Logix
®
520MD+ and 510+ Digital Positioners FCD LGENIM0105-15-AQ – 05/16
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17.9 Lifetime limits
The expected lifetime of the Flowserve 520MD+ Positioner is approxi-
mately 10 years. The reliability data listed the FMEDA report is only valid
for this period. The failure rates of the Flowserve 520MD+ Valve Posi-
tioner may increase sometime after this period. Reliability calculations
based on the data listed in the FMEDA report for lifetimes beyond 10
years may yield results that are too optimistic, i.e. the calculated Safety
Integrity Level may not be achieved.
17.10 Proof Testing
The objective of proof testing when used in low demand mode of oper-
ation is to detect failures within the Flowserve 520MD+ Valve Positioner
and its associated sensors and actuators that may not be detected by
the normal self-diagnostics. Of main concern are undetected failures
that prevent the safety instrumented function from performing its
intended function.
The frequency of the proof tests (or the proof test interval) is to be
determined in the reliability calculations for the safety instrumented
functions for which the Flowserve 520MD+ Valve Positioner is applied.
The actual proof tests must be performed at least as frequently as
specified in the calculation in order to maintain required safety integrity
of the safety instrumented function.
The following tests need to be specifically executed when a proof test
is performed. The results of the proof test need to be documented
and this documentation should be part of a plant safety management
system.
NOTE:
Positioner failures that are detected should be reported to
Flowserve.
To perform the proof testing, an LCD display or HART communicator
such as a 375 Handheld or software such as ValveSight DTM for Logix
520MD+ are required.
Steps for Partial Stroke Test (PST)
Step Action
1. Verify the control loop is ready for valve movement in the amount
set for the PST.
2. Execute the PST via the LCD menu, DD, or DTM.
3. View the results of the PST via the LCD menu, DD, or DTM.
4. Check the errors generated by accessing the Alerts and Alarms
menu on the LCD menu, DD, or the Alarm Annunciator in the DTM
or other HART system using command 48.
When the tests listed above are executed, a proof test coverage of 95%
for the 520MD+ can be claimed if PST has not been implemented as a
diagnostic. To be considered as a diagnostic the PST has to be imple-
mented in a SIL rated logic solver. If PST has been implemented then
no additional failure modes will be detected by the proof test. Failure
modes not covered include possible valve sticking in the travel range
not tested and leaking of the valve seat for fail closed valves.
Steps for Proof Test
Step Action
1. Bypass the safety PLC or take other appropriate action to avoid a
false trip.
2. Set the analog input command to less than 3.6 mA.
3. Ensure that the attached valve is fully in the safe state (defined
by application) and has moved to that position within the allowed
time. This will test for all failures that could prevent the closure of
the valve, including electronic and mechanical faults, as well as
valve faults.
4. Inspect the 520MD+ Valve Positioner for any visible damage or
contamination and ensure the follower arm has sufficient spring
bias if applicable.
5. Check the errors generated by accessing the Alerts and Alarms
menu on the LCD or the Alarm Annunciator in the DTM or other
HART system using command 48.
6. Remove the bypass from the safety PLC or otherwise restore
normal operation.
When the tests listed above are executed, a proof test coverage of 95%
for the 520MD+ can be claimed if PST has not been implemented as a
diagnostic. To be considered as a diagnostic the PST has to be imple-
mented in a SIL rated logic solver. If PST has been implemented, then
no additional failure modes will be detected by the proof test. Failure
modes not covered include possible leaking of the valve seat for fail
closed valves.
17.11 Maintenance
Follow routine maintenance. See section 18.1 Scheduled Maintenance.
17.12 Repair and replacement
In the unlikely event that the Flowserve 520MD+ Valve Positioner fails,
the failure should be reported to Flowserve. Replace faulty components
according to section 18 of this manual or return the positioner to Flow-
serve for service. With experience and the right parts, repair times for
any component can be less than an hour, however a 24 hour mean time
to repair should be assumed for safety availability calculations.
17.13 Trainng Requirements
Activities specified in this manual shall be performed by a service tech-
nician trained in the installation and maintenance of process instrumen-
tation. See section 1.4 Qualified Personnel.
