Baker Hughes Masoneilan SVIII AP, Installation And Maintenance Manual

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Masoneilan SVI II AP Installation and Maintenance Manual =
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Double Acting An actuator is double acting when it has pressure applied to both
sides of the piston. A positioner is factory assembled and calibrated
as a double acting that has two pressure outputs one that increases
and one that decreases with increasing position setpoint. The SVI II
AP positioner can be single acting or double acting.
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 actua-
tor cycles and totalized valve travel. The program is stored in flash
memory and can be upgraded.
Equal Percentage A valve characteristic designed to compensate for the loss of pres-
sure in a pipeline as a control valve is opened. It is intended to linear-
ize 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.
Fail Safe A mode of the positioner where the valve position is controlled to a
predetermined safe position. This mode is forced by the positioner
program in response to errors. If the errors are cleared then RESET
returns the positioner to the mode prior to the error.
Fatal Error In error which the SVI II AP program treats as non-recoverable. Ser-
vice is required.
Flash Memory A computer memory that is not volatile. It stores all its data even
when the power is off. It performs high speed reads and can be
re-written many times. It is used to store programs and permanent
parameters.
FSK Frequency Shift Keying see HART
®
protocol.
Hall Effect Sensor A semiconductor magnetic-field sensor that measures the magnetic
flux perpendicular to the sensor.