Bulletin 10-02
3
Function and Design
The S8VS is a multi-module platform and is available as a four
position unit with the capability of interchangeable modules in the
fourth position, as shown in Figure 1 . The S8ST is two position as
shown in Figure 2 .
Position 1: Isolation valve (hand shut-off)
Position 2: Strainer (60 mesh)
Position 3: Solenoid
Position 4: Option 1: Isolation valve (hand shut-off)
Option 2: Stop expansion valve
Option 3: Stop check valve
Option 4: Stop check hand expansion
4
3
1
2
Figure 1:
S8VS Modules
3
2
Figure 2:
S8ST Modules
The S8VS can be confgured for many different applications
including liquid feed and as a purge point solenoid .
Isolation Valve (Hand Shut Off) Module
The isolation valves are located in position 1 and optionally in
position 4 . These are designed based on the proven technology of
the R/S hand valve series and serve to isolate the strainer . These
isolation valves feature a proven seat and seal as well as a back-
seating design .
Strainer Module
The RSF refrigerant strainer in position 2 collects foreign materials
and dirt in a refrigerant system at minimal pressure drop to
minimize damage to or prevent malfunction of control valves . This
is extremely important upon start-up of a new refrigeration system
where dirt, scale, and weld particles may be present in the system
and are disturbed and circulated when pressure testing or upon
system start-up . It is also important when an existing system is
revised and any settled dirt or foreign matter may be disturbed and
circulated throughout the system .
S8 - Solenoid Module
The S8 solenoid valve in position 3 is a semi-direct acting valve .
A small pilot port is opened by a magnetically-lifted solenoid
plunger assembly, causing relief of pressure from the top of a
main valve and piston assembly . The resulting pressure difference
between valve inlet and valve outlet allows the main valve to be
lifted . A minimum pressure difference of approximately 1 psi is
required for operation .
Stop / Check / Expansion Module
Position 4 features a isolation valve with an optional expansion
and check feature . The expansion valve feature allows the user to
manually adjust the flow rate . The check valve feature prevents
backflow and is generally used in applications that employ a hot
gas defrost .
Operation is as follows, starting with a closed valve .
1 . When energized, the solenoid coil (1) forms a magnetic feld
which pulls the solenoid plunger (2) upward, striking the valve
needle and pulling it up from its pilot seat . This permits fluid
travel from chamber A (in and above piston plug assembly
[3]), through orifce B in the piston plug assembly, and to the
downstream side of the valve .
2 . When the pressure in chamber A has dropped almost to the
downstream pressure, the higher upstream pressure, acting on
the annular portion of the piston plug assembly (3) outside of
the seat bead, lifts the main valve to its open position .
3 . When the electrical circuit to the valve is broken, the solenoid
coil (1) is de-energized, allowing the solenoid plunger (2) to
drop and the valve needle to close the pilot port (4) in the
piston plug .
4 . Liquid and/or gas leakage through the clearance area
around the piston plug (3) causes a rapid pressure buildup in
chamber A . This pressure, along with the downward force of
the spring in the solenoid plunger (2) and the weight of the
piston plug assembly, forces the main valve disc tight against
the seat bead to stop all flow .
2
3
4
1
A
B
Figure 3:
S8VS/S8ST Function Schematic
Manual Opening Stem Operation
To manually open the S8VS/S8ST solenoid port, frst remove the
bottom seal cap . Turn the manual opening stem in (clockwise
viewed from beneath) . The rising stem will lift the piston
assembly from its seat and permit flow through the valve . To
resume automatic operation, turn the manual opening stem out
(counterclockwise viewed from beneath) until it stops and then
replace the seal cap .
