Flowserve 400MD Logix - Manual (Page 95)

* Must not be selected if a custom curve is to be created or edited.
10.12 Characterization Procedure
The following procedure outlines the basic way setting up a custom stroke characterization takes place.
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 “Custom’ is selected in CURVE_SELECT.
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 corre-
sponding 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 3400MD digital positioner.
6. 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.
7. 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 3400MD 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 3400MD 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).
Logix 3400MD Digital Positioner LGENIM3405-02 11/13
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