Yokogawa EJX930A - Manual (Page 160)

<Appendix 8. Advanced Diagnostics>
A8-10
IM 01C25R03-01E
NOTE
The alarms of "Invalid Ref xx", "Outside
Diagnosis Range" do not link to the signal status
of PV, SV, and TV.
A8.2.6 Condition Check
After the EJX differential pressure/pressure
transmitter was installed, it is necessary to confirm
that the Primary Value (PV) is stable under the
normal operating condition and that fluctuation
amplitude under the normal operating condition is
large enough to detect the blockage.
 Stability of Primary Value
1) Observe the value change of PRIMARY_
VALUE under the normal operating condition
for 10 minutes.
2) Confirm the value change is less than 10%.
If the value change is more than 10%, the error
influences pressure fluctuation value so that the
blockage detection becomes Unreliable. You need
to consider the plant operating conditions.
 Fluctuation Value
NOTE
The blockage detection may not be carried
out correctly when pressure fluctuation
amplitude especially with the pressure and level
measurement, is small.
Confirm that each value of VALUE_FDP, VALUE_
FSPL, VALUE_FSPH, and VALUE_BLKF is more
than the value specified in the below table.
Table A8.3 Requiremnents to apply ILBD
Condition
VALUE_FDP 7×10 -10 or more
VALUE_FSPL 1×10 -10 or more
VALUE_FSPH 1×10 -10 or more
VALUE_BLKF -0.5 to 0.5
 VALUE_FDP is not enough
No blockage can be detected if VALUE_FDP is not
larger than the specified value.
 Only VALUE_FDP is enough
“A Blocking” or “B Blocking” can be detected if
VALUE_FSPL and VALUE_FSPH are not larger
than specified values.
 VALUE_FDP and VALUE_FSPL are enough
“High Side Blocking” and “Large Fluctuation of High
Side” can not be detected if VALUE_FSPH is not
larger than specified value.
 VALUE_FDP and VALUE_FSPH are enough
“Low Side Blocking” and “Large Fluctuation of Low
Side” can not be detected if VALUE_FSPL is not
larger than specified value.
 VALUE_FDP, VALUE_FSPL and VALUE_FSPH
are enough
All alarm modes can be detected even if VALUE_
BLKF is not within the specified values.
A8.2.7 Obtain Reference Values
The pressure fluctuation values are reduced
when the impulse line is plugged. Therefore, the
reference value is required to determine the degree
of reduction
IMPORTANT
• If the impulse line is about to be plugged at
the time when a reference value is obtained,
blockages cannot be detected accurately.
The impulse lines on both the high-pressure
and low-pressure sides need to be cleaned
before a reference value is obtained.
• All air bubbles need to be adequately purged
before a reference value is obtained.
• Reference values must be obtained under
operating condition.
• Do not obtain the reference values when the
BLOCK_MODE of SENSOR Transducer is
OOS. If carried out, an alarm of "Invalid Ref
xx" is generated.