Operation And Maintenance With The Honeywell Stt700; Proof Test - Honeywell HART STT700 Safety Manual

5 — Operation and Maintenance with the

Proof test

The objective of proof testing is to detect failures within the HONEYWELL STT700 that are not
detected by the automatic diagnostics of the transmitter. Of main concern are undetected failures
that prevent the safety instrumented function from performing its intended function.
The frequency of proof testing, or the proof test interval, is to be determined in reliability
calculations for the safety instrumented functions for which the HONEYWELL STT700 is
applied. The Exida exSILentia® tool is recommended for these calculations. The proof tests must
be performed more frequently than, or as frequently as specified in the calculation in order to
maintain the required safety integrity of the safety instrumented function.
The following proof test is recommended. It consists of a simple HART
output test. The results of the proof test need to be documented and this documentation should be
part of a plant safety management system. Any failures that are detected and that compromise
functional safety should be reported to the Global Technical Support Center (GTS).
See STT700 Smart Transmitter User Manual for more details # 34-TT-25-17.
Step
1 Bypass the safety PLC or take other appropriate action to avoid a false trip, following
Management of Change procedures.
2
Send a HART
the analog current reaches that value.
This procedure tests for compliance voltage problems such as a low loop power supply voltage
or increased wiring resistance. This also tests for other possible failures.
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. This test checks for possible quiescent current related
failures.
4 Use the HART® communicator to view detailed critical and non-critical device status to ensure
no alarms or warnings are present in the transmitter.
5 Verify all safety critical configuration parameters.
7 Calibrate the device as per calibration procedure given below.
8 Restore the loop to full operation.
9 Power cycle or cold reset to clear soft errors in memory (RAM).
10 Remove the bypass from the safety PLC or otherwise restore normal operation.
This test will detect approximately 85% of possible DU failures in the transmitter (Proof Test
Coverage).
The person(s) performing the proof test of the HONEYWELL STT700 should be trained in SIS
operations, including transmitter maintenance and company Management of Change procedures.
Tools required are: handheld communicator.
June 2017
HONEYWELL STT700
®
command to the transmitter to go to the high alarm current output and verify that
STT700 Safety Manual
®
Action
driven min to max
5