Flowserve 3400IQ Digital Positioner - Manual (Page 115)


Logix 3400IQ Digital Positioner FCD LGENIM3402-00 – 0/07
flowserve.com
and gain multiplier = 0.05. These values will allow stable control on all Valtek control product actuator
sizes.
Integral Gain (IGAIN): The integral gain is primarily for deviations due to temperature drift within the
inner loop spool control. The factory default value is 10. Although higher numbers can speed the time
it takes to reach zero deviation, it can add overshoot if too large. It is recommended that maximum
and minimum gains be adjusted while leaving Integral Gain fixed at 10. Integration is disabled below
a stem position of 3 percent and above a stem position of 97 percent. This is to prevent integration
windup from calibration shifts due to lower pressure or a damaged seat which may prevent fully
closing the valve.
Integration Summer: The integral summer within the Logix 3400IQ digital positioner is clamped at
+20.00 percent and –20.00 percent. If the integration summer is fixed at +20% or –20%, it usually
indicates a control problem. Some reasons for a clamped integration summer are listed below:
Stroke calibration incorrect
Any failure which prevents stem position movement: stuck spool, handwheel override, low
pressure.
Incorrect inner loop offset
Loss of air supply on a fail in place actuator
Writing a zero to integral gain will clear the integral summer. The integral gain can then be returned to
its original value.
Inner Loop Offset (IL_OFFSET): Referring to Figure 1.3 in section 1, three control numbers are
summed to drive the inner loop spool position control: proportional gain, integral summer, and inner
loop offset. Inner loop offset is the parameter that holds the spool in the null or balance position with
a control deviation of zero. This value is written by the positioner during stroke calibration and is a
function of the mechanical and electrical spool sensing tolerances. However, if replacing the Driver
Module Assembly is necessary, or the software reset has been performed, it may be necessary to
adjust this value. The method below should be used to adjust inner-loop offset. Or simply perform a
new stroke calibration.
From the fieldbus configurator,
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
Table 10.13 Logix 3400IQ Digital Positioner Factory Tuning Sets
Brand Tuning Set GAIN_LOWER GAIN_UPPER GAIN_MULT lgain Comparable
Actuator
Valtek VFactory_A 1.00 2.00 0.05 10.0 25 sq. in.
VFactory_B 1.00 2.50 0.05 10.0 50 sq. in.
VFactory_C 2.00 3.00 0.05 10.0 100 sq. in.
VFactory_D 4.00 5.00 0.05 10.0 200 sq. in.
VFactory_E 4.00 7.00 0.05 10.0 300 sq. in.
Trooper 48 0.40 0.50 0.05 25.0 31 sq. in.
Trooper 49 3.00 4.00 0.05 10.0 77.5 sq. in.
Kammer Trooper 48 0.40 0.50 0.05 25.0 31 sq. in.
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