Siemens PROFIBUS PA SIPART PS2 Manual page 112

Operation
4 Monitoring of number of strokes
5 Monitoring of number of changes of direction
6 Monitoring of the bottom hard stop (valve seat)
7 Monitoring of the top hard stop
8 Monitoring of the dead zone adaptation
110
The two values number of strokes and number of changes of direction
are compared continuously with the limit values which are specified
with the parameters "46. STRK" and "47. DCHG". The fault message
output responds when exceeded. Both functions can be deactivated
with the parameter setting "OFF".
Monitoring of the bottom hard stop is activated when the parameter
"48. ZERO" has a value
with this function for example. Exceeding of the limit value may hint at
deposits or foreign bodies in the valve seat. Exceeding the limit value
may be caused by wear of the valve seat. Mechanical maladjustment of
the position feedback may also trigger this error message.
Monitoring takes place every time the valve is in tight closing bottom
position. The current position is compared with the one determined dur-
ing initialization as a bottom end stop. Activation of the tight closing bot-
tom function (parameter "39.YCLS") is therefore a prerequisite.
Example: 3% is set as a value. Normally the setting 0% is adopted
when closed. If a value >3% or <--3% is determined instead, a fault is
reported.
The fault message remains activated until either a subsequent
monitoring remains within the tolerance or a new initialization is
performed. The deactivation of the monitoring ("48. ZERO"=OFF) also
clears any existing fault message.
This monitoring function supplies no useful results when the stops have
not been determined automatically in initialization but the limits set
manually (manual initialization"5.INITM").
An appropriate diagnosis is made for the top hard stop. The limit value
for this is set with the parameter 49. OPEN. Activation of the tight clos-
ing top function (parameter "35.YCLS") is therefore a prerequisite.
If the dead zone increases unproportionally in operation in automatic
adaptation of the dead zone (parameter 31.DEBA = Auto) this points to
an error in the system (e.g. a marked increase in stuffing box friction,
play in the displacement detection, leakage). Therefore a limit value
can be specified for this value ("50. DEBA", limit value for dead zone
monitoring) which activates the fault message output when it is
exceeded.
OFF. Errors of the valve seat can be detected
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SIPART PS2 PA Manual
A5E00127926-03