21
Logix 3400MD Digital Positioner FCD LGENIM3404-00 – 9/09
flowserve.com
From the fieldbus configurator:
• Set transducer block to OOS
• Enable Diagnostic Variable access in TEST_MODE
• Send a 50 percent command.
• Set integral to zero.
• Locate the DAC_PERCENT
• Write this percentage value to IL_OFFSET
• Write original value to Integral
These tuning sets can be used to obtain initial values for Flowserve
products and comparable actuator sizes. The user may need to adjust
this tuning to achieve optimal performance for a particular application.
Table VIII: Factory Tuning Sets
Mfg.
Tuning Set
GAIN_
LOWER
GAIN_
UPPER
GAIN_
MULT lgain
Comparable
Size (in
2
)
Valtek
VFactory_A
1.0
2.0
0.05
10
25
VFactory_B
1.0
2.5
0.05
10
50
VFactory_C
2.0
3.0
0.05
10
100
VFactory_D
4.0
5.0
0.05
10
200
VFactory_E
4.0
7.0
0.05
10
300
Trooper 48
0.4
0.5
0.05
25
31
Trooper 49
3.0
4.0
0.05
10
77.5
Kammer
Trooper 48
0.4
0.5
0.05
25
31
Trooper 49
3.0
4.0
0.05
10
77.5
Automax
R1
0.3
0.5
0.05
10
3 to 5
R2
1.0
1.5
0.05
10
9 to 12
R3
1.3
2.0
0.05
10
16 to 19
R4
2.0
2.5
0.05
10
27 to 37
R5
2.5
3.6
0.05
10
48 to 75
R6
4.0
5.0
0.05
10
109
7.14 Alerts
7.14.1 FINAL_VALUE_CUTOFF
The FINAL_VALUE_CUTOFF or tight shutoff feature of the Logix
3400MD digital positioner allows the user to control the level at which
the command signal causes full actuator saturation in the closed or
open position.
This feature can be used to guarantee actuator saturation in the
closed or open position or prevent throttling around the seat at small
command signal levels. To enable, use configuration to apply the
desired FINAL_VALUE_CUTOFF threshold.
NOTE:
The positioner automatically adds a 1 percent hysteresis value to
the FINAL_VALUE_CUTOFF_LO setting to prevent jumping in and out of
saturation when the command is close to the setting.
7.14.2 Effects of FINAL_VALUE_CUTOFF on
Operation
With the FINAL_VALUE_CUTOFF_LO set at 5 percent the positioner will
operate as follows: Assume that the present command signal is at 50
percent. If the command signal is decreased, the positioner will follow
the command until it reaches 5 percent.
At 5 percent, full actuator saturation will occur. The actuator will
maintain full saturation below 5 percent command signal. Now, as
the command increases, the positioner will remain saturated until the
command reaches 6 percent (remember the 1 percent hysteresis value
added by the positioner). At this point, the stem position will follow the
command signal.
If the FINAL_VALUE_CUTOFF_LO is set to 3 percent but the valve
will not go below 10 percent, STOP_LO_POS may be enabled. The
lower soft limit must be less than or equal to 0 percent in order for the
FINAL_VALUE_CUTOFF_LO to become active.
If soft stops are active (ie: STOP_LO_POS = 0 or STOP_HI_POS = 100)
FINAL_VALUE_CUTOFF is disabled.
7.14.3 Soft Limits
Unlike position alerts, soft limits prevent the stem position from going
below or above the configured limits. If the command signal is trying to
drive the position past one of the limits, the yellow LED will blink but the
stem position will remain at the set limit.
7.14.4 Travel Accumulator
The travel accumulator is equivalent to a car odometer and sums the
total valve movement. Using the user defined stroke length and travel
dead-band, the Logix 3400MD digital positioner keeps a running total
of valve movement. When the positioner first powers up, high and low
dead-band limits are calculated around the present position. When the
stem position exceeds the travel dead-band, the movement from the
center of the deadband region to the new position is calculated and
added to the travel accumulator. From this new position, deadband high
and low limits are again calculated.
ExAMPLE:
The Logix 3400MD digital positioner has a default dead-
band configuration of 20 percent. The valve has a 4 inch linear stroke.
When the valve first powers up, the command signal is 50 percent.
The unit will calculate a high travel threshold of 70 percent (50
percent present position plus 20 percent dead-band) and a low travel
threshold of 30 percent (50 percent present position minus 20 percent
dead-band). As long as the stem position remains greater than 30
percent and less than 70 percent, no additions are made to the travel
accumulator. Now, assume the stem position moves to 80 percent that
is outside the present dead-band. The Logix 3400MD digital positioner
calculates the stem movement and adds this number to the travel
accumulator.
