Safety and commissioning information for Ex areas
14.2 Dry-running protection for centrifugal pumps by active power monitoring
SIMOCODE pro
324 System Manual, 05/2019, A5E40507475002A/RS-AD/004
System test with operating medium
A system test with operating medium is an integral part of any commissioning procedure
(e.g. after changes to parameter settings) and of the "General system test". It might also be
required at shorter intervals if demanded by statutory regulations.
f you wish to reduce the amount of manual intervention, you can store appropriate
sequences in your process control system for (partially) automated running of the system
test with operating medium.
● Checking a potential drift:
– Set the same operating conditions (medium, flow rate, temperature, pressures, etc.)
as for the previous test.
– Measure the active power (at least two measured values, e.g. P
OPT
and P
MIN
).
– Compare the measured values with those from the previous test.
– Eliminate any causes of deviation.
● Checking the effectiveness of shutdown:
– If not yet done: First enter the relevant values for plant configuration for the trip level of
the active power monitoring P
TRIP
and for the delay time for ongoing operation t
V,TRIP
.
– If necessary, carry out a teach-in to determine the trip level (see Chapter "Dry-running
protection for centrifugal pumps" in the manual Parameterizing SIMOCODE pro
(https://support.industry.siemens.com/cs/ww/en/view/109743958
)).
– Set the start-up bridging time t
BRIDGE
to 0 s.
– Start the centrifugal pump filled with operating medium; the pressure-side shut-off
valve must be closed. The "dry-running protection" function must shut down the pump
immediately.
– Set a sufficiently large value for the start-up bridging time t
BRIDGE
– coordinated with
the procedure used when starting up the centrifugal pump.
– Start the centrifugal pump filled with operating medium.
– Begin by setting a sufficiently high flow rate for ongoing operation.
– Reduce the pump's flow rate incrementally until the active power value detected by
SIMOCODE pro falls below the trip level. The time span during which the flow-rate
remains at a certain value for the active power at each step must be longer than the
delay time t
V,TRIP
that has been set. After undershooting the trip level P
TRIP
, the pump
must shut down once the delay time t
V,TRIP
has expired. The system's response
(shutdown and delay time) must correspond to the preset parameter values.
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