Instruction Manual

DVC6000 SIS
September 2013
4-10
Travel/Pressure Control
Tvl/Press Cutoffs (1-2-2-2-1)
 Cutoff Hi—Defines the high cutoff point for the
travel in percent (%) of ranged input current.
 Cutoff Lo—Defines the low cutoff point for the
travel set point.
 Change Cutoffs—Allows you to set Cutoff Hi and
Cutoff Lo. When a cutoff is set the corresponding
travel or pressure limit is disabled.
Travel cutoffs are adjustable when the DVC6000 SIS
is operating with a 4-20 mA current input. The Setup
Wizard automatically sets travel cutoffs at 50%,
making the DVC6000 SIS work like an on-off device.
At current levels from 4.0 to 11.99 mA, the DVC6000
SIS will provide minimum output pressure, and at 12
to 20 mA, the DVC6000 SIS will provide full output
pressure.
You can customize valve response to the control
signal by changing the travel cutoffs. For example, it is
possible to have the valve throttle between 10 and
90% travel, but work as an on-off valve between 0% to
10% and 90% to 100% travel. The user now has a
standard throttling control valve between 10% and
90% travel. Outside of this range, the valve will move
to its travel extreme (0% or 100%).
Note
If you run the Setup Wizard after
adjusting the Travel Cutoffs, they will
revert back to the default values. You
will need to reset the Travel Cutoffs to
the desired settings.
Note
The partial stroke test cannot be
conducted by the Field Communicator
or ValveLink software while the digital
valve controller is in its normal travel
control mode (with adjustable cutoffs
set to a different value than the
default).
WARNING
Using the auxiliary terminal (push
button) for partial stroke testing while
the DVC6000 SIS digital valve
controller is in point-to-point mode
may cause changes in output
pressure and travel, resulting in
process instability. Depending on the
application, these changes may upset
the process, which may result in
personal injury or property damage.
If the auxiliary terminal button is
pressed for more than 3 seconds, but
less than 5 seconds, the digital valve
controller will drive the valve from its
existing travel position to 100% travel
condition for a fail close valve (or 0%
travel for a fail open valve) and
perform the partial stroke test. Once
the partial stroke test is completed,
the digital valve controller will bring
the valve back to its original travel,
corresponding to the control set
point.
Note
In a typical 0-24 VDC de-energize-
to-trip operating system, a digital valve
controller with the single-acting direct
relay will provide full output pressure
to port A when 24 VDC is applied, and
minimum (near 0) output pressure to
port A when 0 VDC is applied. With the
single-acting direct relay, there would
be no output pressure from port B.
Other configurations of the relay are
available (see table 3-2). An example of
this flexibility is the use of a
single-acting reverse relay that will
supply full pressure output at 0 VDC
input. This configuration can be useful
to provide the benefits of Partial Valve
Stroke Diagnostics but minimize the
spurious trip rate (the power to the
digital valve controller can be lost
without tripping the valve), but would
only be recommended when a
solenoid is provided to take the valve
to the safe position
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