Information On The Determination Of Safety-Relevant Parameters; Decommissioning The Transmitter - WIKA T32.1S Sicherheitshandbuch

2. Safety
WARNING!
After the proof test of the instrument, start a functional check of the entire
safety function (safety loop) in order to test whether the transmitter ensures the
safety function of the system. Functional checks are intended to demonstrate
the correct function of the whole safety-related system, including all
EN
instruments (sensor, logic unit, actuator).

2.9 Information on the determination of safety-relevant parameters

The failure rates of the electronics were determined through an FMEDA in accordance
with IEC 61508. The calculations have been based on component failure rates per
SN29500. Specifically for temperature resistance sensors and thermocouples connected
to the temperature transmitter, the failure rates determined by Exida.com LLC are used.
The following assumptions have been made:
The transmitter is only operated in Low Demand Mode applications
■
The mean ambient temperature at the temperature transmitter during the period of
■
operation is 40 °C
The MTTR following an instrument failure is 8 hours.
■
Following ISO 13849-1, a maximum service life in the safety application for the transmitter
of 20 years is assumed. Replace the instrument after this time.

2.10 Decommissioning the transmitter

WARNING!
Ensure instruments that have been taken out of service are not accidentally
recommissioned (e.g. through marking the instrument). After decommissioning
the temperature transmitter, a functional test of the entire safety function
(safety loop) should be initiated, in order to test whether the safety function
of the system is still ensured. Function tests are intended to demonstrate the
correct function of the whole safety-related system, including all instruments
(sensor, logic unit, actuator).
16 WIKA safety manual temperature transmitter T32.xS