Proof Testing - Endress+Hauser Proline Prosonic Flow P 500 Functional Safety Manual

Use in protective systems
5.3

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.
5.3.1 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
 In the case of a single-channel system architecture, the average probability of
failure (PFD
rate for dangerous undetected failures λ
assumed mission time by close approximation as follows:
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→  28, e.g. sensor, is permitted as an alternative to testing the
safety function of the entire system.
26
) of the sensor is derived from the proof-test interval T
avg
PFD ≈ λ × (PTC/2 × T + (1 - PTC) / 2 × MT)
avg du
of the sensor system.
avg
, the proof test coverage PTC and the
du
i
Proline Prosonic Flow P 500 HART
, the failure
i
Endress+Hauser
A0023571