A4AOM
operates as an outlet pressure regulator. Available in standard Range V or
Range D.
The A4AOMS Regulator combines the Electrically Compensated Outlet
Pressure Regulator with the Modular Solenoid Pilot to provide Electric
Shut-off (see Page 7 for electric shut-off operation). It operates the same
as the A4AOM when the solenoid pilot is energized and closes when the
solenoid is de-energized regardless of the pressure setting or the pressure
in the regulator.
