Flowserve 420 IOM - Manual (Page 29)

User Instructions - Logix® 420 Series Digital Positioners FCD LGENIM0106-06 12/13
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12.9 Proof Testing
The objective of proof testing when used in low demand
mode of operation is to detect failures within the Flowserve
420 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 420
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. 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 420 are required.
Steps for Proof Test
1. Bypass the safety PLC or take other appropriate
action to avoid a false trip.
2. Set the trip output to the trip state (below 3.6mA) and
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 tests for failures
that could prevent the closure of the valve, including
electronic and mechanical faults, as well as valve
faults.
3. Inspect the Logix 420 Digital Positioner for any visible
damage or contamination.
4. 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 % can be claimed. Failure modes not
covered include possible leaking of the valve seat for fail
closed valves.
Steps for Partial Valve Stroke Test
Step Action
1. Verify the control loop is ready for valve movement in
the amount set for the Partial Stroke Test (PST).
2. Excecute 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 partial valve
stroke coverage of 95% can be claimed. Failure modes
not covered include possible valve sticking in the travel
range not tested and leaking of the valve seat for fail closed
valves.
12.10 Maintenance
Follow routine maintenance. See section 13.1 Scheduled
Maintainance.
12.11 Repair and replacement
In the unlikely event that the Flowserve 420 valve
positioner fails, the failure should be reported to Flowserve.
Replace faulty components according to section 13
MAINTENANCE AND REPAIR or return the positioner to
Flowserve 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.
12.12 Training Requirements
Activities specified in this manual shall be performed by a
service technician trained in the installation and
maintenance of process instrumentation. See section 1.4
Qualified Personnel.