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9 Functional Safety Volume 1
9.8 Recurrent Performance Test
The recurrent performance test is used to check the safety function
to uncover possibly undetected dangerous failure. The operational
capability of the measuring system has to be checked in adequate
intervals.
It is in the responsibility of the operator to select the type of test
and the proof test interval. The intervals are dependent on the
PFD
avg
value defined in the table and chart in the section “Safety-
Technical Data” (see also FMEDA report).
The test has to be carried out such that the proper safety function
will be proven through interaction of all components.
This is the case when the level is controlled within the scope of a
filling. If a filling is not feasible, the measuring system has to be
triggered to respond by suitable simulation of the level or of the
physical measurement effect.
The methods and procedures used in the tests have to be named
and their degree of suitability has to be specified. The tests have to
be documented.
If the function check is negative, you have to take the entire mea-
suring system out of service and keep the process in a safe state
through other measures.
During the test, the person in charge of the test has to ensure the
safety-technical monitoring of the process through other technical
and organizational measures.
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