Characterization retention, Initiating a valve signature – Flowserve 1400 Valtek Logix User Manual
Page 21
46-21
Flowserve Corporation, Valtek Control Products, Tel. USA 801 489 8611
FINAL_VALUE (% FS)
CMD_USED (% FS)
0 20 40 60 80 100
100
90
80
70
60
50
40
30
20
10
0
Quick Open
Equal Percent
Linear
3. Make sure that
Quick Opening Curve, Equal Percent
Curve, nor Custom Characterization Active are se-
lected 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 de-
scending. The response is a linear interpolation, or
straight-line, response between points. All 21-points
must be defined. (i.e. If only five point sets were
needed to define the desired operation, the remain-
ing 16 points would need to be set to 110.).
5. Write changes to the Logix 1400 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.
7. Write the changes to the Logix 1400 digital posi-
tioner.
8. Verify the proper operation of the stroke response by
incrementally writing values to FINAL_VALUE. (The
AO 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 the AO
and FVPTB blocks to auto mode.
Characterization Retention
Once a custom curve has been loaded into the Logix
1400 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 acti-
vated again when the factory curve is deselected.
Initiating a Valve Signature
A feature of the Logix 1400 positioner is the ability to
capture and store a valve diagnostic signature. A signa-
ture 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.
Table II: Logix 1400 Digital Positioner
Characteristic Curves
Figure 18: Characterization Curve
_
L
A
N
I
F
E
U
L
A
V
)
S
F
%
(
X
E
V
R
U
C
Y
E
V
R
U
C
)
S
F
%
(
D
E
S
U
_
D
M
C
n
e
p
O
k
c
i
u
Q
l
a
u
q
E
t
n
e
c
r
e
P
r
a
e
n
i
L
0
0
.
0
0
0
.
0
0
5
8
.
8
1
0
0
.
1
5
0
1
6
.
7
3
0
0
.
2
0
1
5
1
4
.
6
5
0
0
.
3
5
1
0
2
0
.
4
7
0
0
.
4
0
2
5
2
3
.
4
8
4
2
.
5
5
2
0
3
0
.
0
9
7
4
.
6
0
3
5
3
0
.
2
9
2
0
.
8
5
3
0
4
4
.
3
9
7
5
.
9
0
4
5
4
2
.
4
9
6
8
.
1
1
5
4
0
5
8
.
4
9
5
1
.
4
1
0
5
5
5
5
.
5
9
4
5
.
7
1
5
5
0
6
0
.
6
9
3
9
.
0
2
0
6
5
6
5
.
6
9
4
9
.
5
2
5
6
0
7
0
.
7
9
5
9
.
0
3
0
7
5
7
5
.
7
9
6
3
.
8
3
5
7
0
8
0
.
8
9
7
7
.
5
4
0
8
5
8
5
.
8
9
6
6
.
5
5
5
8
0
9
0
.
9
9
8
6
.
7
6
0
9
5
9
5
.
9
9
1
3
.
2
8
5
9
0
0
1
0
0
1
0
0
1
0
0
1