Flowserve 3400IQ Digital Positioner - Manual (Page 120)

Logix 3400IQ Digital Positioner FCD LGENIM3402-00 – 0/07
20
Steps:
1. Verify the process is in a safe condition and that the valve may be taken out of service.
2. Put the Transducer block MODE_BLK OOS
3. Make sure that ‘Quick Opening Curve’, ‘Equal Percent Curve’, nor ‘ Custom Characterization
Active’ are selected in CONTROL_FLAGS.
4. Enter the values for CURVEX and CURVEY to define the desired response. Care must be taken
to assure that each CURVEX value has the correct corresponding CURVEY value. The user may
choose any number in the range to define the curve. The 21 CURVEX points do not need to be
evenly spaced, if so desired. However, the CURVEX values must be in ascending (or equal) order.
The CURVEY points may be any value in the range, ascending or descending. The response is a
linear interpolation, or straight-line, response between points. All 21-points must be defined. (i.e.
If only 5 point sets were needed to define the desired operation, the remaining 16 points would
need to be set to 110.).
5. Write the changes to the Logix 3400IQ digital positioner.
6. Activate the custom curve by selecting ‘Custom Characterization Active’ in CONTROL_FLAGS.
(NOTE: Make sure that neither ‘Quick Opening Curve’ nor ‘Equal Percent Curve’ has been
selected, if you are using your own custom curve.)
7. Write the changes to the Logix 3400IQ digital positioner.
8. Verify the proper operation of the stroke response by incrementally writing values to FINAL_
VALUE. (The Resource Block must also be OOS first.) CMD_USED, FINAL_POSITION_VALUE,
and the valve response should track the desired curve.
9. Return the valve to service by returning both MODE_BLKs back to Auto.
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 curve will
automatically be activated again when the factory curve is deselected.
10.13 Initiating a Valve Signature
A feature of the Logix 3400IQ positioner is the ability to capture and store a valve diagnostic
signature in the positioner’s volatile RAM. A signature is the collected data response of the valve to
a pre-defined 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.
System Preparation
CAUTION: By definition, the collection of the signature requires the unmanaged operation
of the positioner. Therefore, the process must be in a safe operating mode where unexpected move-
ment of the valve will not cause a hazardous condition.
Before a valve signature can be run, the Transducer Block must be out of service (OOS).