16
E. Optional Features (Main Stage)
Control of the main stage spool can be modified with certain
optional features. The most common features are discussed
in the following paragraphs.
1.
Stroke Limiter Adjustment
: Main stage spool travel
can be limited by using stoke adjust covers. Stroke adjust
covers may be used on one or both ends of the main stage
section. When the stoke is limited, maximum flow through
the valve is reduced (assuming the same inlet pressure).
This slows the actuator movement.
To limit the spool travel, loosen the jam nut and turn
adjusting screw clockwise. Figures 9 and 10c illustrate the
stoke limiter feature.
2.
Pilot Choke Option
: A pilot choke increases the
amount of time it takes to shift the main stage spool from
one position to another. Increasing shift time lowers the
possibility of developing large flow transients in the circuit. A
pilot choke is designed to allow free flow to one end of the
main stage spool but restricts flow out of the opposite end.
The rate of spool travel, in either direction, can be slowed by
loosening a locknut and turning an adjusting screw
clockwise. To increase the rate of spool travel, turn the
adjusting screws counterclockwise. When a pilot choke is
used, pilot pressure should be taken from a constant
pressure source. The pilot choke is mounted between the
pilot valve and the main stage sections. See Figures 10a,
10b and 10c for pilot choke details.
3.
Fast Response Option
: Some applications require
the main stage spool to shift at a faster than normal rate. For
such applications, the fast response option is used. This
option requires the removal of an orifice plug within the main
stage body. When the orifice plug is removed, larger
volumes of fluid will enter the pilot valve section. When the
pilot valve shifts, the main stage spool responds at a faster
rate. However, this also generates transients that increase
system shock. For this reason, the fast response option is
not recommended when pilot pressures exceed 140 bar
(2000 psi). Fast response models have the letter “X”
stamped into the unit nameplate (i.e. DG5S4-062**X-51).
Table 3 compares standard shift times to the fast response
option. Figure 23a and b through 27a and b show the
location of the orifice plugs that must be removed for the fast
response option.
Typical Shift Times in Seconds for AC Models
Table 3. DG5 Shift Times (AC Solenoids)
Pilot Pressure (psi)
Standard
Fast Response
Center to “A” or “B”
Center to “A” or “B”
Model 06
Model H06
Model 100
Model 06
Model H06
Model 100
500
.100
.130
.135
.045
.070
.090
1000
.060
.085
.090
.035
.060
.060
2000
.050
.070
.070
.035
.060
.050
3000
.050
.070
.055
.035
.060
.050
All spring centered models require approximately .08 (06), .15 (H06), .19 (100) of a second to center from either side.
DC solenoid shift times will be approximately three or four times the above AC values.
Part No.
Part Name
1
Cover
2
Spring
3
O-Ring
4
Washer
5
Piston
6
O-Ring
7
Jam Nut
8
Adj. Screw
Figure 9. Part Tab
Figure 9. Stoke Adjuster Feature
Main
Stage
Spool
5
6
7
8
4
3
2
1
