Maintenance And Service - Parker A4W Series Installation And Service Information

To replace the Seal Ring 10 on the Power Piston 9 install in place by
starting the new ring over the top of the Piston. Gradually engage the ring
into the slot, rotating the force on the ring as it is pushed into place. The
Seal Ring must be installed as shown in Fig. 11 with the open edge of the
ring pointing up.
Before installing the Power Piston 9 in the body bore be sure that the
bleed hole in the top of the piston is clear. Insert the Piston into the Body
1 so that the top of the Piston is parallel with the top of the Valve Body
and, with an even force, push the Piston into the Body. There is no fastening
between the Piston and the Modulating Plug 7; the Piston Stem only slides
into the receptacle in the center of the Modulating Plug. The Piston should
not bind and must move up and down easily.
If the Manual Opening Stem 11 has been removed, it must be re-installed
before the Adapter Cover 22 is installed. Insert the Opening Stem into the
opening on the bottom of the Adapter Cover and push it through the Stem
Packing 13 until it is ready to engage with the threads in the casting.
Grasp the Stem at its top end and pull while, at the same time, turning it
counterclockwise (when viewed from the top of the Stem) to begin to
engage the threads, and, then, complete the turning with a wrench until
the bottom of the stem is about flush with the bottom of the Adapter Cover.
Install the Packing Nut 12 at the top of the Stem.
Clean the sealing surfaces where the Adapter-to-Body Gasket 5 is to be
installed and insert a new Gasket in position, making sure to line up the
hole in the Gasket with the passage "N" hole (see Fig. 1) in the Valve
Body 1. The gasket should have a very light film of refrigerant oil applied
to both surfaces before inserting in place.
Position the Adapter Cover 22 so the extension of passage N in the
Adapter lines up with the matching hole in the Valve Body 1. Insert the
bolts (and nuts) and tighten to the torques listed in the table below.
These should be tightened in a pattern that provides a uniform pull-down
of the Adapter Cover to the Valve Body.
Inspect the top surface of the Pilot Seat 44 to be sure that it is smooth
and unblemished. This is essential for reliable performance and for a
tight shut-off. If the surface is not good replace the Pilot Seat with a new
part. There is no gasket or O-ring under the Pilot Seat. Tighten the seat
to the torque listed in the table below.
Inspect the Diaphragm 45 surfaces to be sure they are clean and free
from scratches, bends or cracks. If range "A" or "V", there is only one
Diaphragm: if range "D", there will be two Diaphragms. Replace any
Diaphragms that are defective.
Two Diaphragm Gaskets 43 and 46 are a part of each installation. A
thick, black gasket goes under the Diaphragm 45 against the Valve
Body. and a thin, black gasket goes on top of the Diaphragm. The
Diaphragm(s) is installed bowed toward the Diaphragm Follower 47 and
Range Spring 49. That is, the center of the Diaphragm is higher than its
perimeter.
Before installing the Bonnet 51 be sure that the Adjusting Stem 52 is
backed out far enough so that when the assembly of Range Spring 49.
Spring Rests 48 and 50, Diaphragm Follower 47 and Bonnet are put in
place, there will be no compression of the Spring. Place the Diaphragm
45 and both Diaphragm Gaskets 43 and 46 in place on top of the
Adapter Cover 22 as described above. Assemble the Range Spring,
Range Spring Rests and Diaphragm Follower into the Bonnet in the
sequence shown in Figs. 1 or 9. This assembly procedure is most
convenient if done in the mechanics hands and not in place on the top
of the valve. These parts can be held in place within the Bonnet as the
assembly is positioned on top of the Adapter at one edge and then slid
over to its proper location. There is no specific orientation for the Bonnet.
Insert the Cap Screws 58 and tighten to the torque listed in the table
below. Tighten in a manner that provides a uniform pull-down of the
Bonnet.
Check the assembled valve for leaks to atmosphere. Check the position
of the Manual Opening Stem 11 to be as desired. Set the Range
Adjusting Stem 52 to control the pressure as required. Tighten Stem
Packing Nuts 12 and 55 and install Seal Caps 15 and 57.
Refrigerating Specialties Division

Maintenance and Service

Dirt in the system is the greatest single cause of regulator malfunction.
All screens or filters must be cleaned or replaced when they become
dirty. At start up or when changes or additions are made, it is especially
important that these items are cleaned or changed frequently. When the
RSW companion strainer or 13mm (1/2") pilot circuit strainer is used,
maintain according to instructions in Bulletin 00-10. Moisture in halocarbon
systems, in particular, can cause corrosion or form ice, causing the
Piston to freeze in position. Filter-driers should be used and maintained
for halocarbon systems.
Before deciding to disassemble a regulator for servicing, the following
investigations should be made:
Check the Manual Opening Stem; it should be turned out
(counterclockwise) for automatic operation.
Check the regulator setting to make sure it is properly adjusted.
Turn Adjusting Screw slowly to see if the regulator responds. Check
regulator pressure range; if wrong, range spring must be changed
or a Vacuum Cartridge installed.
Check other system components for proper operation.
Check hand valves in the system to make sure they are open or
closed as required and the system is receiving liquid or vapor as
the case may be.
Before disassembly of Regulator, make certain that all refrigerant
has been removed (pumped out) from the Regulator and its
corresponding Strainer where one is used. Read Safety Bulletin
RSBCV.
TABLE OF TORQUES FOR A4W
FASTENERS AND VALVE SEATS
Valve Seat
Retaining Screw
Bonnet Cap Screws
Adapter Cover Nuts
Pilot Seat
A2D Body Bolt
S6A Body Bolt
8
Metric Units U.S. Units
Item mkg
No. (AlI sizes) (AlI sizes)
(2) 13.8
(4) 2.1
(58) 1.5
(18) 14.5
(44) 2.8
(60) 0.83-1.1
(42) 0.83-1.1
ft/lbs
100
15
11
105
20
6-8
6-8