Emerson Fisher FIELDVUE DVC6000, Инструкция по эксплуатации

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Viewing Device Variables and Diagnostics
September 2013 6-5
Step to Target—Steps the travel to the specified
target.
Partial Stroke Test (2-5)
Note
Partial Stroke Test is only available for
instrument level ODV.
WARNING
During the partial stroke test the valve
will move. To avoid personal injury
and property damage caused by the
release of pressure or process fluid,
provide some temporary means of
control for the process.
The Partial Stroke Test allows the DVC6000 digital
valve controllers with instrument level ODV to perform
a Valve Signature type of test while the instrument is
in service and operational. In some applications, it is
important to be able to exercise and test the valve to
verify that it will operate when commanded. This
feature allows the user to partially stroke the valve
while continually monitoring the input signal. If a
demand arises, the test is aborted and the valve
moves to its commanded position. The partial stroke
valve travel is configurable between 1 and 30%
maximum travel, in 0.1% increments. Data from the
last partial stroke test is stored in the instrument
memory for retrieval by ValveLink software.
The Partial Stroke Test allows you to perform a partial,
10%, stroke test (standard) or a custom stroke test.
With the custom stroke test, the stroke may be
extended up to 30%. Be sure to check plant guidelines
before performing a custom stroke test. The purpose
of this test is to ensure that the valve assembly moves
upon demand.
A partial stroke test can be initiated when the valve is
operating at either 4 or 20 mA (point-to-point mode). In
applications where a spurious trip is to be minimized, 4
mA is the normal operating position.
When enabled, a partial stroke test may be initiated by
the device (as a scheduled, auto partial stroke test), a
remote push button located in the field or at the valve,
the 475 Field Communicator, or ValveLink software.
Device (Digital Valve Controller)
The Auto Partial Stroke Test allows the partial stroke
test to be scheduled by the DVC6000. The test is
scheduled in number of hours between tests. Any
power cycle will reset the test clock timer.
Auxiliary Terminal
The auxiliary terminal can be used for different
applications. The default configuration is for a partial
stroke test initiated by shorting the contacts wired to
the aux/
−
terminals of the DVC6000. Refer to
Auxiliary Terminal Wiring Length Guidelines below.
Local Push Button
A partial stroke test command may be sent to the
digital valve controller using a set of contacts wired to
the aux/
−
terminals. To perform a test, the
contacts must be closed for 3 to 5 seconds and then
opened. To abort the test, close the contacts for 1
second. The last set of diagnostic data is stored in the
instrument memory for later retrieval via ValveLink
software.
Local DI
When configured by the user interface, the Auxiliary
Terminal can be used as a discrete input from a
pressure switch, temperature switch etc., to provide an
alert.
Auxiliary Terminal Wiring Length Guidelines
The Auxiliary Input Terminals of a DVC6000 with
instrument level ODV can be used with a
locally-mounted switch for initiating a partial stroke
test. Some applications require that the partial stroke
test be initiated from a remote location.
The length for wiring connected to the Auxiliary Input
Terminals is limited by capacitance. For proper
operation of the Auxiliary Input Terminals capacitance
should not exceed 18000 pF. As with all control signal
wiring, good wiring practices should be observed to
minimize adverse effect of electrical noise on the Aux
Switch function.
Example Calculation: Capacitance per foot or per
meter is required to calculate the length of wire that
may be connected to the Aux switch input. The wire
should not exceed the capacitance limit of 18000 pF.
Typically the wire manufacturer supplies a data sheet
which provides all of the electrical properties of the
wire. The pertinent parameter is the highest possible
capacitance. If shielded wire is used, the appropriate
number is the “Conductor to Other Conductor &
Shield” value.
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