VICI DVSP - Manual (Page 10)

4.
DEMONSTRATION SEQUENCE
This example demonstrates use of the DVSP-4 to control the positioning of two
Valco switching valves. Valve 1 (V1) is used for sample injection and Valve 2 (V2)
is configured for column backflushing. Both valves are air actuated, but V1 is
controlled by a Valco Digital Valve Interface (DVI) while V2 is controlled by a pair of
3-way solenoid valves (MSVA). Each valve requires two intervals of the DVSP;
one for clockwise rotation and one for counterclockwise. (All references to direc-
tions are as seen from the actuator end of the valve.)
In the ready (rest) state, both valves are in the counterclockwise position. (Figure
8) After the process is begun by charging the sample to V1, V1 will be switched
clockwise to inject the sample. (Figure 9) After two seconds for sample injection,
V1 is returned to the counterclockwise position to load the next sample. In this
example, fifteen minutes will elapse before V2 is switched clockwise and the
contents of the column are backflushed to the detector. (Figure 10) After nineteen
minutes for desorbtion of the column contents into the detector, V2 is switched
counterclockwise for the next sample analysis. Four and a half minutes will be
allowed for equilibration before the next cycle begins.
Broken down into its component intervals, the process appears like this:
Interval 1 (2 seconds)
Relay A is energized, switching V1 to its clockwise position and injecting the
sample onto the column.
Interval 2 (15 minutes)
Relay B is energized, switching V1 back to the counterclockwise position,
ready for the next sample.
Interval 3 (19 minutes)
Relay C is energized for two seconds (through relay E), switching V2 and
backflushing the column to the detector.
Interval 4 (4.5 minutes)
Relay D is energized for two seconds (through relay E), switching V2 to the
column forward position, ready for the next run. If the DVSP is in the AUTO
mode, the next cycle will begin after 4.5 minutes.
SAMPLE OUT
SAMPLE IN
CARRIER IN
TO DETECTOR
COLUMN
V2
Figure 8: V1 and V2
in counterclockwise
position
(Rest and Intervals 2, 4)
Figure 9: V1 in
clockwise
position
(Interval 1)
Figure 10: V2 in
clockwise
position
(Interval 3)
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