Flowserve Logix MD+ ValveSight - Manual (Page 143)

ValveSight™ Diagnostics DTM Manual for Logix MD+ Positioner with HART®
FCD- LGENSF0014-00
© Flowserve Corporation
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Continuous Stroke Test
The Continuous Stroke Test page allows you to set parameters and enable the continuous
stroke testing (CST) feature.
NOTE: This feature will add a small deviation to the valve position. This feature is not
recommended for valves intended for high accuracy or stability.
For valves that are normally held at a constant position for extended periods of time, the
CST feature can provide assurance that the valve is still responsive. When CST is
enabled, the positioner will cause a very small amount of valve movement. From this
movement, the positioner can find information about the health of the valve, actuator and
positioner.
To achieve the CST function, the positioner adds a small deviation to the command. By
default, the deviation is ramped at a rate of 0.05%/second up to 5%. However, the instant
the valve moves, the ramp reverses and begins to grow in the opposite direction. So, with
low friction, the actual movement will be quite small. If the valve does not move by the time
the deviation equals 5%, the ramp reverses and a counter will start. After 5 consecutive
failed attempts to move, the CST warning will appear. This is cleared by either disabling
CST mode or by the positioner detecting movement in the valve. The ramp rate, maximum
limit, and frequency of the CST can be adjusted as shown below.
Status Area
The Active Indicator area shows the status of the most relevant active indicator. The color
of the "LED light" corresponds to the Active Indicator and the first color of the blink code
sequence on the positioner. Generally green indicates no immediate issues. Yellow
indicates a developing issue. Red indicates the ability to control may be compromised. A
detailed list of the indicators is given in the
Alarm Congfiguraion - Alarm Annunicator page.
The Command Source field indicates weather the positioner is being controlled by digital or
an analog (4-20 mA) command source.