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Refrigerating Specialties Division
ADAPTOMODE WELD-END
PRESSURE REGULATORS
Types: A4W-DN, A4WE-DN,
A4WS-DN, A4WB-DN, A4WD-DN,
A4WP-DN, A4WOE-DN, A4WR-DN
Port Size 125-200mm (5”-8”)
FOR AMMONIA, R12, R22, R502
AND OTHER COMMON REFRIGERANTS
FEATURES
• Cast Steel Body – Strong, Lightweight.
• Welds Directly in the Line – No Flanges.
• Removable Seat – Serviceable from Top Side.
• Streamlined Fluid Flow Pattern.
• Unique Modular Construction – Same Modules
as A4A-DN Series.
• Interchangeable Parts.
• Pilot Operated Characterized Modulating Plug for
Precise Control.
• Suitable for All Common Refrigerants and Oil
• 25 bar (362 psig) Design Pressure (PS).
• Many Control Variations are Possible with the Use
of a Few Modules and Kits.
• Stainless Steel Diaphragm.
• Stainless Steel Pilot Seat.
• Manual Opening Stem.
• Complies with Pressure Equipment Directive 97/23/EC
BULLETIN DN23-20
A4W Series
February 2002
Installation and Service Information
I S O 9 0 0 1 C E R T I F I E D
Description
These heavy duty, cast steel bodied (ASTIM No. A352 Grade LCB),
pressure regulators weld directly in the line and do not require flanges.
They are used for control of Ammonia, R-12, R-22 and R-502, and other
common refrigerants, certain oils and other fluids approved for use in
refrigeration systems.
The A4W Series Regulators are pilot operated, using upstream pressure
for the moving force, and require a minimum 0.14 bar (2 psi) pressure
drop to fully open. The basic Type A4W is an Inlet Pressure Regulator
which tends to open on a rise in upstream pressure above set-point and
to close on a drop in pressure below set-point.
These valves can be ordered with the Type RSW Strainer to be welded
directly to the inlet of any of the Type A4W Regulators or use a 13mm (1/
2") Type RSF Strainer in only the pilot circuit
of a Type A4WE or A4WR
version
of the regulator.
The A4W Series
of regulators uses the same Modules as does the A4A
Series to configure many possible variations.
Fig. 1 – A4W, A4WE
SEAL CAP
ADJUSTING STEM
RANGE SPRING
DIAPHRAGM
GAUGE CONNECTION
MODULATING PLUG
PILOT SEAT
CLOSING
SPRING
REMOVABLE
SEAT
POWER PISTON
MANUAL
OPENING
STEM
SEAL CAP
Purpose
The purpose of the Type A4W Series of Pressure Regulators is to modulate
the flow of refrigerant gas and/or liquid so as to maintain a constant set
for pressure, regardless of load fluctuations. The regulators described in
this bulletin control upstream (inlet) pressure except for the Type A4WOE,
which controls downstream (outlet) pressure.
The fluid temperature range for the A4W Family of Regulators is -45° to
105°C (-50° to 220°F).
Principles of Operation (See Fig. 1)
The inlet pressure enters the space under the Diaphragm through passage
N. When the force created by the pressure exceeds the force of the Range
Spring, the Diaphragm is lifted off of the Pilot Seat, allowing pressure to
enter on top of the Power Piston. This causes the Power Piston to move
downward, forcing the Modulating Plug to open and modulate to maintain
constant inlet pressure. (See pages 3 - 5 for principles of operation of
other A4W Variations.) An increase in inlet pressure lifts the Diaphragm
further, allowing more pressure on top of the Power Piston and opening
the valve wider. A decrease in inlet pressure causes the Diaphragm to
move closer to the Pilot Seat reducing the pressure on the top of the
Power Piston and allowing the Closing Spring to reduce the valve
opening.
The degree of valve opening is controlled by the amount of pressure on
top of the Power Piston, which in turn is controlled by the flow through the
Pilot Seat and the bleed off through the bleed hole in the Power Piston to
the outlet of the valve. The volume of bleed flow from the top of the Piston
to the valve outlet through the clearance between the Power Piston and
the piston bore is very small because the Power Piston is fitted with a
Seal Ring.
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