60
EB 8389-1S EN
Leakage sensor
−
Relation 2: Valve position and sound lev-
el at the point where the curve in the
'Leakage detection process reference'
graph starts to rise monotonously
−
Relation 3: Valve position and sound lev-
el at the last measurement
9.1.2.2
Alarm settings
After connecting the leakage sensor and
performing the manufacturer and process
reference tests, the positioner is able to pin-
point any seat leakage. To do this, it records
the sound level in closed-loop operation
while the valve is tightly shut. The seat leak-
age monitoring is performed automatically
while the process is running.
The alarm limits detected in the manufacturer
reference test, process reference test or user-
defined settings can be selected. When user-
defined limits are entered, the alarm limits
must rise continuously from 'Alarm limit 1' to
'Alarm limit 3'.
During closed-loop operation, the mean
sound levels while the valve is tightly shut are
compared to the alarm limits. Which mean
sound level is to be used for comparison can
be selected in 'Response time':
−
Very quick
: The mean value calculated
from the current sound level and from the
last four sound levels measured while the
valve is tightly shut is used for monitoring
(Fig. 12: Tight-closing event 31 and
sound level E to I).
−
Quick
: The mean value calculated from all
sound levels measured while the valve is
tightly shut is used for monitoring (Fig. 12:
Tight-closing event 31 and sound level A
to I).
A B
C
D
E
F
G H
I
0
1
2
3
30
31
4 … 29
x [%]
t [s]
[dB]
t [s]
Fig. 12:
Tight-closing process and calculated mean values for analysis of the process reference test
