Periodic Proof Test And Maintenance; Proof Test - ABB TTH300 User Manual

TTH300, TTF300 TEMPERATURE TRANSMITTER | SM/TTX300/SIL-EN REV. E

7 Periodic proof test and maintenance

According IEC 61508-2 proof tests shall be undertaken to reveal dangerous faults which are undetected by automatic diagnostic
tests.
The End User is responsible for selecting the type and the intervals according the overall safety system demands.
The inspections must be conducted in a manner that enables users to verify the proper function of the safety equipment in
combination with all related components.

Proof Test

The below described proof test is a recommended variant which could be performed within the required periodical proof test interval
derived from the safety instrument system engineering demands (e. g., 1oo1, 1oo2 or 2oo3 architecture) and related PFD
calculations.
Step Test Action (consecutive steps)
1 Bypass the safety DCS or take other appropriate action to avoid a false trip.
2 Restart, Power Down and Power Up the Device.
3 Deactivate the device write protection (refer to the relevant operating instructions).
4 Send a HART command, e. g., via EDD / DTM / FDI simulation functionality to the transmitter to go to the high alarm current output
and verify that the analog current reaches that value.
(Test for voltage problems such as a low loop power supply voltage or increased wiring resistance. This also tests for other possible
electrical part failures).
5 Send a HART command, e. g., via EDD/DTM/FDI simulation functionality to the transmitter to go to the low alarm current output and
verify that the analog current reaches that value.
(Test for possible quiescent current related failures)
6 Activate the device write protection. (Refer to the relevant operating instructions) and wait at least 20 seconds for the non-volatile
storage.
7 Restore the loop to full operation by Restart, Power Down and Power Up the Device.
8 Check the current output in performing a multi-point calibration (e. g., 5-point calibration) measurement of the temperature
transmitter covering the applicable temperature range. (Test for possible sensor and electronics failures)
9 Apply an adequate input signal (e.g., short circuit, wire break) to reach the pre-defined alarm level and verify that the safe state is
reached.
(Test for electronics failures that the analog current output corresponds to the provided input signal).
10 Remove the bypass from the safety DCS.
Table 1: 'Suggested steps for proof test'
The test is assumed to detect 95 % of possible dangerous faults on the related temperature transmitter and sensor assembly.
An appropriate simulator (Pt100 simulator, reference voltage sources) can also be used to check the transmitter electronics
without sensor.
9
AVG