<Appendix A. Safety Instrumented Systems Installation>
A-2
IM 01C50T01-02EN
A.2.5 Proof Testing
The objective of proof testing is to detect failures
within the transmitter that are not detected by the
diagnostics of the transmitter. Of main concern
are undetected failures that prevent the safety
instrumented function from performing its intended
function. See table A.2.3 for proof testing method.
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 YTA is applied. The actual proof tests
must be performed more frequently or 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. Failures that are detected
should be reported to Yokogawa.
The personnel performing the proof test of the
transmitter should be trained in SIS operations
including bypass procedures, YTA temperature
transmitter maintenance, and company
management of change procedures.
Table A.2.3 Proof Testing
Testing method
Tools required
Expected outcome
Remarks
Analog Output Loop Test:
1. Bypass the safety PLC or take other
appropriate action to avoid a false trip.
2. Send a HART command to the
transmitter to go to the high alarm
current output and verify that the
analog current reaches that value.
3. Send a HART command to the
transmitter to go to the low alarm
current output and verify that the
analog current reaches that value.
4. Use the HART communicator to view
detailed device status to ensure no
alarms or warnings are present in the
transmitter.
5. Perform reasonability check on the
sensor value(s) versus an independent
estimate (i.e. from direct monitoring of
BPCS value) to show current reading
is good.
6. Restore the loop to full operation.
7. Remove the bypass from the safety
PLC or otherwise restore normal
operation.
• Handheld terminal
Proof Test Coverage *
for TC input: 61%
for RTD input: 69%
The output needs to
be monitored to assure
that the transmitter
communicates the
correct signal.
Analog Output Loop Test and Temperature
Spot Check:
1. Bypass the safety PLC or take other
appropriate action to avoid a false trip.
2. Perform Analog Output Loop Test.
3. Verify the measurement for two
temperature points.
4.
Perform reasonability check of the
housing temperature.
5. Restore the loop to full operation.
6. Remove the bypass from the safety
PLC or otherwise restore normal
operation.
• Handheld terminal
Proof Test Coverage *
for TC input: 86%
for RTD input: 86%
The output needs to
be monitored to assure
that the transmitter
communicates the
correct signal.
*: For details of the proof test coverage, refer to the FMEDA No. YEC 15-10-041 R001 V3R7 or No.YEC 15-10-041 R002 V1R6.
Website address: http://www.yokogawa.com/fld/
