16
3. Pilot Pressure Conversions: If it is necessary to convert
your unit from external pilot pressure to internal pilot
pressure or vice versa, internal plug(s) must be removed or
added to the main stage body. See the figures noted in
installation plug tables for internal plug locations.
4. Pressure Centered ‘‘D’’ Models (H06 & -10 Series only):
A pre-set pilot pressure can be obtained in these models.
Refer to the model code in Table 2 for pressure settings.
Pilot pressure can be increased or decreased by simply
changing internal plugs in the main stage body. Refer to plug
table in parts drawing for part numbers and see the figures
noted in installation plug tables for internal plug locations.
C. Pilot Valve Drains
1. Internal Drain: Internal drain models are used when
pressure surges in the tank line are small and CAN NOT
overcome pilot pressure.
To shift a pilot spool, pilot pressure must always exceed tank
pressure by a minimum amount. Figure 14 is an example
showing pilot pressure vs. tank pressure. Refer to the unit
installation drawing for minimum pressure ratings. Internal
pilot drain models have the letter ‘‘T’’ stamped on the unit
nameplate (i.e. DG5V-10-S-2C-*-T-M-*-10).
Note
A 10 bar (150 PSIG)
n
P must always be maintained to
shift closed center spools. A 5 bar (75 PSIG)
n
P must
always be maintained to shift open center pilot spools.
Figure 14. Pilot Valve-Internal Drain
–1000
–900
–800
–700
–600
–500
–400
–300
–200
–100
–0
150
PSIG
n
P
Pilot Pressure (1000 PSIG)
Tank Line Pressure Surge (850 PSIG)
Tank Line Pressure (750 PSIG)
Note
This tank line pressure subtracts
from the applied pilot pressure.
2. External Drain (Standard): External drain models are
recommended if pressure surges in the tank line CAN
overcome pilot pressure. Drain connection ‘‘Y’’ is used for
externally drained models. Pressure centered ‘‘D’’ models
use two drain connections ‘‘Y’’ and ‘‘W’’. All external drain
connections MUST be piped directly to tank through surge
free lines. Refer to the installation drawing (Table 1) for
further information.
3. Drain Conversions: If it is necessary to convert your unit
from external drain to internal drain or vice versa, an internal
‘‘T’’ plug must be added or removed to the main body
section.
D. Integral Check Valves
Check valves are located within the pressure port of the
main stage section. The purpose of the check valve is to
develop back pressure, at the pressure port, when open
center or tandem main stage spools are used. Back
pressure is necessary to maintain internal pilot pressure
when the main stage spool shifts to open center position.
Table 3 indicates when an integral check valve is required.
Pilot
Pressure Source
Integral Check
Valve Required
Main Stage
Spool Type
Internal
Yes
0, 1, 4, 8, 9, 11
No
2, 3, 6, 31, 33
External
No
All spools
Table 3. Integral Check Valve Circuit Requirements
Integral check valves are available at various cracking
pressure ranges. The unit nameplate identifies which check
valve is used (i.e. DG5V-10-S-2C-*-T-M-*-10). Refer to
installation drawing (Table 1) for additional check valve
information.
Note
As an alternate to the integral check valve, a 3.5/5 bar
(50/75 PSI) check valve can be installed in the tank line
of the valve to obtain pilot pressure.
Section VI - Installation
A. Service Drawings
The service drawings listed in Table 1 show installation
dimensions, port locations and operating parameters.
Manifold, subplate and bolt kit information is also included.
Note
Detent valves must be installed with the valve spool in
the horizontal position for good machine reliability. The
mounting position of spring offset and spring centered
models is unrestricted.
