SVI-II Instruc Man.book - Fagerberg

Glossary
Padj (%)
Valves often have significantly different response when filling versus
exhausting. The proportional gain is adjusted by adding Padj to P when the
valve is exhausting. Padj is normally less than P.
Position Compensation The response of the valve is different when the valve is nearly closed
Coefficient
than when the valve is nearly open. The position compensation
coefficient, which is a number between 0 and 9, allow the control
algorithm to optimize the valve response.
Damping Coefficient: The valve response may be made slower for some applications. A value of 0
gives no damping, and a value of 9 gives maximum damping of valve motion.
Dead Zone(%):
Quick Opening
Relay, Pneumatic
Safe Area
Sig Hi
Sig Lo
Single Acting
Split Range
STOPS
Stroke
Tag
When the valve position is within the setpoint +⁄- the dead zone, no additional
position control is performed. This value is normally 0%, however for high
friction valves (e.g. valves with graphite packing) a higher dead zone will help
avoid limit cycling due to the stick⁄slip action of the valve. In these cases the
dead zone chosen might be 0.2% to 1%.
(see Characteristic)
The component that amplifies the pneumatic control signals to provide a wide
range of actuation pressure and to supply and vent at high flow rates for
responsive control.
The area of a plant where there never is an explosion hazard present, such as
the control room or a wire marshalling rack area.
In the SVI II AP configuration, the input current setting at which the valve is
fully open (ATO) or fully closed (ATC)
In the SVI II AP configuration, the input current setting at which the valve is
fully closed (ATO) or fully open (ATC)
The action of a position with a single pneumatic output for operation with a
spring return actuator. (see double acting).
A control configuration where a single control output is sent to two or more
control valves. Each control valve positioner is calibrated to respond to a
separate portion of the control signal. An example is a steam valve and a
cooling water valve arranged to be both closed at 50% and the steam valve to
open.
The SVI II AP runs STOPS procedure to adjust the positioner to actual valve
travel. First the output pressure is reduced to zero and the position is
recorded. That will be the position corresponding to 0%. The output pressure
is raised to its maximum based on supply pressure. The position is recorded
and corresponds to 100%.
The total range of valve travel. Often used as a verb to describe the process of
moving the valve.
The formal designator the control valve used in control loop documentation.
G-6