Endress+Hauser HART Proline Promass 500, Специальная документация

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Proline Promass 500 Use in protective systems
Hauser 31
6.3 Proof testing
NOTICE
The safety function is not guaranteed during a proof test.
Nevertheless, process safety must be guaranteed during proof testing.
‣
The safety-related output signal 4 to 20 mA (output; input 1) may not be used for the
protective system.
‣
Take alternative monitoring measures if necessary.
6.3.1 Proof-testing the safety function of the entire system
1. Check the functional integrity of the safety function at appropriate intervals.
2. The operator specifies the testing interval and this must be taken into account when
determining the probability of failure PFD
avg
of the sensor system.
 In the case of a single-channel system architecture, the average probability of
failure (PFD
avg
) of the sensor is derived from the proof-test interval T
i
, the failure
rate for dangerous undetected failures λ
du
, the proof test coverage PTC and the
assumed mission time by close approximation as follows:
PFD × (PTC/2 × T + (1 - PTC) / 2 × MT)
avg du i
≈
λ
A0023571
MT Mission time
PTC Proof test coverage
Ti
Test interval
3. The operator also specifies the procedure for proof-testing.
 NOTE!
In accordance with IEC 61511, an independent proof test of the
subsystems→  33, e.g. sensor, is permitted as an alternative to testing the
safety function of the entire system.