Flowserve 3400IQ Digital Positioner - Manual (Page 38)

Logix 3400IQ Digital Positioner FCD LGENIM3401-00 – 06/06
3
7.15 Characterization Retention
Once a custom curve has been loaded into the Logix 3400IQ digital positioner’s memory it is retained
in the EPROM until it is either edited or replaced. Turning Custom Characterization Active on or off
now selects between a linear response (off), or the new custom curve (on). If either of the other two
factory curves is selected it will overwrite the custom curve in RAM only. The custom user-defined
curve will automatically be activated again when the factory curve is deselected.
7.15.1 Initiating a Valve Signature
A feature of the Logix 3400 positioner is the ability to capture and store a valve diagnostic signature.
A signature is the collected data response of the valve to a predefined set of operating conditions.
This stored data can later be uploaded to the host system for analysis of potential problems. By
comparing a baseline signature, when the valve is new, to subsequent signatures at later times, a rate
of change can be tracked which can help predict possible faults in the valve before they happen. This
is called ‘predictive maintenance’. It is important to note that the purpose of the positioner is to act as
the data acquisition device for the signature. Analysis of the data is not done on the device, but in the
supervisory system.
NOTE: Signature data is lost if the positioner is reset or if the power is cycled
7.15.2 System Preparation
c WARNING: By definition, the collection of the signature requires the unmanaged opera-
tion of the positioner. Therefore, the process must be in a safe operating mode where
unexpected movement of the valve will not cause a hazardous condition.
Before a valve signature can be run, the Transducer Block must Out-of-Service (OOS).
7.15.3 Signature Procedure
The following steps are an example of how to initiate a ramp signature capture.
1. Make sure the process is in safe condition and notify the control room that the valve will
temporarily be taken off-line.
2. Verify preparedness to proceed.
3. Put the Transducer block MODE_BLK OOS
4. Set SIG_START to desired value.
5. Set SIG_STOP to desired value.
6. Set SAMPLE_TIME to desired value (typically 0.3).
7. In SIG_FLAGS, select; STEP_RAMP, PRESS_MEAS.
8. Write values to the Logix 3400IQ digital positioner.