20
Figure 11b. DG18S4-**-52 Air Operated Pilot Valve
Air pressure is appliedto piston area and shift pilot spool.
Oil under pressure enters main stage section and shifts
main stage spool.
PIston
PIston
Air Connection #2
Connection
Plate
Control Flow to
Main Stage
Control Flow to Tank
from Main Stage
Air Connection #1
A
B
CAUTION
DO NOT energize both (AC) solenoids simulta-
neously. Sustained operation with both solenoids
energized will cause excessive current in the coil
and accelerates burnout.
a.
Electrical Solenoid Types Available
: Three
basic types of electrical solenoids exist: Wet armature, air
gap and oil immersed. The unit nameplate identifies the type
of solenoid being used. See the model code in Table 2. If a
50 or 51 design two stage valve is equipped with a DG4V-3
pilot valve, the letter “M” is stamped into the nameplate (i.e.
DG5S4-062*-*M-51). The letter “M” indicates an adapter
plate is used to provide the necessary DG4V-3 pilot valve
interface requirements.
b.
Wet Armature Type Solenoids
: Wet armature
solenoids are standard on DG4V-3 and DG4S4-01-W/W3
pilot valves only. Wet armature solenoids have many design
advantages over other types of solenoids. Some advantages
include cooler operation, static sealing arrangements,
immunity to moisture and greater burn-out resistance.
DG4V-3 and DG4S4-01*-W wet armature solenoids are not
serviced with individual parts. Service is provided by
replacing the entire core tube subassembly. Parts can be
removed, cleaned and seals replaced on “W3” type
solenoids.
c.
Air Gap Solenoids
: DG4S4-01 pilot valves are
usually equipped with air gap solenoids. Air gap solenoids
are isolated from system fluid and can be removed and
replaced without disturbing the system. A push pin and
sliding seal arrangement couple the solenoid to the valve
spool (see Figure 13c).
d.
Oil Immersed Solenoids
(early type wet
armature solenoid - no longer recommended for new
equipment): DG4S4-01 pilot valves may be equipped with oil
immersed solenoids. This solenoid provides a certain
amount of dampening of the solenoid parts and extends unit
life. The standard wet armature solenoid provides this same
feature. Oil immersed solenoids are not repairable except by
the manufacturer and are not directly interchangeable with
air gap or wet armature type valves. Oil immersed type
solenoids have the letter “H” stamped into the nameplate.
Open Center
12a. Flow Conditions Pressure to “B” - “A” to Tank
A
P
T
B
Solenoid “A” De-energized
Solenoid “B” De-energized
T
Solenoid “A” De-energized
A
P
T
B
T
A
P
T
B
T
Solenoid “B” De-energized
Solenoid “A” De-energized
Solenoid “B” De-energized
12b. Flow Conditions Pressure to “A” - “B” to Tank
12c. Flow Conditions Blocked (Center Condition #2 Spool)
e.
Electrical Solenoid Voltage Requirement
:
Electrical solenoids are available in various AC and DC
voltage ranges. The standard voltage and frequency range is
115 VAC, 60 Hz. Refer to parts and service drawings for
units with non-standard voltage ranges. Fifty (-50) and
fifty-one (-51) design units have the voltage and frequency
range stamped into the nameplate if other than standard.
Ten (-10), twenty (-20) and fifty-three (-53) design units use
an identification letter for the coil voltage and frequency.
f.
Electrical Solenoid Ground Connections and
Wiring Housing
: An electrical wiring housing with a 1/2 inch
NPTF thread connection is available on DG4V-3 and
DG4S4-01 pilot valves. The wiring housing can be rotated
