Dresser Masoneilan SVI II AP, Инструкция по эксплуатации

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DCS Distributed Control System is a generic term for the common con-
trol system architecture that generally performs process control in
networked computers and interacts with field devices through
rack mounted I⁄O cards. A positioner is usually connected to a
DCS output card which controls the 4- 20mA current to the posi-
tioner.
Device Description,
DD The software object installed in the HART Handheld Communica-
tor HHC 375 to allow it to communicate and display the custom
parameters available in a field device.
Diagnostics The suite of software, and hardware tools that allow an SVI II AP
to monitors its own internal condition and to monitor the perfor-
mance of the control valve and actuator system. Depending on
options purchased the diagnostics can evaluate number of valve
strokes, total accumulated valve stem travel, step response times
with graphs, input to position relationships. Often system perfor-
mance signatures are obtained and retained to compare as-built
with future performance to predict remaining useful service life.
Double Acting An actuator is double acting when it has pressure applied to both
sides of the piston. A positioner is factory assembled and cali-
brated as a double acting that has two pressure outputs one that
increases and one that decreases with increasing position set-
point. The SVI II AP positioner can be single acting or double act-
ing.
EEPROM An Electrically Erasable Programmable Read Only Memory. SVI
II AP has two memories that are used for permanent storage of
data that changes during operation. The micro-controller has
EEPROM which permanently stores changing information such
as number of actuator cycles and totalized valve travel. The pro-
gram is stored in flash memory and can be upgraded.
Equal Percentage A valve characteristic designed to compensate for the loss of
pressure in a pipeline as a control valve is opened. It is intended
to linearize the installed flow versus lift characteristic for improved
control.
*
The theoretical curve is y= a

e xln(1⁄a) , where a is.02, 1/R, and
R=50 for a 50:1 equal percentage characteristic. However, the
theoretical curve leaves the valve unseated by 2% at 0% input.
The actual curve, shown here, is corrected to seat the valve at
0%. The corrected curve is Y=(a

e xln(1⁄a ) -a)/(1-a).
Error Messages The positioner stores the reasons for errors. The error messages
can be read by HART or with the local display.