Flowserve MX FOUNDATION Fieldbus Field Unit - Manual (Page 31)

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MX/QX FOUNdaTION Fieldbus Field Unit FCd LMENIM2330-01 – 08/11
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RCAS_IN is a target setpoint and status provided by a supervisory host to an analog control or output
block.
Outputs
OUT is the block output and status.
RCAS_OUT is a block setpoint and status after ramping, provided to a supervisory host for back
calculation and to allow action to be taken under limiting conditions or mode change.
BKCAL_OUT is the value and status required by the BKCAL_IN of another block to prevent windup
and to provide bumpless transfer to closed loop control.
Scaling
The PV_SCALE range is used to convert the SP to percent of span. The XD_SCALE range is used to
convert percent of span to the number used by the hardware. This allows portions of the SP span
to cause full span movement of the output. The Increase to close option in IO_OPTS can be used to
invert the span.
Cascade Operation
The SP supports the full cascade sub-function. In fact, Cas mode must be used to transfer the output
of another block to the SP of the AO. The SP has standard ramp rate and absolute limits. There
are additional I/O options which will cause the SP value to track the PV value when the block is in
an actual mode of LO or Man. If the Output Readback feature is turned on, such as valve position,
that value should be run backwards through the XD scaling to act as the PV for this block. If not
supported, READBACK is generated from OUT. The OUT and READBACK parameters both use
XD_SCALE. The PV and SP use PV_SCALE.
Since the Analog Output block interfaces to the transducer block, there is no BKCAL_IN parameter.
ROut mode is not supported.
For the BKCAL_OUT value, there is an option to use either the SP value after limiting, or the PV value.
Supported Modes
O/S, LO, IMan, Man, Auto, Cas, and Rcas modes are supported. The Man mode can be used in
maintenance or troubleshooting where the OUT value may need to be adjusted directly. This requires
that the manufacturer put operational limits in the transducer block, where they are not accessible to
an operator.
Simulation
Simulation is used to support testing. Simulation can be enabled through the configuration tool and
allows the manual setting of the channel feedback.
This feature requires the installation of a hardware jumper on the MX/QX FF unit, located on header
X5 Pins 7 and 8.
3.5 Discrete Input Function Block
The Discrete Input (DI) function block processes a single discrete input from a field device and makes
it available to other function blocks. The user can configure alarm detection and inversion on the
input signal. The DI block supports mode control, signal status propagation, and simulation.
There are four DI blocks in the Limitorque actuator control system, and seven channels:
Chan. No.2 — DI_POSITION_AND_BUS_MODE_CHAN — Valve status and control mode
Chan. No.3 — DI_POSITION_CHAN — Valve status, moving/stopped