Azbil JTD910S - A3-4-8 Clogging Simulation Test Cannot be Conducted

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Appendix A Maintenance and Troubleshooting of this Device
A3-4-8 Clogging simulation test cannot be conducted.
When the clogging simulation test cannot be conducted, only the index value data under normal
operating conditions (index values collected in section A3-4-2) can be used to determine the
threshold value. When many index values can be collected, calculate the average value (μ)
and standard deviation (σ), and determine the threshold value based on μ ± nσ. To eliminate
misinformation, a value from 4 to 6 is recommended for n.
If only the maximum (xmax) and minimum (xmin) index values are known, the threshold value
can also be determined using these values. For example, the threshold value should be set to a value
that is no more than (xmax−xmin)/2 from the minimum value, as shown in the figure below.
x
max
x
min
( x
max
x
min
)/2
( x
max
x
min
)/2
Index value
Index value range
under the normal
operating conditions
Threshold
value(High)
Threshold
value(Low)
Note that the threshold value determined only using the index value data under normal operating
conditions is not always appropriate. The index value may reach the threshold value due to causes
other than clogging, or the index value may not change to the threshold value even when clogging
occurs. Observe changes in the index value for a short period after the threshold value has been
determined, and then check that the index value does not exceed the threshold value under normal
operating conditions, and that the difference between the correct value range and threshold value
is not large. Revise the threshold value when necessary. Also, if the clogging simulation test is not
conducted, it is difficult to predict the behavior of the index when one side is clogged. Therefore,
even when the threshold value is set to the Press Freq Index High Limit, it is not relevant for
clogging diagnosis.