Masoneilan SVI II AP Installation and Maintenance ... - GE Energy

GE Oil and Gas
SVI II AP Instruction Manual
Non-Volatile Memory
NORMAL Mode
PC
Position
Position Limit
Positioner Tuning
Tuning Parameters
P
I
D
Beta
Computer memory that is not lost when power is turned off. Used
to permanently store calibration, configuration and diagnostic
information in SVI II AP.
The control mode for normal use of a valve positioner. The positioner
receives a setpoint from a controller or DCS and applies
pressure to the actuator to move the valve to the required position.
A personal computer or laptop running under Windows XP or
later operating system.
With a reciprocating valve, the position is the distance of the plug
from its seat, normally measured as a linear motion of the valve
or actuator stem. With a rotary valve the position is the angle of
rotation of the valve plug measured as angular rotation of the
valve shaft.
The actuator can be mechanically set to stop at a predetermined
position by setting an adjustment, sometimes with a handwheel
or screw stop. SVI II AP can be configured to provide the same
limits through software control of position.
The positioner requires six integer parameters to determine the
Parameters response of the positioner to a setpoint change.
Internally, the positioner uses an improved PID control algorithm
to control the valve’s position.
P is a dimensionless gain factor related to the proportioning
action of the algorithm. It ranges from 0 to 5000. Common values
for the positioner are 50 for small valves up to 4000 for large
valves.
(0.1 sec): Integral time or reset time, is the time constant of integral
control. Higher values of I cause slower integral action. Common
values are 10 (1 second) to 200 (20 seconds). A value of
zero disables integral action.
(msec): Derivative time or rate time is the time constant of derivative
control expressed in milliseconds. It ranges from 0 to 200
msec. Common values are 0 to 100. A value of zero disables
derivative action.
Beta is a nonlinear dimensionless gain factor, ranging from -9 to
9. When beta is 0, the controller gain is linear. Otherwise the gain
is the function of error. The larger the beta, the smaller the gain
for small error. Typical beta values for a valve position controller
are between –9 and 0.
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